The Early Years at Allbon

by Adrian Duncan

Click on images to view larger picture,
hover over the images for a description.
    The First Allbon Product: The 2.8 Mk I diesel
    The Allbon 2.8 Mk I On Test
    The Allbon 2.8 Mk II
    Present-day Comparison of the Allbon 2.8 Mk I and II.
    An Unexpected Further Variant—The Allbon 2.8 'Mk. 1.5'
    Towards The Future: Further Developments at Allbon
    The Allbon Arrow
    The Allbon Arrow Re-Evaluated
    Comeback: The Allbon Javelin Mk I
    Turning Point: The Allbon Dart
    The Dart's Influence on Other Manufacturers
    Production Problems at Allbon and their Solution
    The Later Years: A Brief Summary

In other articles on this site we have looked at various aspects of the work of Alan L. Allbon, one of England's foremost model engine designers from the middle years of the 20th century. During his fifteen-year career in the commercial model engine field, Allbon was famously associated with such well-known names as Davies-Charlton Ltd and Allbon-Saunders. We have reviewed his involvement with both of these companies in separate articles.

However, Allbon got his start in the model engine field working independently through his own company which bore his own name. In the present article, we'll complete our in-depth coverage of Allbon's work by looking at his activities during his early period as an independent manufacturer in his own right, beginning with the 1948 Allbon 2.8 diesel and continuing up to late 1952, when he joined forces with Davies-Charlton. His story from that point onward has already been covered in detail in the previously-mentioned articles, although for convenience we will append a brief summary here.

Before getting started, I must acknowledge the outstanding assistance rendered by both David Owen and Ron Chernich. Both of these valued friends and colleagues were most generous in providing images, test reports, advertisements and general information in their possession. No request of mine for assistance went unanswered. I must also thank Eric Offen and Tim Dannels for their kind provision of images and serial numbers. Without such cooperation, these articles would lack any semblance of authority. Thanks, guys!

With that clearly stated, let's explore the background to the Allbon story...


It's always nice to be able to incorporate a touch of the human element into these technically-focused articles. However, to this point I've been unable to confirm anything definite about Alan Allbon's personal life, nor do I have any knowledge of any formal technical qualifications or experience which he may have possessed. If any reader is able to enlighten us on any of these subjects, we'd be extremely glad to hear from you!

Most unusually, an in-depth online search of several supposedly comprehensive 20th century British genealogical records has turned up only one individual named Alan Allbon having both the correct surname spelling (two I's) and middle initial L. This is a certain Alan Leslie Allbon, who was born on July 4th, 1906 at Hitchin, a small market town in northern Hertfordshire. The same individual was married in 1935 at the age of 29 to Elsie Milnes. This happy event took place at Bedford, which is only some eighteen miles to the north-west of Hitchin in neighbouring Bedfordshire.

The above facts constitute some purely circumstantial evidence that this may well be our man, since we know for sure that Alan L. Allbon of model engine fame spent a considerable portion of his later professional life living and working near Bedford, perhaps representing a return to former haunts after some time spent in the Big Smoke of London. If this is indeed our man (and no other possibilities were identified by my extensive search), he would have been 42 years old in 1948—a perfectly appropriate age at which to be establishing his own engineering business following an earlier career spent working for others in the precision engineering field, thereby gaining relevant experience while presumably saving the funds required to go out on his own.

The death record for Alan Leslie Allbon shows that he died at Wharfedale in Yorkshire in late 1978 in his 73rd year. By this age, "our" Alan Allbon would most likely have been retired from a very successful later career in the optical industry, making his death at distant Wharfedale entirely possible regardless of his earlier residential location. The fact that his wife originally hailed from Yorkshire may have led them to relocate there upon Allbon's retirement. Alternatively, Allbon could well have been on a visit to Wharfedale when he succumbed, perhaps to an accident—the available record does not clarify his residence at the time or the cause of his seemingly premature death, only its location. The fact that Wharfedale is a geographic location rather than a specific community lends some weight to the accident possibility.

I've been unable to find any obituary for this individual. Nonetheless, the absence of any record of alternative candidates having the correct names and initials means that this undoubtedly could be our man. That said, we cannot regard this identification as secure unless we receive confirmation from someone who knew him. Let's hope that such an individual reads this article and steps forward...if so, we will of course update this information with full acknowledgement.

In a modelling context, the name Alan Allbon first appears in early 1948 as the owner of his own company called Allbon Engineering Co (Sunbury) Ltd, working from an address on Thames Street in Sunbury-on-Thames. The actual street address of the company was 51a Thames Street, although the full street address was not used initially. At the time in question, Sunbury was located in the county of Middlesex, although it was later incorporated into the county of Surrey as part of the 1965 county boundary reorganization resulting from the work of the Royal Commission on Local Government in Greater London.

The Allbon workshops at the above address were clearly quite small. Thames Street has moved well upmarket since Allbon's time there, many of the buildings on the street having been converted into riverside flats, restaurants or office space. The modest red brick building at 51 Thames Street, which may well be the one formerly occupied by Allbon, is today (2012) occupied by a branch office of A. A. Telecom Ltd. Looking at the building and the location as they appear today, it seems not unlikely that this was Allbon's residence as well as his business location. Such a combination of functions would make complete economic sense.

As far as we can tell at this distance in time, the sole business of Allbon Engineering was the manufacture of model engines. A prior involvement on Alan Allbon's part with aeromodelling and/or model engineering is clearly implied here—he is highly unlikely to have leapt into a business line in which he had no previous interest or experience. He must surely have had a sufficient involvement with the aeromodelling community to be able to gauge his commercial prospects when planning to enter this business. However, we currently have no knowledge of his earlier model-related activities. Again, we need to hear from someone who knew him.

There's no doubt that the Allbon enterprise began quite modestly in terms of production capacity. The production figures achieved at this stage were seemingly comparable with, say, those for the Kemp workshops in Gravesend, Kent, which operated with a staff of three full-time employees (including owner Harold Kemp) plus one part-timer. It's doubtful that staffing levels at Allbon Engineering were any greater.

The first model to appear was the Mk I version of the Allbon 2.8 sideport diesel. Let's begin our review of Allbon's early work by taking a close look at this design.

The First Allbon Product: The 2.8 Mk I diesel

By early 1948, when the first commercial Allbon design appeared, model engine manufacture was a well-established and highly competitive business in Britain. In entering the model engine field, Allbon was going head to head with such nationally-established names as ED and International Model Aircraft (IMA—FROG), both of whom were located just across the River Thames from Sunbury, as well as Mills Brothers of Central London, Kemp (later K) in Gravesend, Kent and Davies-Charlton of Barnoldswick in Lancashire. There was also localized competition from a number of small-scale manufacturers who mostly sold their products in their immediately-surrounding areas—Aerol Engineering of Liverpool (later famous as the makers of the Elfin engines) was one of these, as was Edward Reeves of Shifnal in Shropshire. It was thus important for Allbon to get it right first time—initial impressions can make or break a newly-formed commercial enterprise, particularly in the face of well-entrenched competition.

As it happens, Allbon's initial commercial offering, the Allbon 2.8 diesel, proved to be a well-made and dependable unit with a useful enough performance by the standards of its day. It was thus instrumental both in getting the new company off to a good start and in establishing the name of Alan Allbon as a model engine designer to be reckoned with.

As far as we can determine, the initial national announcement of this model took the form of its inclusion in Henry J Nicholls' advertisement in the February 1948 issue of Aeromodeller. Allbon seems to have enjoyed a positive personal relationship with Henry J Nicholls, since Nicholl's Mercury Model Aircraft Supplies Ltd of 308 Holloway Road in London acted as the trade distributor and service provider for Allbon from the outset.

Given the engine's apparent early 1948 release, it seems a little odd to have to record the fact that the first advertisement placed by Allbon himself for the Allbon 2.8 apparently did not appear until the October 1948 issue of Aeromodeller. It seems that Mercury Model Aircraft Supplies was able to absorb all of Allbon's limited production at the outset, most likely by supplying initial demand in the Greater London area either over the counter at "308" or through other London-area retailers. Such a situation would naturally obviate the need for any wider promotion on Allbon's part. Certainly the wording of that initial Allbon advertisement of October 1948 implies that the engine had been on sale and in use for some time prior to its placement, since it made reference to the engine's excellent service record.

The engine sold for the reasonably competitive price of £4 16s 0d. (£4.80 in "modern" money). For comparison, the competing ED 2.49 cc Mk III sold for £5 10s 0d (£5.50) at the same time. The Allbon's price was clearly acceptable to consumers, since the market evidently absorbed all of the limited production which Allbon was able to achieve from his Sunbury premises.

The Mk I version of the Allbon 2.8 was a very workmanlike long-stroke sideport diesel bearing more than a passing resemblance to the ED 2 cc sideport models, notably the Comp Special version which appeared in December 1947. Like the ED engines, it featured a steel cylinder having twin exhaust ports at the sides; a single front bypass passage formed from a soldered-on brass channel; a soldered-on boss at the rear for the screw-in carburettor; a surface jet needle valve; a bolt-on main bearing housing attached by four 6 BA machine screws; and an integrally-cast backplate. Like the Comp Special version of the ED 2 cc model, it also sported a screw-on aluminium alloy cooling jacket with a conventional vernier compression control. A further similarity was the attachment of the cylinder to the main crankcase with four 6 BA screws. It's difficult to avoid the conclusion that the design of the very successful ED sideport models exerted a strong influence upon the design of the Allbon 2.8.

That said, there were some very clear distinctions between the competing designs from Allbon and ED. For one thing, there was the displacement of 2.8 cc as opposed to the ED's 2 cc. One gets an impression that the idea may have been to make what was in effect an enlarged version of the very popular ED models having greater torque development. The resulting product would be able to pull a larger model aloft while allowing its manufacturers to cash in on the comfortable similarity of the engine to the earlier ED designs.

To present-day modellers, both the 2 cc and 2.8 cc displacements appear offside, although the 2.8 cc figure for the Allbon seems particularly so. To understand this point, it's essential to look at the matter in a 1948 context rather than from a present-day viewpoint. At the time in question, competition aeromodelling in Britain was still very loosely organised in terms of displacement categories. In particular, the "magic" displacement of 2.5 cc (0.15 cu. in.) had not yet been adopted by the FAI for International competition. Consequently, no particular displacement really had much of an edge over another in terms of consumer appeal or competition applicability. The only issues were what size of model was desired and whether or not a given engine could do the job of flying that model to the standard required. As a result, at the time in question engines having all kinds of odd-ball displacements were routinely being released in Britain.

Seen in this 1948 context, there was actually nothing at all extraordinary about Allbon Engineering releasing a new model having a displacement of 2.8 cc. It was only later, when the 2.5 cc limit was formally adopted by the FAI and then by the British Society of Model Aeronautical Engineers (SMAE), that the attention of manufacturers became progressively more focused on engines built to the new competition limits and the 2.8 cc displacement category became something of an orphan which did not conform to any particular competition class. By that time the Allbon 2.8 had been withdrawn from production in any case.

The new model featured nominal bore and stroke measurements of 9/16" (0.5625"—14.287 mm) and 11/16" (0.6875"—17.462 mm) respectively for a displacement of exactly 2.80 cc (0.171 cuin). The stroke/bore ratio was 1.22 to 1—a fairly standard figure for the long-stroke sideport diesels of the era. The engine was clearly designed for torque at moderate speeds rather than for all-out power. Weight was 6 ounces exactly (170 gm), complete with tank.

We previously highlighted the marked resemblance of the Allbon 2.8 to the ED Comp Special which was one of its main competitors at the time. This similarity was carried over to the crankshaft, which featured a heavily counterbalanced web to help control the inevitable vibration from the rather heavy cast iron piston. The crankpin had a very substantial diameter of a full 1/4"—no shortage of strength there! In fact, the crankshaft as a whole was far more sturdy than that of its admittedly smaller-displacement ED counterpart.

The crankcase also bore some similarity to that of the competing ED models, having an integrally-cast backplate. However, it was far more lightly constructed. In particular, the mounting lugs appear to be very fragile indeed, especially for an engine of this weight and displacement. Frankly, I wouldn't give much for the chances of the lugs surviving a really hard crash ... those used on the smaller ED models were far more appropriately dimensioned in my personal opinion.

The fragility issue was somewhat exacerbated by the fact that the casting alloy used by Allbon throughout this period appears to have been of rather indifferent quality. All of the original Allbon models suffered from a tendency to break mounting lugs and other cast features, perhaps explaining why a relatively low proportion of those that were made seem to have survived intact. This is as true for the later Arrow, Javelin Mk I and Dart Mk I models as it is for the 2.8.

Like the ED models, the front cover incorporating the main bearing housing was attached to the crankcase by four 6 BA screws. Again, the comment may legitimately be made that the Allbon's front cover was far less sturdy than that of the ED models, seemingly possessing rather marginal crash resistance. The main bearing itself consisted of a pair of white metal bushings pressed into the ends of the main bearing housing. This was in contrast to the ED designs, which used cast iron bushings.

Indeed, the direct similarities between the ED and Allbon designs ended at this point. The prop attachment arrangements were quite different, the Allbon using a plain one-piece prop driver in combination with an aluminium alloy spinner nut mating with a 1/4-26 BSF thread. The Allbon's prop driver was very sensibly backed up by a steel thrust washer to prevent scuffing between the alloy faces of the driver and main bearing housing. In common with a number of contemporary British engines, the prop driving face was not knurled in any way, reliance being placed upon friction between the prop and the faces of the driver and spinner nut. Presumably the idea was that this would allow for some slippage in the event of a crash and thus protect the engine's working parts from crash damage. A pair of holes was drilled through the driver in case an owner wished to add the security of a pair of pins to lock the prop.

Unlike the ED with its conventional one-piece piston design, the Allbon used a composite piston construction in which the gudgeon pin and con-rod were mounted in an aluminium alloy yoke which was secured inside the piston using a countersunk screw through the piston crown. This eliminated the appearance of the ends of the gudgeon pin at the piston surface, thus preventing any possibility of the pin fouling the transfer or induction ports. According to the company literature, the final lapping of the piston into the cylinder was completed after the installation of the carrier to allow for any distortion during assembly.

While this was a very neat approach to the mounting of the con-rod small end in the piston, it did have two downsides. One was the possibility of the screw coming loose, which could have rather drastic results! The consequent necessity of tightening the screw really hard to begin with might also make loosening of the screw to permit removal of the carrier for rod replacement somewhat problematic, particularly insofar as it might cause piston distortion when re-tightened.

Another potential problem stems from the differential thermal expansion coefficients for the two materials involved. Once the engine got well warmed up, I could foresee the alloy yoke exerting a considerable expansive pressure against the inner piston wall, causing a piston that was well fitted when cold to become tight when hot. My own Mk II example (which has had very little running) may possibly suffer to a degree from this problem, although my very "experienced" Mk I appears quite immune to this issue. However, even if this didn't happen, the two components might be expected to "work" relative to one another, eventually causing the retaining screw to come loose. Up to now, I have yet to experience such an issue with an Allbon engine, although that is not to say that it couldn't occur.

One good design feature connected with this assembly was the use of a sturdy forged alloy con-rod. A well-finished rod of this material will generally wear far better than a hardened steel rod as used in the ED models. My example of the Mk I Allbon 2.8 has clearly had (and survived!) quite a bit of use, but there is almost no detectable play in the con-rod assembly.

The Allbon Mk I cylinder featured drilled circular holes for both the induction and transfer ports. The use of the internal yoke to mount the con-rod inside the piston eliminated any possibility of the pin fouling these ports, which were accordingly formed as single holes of quite large diameter rather than having to be twinned or depth-limited to discourage fouling.

We noted earlier that the soldered-on bypass passage was formed from brass sheet, exactly as in the ED designs. This bypass passage was fed at its base by a pair of 5/32 (0.156)" dia. holes drilled through the cylinder location flange. These holes were supplied with mixture by means of a channel formed at the front of the main crankcase casting immediately below the cylinder mounting flange. Gas access to the bypass entry point was thus relatively unimpeded.

The Allbon piston did not feature a deflector "step" along the lines of the ED models, being perfectly flat-topped. Such a step would have been impracticable given the impossibility of guaranteeing the piston alignment following the tightening of the yoke screw through the piston. Instead, the Allbon's drilled transfer port was located further up the cylinder wall than in the ED models, with no provision for any kind of deflector. The transfer port actually overlapped the exhaust ports to a large extent, giving a quite reasonable transfer period together with a short blowdown period. That said, the design clearly implies that mixture losses through the exhaust ports must have been quite high.

The cylinder was attached to the case with four 6 BA screws, again as in the case of the ED models. The thread length was a bit marginal, especially when one considers the somewhat indifferent casting alloy used. These screws should be tightened with care and not disturbed unnecessarily. The length of the piston skirt coupled with the dimensions of the exhaust ports was such that there was no sub-piston induction, at least at this stage.

The engine was completed by the attachment of a very neat combined carburettor/fuel tank assembly. The carburettor body was a casting to which the tank was secured using an integrally-cast tank top as a mounting. Somewhat unusually by the standards of the day, no cut-out was fitted. The needle itself was threaded 6 BA and was very effectively tensioned by a coil spring. The tank was of bowl form, with ample capacity for free-flight purposes.

It must be said at this point that the venturi tube was highly vulnerable to fracture at the start of its externally-threaded section which screwed into the cylinder boss. Examples of the engine with missing or broken original tank units are not uncommon, presumably for this reason. ED began with a similar arrangement on their Mk II model but quickly switched to the familiar and far stronger internally-threaded venturi after experiencing a rash of failures.

All working fits and finishes in my own example may objectively be described as above average. The standard of workmanship displayed in this engine is at least equal to that of any of the "consumer-grade" competition. This concern with good workmanship where it counted was to remain an Alan Allbon trait throughout his career as a model engine manufacturer—indeed, as we shall see much later, it was to lead directly to his eventual departure from the model engine field.

The fact that the Allbon 2.8 was designed with high torque production at modest speeds as the primary goal is reflected in the manufacturer's airscrew recommendations. For free flight applications, an 11x6 prop was suggested, while for control line use either a 10x8 or 9x8 were the recommended sizes. All of these are of course quite substantial for an engine of only 2.8 cc displacement.

The Allbon 2.8 Mk I can best be summed up as a well-made engine of generally sound but perhaps rather uninspiring design, also appearing somewhat fragile in terms of crash resistance. It's clear that Allbon had yet to find his feet as a model engine designer, relying at this stage to a large extent upon insights gained through the examination of the products of other manufacturers. Still, the Allbon 2.8 was undoubtedly a very useable engine which served its purpose in getting the Allbon Engineering venture off to a good start.

Production of the Allbon 2.8 Mk I appears to have continued without a break up to October 1948. The engines were given serial numbers which were stamped onto the upper surface of the right-hand mounting lug. Eric Offen has reported the existence of engine number 1132, while my own Mk I engine bears the number 1277, seemingly proving that at least that many were made. There are currently no reported numbers below 1000, although it would be wrong to read too much into this given the very small and hence statistically unreliable sample which proved to be available. Allbon's practise with all of his other numbered models was to start the numbering sequence at 1, and there seems little reason to suppose that he would have approached the 2.8 any differently.

The key point to note here is that only some 1300-1400 examples of the Allbon 2.8 Mk I appear to have been manufactured in total—an unusually low figure for the model's production life of some nine months or so. The implied production rate of around 150 engines monthly emphasizes the very small production capacity of the original Allbon workshops at 51a Thames Street—ED made far more engines every month than the total nine-month figure for the Allbon 2.8! We shall have occasion to recall this later.

The Allbon 2.8 Mk I On Test

It turns out that the Allbon 2.8 Mk I was never the subject of a published test in the contemporary modelling media. Although it was not explicitly stated in the article, the elevation drawings published with the test report by Lawrence H Sparey which eventually appeared in the December 1948 issue of Aeromodeller prove beyond doubt that the subject of that test was in fact a different model, described next.

Accordingly, we'll have to do our best using our own resources. My own illustrated example of the 2.8 Mk I bearing the serial number 1277 was tested recently to provide background for this article. I found the engine extremely easy to start, not requiring a prime at any time provided a couple of choked flicks were given as a preliminary. The engine required that compression be raised a little above the running setting for a cold start—a not-uncommon characteristic of low-speed diesels. It also liked the needle to be opened a little from the running setting.

Once running, the needle could be closed down (in this case from 1-1/2 turns open down to I turn) and the compression backed off to establish the best settings. As reported by Sparey in his test of his test example, control response was excellent, making the optimization of settings very easy. Hot restarts were found to be immediate at running settings, again following a couple of choked flicks. Despite the un-knurled prop driver face, I experienced no problems at any time with prop slippage. I ran tests on a number of airscrews, obtaining the following figures:

APC 11x65,800 rpm0.110
APC 10x76,200 rpm0.116
APC 10.5x66,400 rpm0.124
APC10x66,900 rpm0.122
APC 9x67,800 rpm0.116
APC 9x48,400 rpm0.110

The power outputs given are only approximate since they are based on estimated power absorption coefficients for the props in question. Nonetheless, these figures yield a reasonably coherent power curve which implies an output of around 0.125 BHP @ 6,500 rpm—a little less power than Sparey was able to extract from his test example, but at pretty much the same speed. The engine was running on the bench at its peak using the 10-1/2 x6 prop, which is thus a very appropriate test airscrew. However, it would be under-propped for flying using this airscrew since it would over-speed past the peak in the air. Overall, I get the feeling that the manufacturer's recommended prop sizes given earlier would be entirely appropriate for in-flight service.

I would summarize my experiences by saying that the Allbon 2.8 Mk I proved to be a very user-friendly engine which starts extremely easily and runs very well indeed within the bounds of its inherent performance limitations. It would have made a more than acceptable powerplant for general sport flying by 1948 standards. However, it must be admitted that the engine's power output is very much on the modest side, as is its seeming ability to withstand "hard landings".

The Allbon 2.8 Mk II

We noted previously that production to the Allbon 2.8 Mk I appears to have continued up to October 1948. The highest serial number yet reported for a Mk I model of the engine is my own engine number 1277.

By the time that we get to my own engine number 1428 as well as identical engine number 1449 in the possession of my good mate David Owen, we see a few changes. These units are in fact examples of the Mk II version of the Allbon 2.8 which seems to have entered production in November 1948. All that we know for certain is that advertisements for the Mk II first began to appear in December 1948. The revised model sold at an unchanged price of £4 16s 0d.

The Mk II version of the Allbon 2.8 was very similar to the Mk I version for the most part. However, the two major changes were potentially quite significant. It cannot have escaped Alan Allbon's notice that his original design was somewhat lacking in performance by comparison with an increasing number of competing designs, including several of significantly lesser displacement such as the various Elfin plain bearing models which had begun to appear in mid 1948.

It's clear that Allbon had all along been influenced by the emerging designs of others. In the present instance, he appears to have taken a hard look at the concept of sub-piston induction which had been pioneered in Britain by ED with their Comp Special design of December 1947 and had subsequently been taken up by a number of other manufacturers. He evidently decided that one way to get more power out of the 2.8 model was to incorporate sub-piston induction into the design.

Consequently, the Mk II version of the Allbon 2.8 featured a pair of slots beneath the exhaust ports which were opened by the piston skirt near top dead centre to give sub-piston induction. The same effect could have been achieved (as it was by ED) by simply making the exhaust ports deeper, but the length of the piston skirt in the 2.8 evidently led Allbon to the conclusion that this would remove far too much of the piston support area from the cylinder wall. Looking at the engine, one can only agree with him! Such a move would have required a substantial shortening of the piston skirt along with a matching upward relocation of the induction port.

Another change which was applied at the same time was the "squaring-off" of the upper edge of the transfer port. This seems to have been done with a hand file following the drilling of a round hole as before—indeed, there is evidence of quite a bit of hand finishing in these engines. The intent of this modification was clearly to increase the opening rate of the transfer port, thus theoretically helping the engine to breathe at higher speeds. Both my own example and that owned by David Owen incorporate the same feature, so it definitely appears to be part of the factory Mk II upgrade as opposed to an owner modification.

These were in fact the only functional changes to the design—in all other respects, the Mk II was identical to the Mk I. The cylinder of the Mk II was painted black to distinguish it from the Mk I at a glance, but this of course had no effect on performance. However, the same could not be said for the sub-piston induction and transfer port reconfiguration! The manufacturers specifically drew attention to the sub-piston induction in their advertising for the Mk II, claiming that it extended the peak speed range by 2,000 rpm. The advertising also claimed that the revised model was "definitely a competition diesel", a statement which implies that this accolade had not been widely accorded to the original design!

The Allbon 2.8 must already have acquired a good reputation within the modelling community at large, since at around the same time as the Mk II version was under development the engine was chosen as the subject of a published test by Lawrence H. Sparey. This was the eighth such test carried out by Sparey for Aeromodeller magazine. His report appeared in the December 1948 issue, implying that the test itself must have been conducted in October or early November of that year.

Sparey's test report did not specifically characterize the tested unit as a Mk II, nor was the sub-piston induction feature mentioned in the text at any point. However, the very clear elevation drawings of the tested model which accompanied Sparey's report leave no room for doubt that his test example exhibited this feature—the two sub-piston induction slots are clearly depicted on those drawings. It actually appears quite possible that Sparey was unaware that there had been an earlier version of the engine.

The fact that Sparey was able to obtain his test example, get it run-in and tested and then have the report prepared in time to meet the mid-November editorial deadline for the December 1948 issue would at first appear to imply that the Mk II version must have been available by early October at the latest. Even then, this was remarkably quick work. However, the alternative possibility exists that Allbon sent what was in effect a pre-production example to Sparey in the expectation that its performance on test would prove to be sufficiently impressive to enhance its status in the marketplace.

Subsequent research has reinforced the above possibility - a further example of the engine acquired following the original publication of this article has greatly informed our understanding of this issue. We will deal with that in a subsequent section of this article. Suffice it for now to say that the example tested by Sparey does indeed appear to have been a pre-production model of the Mk. II which may in fact have lacked one of its main features.

If this was Allbon's strategy, it was certainly effective—Sparey's report was entirely favourable. He noted that "good starting was a feature of the engine" and reported that it ran "extremely well over a fairly wide range of speeds". He also commented upon the engine's excellent response to the controls, together with a general absence of "fussiness". He characterized the measured peak output of 0.144 BHP @ 6,500 rpm as "exceptional for an engine of this capacity". This is a substantially higher output than that obtained in my own testing for the Mk I version as reported above.

Sparey summarized his findings by stating that the Allbon appeared to be "one of the most efficient engines yet tested". It may well be imagined that this very laudatory report did no harm at all either to Alan Allbon's reputation as a designer or his prospects as a manufacturer.

Oddly enough, Peter Chinn of the rival Model Aircraft magazine never got around to testing the Allbon 2.8. Spareys' report thus became the engine's one and only appearance in a published test.

Present-day Comparison of the Allbon 2.8 Mk I and II.

As stated earlier, the Allbon 2.8 Mk I was never the subject of a published test in the British modelling media. This was a pity, because a comparison of results obtained by the same tester using the same methods applied to the two models would have afforded an excellent opportunity to assess the effect of adding sub-piston induction to a given design of this general type. Since the only functional changes were the incorporation of sub-piston induction and the squaring-off of the transfer port, any performance differences must be primarily down to those features (allowing for the usual minor differences between different examples of the same basic design).

To remedy this deficiency, I decided to undertake a direct comparison between the two models, using the same props and fuel on the same day to minimise any atmospheric differences. This of course involved a re-test of Mk I engine number 1277 along with a test of Mk II engine number 1428. Since the primary object of the exercise was to assess the effect of the sub-piston induction, I went so far as to use the Mk II's venturi on both models for the purposes of this test, thus eliminating one potential variable from the mix.

First up was previously-tested Mk I engine number 1277. The engine proved just as easy to start and adjust as before, making the testing a really painless and enjoyable process. Either the Mk II venturi was a little "faster" or the extra running had freed things up a touch, because despite the fact that I used the same batch of carefully-stored fuel from the previous test, speeds on most props tested were slightly up on the previous results. However, the general performance picture was little changed in an overall sense.

Then it was the turn of Mk II engine number 1428. This unit proved just as easy to start as its Mk I relative, also being just as responsive to the controls. Running was smooth and consistent on all props tested. However, the actual results achieved were a real shock—the Mk II failed to match the Mk I on any of the tested loads! The difference on the first few props was so marked that I actually returned the engine to the workbench for a partial tear-down to see if there were any leaks or obstructions that could affect the engine's pumping efficiency. I could find absolutely nothing wrong—the engine was completely free from base leakage and either intake or bypass obstructions. This was not actually much of a surprise—the engine started too easily and ran too smoothly for there to be any major internal issues. Accordingly, I re-assembled the engine, gave it a few shake-down runs and then repeated the tests with the results shown in the table below.

PropRPMBHP (approx)
APC 11x65,800 rpm0.1105,400 rpm0.089
APC 10x76,300 rpm0.1225,900 rpm0.100
APC 10.5x66,400 rpm0.1246,100 rpm0.108
APC 10x66,900 rpm0.1226,700 rpm0.111
APC 9x67,900 rpm0.1207,800 rpm0.116
APC 9x48,600 rpm0.1188,500 rpm0.114

Both test examples were clearly well run-in, although the Mk I had undoubtedly received considerably more use. Still, the differences based upon relative running time should not have been large. When cold, both engines felt equally well freed-up, with piston/cylinder fits that seemed to me to be absolutely perfect along with outstanding base compression. The Mk II exhibited a slight loss of power as it became hot, perhaps indicative of a certain tendency for the Mk II's piston to tighten up at higher temperatures as a result of the differential expansion of the alloy yoke and cast-iron piston. This might well have influenced the results. It's also true to say that the Mk II had pretty much caught up with the Mk I by around 8,500 rpm. However, both models were clearly past the peak at that point. It does appear that the Mk II peaks at a somewhat higher speed than the Mk I, but the peak output is clearly lower. I remain at a complete loss to explain these findings—I can only report them!

What can I say about these results?!? They certainly don't bear out the Allbon advertising claim of "Peak R.P.M. 2,000 Higher" for the Mk II version! Come to that, neither did the figures reported by Sparey. It must be recalled that both of my test engines were using the same venturi and fuel tank assembly, so that was not a possible factor in the difference. I suppose the results must be put down to those indefinable differences between two examples of the same product (which these are apart from the two Mk II cylinder modifications) that can undoubtedly affect relative performance in ways which defy rational analysis.

One point that was clarified by these tests was the fact that the Mk II with its sub-piston induction had apparently lost a little of its suction draw—scarcely a real surprise. Using the same venturi/tank assembly, the needle setting for a given prop was on average about 1/4 turn greater for the Mk II than for the Mk I, just as we might expect. Suction remained perfectly adequate, however, allowing both engines to run the tank out cleanly.

If I didn't have the results for the Mk I for comparison, I would have given the Mk II a passing grade on the basis of its figures viewed in isolation—not much power for its displacement, but a very user-friendly and smooth-running engine with an adequate performance for sport flying. However, it's a little disappointing that the sub-piston induction appears to have fallen well short of giving the Mk II the kind of performance edge that its makers claimed. Perhaps I simply have a bad example of the Mk II, or an exceptional Mk I example...if so, I can't identify the factors which make them so!

Be that as it may, neither of my engines came close to equaling the output reported by Sparey in his test. It seems entirely possible that his results were more typical of those to be expected from a good example of the Mk II.

An Unexpected Further Variant—The Allbon 2.8 'Mk. 1.5'

It's a very strange thing, and a phenomenon which I can't fully explain, that the publication of one of these articles in MEN very often coincides with the near-simultaneous acquisition from a completely independent source of further information relating to the topic. The present Allbon article proved to be no exception. Immediately following the initial publication of this article, another example of the Allbon 2.8 came my way which proved to have a most interesting tale to tell!

At first sight, this engine appeared to be an Allbon 2.8 Mk II which had lost its black paint. Indeed, that was how the previous owner characterized it. My man interest in acquiring it was simply to get my hands on another example of the Mk II for comparison with my existing Mk II which had seemingly under-performed on test. However, a very close examination of the new arrival's cylinder using a powerful magnifying glass revealed absolutely no trace of paint despite the fact that the engine appeared little used. In my experience, this is highly unusual—minute traces of paint almost invariably cling to tiny crannies in the metal. Hence I'm pretty certain that this cylinder was never painted.

Further examination revealed that the engine exhibited another significant departure from the Mk II pattern, and this time one which could not be explained as a result of wear and tear. This was the fact that the top of the transfer port remained round as in the Mk I models, with no evidence whatsoever of any attempt to square it off as in the Mk II.

A final divergence from the established pattern was the fact that this engine bore no serial number. There appear to be only two possible explanations for this—one, the engine had a replacement case following damage to the original in service; or two, the engine was a factory experimental model which they didn't bother to number.

The near-new state of the engine made it appear that if the first possibility was the explanation for the absence of a serial number, then the original owner had been extremely unlucky—he must have broken the case on the very first flight! Moreover, there are no other signs of the kind of collateral crash damage which we might expect to result from an impact of that magnitude.

However, the second possibility certainly warrants serious consideration. We saw earlier that the Mk II Allbon 2.8 was created by adding the sub-piston induction slots (which appear on the new example) as well as squaring-off the transfer port's upper edge. It would be entirely natural for Alan Allbon to test these concepts independently to determine their effect in isolation. Indeed, we would logically expect him to build a few examples of the engine which were in effect Mk I models with the sub-piston induction added but with no other modifications. He would also quite naturally omit the cylinder painting step, since this would contribute nothing to the tests. Finally, why bother adding a serial number to a factory test engine? The new example displays all of the above characteristics.

How to interpret this? Well, it appears to me that by October 1948 (at which time he was still advertising the Mk I model, remember), Alan Allbon had decided that something needed to be done to improve the performance of the 2.8. The E.D. Comp Special had demonstrated the effectiveness of sub-piston induction, so what could be more natural than for Allbon to try this himself?

It now appears likely that this is exactly what he did. He evidently took a few Mk I engines out of the production line and added the sub-piston induction slots just to see how effective this modification was. He may also have made a few examples with the squared-off transfer port but no other changes, just to test that modification as well. After testing was completed, these engines may well have simply been put back into stock for sale to the public, or alternatively (and perhaps more probably) given to selected individuals for field testing. Indeed, a few examples of the Allbon 2.8 may have actually been produced for sale with the sub-piston induction but no other modifications, a change of Mark number not being seen as necessary until the December 1948 addition of the squared-off transfer port and black paint. However, it's probable that any such engines would have received serial numbers.

The fact that advertising for the 2.8 Mk II did not commence until December 1948 despite the irrefutable evidence from Sparey's test that examples having sub-piston induction existed several months prior to that date is now readily explained. The testing program occupied a period of several months, and it was not until late November of 1948 that Allbon had finally settled on the optimal mix of design changes to produce the Mk II version which he then proceeded to advertise.

This raises the possibility, amounting almost to a probability, that the example tested by Sparey was of this intermediate 'Mk 1.5' type. The timing is exactly right, plus the fact that Sparey did not characterize the tested unit as a Mk II (which had yet to be announced at the time when he conducted his test) despite the undoubted presence of the sub-piston induction slots is entirely consistent with the above scenario. Indeed, it's difficult to explain the appearance of the sub-piston slots in advance of the announcement of the Mk II in any other way.

This engine provides clear evidence of the very focused and methodical approach taken by Alan Allbon to the testing of improvements to his model engine designs. How well did this particular modification work on its own? Only one way to find out—follow in Allbon's footsteps by running a test! So that's what I did—I tried the new model on the same props and fuel as used for the earlier tests on the Mk I and Mk II versions.

The engine proved to be every bit as user-friendly as the other two examples tested earlier. Starting was about as fool-proof as it can be with a model diesel, a few flicks following a couple of choked turns being all that was ever required. Settings were easily established, with extremely smooth and steady running. The results were as follows:

APC 11x66,1000.129
APC 10x76,8000.153
APC 10.5x66,9000.156
APC 10x67,3000.144
APC 9x68,0000.125
APC 9x48,5000.114

Now that's more like the kind of performance that we might reasonably hope to see from an engine featuring sub-piston induction! It would appear that the engine peaks at right around 6,900 rpm, at which speed it's developing approximately 0.156 BHP. This is a significant improvement over the figures obtained for my Mk I version of the engine. Since the only difference between the two engines is the sub-piston induction, this seems to represent a persuasive endorsement of that modification's effectiveness.

The Mk '1.5' also performed at a level which was streets ahead of my Mk II example. I have to conclude either that the Mk II failed to meet its potential during the test which I conducted or that the squared-off transfer port actually reduces performance. In reality, if that had been the case there's no way that Alan Allbon would have included it in the final design of the Mk II model. I suspect that I simply have a "slow" example, or one that requires more running time.

A particularly interesting observation is the fact that all three tested examples were more or less level by the time 8,500 rpm had been reached. This implies that the main benefit of the sub-piston induction was improved torque development in the 6,000—7,000 rpm speed range. Clearly other common factors continued to limit the engine's performance above that range.

The above figures also exceed those obtained by Sparey, both in terms of peak output and peaking speed, making it quite clear that the performance which he obtained from what was probably a Mk '1.5' like that tested above was typical for the design, not flattering it in any way. However, we still look in vain for any sign of support for Allbon's claim that the addition of sub-piston induction raised the engine's peaking speed by 2,000 rpm!

Towards The Future: Further Developments at Allbon

Whatever may be said about the above figures, it's clear that by late 1948 the Allbon 2.8 had been developed into a very useful engine for non-competition purposes. However, Allbon didn't stop at this point. The next step in the engine's development was to reduce friction losses by adding a ball race shaft to the mix. A revised front housing was produced which accommodated a single ball-race at the rear of the shaft in its most heavily-loaded location. The resulting ball-race version of the Allbon 2.8 Mk II is extremely rare, indicating that production figures were very small. However, examples do exist to attest to Allbon's efforts to further improve the performance of his design.

At the moment, we don't have enough serial numbers to form any convincing estimate of overall production figures for the Mk II version of the Allbon 2.8. Suffice it to say that by mid 1949 Allbon's attention was being increasingly drawn to the challenge of joining the move away from the old sideport era towards far more potent rotary valve designs. The development of the ball-race version of the 2.8 was evidently Allbon's swan-song in terms of attempting to keep his original model competitive. This makes it appear likely that production figures for the Mk II model of the 2.8 were somewhat less than those for the Mk I version.

There is ample evidence to the effect that Allbon did not confine himself to the further development of the 2.8 during the period just covered. On the contrary, he initiated a number of experiments covering a relatively wide design field. In part, this may have been due to the 1949 arrival of Dennis J Allen (the future Allen-Mercury manufacturer) to join Allbon at Thames Street. Allen was a prominent member of the West Essex club and a noted pioneering control-line stunt flier with some very well-known model designs like the "Boxcar" to his credit. He knew model engines very well indeed, both as a practical user and on account of his employment with the engine repair service operated by Henry J Nicholls as an adjunct to his famous shop at 308 Holloway Road in London. Since Nicholls had been the distributor and servicing agent for the Allbon 2.8 since its introduction at the beginning of 1948, Allen already had a close familiarity with that engine.

Initially, Allen remained an employee of Henry J Nicholls Ltd, being in effect "loaned" to Alan Allbon to assist him in the ongoing production of the 2.8 and the development of potential new models. However, it turned out that the proportion of Allen's time required to meet Allbon's need for assistance soon made this arrangement impracticable. The result was that Allen became a full-time employee of Allbon Engineering later in 1949.

In this capacity, Allen was closely involved in the ongoing development and manufacture of the company's various products which appeared over the course of the following two years. There is always a synergistic effect when two talented individuals get together to work towards common goals, and there can be little doubt that both Allen and Allbon gained immensely from their collaboration in terms of their grasp of the challenges inherent in model engine design and manufacture.

Allen's arrival appears to have coincided with a period of intensive development at Allbon Engineering. Apart from the ongoing development of the 2.8, a number of other projects were being pursued in addition. For example, the Allbon 2.8 is included in the table of British diesels which forms an appendix to Ron Warring's 1949 book "Miniature Aero Motors". Most interestingly, there is also an entry for an engine called the Allbon 3.5! Bore and stroke of this engine are given as 0.625" and 0.7375" respectively for a displacement of 0.226 cuin (3.70 cc). The bore and stroke figures prove that this was not simply a bored-out 2.8, since both dimensions were increased. However, the fact that no selling price was included in the table implies that this was a prototype model which never actually saw production. Certainly, no more was ever heard of the 3.5 to my knowledge. I am not aware of the existence of any actual examples.

There's no doubt however that prototypes of other potential new models were completed during Allbon's independent period prior to joining Davies-Charlton in 1952 (see below). Examples exist of such rarities as a 10 cc spark ignition twin, several progressively more refined variants of a 5 cc glow-plug model and a 2.5 cc diesel. None of these ever saw production either—Allbon was evidently merely exploring the possibilities.

However, several designs which had their genesis during this early period undoubtedly did make it onto the market. The limited production capacity to which reference was made earlier forced Allbon to make some hard choices, evidently causing him to decide at some point later in 1949 that the old 2.8 had no future. That design looked very much to the past, while Allbon now had his eyes very much focused ahead, no doubt encouraged in this by Dennis Allen.

The consequence was Allbon's decision to give up on the 2.8. By October 1949 the engine had disappeared from Allbon's advertising, being supplanted by the then-new Allbon Arrow 1.5 cc glow-plug model (see below). The final listing of the 2.8 by its distributor Henry J Nicholls appeared in Nicholl's advertising placement in the December 1949 issue of Aeromodeller. The clear implication is that production of the engine had ceased prior to that time, leaving Nicholls with no further stock to supply his customers as 1950 rolled around. However, it seems that he had previously distributed a number of examples to other retailers, since (presumably) New Old Stock examples of the Allbon 2.8 continued to be offered by Ripmax as late as November 1951.

From this point onwards, Allbon focused his full attention upon the development and manufacture of the engine style for which he is best remembered—the radial-ported reverse-flow scavenged crankshaft front rotary-valve layout which was to dominate British model diesel design for the next three decades and more. Let's move ahead to that stage of Allbon's work.

The Allbon Arrow

Although the concept of glow-plug ignition had originated during the early years of full-sized internal combustion engine development, the miniature commercial glow-plug was a late 1947 American innovation which was largely the creation of Ray Arden. Word of this then-revolutionary form of model engine ignition had spread rapidly to England, with ED taking the first decisive step towards commercialization in that country by including a glow-plug conversion kit with their 2.49 cc Mk III front rotary diesel introduced in March 1948.

By mid 1948, increasing attention was being paid to the potential of the glow-plug motor both by modellers and manufacturers in Britain. The manufacture of miniature glow-plugs in Britain began at around this time, with the firm of Smith's Motor Accessories Ltd taking the lead by having their subsidiary KLG Sparking Plugs Ltd commence production of the famous "Miniglow" plugs in various sizes. The Yulon range of purpose-built glow-plug engines quickly achieved great renown, while Nordec created quite a stir with the glow-plug version of their 10 cc racing engine. But perhaps the greatest boost to the glow-plug cause in Britain came with the mid 1948 release of the FROG 160 glow-plug version of IMA's established FROG 180 diesel. This neat little unit proved extremely popular right out of the starting gate. Not to be left out, Davies-Charlton offered a glow-plug conversion kit for their 5 cc Wildcat diesel.

The British glow-plug movement continued to gain momentum in 1949 with the March 1949 release of the first version of the soon-to-be-famous ETA 29 racing engine. AMCO continued the trend by offering a glow conversion kit for their highly-regarded 3.5 cc plain bearing model which first appeared in May 1949, while a similar kit was offered by the K Model Engineering Co for their 5 cc Vulture. IMA re-joined the fray late in 1949 with their excellent FROG 500 glow-plug model, of which more elsewhere. The sun appeared to be rising upon the glow-plug engine in Britain, a trend which Alan Allbon evidently could not ignore.

The result was the late 1949 appearance of Allbon's second commercial design, the 1.49 cc Arrow glow-plug motor. The first advertisement for this engine that we can find appeared in the October 1949 issue of Aeromodeller. Interestingly enough, the engine was claimed to be "Britain's first entry into the small glow-plug engine field". Given the fact that their FROG 160 model had been on the market and selling well for over a year at the time, one wonders what IMA made of this statement ...It's also interesting to note in passing that while earlier Allbon advertisements relating to the 2.8 had been placed directly by Allbon Engineering, mentioning Mercury as the "sole distributor", the Arrow was announced by Mercury Models, as were a number of subsequent Allbon models.

Although the Arrow must be viewed as an Alan Allbon design given the fact that he owned the company and thus had the final say on design matters, there can be no doubt that Dennis Allen had a lot to do with the development of this and following Allbon models. The Arrow was apparently intended primarily for control-line speed model work. Hoping to encourage wider participation in this branch of the hobby, the SMAE had then recently introduced the new "low budget" Class 1 speed model category for engines of up to 1.5 cc. The Arrow was in fact the first British engine specifically produced to meet that displacement limit.

This marked the beginning of a trend towards more tightly regulated competition engine displacement limits which spelled the end of the various "odd-ball" displacements like that of the Allbon 2.8 which had previously been very common. The later adoption of the 1.5 cc displacement limit for the British 1/2-A competition category consolidated this change, making the 1.5 cc displacement category a very important one in the context of the British model engine market.

The Arrow was about as different from the old 2.8 diesel as it was possible to get! For starters, it utilized glow-plug ignition. In addition, it dispensed with side-port induction by joining the emerging design trend towards crankshaft front rotary valve (FRV) induction allied with radial cylinder porting along with reverse-flow scavenging. It was very much a short stroke design, having bore and stroke measurements of 0.526" (13.36 mm) and 0.420" (10.67 mm) respectively for a displacement of 1.49 cc (0.091 cuin). It was extremely light for its displacement, having an all-up weight (with plug) of 2.2 ounces even (63 gm). Finally, it was substantially cheaper than the 2.8 at only £2 15s 0d (£2.75).

The construction of the Arrow was about as simple as one could get and still end up with an operable engine. The construction was based entirely upon screw-in assembly, no fasteners being used at any point other than to secure the spraybar and mount the prop. As a result, the Arrow used only 18 separate components, including the glow-plug and all prop and needle valve fasteners as well as the head gasket. Of these, only 12 items had to be manufactured—the rest were off-the-shelf items obtainable in bulk from outside suppliers. Clearly, control of production costs was foremost in the minds of the design team.

The Arrow was basically a completely conventional plain bearing radial-ported FRV motor built very much in accordance with the emerging British "style" which had been pioneered in the USA by Arden and first adopted in Britain by Elfin. The only major departure from established British practise was the use of glow-plug ignition in place of the more usual compression ignition. As such, there seems to be little need to enter into a detailed description here—the images tell the story.

A few points are however worth noting. One design feature of the old 2.8 that was carried over to the Arrow was the use of an aluminium alloy yoke for the steel gudgeon pin and forged alloy con rod which was secured inside the piston with a countersunk screw through the piston crown. As noted in connection with the 2.8, the potential for problems with this screw becoming loose during operation was obvious.

The Arrow used three sawn exhaust ports with three drilled transfer ports between them. The screw-on combined cylinder head and cooling jacket was anodized a very attractive blue colour, although this tended to fade very rapidly as a result of the repeated heat cycles to which it was subjected during operation. The head seal was provided by a soft copper washer which served as a gasket. Herein lay another of the engine's Achilles heels—it was necessary to tighten the jacket quite forcefully to maintain a seal and prevent the jacket from unscrewing during running. When this was done, the wedging effect of the screw threads acting directly upon the cylinder liner tended to pinch the bore near the top of the stroke, resulting in an excessively tight spot at that point.

Otherwise, the engine's construction was completely conventional, right down to the forged alloy con-rod, screw-in backplate and plain-bearing shaft running directly in the material of the crankcase casting. Like the 2.8, the Arrows were given serial numbers, although in the case of the Arrow these were hand-engraved into the underside of the crankcase. The fact that our friend Eric Offen has engine number 952 implies that the numbering sequence started at 1 or perhaps 100. The highest number of which I am presently aware is 1292 reported by my good mate David Owen, seemingly confirming that at least that many were made. At some later date, the practise of numbering the Arrow cases was discontinued, as we shall see in a following section of this article.

The main problem with the Arrow was a marked lack of performance, at least on the straight fuel then in general use in Britain. It must be recalled that the use of glow-plug ignition was still relatively new in Britain at the time, the result being that most British manufacturers fell into the trap of creating their glow-plug models by simply converting their existing diesel models to glow-plug operation. ETA, Nordec and IMA (FROG) were the only British manufacturers at this stage to recognize that the design requirements for successful glow-plug operation were quite distinct from those for diesels. Consequently, these manufacturers wisely used successful existing American glow-plug designs as the basis for their respective glow-plug offerings from 1949 onwards. The Arrow was at heart a conventional diesel design which had been adapted to glow-plug ignition. This pretty much doomed it from the start as a performance contender.

Nevertheless, the Arrow was undoubtedly different! Its very light weight and handsome appearance coupled with the solid reputation which Allbon had established with the 2.8 led a good few modellers to give it a try, at least initially. Moreover, our old mate Lawrence Sparey was sufficiently intrigued to put it through a test. The resulting report appeared in the January 1950 issue of Aeromodeller, only four months after the engine's initial appearance.

Sparey's test report probably did as much as anything else to doom the poor old Arrow. For one thing, he encountered both of the issues noted during our earlier description of the engine. The screw which retained the gudgeon pin carrier inside the piston came loose, fortunately without doing any lasting damage. In addition, it was found impossible to keep the head sufficiently tight to maintain a seal without excessive tightening, as a result of which the bore was badly pinched at the top of the stroke during the test. Finally, the blue anodizing on the cooling jacket was found to resist the passage of electrical current, creating difficulties in getting the plug to light up for starting. The cure was of course to scrape the anodizing off the plug seating area.

As a result of these factors, Sparey stated that he was conscious of the fact that the engine "was not giving of its best" during the test. For this reason, he actually made the somewhat unfortunately-worded statement that this test had been "one of the most unsatisfying—from my point of view—of any yet undertaken". In making the latter statement, he was actually trying to be kind to the manufacturers by implying that the engine could doubtless do better, but many readers probably took this statement at face value.

There's little doubt that Sparey was quite right about the negative effect of the tight pinch at the top of the stroke. Had this tight spot not been present, there seems to be no question that he would have been able to report a more encouraging set of figures than the very lacklustre 0.051 BHP @ 11,500 rpm that was actually recorded. A healthy dose of nitromethane would doubtless have helped too, but that additive was almost unobtainable in Britain at the time as well as being prohibitively expensive even if a source could be found.

On the bright side, and doubtless wishing to find something positive to say, Sparey reported that the Arrow was "the most easy starting engine I have ever handled". Needle response was characterized as "exceptional". While these are doubtless valid points, they do appear to represent a case of Sparey trying to repair the damage by praising the engine with faint damns ...

No doubt in large part due to this doubtless fair but inescapably negative report, the Arrow failed to make much of a long-term impression upon the market. It continued to be listed in Allbon advertisements into 1951 at the same price of £2 15s 0d but faded away very quietly during that year, after which no more was heard of it. Clean original examples are relatively uncommon today.

The Allbon Arrow Re-Evaluated

Don't ever let anyone tell you that lightning never strikes twice! At around the same time as the original publication of this article, not only did the aforementioned example of the Allbon 2.8 'Mk 1.5' drop into my lap, but I also acquired an example of the Allbon Arrow—my first ever! This engine was in far from pristine condition, having clearly seen a lot of hard service. However, it remained in excellent mechanical condition. It was also completely original, including a K.L.G. Miniglow plug in working order!

The opportunity to examine this engine at first hand proved highly instructive from a number of standpoints. For one thing, the engine bears no serial number. This implies that the hand-engraving of serial numbers onto the underside of the crankcase ceased at some point, presumably for production reasons. We will see later that the similar hand-engraving of numbers on the Allbon Dart which appeared in October 1950 also ceased very early in that engine's career, so it seems to be a quite reasonable assumption that the practise was discontinued for the Arrow at the same time, probably in late 1950 when Allbon began to experience difficulty in meeting the growing demand for his products (see below).

A problem arising from this finding is that we can no longer rely upon serial numbers for an accurate estimate of production figures for the Arrow. We have evidence for the production of at least 1292 numbered examples of the engine, to which we now have to add an unknown number of engines which were not engraved. All indications continue to be that the number of Arrows produced in total was not large, but we need a far greater sample of serial numbers to establish a well-reasoned figure. This includes reports of non-engraved examples so that we can form an estimate of the relative occurrence of numbered and un-numbered engines. All contributions welcome .........

A further highly significant indication from this engine is the fact that by no means all of them suffered from the issues encountered by Sparey in his test. The cylinder head on this example is well screwed down to create a very good seal, but the engine exhibits no sign whatsoever of any pinching at top dead centre or indeed at any other point of the stroke. The engine turns over very freely, with good compression and relatively little bearing wear despite the extensive use which it has clearly received. I was able to confirm by direct volumetric measurement that the compression ratio of this example is 8.5:1—a quite reasonable figure, albeit a little less than the 10:1 figure reported by Sparey.

All of this naturally opened the door to a present day test of an example of the Arrow which is free from the issues which evidently held Sparey's example in check. No sooner imagined than done! My new acquisition went into the test stand for a few runs on some appropriate airscrews. I used an oily fuel containing 10% nitromethane—probably a fairly typical "hot" brew in 1950 Britain where nitro was both hard to get and prohibitively expensive when you could find it.

As noted by Sparey, the engine was a doddle to start. It needed a fairly hefty prime, but once that was given it gave no trouble at all—a few lazy flicks, and it was away. Needle settings were easily found, and the engine ran very smoothly, particularly at the higher speeds. The results achieved were as follows:

PropRPMBHP (approx)
8x4 APC7,2000.040
7x6 APC7,6000.045
7x4 Taipan9,3000.057
7x4 APC9,5000.059
7x4 KK N10,3000.066
6x4 KK N12,5000.064

Frankly, although it does represent an improvement over the figures obtained by Sparey, this is still a pretty dismal performance for a 1.5 cc engine, even by 1950 standards. The engine clearly produces little in the way of torque, requiring a very small prop to deliver its best output. In fact, running qualities improve noticeably as speed goes up. There's a gap in the above figures which clearly lies around the peak. It's possible to infer a probable output of around 0.072 BHP in the general vicinity of 11,500 rpm, with a sharp falling-off thereafter.

Just for fun, I tried the effect of running the engine on a few of the faster props using a fuel containing 30% nitro. Quite a difference—the Arrow now got the Taipan 7x4 up to 10,200 rpm (c. 0.075 BHP), while the APC 7x4 reached a speed of 10,500 rpm (c. 0.080 BHP). The KK nylon 7x4 did even better, getting up to 11,400 rpm (c. 0.089 BHP). I didn't bother with the KK nylon 6x4 since it clearly took the engine well past its peak and there was no point in stressing the old beastie.

This is certainly more promising, since it implies a peak output of somewhere near 0.095 BHP at around 12,000 rpm. However, these figures still fall somewhat short of those which were later to be reported for the soon-to-appear diesel version of the Arrow—the famous Javelin Mk. I to be discussed in the following section. Moreover, there could have been few modellers in Britain at this time who could even contemplate running this amount of nitro. The stuff was near impossible to get and prohibitively expensive when it could be found. All in all, while the Arrow wasn't quite as bad as Sparey's test suggested, it remains hard to see the engine as anything other than a failure in performance terms.

A recent (2013) communication with Gordon Cornell of E.D. fame reinforced this impression. Gordon recalled that he and a few of his fellow Croydon Model Aero Club members tried the Arrow but quickly gave up on it after they discovered that as far as they were concerned, it didn't have enough power to fly a control-line model satisfactorily! Reputations like that travel fast.

Comeback: The Allbon Javelin Mk I

The story so far has been one of qualified success with the Allbon 2.8 followed by what can really only be regarded as a failure with the Arrow. Unless something was done very quickly, the Arrow set-back could have had very negative consequences in terms of the ongoing position of the Allbon range in the marketplace.

Fortunately, Alan Allbon was not the man to waste time worrying about setbacks which lay in the past and hence could not be undone—rather, his approach was to take immediate action to move things forward and get the Allbon marque back on track. He seems to have recognized immediately that Sparey's criticisms of the Arrow were not unjustified. What to do? The clear answer was—come up immediately with a new product that would perform at a level which would cause the modelling public to quickly forget about the shortcomings of the Arrow!

The main challenge inherent in the above concept was the word "immediately"—only fast and effective action would re-establish Allbon's credentials. The quickest way to develop a new model and get it into production was undoubtedly to take an existing model for which tooling was already in place and rework it into the product that was required.

Fortuitously enough, a potentially-suitable existing model was ready to hand—the Arrow! It hadn't worked out as well as expected in glow-plug form—how would it perform if converted to compression ignition? The conversion would be very simple indeed—just make a new taller cylinder to accommodate a contra-piston, add a new cooling jacket with a comp screw, and there you are! All of the other components were already in the Arrow production program, thus requiring no additional tooling. A side benefit arising from this conversion would be that the head-sealing and cylinder distortion issues with the Arrow would be completely eliminated.

So this is what Allbon did, no doubt assisted by Dennis Allen. A new diesel model to be known as the Javelin (sticking with the missile motif!) was quickly brought into production. This was an interesting case of a reversal of the usual sequence—while most British glow-plug engines were glow conversions of existing diesel models, the Javelin was a diesel conversion of an existing glow-plug model. Indeed, the introductory advertisements said as much, proclaiming the Javelin to be "the Diesel version of the famous Allbon Arrow 1.49 Glow-Plug" rather than the other way round.

The first advertisement for the Javelin appeared in the form of an insert in the full-page Mercury Models placement in the February 1950 issue of Aeromodeller. Mercury Models' action in stepping in to advertise the new Allbon model directly may perhaps represent an effort to shore up the new product given the negative aura then surrounding the Arrow. If so, the need for this didn't last long—within a very short time Mercury was back to focusing very much upon their expanding kit range while the ongoing advertisements for the Allbon engines reverted to being placed directly by Allbon Engineering, with Mercury Models remaining the sole distributors.

The Javelin has been covered in an earlier article on this site. However, a few descriptive points are included here for convenience. Apart from the revisions to the cylinder and cooling jacket, the Javelin was identical to the Arrow. Continued use was made of an aluminium alloy yoke for the con rod small end which was secured inside the piston with a countersunk screw. The Javelin also retained the same bore and stroke measurements, the only change being a slight increase in weight from 2.2 ounces to 2.4 ounces (68 gm), due no doubt to the taller cylinder with its contra-piston.

Accordingly, the introduction of the Javelin required only very minor changes to the established production schedule. The two models shared everything but the cylinders and cooling jackets (with contra piston and comp screw), meaning that very few additional components had to be added to the production program. This allowed Allbon to get the Javelin onto the market very quickly indeed following Lawrence Sparey's less-than-stellar report on the Arrow.

It didn't take Sparey long to get around to testing the Javelin. Presumably he welcomed the opportunity to make amends for his rather negative (albeit fairly so) test of the ill-fated Arrow! Be that as it may, Sparey's report on the Javelin appeared in the July 1950 issue of Aeromodeller.

Sparey was careful not to mention the Arrow in his report on the Javelin! The tone of the new test was as different as it could have been from the earlier effort—the engine received the very highest marks in all respects. After commenting at some length upon the ever-improving power-to-weight ratio being achieved by the latest smaller-displacement engine designs, Sparey went on to praise the way in which the Javelin withstood the fairly arduous conditions to which it was subjected during the test, clearly implying that its structural design was well up to the task. He characterized the engine as "exceptionally flexible for one of this type" and stated that starting was "excellent under all conditions".

The engine was reported as running "well and evenly at all speeds from 5,000 to 14,000 rpm" and was said to have "performed well throughout (the) tests", with particularly steady running at the higher end of the speed range. A peak output of 0.99 BHP was found at 12,000 rpm, which Sparey clearly considered to be exceptional for an engine of this displacement. Overall, this test represented a complete vindication of Allbon's design approach following the set-back with the Arrow.

A further test of the Javelin Mk I appeared in the Summer 1950 issue of the British periodical "Model Aviation". This time, the author was Peter Chinn, whose report was every bit as favourable as Sparey's had been. Chinn found the engine to be exceptionally easy to start, the one reported problem being that there was a marked falling-off in power as the engine warmed up. This is by no means an uncommon characteristic of many model diesels, as Chinn very fairly pointed out.

Despite this issue, Chinn actually recorded a higher peak output than Sparey, albeit at significantly lower revs, measuring a peak of 0.105 BHP @ 10,000 rpm. It appears that Chinn's example out-torqued that tested by Sparey by a considerable margin. Chinn summarized his findings by stating that the Javelin was "one of the most powerful of 1.5 cc class engines currently available", commenting also upon its exceptional power-to-weight ratio. He felt that the engine should be "a popular choice for all types of small high-performance power models".

The modelling public certainly agreed with this assessment, consequently lining up to buy the engine in substantial numbers. Despite its less-than-stellar reputation, the Arrow continued to be listed alongside its new sibling for a considerable time, although it's unclear whether or not this represented ongoing manufacture or merely the selling-off of existing unsold stock.

Regardless, the name Allbon was definitely restored to its former high status in the eyes of the modelling public as a result of the Javelin's appearance. This seems to have encouraged Alan Allbon and Dennis Allen to begin looking ahead once more to the further expansion of the range.

Turning Point: The Allbon Dart

Up to the point which we have now reached, Allbon Engineering had remained a small company, still operating from rather confined premises at 51a Thames Street in Sunbury-on-Thames. It appears that the scale of their manufacturing facilities limited the company's ability to meet the growing demand for their products. This situation was about to be further exacerbated by the introduction of their next new design ...

As of mid 1950, the smallest displacement category which was generally viewed by British manufacturers as being worth pursuing was 1 cc or a little less. The Mills .75 was selling like hot cakes, but it was the smallest-displacement model engine that remained widely available in Britain at the time. It was also a rather "old-fashioned" sideport design, which limited its ultimate performance.

There had of course been previous British attempts to tap into the market for sub-miniature diesels. The Ace 0.5 cc of mid 1947 had started something of a "race to the lower limit" among British manufacturers, being quickly followed by a number of progressively smaller British commercial designs such as the Comet 0.4 cc, the Kalper .32 cc, the mega-rare Weston "A" of 0.25 cc and finally the 0.196 cc Kemp Hawk. However, none of these models lasted long on the market, being successively phased out during the late 1940's.

A major reason for the failure of these early sub-miniatures to maintain a foothold in the marketplace was the fact that their relatively modest performance limited their applicability to small sport free-flight models. Control-line was all the rage as Britain entered the 1950's, and none of the earlier miniatures were really suitable for that application. It appears to have occurred to Alan Allbon in around mid 1950 that this opened up a potential market niche which remained untapped. If a miniature engine having sufficient power to fly a small control-line model could be developed, the market prospects would almost certainly be very bright indeed!

The Javelin diesel had proved itself to be an exceptional performer by the standards of its day. Allbon evidently reasoned that a scaled-down version of the Javelin might well have a level of performance which would overcome the prevailing prejudice against really small engines, thus in effect opening up a whole new market area.

With the assistance of Dennis Allen, such a model was soon developed. In-house tests showed that it did indeed have a level of performance that vastly exceeded that of any previous miniature diesel. Accordingly, the decision was made to proceed to the production stage, the result being that the iconoclastic Allbon Dart was born. The missile-based nomenclature was continuing!

The Dart was introduced in the latter part of 1950. As far as we can determine, the first advertisement for this engine appeared in the October 1950 issue of Aeromodeller, again referring to Mercury Models as the distributors rather than Allbon Engineering as the manufacturers. The engine was an immediate and overwhelming success, fully vindicating Allbon's foresight in making the commitment to its development and manufacture.

To all intents and purposes, the Dart was a reduced-scale version of the highly successful Javelin. The engine followed the general layout of the Javelin in almost all respects. It featured square bore and stroke measurements of 0.350" (8.89 mm) apiece for an actual displacement of 0.55 cc (0.034 cuin). There have been reports that the early Darts had a displacement of only 0.50 cc, but this is incorrect—direct present-day measurements from early examples confirm the above figures. Weight was a remarkably low 1.2 ounces (34 gm) without tank, since none was fitted as supplied.

Induction and cylinder porting were effectively identical to those of the Javelin. The earliest examples of the Dart retained the internal yoke system for con-rod installation in the piston, although they were the last Allbon products to do so. These earlier examples also received serial numbers which were hand-engraved on the underside of the crankcase. However, this practise was soon stopped, doubtless due to the production pressures which demand for the engine imposed upon the company. Eric Offen has engine number 144, while my own example bears the serial number 295. I have no idea how much further the numbering sequence went. All I know is that numbered examples of the Dart are extremely rare today, implying that the quantity to which serial numbers were assigned was not large.

The cooling jackets on the original batch of Darts were mostly anodized dark green. These early examples also featured L-shaped single-arm compression screws. At some point, a small batch of heads was anodized blue, doubtless as a result of having been included in an anodizing batch for some Arrow jackets. Later still, the anodizing was changed to a paler shade of green. Concurrently with this latter change, the piston design was amended to eliminate the alloy yoke in favour of a conventional fully-floating gudgeon pin. In addition, a change was made to a Y-shaped two-armed compression screw.

On this occasion, Lawrence Sparey was clearly itching to get his hands on an example of this latest British attempt to create a successful miniature diesel. His test of the Dart appeared in the January 1951 issue of Aeromodeller, only four months after the engine's introduction.

To say that Sparey was impressed with the Dart would be if anything an understatement. He started right out by noting that the engine's power-to-weight ratio of figure of 0.575 BHP per pound represented "a big advance on anything previously found for engines of under 1 cc capacity", going on to note that this figure compared favourably with that of many far larger engines. Equally impressively, the actual measured peak power output of 0.0445 BHP @ 13,300 rpm represented a significantly higher specific output (BHP/cc) than that found earlier for the larger Javelin model.

Interestingly enough, the Low Speed Aerodynamics Research Association (LSARA) later reported even higher performance figures of 0.053 BHP @ 14,500 rpm. In his 1952 advertising for the Dart, Allbon quoted a statement from the Association to the effect that they had delayed publishing their figures pending a series of re-checks since they found this level of performance from such a small engine difficult to accept! Clearly Sparey's results were by no means unrepresentative.

Sparey characterized starting as "extremely good", although he did comment quite rightly that such small engines required a little more care in use than their larger brothers if handling damage was to be avoided. Running was described as "very steady over a wide range of speeds".

The publication of a further positive test by Peter Chinn in the April 1951 issue of Model Aircraft reinforced Sparey's findings in every respect. Overall, these test reports were about as positive as Alan Allbon could have wished for. Small wonder that modellers immediately started rushing out in droves to buy their own examples! This was to force Allbon to make some very hard decisions, as we shall see in a later section of this article.

However, before moving on to that part of our tale, we need to spend a little time briefly reviewing the influence which the success of the Dart had upon the activities of other British manufacturers.

The Dart's Influence on Other Manufacturers

Allbon's immediate and overwhelming success with the Dart was by no means lost upon other British firms. Indeed, it appears that a form of "gold-rush" mentality took over, with other manufacturers falling over themselves to get in on what they saw as the insatiable market for miniature diesels. No-one seems to have stopped to think that the sudden saturation of what had yet to be shown to be more than a "surge" market could have negative consequences upon the potential long-term return on investment.

Regardless, no fewer than three other competing manufacturers (Aerol Engineering (Elfin), International Model Aircraft (FROG) and ED) quickly followed Allbon's lead by developing 1/2 cc diesels of their own. This gave rise to the British 1/2 cc diesel "revolution" of 1951/52, which foreshadowed the similar contest of 1959-60 featuring British-made 0.8 cc (.049 cu. in.) glow-plug motors. It also resulted in the rapid saturation of the market for miniature diesels in Britain.

The attractiveness of these small engines to mainstream British modellers arose from a number of factors. They weren't significantly cheaper than many of their larger brethren since they required if anything even more care and precision in their manufacture. However, models for these little units were both easy and inexpensive to build (this was in the far-off days when most aeromodellers lived up to their hobby's name by actually building their own models!). Moreover, such models (particularly those of the control-line variety) could be flown on smaller fields. And finally, the noise levels and fuel costs associated with running these little powerplants were far lower than those of the larger engines generally used by competition fliers.

Although the new breed of 1/2 cc diesels handily outperformed their sub-miniature 1940's predecessors, to the point where the best of them could actually give a few of the contemporary American .049 glow-plug models a run for their money, they undeniably had their limitations. For one thing, they were trickier to manage and more susceptible to handling damage than their larger counterparts, which made them less suitable for beginners. For another, their power output was still on the marginal side, especially when it came to the control-line field which was then so popular in Britain. Finally, they tended to wear out more rapidly than their larger contemporaries due to the greater sensitivity of smaller diesels to piston/cylinder wear in particular—the same amount of wear has a far greater negative effect with small bores.

For the above reasons, the immediate surge in demand for miniature diesels in Britain was soon satisfied. Consequently, the 1/2 cc fad in Britain didn't last all that long, even though several of the protagonists remained in production for quite a few years. The Dart proved to be the only long-term survivor, outliving all of its rivals by several decades in its later versions as manufactured by Davies-Charlton Ltd. How that situation came about forms the subject of the following section.

Production Problems at Allbon and their Solution

As 1951 rolled around, the immediate and overwhelming popularity of the Dart presented Alan Allbon with a significant challenge, albeit one with which some of his competitors would doubtless have liked to have been faced! On the one hand, people were beating a path to Allbon's door wishing to buy his little masterpiece—he was having no trouble selling all that he could make. On the other hand, he was also facing a steady ongoing demand for the Javelin Mk I. The competing demands for the Dart and Javelin pushed Allbon's production capacity to the limit and beyond. This forced Allbon to progressively limit production of models other than the Dart, the Arrow in fact being dropped altogether.

Even with these changes to the production schedule, the demand for the Dart evidently outstripped Allbon's ability to produce it at his existing facility. As a result, by mid 1951 Allbon found himself faced with a significant challenge—he had an extremely successful product but was unable to produce it at a rate which matched the demand.

There were three potential approaches to the resolution of this issue. First, Allbon could make a further personal investment in expanded production facilities, retaining full ownership and control of the enterprise. Second, he could seek an outside investor who would put up the required additional funding at the cost of the surrender of Allbon's autonomy in terms of controlling the future of the business—he alone would no longer call the shots. Moreover, he would still have a sizeable amount of his own capital tied up in the production facilities.

However, there was a third option which would resolve the personal investment issue very neatly—Allbon could enter into some form of working arrangement with an established manufacturer who might be willing to take on the task of producing the Dart at levels which would match demand—something which Allbon was clearly unable to do at Thames Street. This latter approach would at least allow Allbon to retain control over the evolution of the Allbon range.

For better or worse, Allbon was unwilling to increase his personal investment in his model engine business, however successful it was in the process of becoming. In part, this may well have been because by this time he appears to have developed a desire to move out of London and perhaps resume a former residence in a more rural location. Such a move would of course require the diversion of his personal resources into the purchase and upkeep of a suitable property, leaving nothing to apply towards an increased level of investment in the company.

The notion of bringing in an outside investor who would then exercise a measure of control over the business seemingly did not appeal to Allbon either. Apart from the loss of control, it would also force Allbon to maintain a significant personal investment in the business. These considerations appear to have resulted in Allbon following the third course of action by entering into discussions with the well-established firm of Davies-Charlton of Barnoldswick in Lancashire regarding the possible mutual benefits of some level of cooperation.

Hefin Davies of Davies-Charlton was doubtless open to such discussions, since his time was increasingly being diverted away from the model engines which were his first love towards the very lucrative high-tech sub-contract work for Rolls-Royce and others which formed the mainstay of Davies-Charlton's business at the time. The ability to tap into the expertise of an experienced model engine designer and manufacturer like Allbon would solve this problem at one fell swoop. Moreover, at the time in question Davies-Charlton's model engine manufacturing activities were confined to their established 350 models in both diesel and glow-plug configuration, thus not placing them in competition with the Allbon range while also leaving substantial excess manufacturing capacity to be applied to other designs which Davies lacked the time to develop.

The immediate consequence of these discussions was Allbon's late 1951 closure of his Sunbury-on-Thames facility. This closure resulted in a period of non-availability of the entire Allbon range, as reflected in an advertisement placed by RipMax in the December 1951 issue of Aeromodeller. As matters turned out, the Dart would quickly re-appear, while the rest of the range would remain dormant for most of 1952.

By January 1952 Allbon was advertising the Dart from a far more bucolic address at The Forge, Cople, Bedfordshire. The village of Cople was (and remains as of 2012) a small rural community lying out in the countryside a few miles to the east of Bedford. Assuming that we are speaking of the Alan Leslie Allbon who appears in the previously-mentioned genealogical records, this would in fact represent a return to the area in which he had grown up and married—an entirely logical supposition.

Initially there was no mention of any involvement on the part of Davies-Charlton (who continued to advertise separately), creating an impression that the Allbon engines were still being independently manufactured by Allbon Engineering, albeit now at the Cople location. However, in his "Accent on Power" column in the April 1952 issue of Model Aircraft, Peter Chinn let slip the fact that the manufacture of the Dart had actually been taken over by Davies-Charlton.

It was undoubtedly this move that had permitted the closure of the Sunbury-on-Thames plant and prompted Allbon's relocation to Cople, an odd location for a model engine manufacturer if ever there was one! It appears that Allbon had simply moved his combined residence and business office to Cople, leaving Davies-Charlton with the job of actually making the engines.

During this period, Allbon continued to advertise the Dart independently from his Cople address under the Allbon Engineering banner, while Davies-Charlton in turn continued to advertise their own distinct range from their Barnoldswick location. As noted earlier, the Dart was the only advertised Allbon model during most of 1952, implying that the manufacture of the Mk I Javelin had joined the Arrow in being suspended due to the pressure on Allbon's new production arrangements to meet demand for the Dart. New Old Stock examples of both the Javelin Mk I and the Arrow which had been manufactured by Allbon Engineering remained available from specific retailers during this period, but there's little or no doubt that the sole model manufactured by Davies-Charlton during most of 1952 was the Dart, the demand for which was continuing unabated.

The fact that the two companies continued to advertise independently clearly implies that at this stage no actual merger had taken place. In all probability, Allbon had taken advantage of Davies-Charlton's well-known willingness to undertake contract work for others by simply contracting out the manufacture of the Dart to Davies-Charlton. Hence the relationship at this stage was purely contractual.

This arrangement must have worked out well for both parties, since the next step towards a full merger was the combination of the distribution arrangements for the Allbon and D-C ranges. This was a logical move given the fact that the Dart was in reality being manufactured by Davies-Charlton despite Allbon's ongoing reluctance to openly admit this fact! By mid 1952, Allbon's advertisements were confirming that the distribution (as opposed to the manufacturing) of the Dart had been taken over by Davies-Charlton, although Allbon still continued to advertise separately from his Cople location and still stopped short of crediting Davies-Charlton with the manufacture of the Dart.

Allbon was still advertising the Dart independently from his address at Cople in October of 1952, but the distribution of both the Allbon and D-C ranges had then been taken over by E. Keil & Co. This arrangement was to continue for some time following the completion of the merger.

The amalgamation of the two companies was apparently completed prior to December 1952, when advertisements for the Mk II versions of the Dart and Javelin began to appear together with the open identification of Davies-Charlton Ltd as the manufacturers. No more was heard of the Cople location, although it's very likely that Allbon maintained his combined residence and design office there. Christina Crosby, who worked at Davies-Charlton at this time, has confirmed that while she was aware of Alan Allbon's existence, he was an infrequent visitor to Barnoldswick who never put in an appearance at Davies-Charlton's head office where she worked alongside Hefin Davies. This supports the notion that Allbon continued his design work from his own residential office at Cople, only making the fairly long trip to the Davies-Charlton plant when there were design and production issues requiring direct discussion. As far as Christina is aware, Allbon confined his personal interactions to meetings with Hefin Davies' "silent" partner Mr. Charlton (first name unknown), a quiet and studious individual who apparently maintained his own design office in Barnoldswick at a separate location from the main office and manufacturing facility.

Regardless of how it worked, there were clear benefits for both parties. The merger allowed Hefin Davies to put most of his energies into leading the doubtless-lucrative contract work for Rolls-Royce and others which was a mainstay of Davies-Charlton's business plan at this time, while Allbon assumed primary responsibility for the subsidiary model engine development and manufacturing programs, evidently working in conjunction with Charlton rather than with Davies. The arrangement also solved Allbon's own production problems, allowing the expansion of the Allbon range at production levels which could be tailored to meet demand. Finally, it allowed him to liquidate his investment in the facilities at Thames Street, thus freeing up capital to finance his move to Cople.

The end result was that manufacture of the Allbon engines by that name was now openly consolidated at Davies-Charlton's Barnoldswick plant in Lancashire along with that of the continuing Davies-Charlton models. This marked the beginning of a seven-year hiatus in Alan Allbon's career as an independent model engine manufacturer.

An interesting sidebar matter is the fact that Allbon appears never to have got around to formally dissolving his old company! A notice published in the London Gazette for November 22nd, 1974 served three month's official notice that Allbon Engineering Co (Sunbury) Ltd was about to be struck off the British Company Register unless reasonable cause was shown why this step should not be taken. This notice was published pursuant to Section 353 of the Companies Act (1948) which permitted removal if the Registrar of Companies had unchallenged reason to believe that the company in question was no longer in business. Clearly, Allbon did not bother to present any arguments to counter this decision, which accordingly took effect on March 14th, 1975 through the publication of a further notice in the London Gazette of that date.

Returning to 1952 and resuming our main thread, the merger just described had one unfortunate side effect—it left Dennis Allen out of a job as of late 1951. However, Allen landed firmly on his feet! After spending some time working in general precision engineering, he returned to the model engine field by accepting a late 1952 invitation to assist the newly-established Aeronautical Electronic & Engineering Co in resuming production of the AMCO models to which they had acquired the rights from the original manufacturers, the Anchor Motors Co of Chester.

Allen spent over a year working on the revived AMCO range, which benefited considerably from his involvement, as we have shown elsewhere. However, in his spare time he continued to pursue his own model engine design concepts, notably a 2.5 cc diesel which he believed to have great commercial potential. According to an article on Allen-Mercury which appeared in the June 1958 issue of Model Aircraft, he offered this design to his new employers, who were not interested. This rejection had far-reaching consequences for all concerned, since Allen's unswerving belief in his new design led him to seek other avenues for getting it into production.

Allen had all along maintained his close ties with Henry J Nicholls and Mercury Models going back to the late 1940's. In mid 1954 this association resulted in Allen's departure from Aeronautical Electronic & Engineering Co to commence the independent manufacture of the first diesel to be marketed under his own name, the Mk I Allen-Mercury (A-M) 25. This was of course the very design which had been rejected by Aeronautical Electronic & Engineering Co. It's interesting to contemplate how differently matters might have unfolded if it had been released as the AMCO 2.5! As it was, Allen's departure from Aeronautical Electronic & Engineering Co dealt that company a blow from which it never recovered, finally departing the scene in early 1955 and taking the AMCO range with it into history.

The A-M 25 was manufactured by Allen's own company, DJ Allen Engineering of Edmonton in North London. Allen was joined in this venture by his old West Essex club-mate and competition rival Len "Stoo" Steward, formerly of the K Model Engineering Co Ltd of Gravesend in Kent. The range was marketed by Mercury Models, hence the name. The rest, as they say, is history be recounted elsewhere when time permits!

The Later Years: A Brief Summary

In other articles on this site, we have traced the histories of the Davies-Charlton and Allbon-Saunders enterprises with which Alan Allbon was destined to be involved for the remainder of his career as a model engine designer. Readers requiring more detail on these later phases of Allbon's career are referred to those articles.

For the sake of completeness and convenience, we will briefly summarize the main events here. Allbon worked with Davies-Charlton for most of the balance of the 1950's, during which time the new engines introduced by D-C Ltd were generally presented as Allbon models. These included the Mk II versions of the Javelin and Dart as well as the 1 cc Spitfire Mk I, the 0.15 cc Bambi, the 0.76 cc Merlin and the Spitfire Mk II and Sabre "twins" of 1 cc and 1.5 cc displacement respectively.

By all accounts, Hefin Davies was not an easy man to work with, the result being that a gulf progressively developed between Davies and Alan Allbon as the ‘50's wore on. Although the 1957 2.5 cc Rapier was initially presented under the Allbon banner, that name was progressively dropped thereafter, seemingly disappearing entirely in 1958 after lingering for a while on the company's diesel fuel labels. Matters evidently came to a head in early 1959, at which time Allbon finally severed his connection with Davies-Charlton. His departure was very much Davies-Charlton's loss, since it is from this time onwards that we can trace the onset of the progressive erosion in quality which was to bedevil the D-C range in later years.

Following his departure from Davies-Charlton Ltd, Allbon made it immediately clear that he was by no means done with the model engine business. It's possible, albeit completely unproven at this point in time, that he felt that he had something to prove to Hefin Davies and that he saw the best way of going about this as being the introduction of his own successful design with which to compete with D-C Ltd for sales.

Accordingly, Allbon joined forces with a Mr Saunders to form the Allbon-Saunders company of Milton in Berkshire, which produced the excellent little 0.55 cc A-S 55 diesel. This fine little unit made its initial appearance in November 1959 to widespread critical acclaim. As detailed elsewhere, the A-S 55 was an outstanding product which did great credit to Allbon's reputation as a designer but which failed to make much of an impression in the marketplace. This was due not to any shortcomings in the engine itself but rather to Allbon's insistence upon the maintenance of construction standards which precluded its being priced competitively. Rather than continuing to compete in a marketplace which had become dominated by low prices rather than high quality and performance standards, Allbon and Saunders chose to divert their efforts towards participation in the optical industry, a venture which proved to be eminently successful.

This ended Alan Allbon's involvement with model engines once and for all. It would be difficult to overstate the loss to the modelling world which his departure represented.


We hope that you've enjoyed this retrospective look back at the early career of an individual who richly deserves to be remembered as one of Britain's most successful and influential model engine designers of the mid 20th century. It's been both a pleasure and a privilege to record this tribute to Alan Allbon's immense contribution to our favourite hobby during the pioneering era!

As always, we don't claim to know it all, nor can we guarantee that we've got it all right. Accordingly, if anyone out there is able to correct us at any point or add to our knowledge as presented here, please get in touch! Any published contributions will be gratefully and openly acknowledged!