The Kemp and "K" Hawk

by Adrian Duncan

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Hover over images for captions.
See also K Hawk mini-review.

Here's a little gem from the early years of the post-war British model engine manufacturing industry—the Kemp (later K) Hawk. This cute little powerplant was one of the first and most successful true sub-miniature model diesels to be produced commercially in Britain. Although it's a much sought-after collector's item today, it appears to be rather sketchily documented. Let's have a go at setting this right...

    In The Beginning
    Production Commences
    The Hawk Arrives on the Scene
    Change of Ownership
    The Kemp (later K) Hawk—Description of Variants
    The Hawk Mk I Series I
    The Hawk Mk I Series II
    The Hawk Mk I Series III
    An Anomaly From a Familiar Source
    The Hawk Mk I On Test
    The FRV Hawk models
    Serial Numbers and Production Figures
    The End of the Line


The basic principle of the model diesel (or more correctly, compression ignition engine) originated well before WW2. However, it took some time for the potential of the concept to be realized, and it was not until the WW2 years that it finally took shape in the form of a practical model powerplant. This development was initially confined to Switzerland and a few other European and Scandinavian countries—other matters engaged the attention of much of Europe and indeed the world at the time!

Following the conclusion of the war, information regarding this new form of model power unit quickly spread to England. Initial development was carried out predominantly by the model engineering fraternity—the Motor Boys of their day—but it was not long before a number of commercial interests began to take notice of their efforts. An article by pioneer British diesel experimenter and later engine tester, Lawrence L Sparey, entitled "The Gen on Diesel Engines" appeared in the December 1945 issue of Aeromodeller. This article was highly influential in this regard and beginning in the latter part of 1946, an ever-increasing number of British manufacturers began to enter the marketplace with model diesels of their own.

Progress was rapid and within a year or two, the best British diesels were well up to par with the majority of their Continental rivals. This chain of events initiated the love affair between the modellers of Britian and her Colonies and the diesel engine which was to survive for the following three decades or more. For some of us, the affair has never ended!

One of the great advantages of the model diesel over its spark-ignition counterpart was the potential for its construction down to extremely small displacements. The absence of the complex and heavy ignition components as well as any form of plug were the keys to making this possible. The consequent potential for sub-miniaturization was quickly recognized, and experiments were soon underway to probe the lower limits of practicable construction.

The French took the early lead with the neat little Allouchery Éclair 0.16 cc sideport diesel of 1946, although this was produced in extremely small numbers and was likely more of a "manufacturer's statement" than anything else. But perhaps the ultimate early post-war expression of the potential lower limit of model diesel displacement came from a talented 36 year old Swedish home constructor by the name of Harry Fjellström. His beautifully-made sub-miniature version of the Swiss Dyno appeared as the cover feature in the December 1946 issue of the Swedish technical magazine "Popular Teknik". It was claimed at the time (probably quite justifiably) as the smallest operating diesel engine in the world.

Amazingly enough, Harry Fjellström's little masterpiece still exists and forms part of the Harry Fjellström collection at the Stockholm Technical Museum in Sweden. The original bore and stroke of this incredible creation were 3.16 mm and 5.2 mm respectively for a displacement of 0.041 cc! Following a good deal of demonstration running at exhibitions, the engine was rebored to 3.3 mm, which increased the displacement to 0.044 cc, where it remains today. The unit weighs a mere 9.5 gm and reportedly turned a matching hand-made aluminium airscrew at over 5,000 rpm. Quite an achievement!

Harry Fjellström attended both the 1947 and 1948 Model Engineer Exhibitions in London, where he demonstrated a slightly larger version of this engine (which also still exists at the Museum) having a bore of 4 mm and a stroke of 6.5 mm for a displacement of 0.082 cc. This certainly caught the attention of the redoubtable Mr. Sparey! In his October 1949 Aeromodeller test report on the Mk I ED Bee, Sparey included the statement that "a diesel of only 0.08 cc has been successfully run", a comment which must surely relate to this engine. It's possible that Harry Kemp may also have seen this engine in operation.

In passing, one wonders what Sparey's reaction would have been to the astonishing near-microscopic diesels made today in the USA by Ronald Valentine! Ronald's current record for the smallest operating model diesel is held by his amazing little Nano Bee model, a precision masterpiece which checks out at an almost unbelievable 0.006 cc (no, we didn't skip a decimal point—that really is 0.00037 cuin!) and it really does run!

All well and good in terms of showing what could be done in a purely technical sense, but the series manufacture of model diesels of this near-microscopic displacement could never have been seen as a mainstream commercial proposition—quite apart from the limited practical application of such a "novelty", the amount of detailed individual work and consequent production costs required to achieve the necessary precision would doom such a project commercially. Series manufacturers therefore quite understandably set their sights a little higher in terms of displacement.

The first British commercial move towards the true sub-miniature diesel came in mid 1947 with the introduction of the London-made Ace 0.5 cc model. This triggered something of a "race to the lower limit" among British manufacturers, and the Ace was quickly followed by a number of progressively smaller British designs such as the Comet 0.4 cc, the Kalper .32 cc, the Weston "A" of 0.25 cc and finally the 0.2 cc Kemp Hawk Mk I diesel—remember that? It is afer all, the main subject of this discussion!

The makers of the Kemp (later "K") engines were among the most successful and prolific manufacturers of sub-miniature diesels in the early post-war period. Their various Hawk models were reportedly in great demand for several years, consequently being produced in relatively substantial numbers. This has had the happy result of ensuring that a fair number of them still exist today and they remain probably the best-known of the early British sub-miniatures. In this article we'll attempt to sort out the various forms in which this fine little motor appeared.

However, it's important to remember that no particular series of engines from a given manufacturer evolves in isolation—there's always the question of context, and the story of a particular model can only be fully appreciated if the context in which it was designed and manufactured is understood. Those who do not feel the need for any discussion of this aspect of the matter are invited at this point to proceed directly to the description of Hawk variants which constitutes a later section of this article. For those desiring the complete picture, we'll start by having a look at the background to the inception and manufacture of the Hawk series.

But before we do so, a few acknowledgements are very much in order.


An amazing number of people helped in various ways to make this study a reality, and I freely admit that I could not have completed it without their contributions. Although I accept full responsibility for the following text, I wish to go on record as stating that this study is as much their effort as it is mine, as is the credit for any merit which it may possess.

First and foremost, much of the following discussion about company founder Harold Kemp and the manufacturing operations which he initiated was developed from information supplied by Harold Kemp's daughter Jean Hards-Nicholls (nee Kemp). Mrs Hards-Nicholls gathered a great deal of information about her father's activities both from other family members and through an open request for information from outside the family. The response to this request was extremely gratifying, not least because it put her in touch with Harold Kemp's early associate Les Duffy, who was an invaluable source of eyewitness information.

All of us are deeply indebted to Mrs Hards-Nicholls for her initiative and effort in gathering as much information as possible about her late father's activities while it was still there to be gathered and then so generously sharing it with the rest of us. I freely acknowledge that much of the following material could not have been presented without her invaluable contribution, which may be read in full elsewhere on this web site.

Secondly, I must thank Eric Offen for his unstinting help in providing photos, measurements and serial numbers to support the findings presented below. Eric's contribution has done much to add authority to what follows.

My valued Swedish friend Lars Gustafsson also deserves great credit for shedding light upon pioneering model diesel developments in Sweden, including the activities of Harry Fjellström. It's solely due to Lars's efforts that the above information on Harry Fjellström's tiny diesels became available. We hope to present the full story of Fjellström's remarkable achievements in due course.

I wish to extend very sincere thanks to my friend and colleague Paul Rossiter of Rochester, Kent, England, who shared his wealth of knowledge about Kemp engines and was kind enough to make a trip to Gravesend to photograph the various locations associated with the Kemp story as they appear today. This really helps to relate the past to the present, always a valuable perspective from my point of view.

I'm also most grateful to David Owen for digging deep among his images to find some more serial numbers. And finally, not forgetting our long-suffering Editor Ron Chernich was kind enough to undertake yet another trawl through the early issues of the various modelling magazines to find advertisements for the Kemp and K engines, as well as formatting my text for the web, resizing all the images, and generating the thumb-nail pictures. Thanks, mates!

OK, on with our tale...

In The Beginning

The company which introduced the Hawk series was founded in 1946 by Harold Kemp. During the preceding war years, Kemp had worked in the full-size aircraft industry for Short Brothers in Rochester, Kent, but like so many others he faced some difficult choices at the conclusion of the war as a result of the termination of government defence contracts and the company's consequent moves towards downsizing and reorganization.

Even assuming that the option of remaining with Short Brothers was open to Kemp, it would have required him to relocate to Belfast in 1947 along with the company. If he did not wish to relocate or if he was in any event made redundant, a second option would have been to seek employment with another English firm. This of course would have placed him in competition with large numbers of similarly redundant and perhaps equally qualified individuals.

As matters transpired, Kemp took neither of these steps—instead, he elected to move to nearby Gravesend and start his own specialty engineering business. His chosen field was the manufacture of model aero engines, and the original name of the company which he founded was Kemp Engines. A prior interest in model aircraft or at least an interest in model engineering are implied here, but unfortunately we know nothing definite about any previous involvement which Harold Kemp may have had with either field.

The one straw in the wind is the long-standing oral association of Kemp's name with the K6 spark ignition engine which was marketed by Eddie Keil for several years following the conclusion of WW2. Although I have been unable to confirm this connection, the name is suggestive given the fact that Harold Kemp's first definitely attributed design was the similarly-identified K4 diesel of 1946. There was undoubtedly a connection between Eddie Keil and Harold Kemp, since Keil was one of the distributors of the Kemp engines. It thus remains entirely possible that the K6 was in fact Kemp's first model engine design, albeit marketed by others. If anyone knows more, let's hear from you.

However it came about, it's readily apparent that Kemp must have had some rational basis for believing that a viable business could be based upon the manufacture of model engines and must in addition have begun with some well-formed ideas with respect to model engine design. A measure of practical experience with model engines either as a user or a designer (or both) would certainly best explain these factors.

Regardless, once he had decided to engage in the model trade as an engine manufacturer, Kemp did so with energy and enthusiasm coupled with a considerable measure of obvious talent. At the conclusion of the war, significant quantities of machine tooling which had been used in wartime production became available for sale at competitive prices as being surplus to peacetime requirements, and we may safely assume that Kemp (like many others) took full advantage of this in assembling the necessary production equipment. Much of this machinery was doubtless well-used and rather "tired", but the price was right and a combination of realistic tolerances and skilled operation could do much to overcome any deficiencies.

Premises were established at 7 Bank Street, Gravesend, Kent, and Kemp took up residence at 3 Bank Street almost right next door. Fortuitously, another engineering firm had premises opposite the Kemp workshop and Kemp would sometimes exchange materials and other bits and pieces with his neighbors.

In staking his future upon this entrepreneurial participation in the post-war model industry, Kemp was far from being alone. To take one other well-known example, the soon-to-be famous ED company was also founded in 1946 by a group of redundant former employees of the Parnall Aircraft Company. Both ED and Kemp Engines thus had a very similar genesis. However, the Kemp operation was established on a far smaller and more personal scale than that of ED. Harold Kemp was very much a "hands-on" businessman, being personally involved in all aspects of the company's operations. Apart from handling the sales and other business matters, he did all of the engineering design and also worked in the machine shop alongside the other employees.

In addition to Kemp himself, the operation initially employed only three other men—two full-time and one part-time. A far cry from ED, who started with a full-time workforce of some 50 individuals! The part-timer at Kemp Engines was Les Duffy, a colleague of Kemp's who was still working full-time during the day as an apprentice at the downsized but still operational Short Brothers plant in nearby Rochester.

Les supplemented his income and helped his mate Harry by working at Bank Street in the evenings for a couple of hours, turning, milling and honing engine parts before returning to his home in Tilbury, Essex on the opposite bank of the River Thames. This was made possible by the existence of a ferry which ran—and in fact still runs in 2010—across the River Thames from the Gravesend Town Pier (a very short walking distance from 7 Bank Street) direct to Tilbury. A long-distance commuter by the standards of the day!

Speaking many years later to Harold Kemp's daughter Jean, Les retained a very clear recollection of the workshop at 7 Bank Street. His evocative eyewitness description constitutes an invaluable insight into the way that small-scale "cottage industry" engine manufacturing operations like this typically worked.

It appears that the premises had originally been a residence and had been converted to a workshop at some time prior to Kemp taking up occupancy. This kind of adapted accommodation was probably entirely typical of such small-scale engineering operations—large purpose-built factories like those of International Model Aircraft (IMA) and ED were undoubtedly the exceptions rather than the rule.

Les recalled that as one approached the premises one would usually find a motorcycle leaning against the outside wall. As one entered the building, there were large doors on the left which opened into the main workshop and a large window looking into another room on the right. The main workshop on the left had a large capstan lathe and an extremely oily work bench, also used for counter sales which were usually handled personally by Harold Kemp. The downstairs front room on the right with the large window accommodated additional lathes and other machinery. These two downstairs rooms were probably the living room and the dining room of the original residence!

One of the upstairs rooms (likely a former bedroom) was used for assembling the engines, after which each and every one was test-run on the premises. Try that today—Harold must have been popular with the neighbors! Those engines that passed their test were packed into plain brown cardboard boxes ready for dispatch, while the failures were set aside to have their faults rectified. Seemingly, Kemp had a first-rate hands-on quality control program—others might have done well to copy.

Some of the engine castings were formed in magnesium alloy and were produced at a nearby foundry in Gravesend. They were delivered loose in hessian sacks and had to be individually checked for defects before machining and assembly. The castings were emptied out onto the workbench, examined and sorted. It was quite normal for a proportion of them to have to be returned to the foundry for reprocessing.

Les recalled that the men had great fun burning the magnesium shavings from the machining operations on the plot of waste ground next door, as they burned with a very bright blue flame! No recycling in those days...indeed, fire was one of the hazards of using magnesium castings, and a number of fires at the ED plant in the late 1950's reportedly had much to do with ED abandoning the use of magnesium castings at that time.

Production Commences

The establishment of production facilities and completion of design and tooling seems to have taken up the later part of 1946 with the first commercial product of the new company appeared in early 1947. This was a 4.4 cc sideport diesel engine called the K4 which sold for 7 guineas (£7 7s 0d) upon its introduction—a lot of money in those early post-war days. The castings for the Series I version of this engine were initially produced in plain aluminium alloy, but a switch was soon made to plain magnesium alloy. The change in materials was presumably an attempt to reduce the not-inconsiderable weight of this rather massive unit.

As many of us know to our cost, magnesium alloy has an incorrigible tendency to want to return to its elemental state in the form of corrosion! Kemp evidently received a number of complaints about this problem, and his response was to introduce the Series II version of the engine, which was still based upon magnesium alloy castings but was anodized black like the Mills engines when they switched to magnesium castings. The anodizing did much to reduce the tendency of the castings to corrode. This version of the engine earned a very good reputation for being well made and reliable and was a steady seller, albeit in the relatively small quantities dictated by the production limitations of the very small workshop in which it was made.

Kemp soon carried this design one step further by producing an 8.8 cc twin cylinder in-line diesel colloquially known as the "Black Devil" which was effectively two of the 4.4 cc engines joined together. This was labour-intensive to produce and consequently had to be sold at a very high price in order to generate a profit. As a result, there were few takers and very few of these were manufactured. The rare survivors are highly prized collector's items today.

The fledgling company embarked upon a more significant product expansion phase later in 1947 with the introduction of a small FRV 1 cc diesel engine, which sold for the still considerable sum of £5 0s 0d. The tank, cooling jacket, and spinner of this engine were cast in magnesium alloy, although the rest of the castings were formed in aluminium alloy. Once again, production figures were limited by the very small workforce available at the time, and this is a very rare model today. An image of one appears on page 109 of Mike Clanford's well-known "A-Z Pictorial" book on model engines.

The Hawk Arrives on the Scene

The expansion of the range continued in early 1948 with the initial appearance of the smallest engine that Kemp was destined to design and manufacture—the Hawk. This event followed the adoption of the well-known "K in a circle" trade-mark, since this mark appeared on the Hawk instruction leaflet, albeit not initially on the engines themselves.

The precise date of this model's market entry remains somewhat unclear. Model shop advertisements in the December 1947 issue of Aeromodeller make no mention of the Kemp 0.2 cc model, which they surely would have done if such a novel design had been made available in time for the Christmas rush for that year. However, the engine is mentioned in Henry J Nicholl's advertisement which appeared in the February 1948 issue of Aeromodeller. We must acknowledge that Ron's Library has no issues from the period of Model Aircraft, the rival publication to Aeromodeller which was also the "official organ" for the Society of Model and Aeronautical Engineers (SMAE), so it is possible our research has missed important evidence. As usual, we welcome new material and will happily revise any incorrect information! That said, as far as we are presently aware, this is the initial appearance of the engine in any advertisement, and it appears to date the engine's introduction to around January 1948. It seems likely that the intent had been to get the engine onto the market in time for Christmas 1947 but that production problems had prevented this from happening.

The introductory version of the sideport Hawk Mk I had a displacement of just under 0.20 cc, making it the smallest British diesel produced commercially up to that time. This little gem was usually sold complete with a 5 inch diameter laminated wooden airscrew. The introductory retail price was £4 8s 0d, reflecting the amount of individual work required for each example produced.

Despite the relatively steep price, the novelty appeal of such a tiny engine ensured its immediate acceptance and a steady demand quickly developed. Production figures (see later discussion) certainly reflect its sales success. The design evolved fairly rapidly through a number of variations, as we shall see in due course.

At the time of the Hawk's introduction, the previously-mentioned FRV 1 cc model was still being advertised. However the company was clearly looking towards the popular market by this time, and the £5 selling price of this model was anything but consistent with a desire to tap into that market. Accordingly, the company's next move was to introduce a completely revised version of their 1 cc model, which they named the Eagle, thereby furthering their "bird of prey" naming policy which had begun with the Hawk. The Eagle was a sideport unit which shared a number of key features with the Hawk. It sold for a somewhat more competitive price of £3 18s 6d and was apparently well received. However, its production life was very short, as we shall see.

By this time the little three-and-a-half man operation must have been taxed to the limit to keep up with the demand for the various models now on offer! The constraints upon their production capacity are surely obvious, but their consequently limited output did at least have the beneficial effect of ensuring that they were easily able to sell all the engines that they could produce. There was little danger of supply exceeding demand.

Many of the engines were marketed through a main selling agent—Gamages, of 116-128 Holborn, London. They were dispatched to Gamages by carrier from the workshop, two dozen at a time. Eddie Keil was also a Kemp distributor, and the previously-mentioned firm of Henry J Nicholls, 308 Holloway Road, London was a major retail outlet as well. Later still, a Scots distributor was added to the roster in the form of the Caledonia Model Co of Glasgow.

The engines could also be bought directly from the makers either by mail order or in person over the counter from the workshop at 7 Bank Street. It would have been well worth taking advantage of the latter option since one would then be served in person by Harold Kemp himself!

Change of Ownership

The immediate success of the Hawk seems to have had the concurrent effects of turning the Kemp Engines business into an attractive investment proposition while at the same time creating a production capacity problem for the company. It appears that Harold Kemp was quick to appreciate both issues, and in mid 1948 he was successful in attracting additional investment through the transfer of the Kemp Engines business and premises to a new company, the "K" Model Engineering Co This name was presumably taken from the previously-mentioned trade-mark already being applied to the Kemp engines.

Harold Kemp's daughter Jean Hards-Nicholls has stated that this transaction took place in late 1948. However, the preponderance of evidence is inconsistent with this timing. The first K Model Engineering Co advertisement of which we are presently aware appeared in the August 1948 issue of Aeromodeller. In addition, manufacturing capacity had to be expanded in advance of the appearance of new models from the reorganized company, and such models began to appear in October of 1948. All of this seems to cast considerable doubt upon the late 1948 dating of the change in the company's structure. It actually appears that the sale must have taken place in around July 1948.

Mrs Hards-Nicholls informs us that the workshops at 7 Bank Street, Gravesend were part of the deal and remained in operation following the change of ownership. This may certainly have been true, but there is no doubt at all that the business address of the "K" Model Engineering Co was given from the outset as Darnley Street, Gravesend, rather than Bank Street. Darnley Street lies a little further from the river towards the town centre of Gravesend, but the two locations are within easy walking distance. Accordingly, maintaining the Bank Street workshop in conjunction with the new Darnley Street facilities would have been readily possible.

It actually seems quite likely that production of the well-established and still popular Hawk model, and perhaps the Eagle Mk I design as well, continued uninterrupted at Bank Street in order to maintain a cash flow while the new company consolidated its expanded production facilities at Darnley Street and developed the updated product line that was soon to appear. Certainly, a subsequent advertisement placed by the new company in the 1948 edition of "Model Aviation" focused entirely on the Hawk model while hinting loudly at several new designs which were then in preparation. The date of this advertisement is somewhat uncertain, but it must post-date July 1948 (when the transfer of ownership seems to have occurred) and clearly pre-dated November 1948 given the fact the that the first of the touted new models, the Vulture, actually made its appearance in October 1948.

As stated above, the move to bring in additional investment likely stemmed primarily from the need to increase production capacity due to the success of the Hawk coupled with a desire to update and expand the range. However, the timing suggests the possibility that the sale may also have been motivated at least in part by the impending September 1948 Government decision to bring model aircraft parts and accessories, including "power units of all kinds" under Group 20 ("amusements") of the Purchase Tax Schedules. The immediate result of this decision would be the imposition of a whopping 331/3% increase in over-the-counter domestic prices. Prior to September 1948, kits and accessories of a constructional nature, while classified under "toys and games", were exempt from this tax, and engines had been included in the "accessories" category.

Although a strong challenge was anticipated (and was in fact immediately launched by the model trade), Harold Kemp may have had the foresight to realize that this challenge could fail and that the long-term prospects for his small engineering concern would be adversely affected by such an outcome. The step that he took at a time when these changes in the Purchase Tax schedules were imminent may have been prompted at least in part by a desire to reduce his personal financial exposure to the effects of an adverse outcome. We'll probably never know for sure.

One of the principals in the new company was Len "Stoo" Steward, a jovial-looking character who was very well known in British aeromodelling circles. We may know nothing about Harold Kemp's involvement with modelling prior to his becoming an engine manufacturer, but there's no doubt at all regarding "Stoo" Steward's participation in the hobby! He was a very prominent aeromodeller who was a regular fixture at post-war contests, predominantly in control-line stunt events. He thus brought the invaluable perspective of a practical contemporary power modeller to the newly-reorganized company.

One of Steward's first moves was to discontinue most of the Kemp range as it then existed. The old 4.4 cc Kemp design was dropped immediately and the companion sideport 1 cc Eagle model soon followed. As an active competitor himself, Steward must have realized that as of mid 1948 both engines were too bulky and slow-revving to compete with the significantly updated models which were by then appearing from other manufacturers. Model engine designers were learning fast!

The two discontinued models had in any case been in only sporadic production since the Hawk arrived on the scene, and Steward already had plans to replace both designs. The old 4.4 cc model was supplanted by the far more powerful but highly cantankerous FRV 5 cc K Vulture and the sideport 1 cc Eagle was also replaced by a completely revised Mk II FRV model bearing the same name. Both of these revised models were released before the end of 1948. Other FRV models soon followed, including the 1.96 cc Falcon which appeared in April of 1949.

While all this was going on, Steward maintained production of the still popular sideport Hawk model, merely renaming it the K Hawk and promoting it as the "flagship" model of the new company pending the introduction of the significantly expanded range which was then being planned. The price initially remained unchanged at £4 7s 6d, but was soon lowered to £3 15s 0d.

However, the old Hawk too was starting to fall behind the times in technological terms, and in May 1949 the original sideport version was supplanted by the even smaller K Hawk Mk II of 0.193 cc. This was a completely new FRV design as opposed to being merely a further update of the original Hawk Mk I, as we shall see below. It does not appear to have remained long in production if surviving numbers are any indication. It was joined fairly quickly by a Mk II "Special" version of the same basic design. This latter model seems to have made its initial appearance in an advertisement which appeared in the June 1949 issue of Aeromodeller. It sold for a reduced price of £3 7s 6d.

The question of whether or not Harold Kemp retained some level of involvement with the "K" Model Engineering Co Ltd remains unresolved. According to Harold's daughter Jean, certain members of the Kemp family have recalled information passed down to them from Harold's brothers to the effect that Harold only sold a part-interest in the business and remained a partner in, or at least an employee of, the new company. This would be completely consistent with the notion that the primary intent of the sale was to attract additional investment to allow for the creation of expanded production capacity rather than to dispose outright of what appears to have been a growing business at the time in question.

The idea of an ongoing involvement is also consistent with the indisputable fact that Harold Kemp continued to live at 3 Bank Street for some years following the reorganization of the business. He married in Gravesend in 1949 and remained at 3 Bank Street until at least late 1951, well after the cessation of production by the "K" Model Engineering Co This is apparently confirmed by the address on the birth certificate of one of his daughters. Since this urban location was then very much dominated by industrial activity, it's hard to see why Kemp would continue to live there with his new family unless he had some compelling reason for doing so. An ongoing involvement with the "K" Model Engineering Co would certainly constitute such a reason.

Kemp's daughter Jean also recalls her father invariably referring to the model aero engines that he had once made as "K" engines. Circumstantial evidence for sure, since he may have simply been referring to the "K" trade-mark which was certainly introduced during his sole proprietorship. However, this expression on Kemp's part is undeniably consistent with the notion that he remained somehow involved with the business after the entry of Steward into the operation. He continued to live only a few doors away, and it would have been very hard indeed to "abandon the baby" by steering clear. In his place, I would certainly have been unable to do so!

On the other hand, when interviewed in 2009 Les Duffy expressed the belief (on unspecified evidence) that Harold sold the business in its entirety. Admittedly, Les no longer worked there by that time—he had moved on to Rolls Royce in 1947 after Shorts relocated to Belfast and was living elsewhere. However, he must surely have had some basis for expressing the belief that he did. There seems to be no surviving documentation to confirm either story—the above-quoted information is all that we're ever likely to have. Make up your own mind.

Harold Kemp finally left Gravesend at some point in 1952 (well after the "K" Model Engineering Co had ceased operations) to start a new job as a development engineer for Gyproc (later renamed British Gypsum) back in nearby Rochester, Kent. He designed machinery for them to produce plasterboard products and worked there until he retired in 1969.

Len Steward continued in the model engine field for some time after the late 1950 demise of the "K" Model Engineering Co, spending some years working with Dennis Allen on the Allen-Mercury (AM) range during its initial expansion period beginning in 1954. This association had its genesis on the flying field, since both men were prominent members of the West Essex club and were very active in control-line stunt contests during the early post-war period, often competing against one another and placing well in the events which they entered.

In addition, Allen had been working in the engine repair department at Henry J Nicholl's shop at Holloway Road during Steward's tenure at the "K" Model Engineering Co, and the fact that HJN was one of the main retail outlets for the "K" range doubtless cemented the relationship. Even after his association with Allen-Mercury ended, Steward retained his connection with model engines, operating an engine reboring and repair service during the 1960’s in competition with the likes of Gig Eifflaender of PAW fame. I don’t know how long this continued, but Steward was certainly still advertising his services in Aeromodeller as of July 1969.

Harold Kemp died in 1975 and Len Steward followed him in 1992. Sadly, they both took a great deal of unrecorded information with them, leaving many unanswered questions regarding the pioneering model engine manufacturing venture which they so ably and energetically directed.

Having set the scene as best we can, it's now time to turn our full attention to our main subject—the series of miniature diesels marketed over a two-year period as the Kemp (later K) Hawk. The initial Mk I sideport Hawk and the later FRV versions were the smallest engines ever made by the Kemp company or its successor, and were in fact the smallest British model engines of them all for a number of years until the 0.15 cc Davies Charlton Bambi came along in 1954. So this series occupies an honoured place in British model engine history! Let's take a close-up look at these intriguing little engines.

The Kemp (later K) Hawk—Description of Variants

The original Mk I version of this neat little powerplant was apparently launched upon the market in January 1948 or thereabouts and remained in production for some 15 months, undergoing a number of modifications as time went by. It was named the Hawk almost from the outset, and appears to have been the first Kemp model to receive one of the well-known "Bird Of Prey" names with which the Kemp and K engines are associated. As noted earlier, the sideport version of the 1 cc Eagle appeared after the Hawk and was thus the second model to be so named.

The Mk I Hawk was a typical long-stroke sideport diesel of its day, being set apart from its contemporaries chiefly in terms of its size. In his 1949 book "Miniature Aero Motors", Ron Warring quoted the bore and stroke very precisely as 0.2187 in (5.554 mm) and .3125 in. (7.938 mm) for an actual displacement of 0.192 cc. Precise measurements taken directly from one of my own restored examples of the original Series I version of this engine yielded a bore of 0.223 in (5.66 mm) and a stroke of 0.311 in (7.90 mm), which are near enough allowing for normal manufacturing tolerances and considering the possibility that the engine may have been rebored at some point.

These figures made the Hawk the smallest British model engine to enter commercial production up to that time. The weight of 30 gm (1.06 oz.) complete with tank also set a new lightweight record for British production engines.

Naturally, this very low all-up weight opened up a number of new fields for the intrepid power modeller. The Hawk weighed little more than a typical rubber motor, and hence the possibility existed of using it to power designs originally intended for rubber power, with the advantage of the consistent and controllable power output delivered by a diesel engine. Coupled with its low power and very modest noise levels, this also made it adaptable to small ultra-lightweight models suitable for indoor flying. The manufacturers were to quote both of these possibilities in their future advertising.

There were in fact three quite distinct versions of the Mk I Hawk. The edges between these variants have become somewhat blurred today by the fact that many examples have clearly had original components replaced with equivalents from later models, either acquired "back then" by original owners as spare parts or taken more recently from "bones" examples by collectors. So it's important for us to attempt to sort out the defining characteristics of each variant in its original form.

Although the manufacturers did not differentiate between the successive variants by assigning different names to them, it seems convenient for reference purposes to follow the lead established by Mike Clanford in his useful but often unreliable "A-Z Pictorial" on model engines by referring to the different variants as the Series I, Series II and Series III versions of the Hawk Mk I. We shall adopt this approach from here on in.

The three variants of this engine were fundamentally very similar. The stroke remained unchanged throughout, as did the sideport induction system and most of the working components. All variants used drilled exhaust and induction ports which were arranged in pairs and were of relatively modest area. The round shape of the exhaust ports resulted in progressive opening of the exhaust, giving rise to the fact that these little engines are notably quiet in operation. A welcome feature for flying in urban environments, as often practised in those far-off and more tolerant days!

But there were differences, and some of them were quite significant. Let's see if we can sort them out...

The Hawk Mk I Series I

The earliest version of the Hawk is quite distinct from its successors in four key respects—the cylinder design, the bore, the method of carburettor attachment and the treatment of the main bearing housing. Let's examine these features in turn.

Looking first at the cylinder, this component differed from those of the later variants in terms of the bypass arrangements employed. This type is easily spotted—there's no sign of any external bypass passage at the front as there is with later versions. Instead, the Series I cylinder features a bypass which consists of a single flute milled internally into the cylinder wall at the front. The cutter was slightly angled so that the passage began some distance up the bore from its open end and became progressively deeper and wider as it progressed up the bore to the actual transfer discharge location—a very tricky piece of machining at this tiny size, requiring an ultra-precise set-up! The slightest error would have resulted in a break-through at the top.

Naturally, the cylinder wall had to be relatively thick to accommodate the internal bypass passage. The Hawk Mk I Series I had a cylinder outside diameter of 0.312 in (measured directly from two examples), which combines with the 0.219 in. bore to give a wall thickness of 0.046 in.—quite generous considering the tiny size of the engine.

The bypass passage was supplied with mixture from the crankcase through a hole in the front piston wall above the pressed-in gudgeon pin, which was set very low in the rather lengthy piston. This hole communicated with the lower end of the bypass passage at and near bottom dead centre. Incoming mixture thus flowed through the piston interior past the small end of the steel con-rod to reach the bypass passage.

The transfer port itself was set well below the exhaust, but the piston crown was chamfered at the front to give a deflector effect and also to advance the opening of the transfer port. Consequently, the opening of the transfer port lagged behind that of the exhaust ports by only a few degrees of crank angle.

The cylinder was externally threaded at the top to accommodate the screw-on alloy cooling jacket and was provided with an integrally-formed flange of square planform located at its base. It was attached to the crankcase using four tiny screws which passed through holes in the corners of this flange to engage with tapped holes in the crankcase. Caution—do not tighten these screws unduly! The threads are prone to stripping and it's not necessary in any case. A gasket was used to ensure a good seal—always critical in any engine of this tiny size. The screw-in rear cover was also provided with a gasket.

A further distinctive feature of this variant was the means of attachment of the carburettor/tank assembly. On the Series I version of the Mk I Hawk, the carburettor mounting boss (which was soldered onto the cylinder) was internally threaded. The delivery end of the cast alloy venturi tube was externally threaded to match, and tank alignment was maintained through the use of a simple brass locknut which bore upon the end of the mounting boss.

The outside diameter of the intake tube on this variant was parallel for its entire length, there being no bell-mouth at the intake. The fuel tank was of metal, and was mounted by screwing onto the full-depth brass fuel delivery pipe. This pipe in turn screwed at its upper end into the main venturi casting and incorporated the very fine fuel jet which protruded into the venturi throat. A rather inconvenient feature was the fact that only a single tiny hole was provided as a vent for the fuel tank. The tank could only be filled through this hole by the use of a needle syringe, and if this was not available the only recourse was the removal of the tank for filling.

An externally threaded needle (10 BA) screwed into a boss on the opposite side from the tank to engage with the fuel jet. Needle tension was provide by a tiny coil spring. A very effective cut-out was included which operated by blocking the intake on the delivery side of the fuel jet. This system was to be applied to all three variants. Even Lawrence Sparey, who had endless problems getting cut-outs to work, should have had no trouble with this one!

Turning now to the main bearing, this was unbushed and was cast integrally with the main crankcase, the material being aluminium alloy. The bearing on this initial variant was completely unbraced and frankly looked a bit sketchy. Furthermore, the engine bore no marks of identification other than a serial number which was usually stamped on the left side of the crankcase (looking forward in the direction of flight).

The final distinctive feature of this variant related to the beam mounting lugs. These were considerably thicker than those which were to appear on the subsequent model. This variant had two mounting holes, one in each lug. The illustrated example is fitted with a modified case from a Series III engine, which explains both the high serial number and the fact that it has four mounting holes! In addition, the exhaust holes on each side have been joined to enlarge their area. It is otherwise in original Series I configuration and is fully representative of that variant.

There appears to have been one change made to this original variant during its production life, which is not in my opinion sufficient to warrant classification as a separate variant since the balance of the engine was unchanged. Experience seems to have quickly showed that the unbraced main bearing was overly susceptible to crash damage. Accordingly, a revised casting was produced which incorporated three small bracing webs for the main bearing. This revised casting also carried the "K in a circle" trade-mark which had now been adopted by the company. This appeared cast in low relief onto the front of the main crankcase.

However, for reasons which are somewhat obscure, the gain in strength which had been achieved with the three bracing webs was significantly offset by the fact that the mounting lugs on the revised cases were considerably thinner than they had been formerly. Go figure! The revised mounting lugs still had only one hole each.

It's worth noting that the illustration in the instruction leaflet supplied with the later examples of the Hawk clearly shows an example featuring the internal-port cylinder and straight screw-in venturi in combination with a three-web crankcase. This confirms the above statement that at least some of the Series I Hawks featured this case—perhaps most of them did. The serial number is not visible in this right-side view, apparently indicating that it continued to be placed on the left side of the case, at least in the initial stages. Later on, it was relocated to the right-hand side of the case.

The Hawk Mk I Series II

The second version of the Mk I Hawk seems to have made its initial appearance by April of 1948, only four months or so after production of the Hawk had commenced. It displayed a number of substantial departures from its predecessor, to the extent that it was in reality a different model, although this was apparently never acknowledged by the manufacturers. Most significantly, the bore was increased and the cylinder design was substantially altered, as was the means of attaching the carburettor assembly.

The increase in the bore of the Hawk is a matter which appears to have escaped previous commentary. Reading between the lines, we may reasonably surmise that experience had shown that the power delivered by the original 0.2 cc Hawk was a bit on the marginal side for practical purposes. It seems likely that customer feedback had indicated the desirability of raising the output somehow, and increasing the displacement was the most obvious means of accomplishing this if it could be managed within the established design parameters for the engine.

For cost control reasons, there were clear advantages in retaining as many of the existing components as possible. The simplest approach would be to bore out the existing cylinder, leaving everything else unchanged. In this context, Harold Kemp evidently took note of the fairly thick cylinder (relatively speaking) which had been forced upon him by the use of the internal bypass passage used in the first model of the Hawk. He took the decision to increase the bore by a matter of around 0.028 in to a diameter of 0.247 in. This still left an adequate cylinder wall thickness (for this tiny engine) of some 0.032 in.

Eric Offen has very kindly taken measurements from his example of the Mk I Series II Hawk, and obtained bore and stroke dimensions of 0.252 in. and 0.312 in. respectively. This is close enough for confirmation purposes, considering the fact that the engine may well have been rebored at some stage of its life.

So far so good, but there was no longer sufficient wall thickness to accommodate the internal bypass formerly used. To get around this, the transfer port was now cut right through the cylinder wall at the front. This port was supplied through a soldered-on external bypass passage similar to that used by ED in their contemporary 2 cc models. Apart from allowing the use of the increased bore, this was clearly a far simpler production job. The piston port used in the Series I variant was no longer necessary and was therefore omitted.

The stroke remained unchanged at 0.312 in. (as indeed it did throughout for the Mk I), but the increased bore resulted in a revised displacement of 0.246 cc—a 20% increase. Interestingly enough, the manufacturers never appear to have acknowledged this, continuing to promote the engine throughout as the "0.2 cc Hawk" and continuing to the last to feature an illustration of the original Series I model in their advertising!

The carburettor mounting system was also changed to resemble that then in use on the companion sideport Eagle 1 cc model. The mounting boss was now unthreaded and was split from the rear. The unthreaded delivery end of the intake venturi simply plugged into this boss and was secured by a split collar which was tightened against the split intake boss with a tiny screw. However, the tank continued to be of metal and the cut-out was retained unaltered as well. Some examples of this model feature a bell-mouth at the intake end of the intake venturi, but this does not appear to be universal.

The change in the carburettor mounting arrangements was in all likelihood a response to the fact that the externally-threaded venturi tube used on the Mk I Series I model was highly susceptible to breakage arising from a crash or some other form of rough handling. My own example of the Series I venturi was broken as received. The new system was undoubtedly stronger because the venturi tube was not weakened by the presence of screw threads.

The modified three-web crankcase which had been applied to the later versions of the Series I variant was retained in this new version. The engines continued to bear the "K in a circle" trade-mark cast in relief onto the front of the case on a small raised circular area. The use of a serial number was also continued, but this now appeared for the most part on the right-hand side of the crankcase.

The Hawk Mk I Series III

Present indications are that the third and final model of the Mk I Hawk appeared in around September of 1948, shortly after the change in ownership recorded earlier. It differed far less from its predecessor than had been the case with the first design change. However, the differences are more than sufficient to warrant the recognition of this version as a distinct variant.

The cylinder was unchanged from that of the Series II model, indicating that the revised design had been found satisfactory. The same bore and stroke measurements were also retained, as confirmed by measurements taken by Eric Offen from his Series III example. The method of mounting the carburettor assembly was also unchanged.

However, the tank assembly was completely revised. The intake end of the induction tube was now standardized with a bell-mouth configuration, and a plastic tank was featured in place of the former metal unit. This tank was secured by a wire spring clip. Like the carburettor mounting set-up, this too mirrored the system used on the companion sideport version of the 1 cc Eagle. The revised tank mount also featured a filler hole of a far more practical size. Customer feedback is implied here.

It must be admitted that these were good moves, since one could now fill the tank without removing it and could also observe the fuel level to time the motor run for sport free-flight applications. Likely for this reason, examples of earlier Series engines are not infrequently encountered with the Series III plastic tank fitted. Such instances are almost certainly the result of a switch made either by an original owner for convenience in operation or by a later collector wishing to complete an engine.

The only other changes related once again to the crankcase casting. The new variant had four stiffening webs for the main bearing, indicating perhaps that experience had shown that there was still a residual weakness with the three webs previously employed. The same comment may have applied to the mounting lugs as well, since these were somewhat thicker on this variant than they had been on the previous model. Each lug now featured two mounting holes rather than the single hole on each side which had been used on the earlier models.

Since the space previously occupied by the letter K on the front of the crankcase was now taken up by the uppermost of the four bracing webs, the letter K now appeared cast in relief inside a circle on the right hand side of the case where the serial number had previously appeared. The serial number was relocated back to its original location on the left side of the crankcase.

In all other respects, this variant was unchanged from its predecessor.

An Anomaly From a Familiar Source

Examples of all three of these variants are illustrated on page 110 of Mike Clanford's "A-Z Pictorial" mentioned earlier. And therein lies a potential source of confusion! Clanford's illustrated example of the Mk I Series I (no bracing webs) features the second type of cylinder with the external bypass! Does this mean that the revised cylinder was applied by the factory to some of the Series I engines?? The serial number of Clanford's Series I example is not visible, so we receive no help there.

The most logical way to resolve the apparent inconsistency here is to accept the probability that the cylinder on Clanford's Mk I Series I was a later replacement for an original cylinder which had become lost or damaged. It's perhaps even more likely that it was a collector-assembled hybrid.

The evidence of the Kemp leaflet appears to confirm that the internal-flute cylinder definitely belongs to the original version, and further confirms that this cylinder was associated with some of the early examples of the engines featuring the first revision of the crankcase with three webs. Conversely, there is no independent evidence for the manufacturer's use of the later cylinder with the original unbraced case, nor is there any logic to support such a possibility.

The Hawk Mk I On Test

A summary retrospective test of one of the Mk I Series III models may be found in the August 1954 edition of Aeromodeller magazine, where it appeared in conjunction with the test of the Allbon Bambi in that issue. The reported output was .0073 BHP, which slightly exceeded that recorded for the admittedly smaller and lighter Bambi (.0065 BHP). However, the Hawk evidently peaked at around 9,000 rpm as opposed to the Bambi's peaking speed of 12,500 rpm. Clearly, as we might expect, the Hawk developed considerably more useable torque than the Bambi and would therefore swing a more efficient airscrew for practical purposes. The test report commented that the Hawk was unhappy at being pushed beyond the peak, a not uncommon characteristic of sideport engines.

A test by Charlie Bruce of a Mk I Series II Hawk which he had owned from new appeared in issue no. 59 of "SAM Speaks", the newsletter of the Society of Antique Modellers, for January/February 2003. This was mainly concerned with the engine's dismantling and reassembly, but a few test figures were included. Using a standard diesel fuel, Bruce obtained 6,900 rpm on a Tornado 5 ½ x 3 nylon prop, and 8,300 rpm with the 5 inch diameter laminated airscrew supplied with the engine. It seems that the laminated wooden prop was well matched to the engine's power curve.

My own experience shows that a leak-free example of the Mk I Hawk is a perfectly straightforward engine to handle once the correct needle setting has been found. However, finding that setting may take some time, and patience is strongly advised! You can't be too forceful with these tiny engines—their working components won't stand it. No electric starters, please! Apart from that, the main thing to be avoided is flooding—if the case becomes flooded, it's a bit of a pain to clear. I often use straight ether-based automotive starting fluid for priming—it's pretty hard to flood the engine using this method.

Once running, the engine is quite responsive to the controls, although the needle tends to be a bit "touchy" as regards the optimum setting. The flywheel effect of the 5 ½ x 3 Tornado nylon prop used by Bruce is helpful for initial starts, but once you have the settings established a 5x3 wood prop seems to be a good choice, allowing the engine to get close to its peak on the bench.

The FRV Hawk models

The Mk I Series III version of the sideport Hawk seems to have survived in production for some time following the take-over by the "K" Model Engineering Co However, the engine had disappeared from the company's advertising by April of 1949 and in May 1949 we find the company announcing a completely revised Mk II model of the Hawk which used radial mounting in conjunction with front rotary valve (FRV) induction.

The new model was a completely re-designed engine from the ground up, owing nothing whatsoever to its predecessor. It featured downdraft FRV induction and a radially-ported screw-in cylinder using three internal-flute bypass passages to go with the three exhaust slots. It was designed expressly for radial mounting, then very much in fashion. Overall, it was a very up-to-date design by the standards of its day and had a performance to match.

The serial numbering sequence was re-started with this model. The letter H was initially appended in front of the numerical digits, after which the engines were simply numbered sequentially as they came off the line. Later, it appears that the H was dropped. Regardless, the numbers encountered do not approach those for the earlier Mk I Hawk, so it appears certain that the revised model was produced in far smaller quantities. This is hardly surprising when we consider the fact that the Mk II Hawk seems to have been in production for only a few months.

The saga of the Hawk's displacement changes was continued with the new model. As noted earlier, the original Hawk Mk I Series I design had featured bore and stroke measurements of 5.55 mm and 7.94 mm for an actual displacement of 0.192 cc. The Series II and Series III Mk I Hawks with their external bypass passages featured bore and stroke measurements of 6.27 mm and 7.94 mm for a displacement of 0.246 cc. We noted previously that the motivation for this increase in the bore was likely the need to extract more power from the design.

However, the revised radial-ported FRV Mk II model could logically be expected to perform far more efficiently than its sideport predecessor. For this reason, the extra displacement was no longer considered necessary. The Hawk Mk II featured both a marginally increased bore and a substantially reduced stroke, which combined to give a smaller swept volume. The two examples of the Hawk Mk II that I have owned both yielded very slightly over-square bore and stroke measurements of 6.35 mm x 6.10 mm for a displacement of 0.193 cc, more or less right back to where the Hawk series started out! At 31 gm (1.13 oz.) with tank and fuel tubing, weight was little changed from that of the Mk I version.

The FRV Hawk was included in a 1951 listing of British model diesels for the period 1948-1951 prepared by Ron Warring for "Model Aircraft" magazine and subsequently re-printed on page 25 of Vic Smeed's 1988 compilation entitled " Favourites of the Fifties". Warring confirmed the above bore and stroke measurements as well as the weight, but inexplicably (and incorrectly) stated that the engine was arranged for beam mounting.

Both of my examples arrived with tiny thimble-style needle controls having no extension, and I would have said that they'd been very neatly trimmed except that the manufacturer's advertising image of the Mk II Special (see below) shows a similar thimble, as does the illustration on page 110 in Clanford's "A-Z" book and the attached illustration of the Mk I and Mk II models side by side. A bit awkward to handle...but seemingly that's how they were supplied after all. Admittedly, a conventional long wire needle control would have been highly vulnerable!

The Hawk Mk II starts and runs really well—much better in both respects than the Bambi and appreciably better in fact than the Mk I sideport version. Mind you, I agree with those who say that the Bambi is not hard to start—it just has to be approached right and is perhaps a little less forgiving of errors than most larger engines. But the Hawk Mk II is like a much larger engine in terms of handling—it really gives no trouble at all and responds perfectly to conventional diesel starting techniques. Easier than most ½ cc diesels of my experience, in fact! And it runs very strongly for its size—handily beats out a Bambi on the same prop, that's for sure! It's also far sturdier than the Bambi. Of course, it's also both heavier and bulkier, so there's a price to be paid for the ease of handling, sturdier construction and greater power.

Mounting is a bit of a pain if you want to use the back tank. The engine is arranged for radial mounting only, and you have to cut a suitable opening in the bulkhead to accommodate the tank. Still, as a power unit for a small free-flight model, the little rotary valve Kemp would have been a very good choice. I flew one myself in such a model years ago, and it did very well indeed. I also made a small ultra-light control-line model for it, which flew just fine in calm air on 15 foot thread lines and would actually manage a loop!

In the latter respect, I was in fact preceded by the well-known British pioneer stunt flyer John W. Coasby, who worked as a draftsman for Aeromodeller magazine in the late 1940's and pioneered the large stunt model in Britain with designs such as "Icarus" and "Yoicks" (the latter using a 10 cc Nordec 60!). Just to make a point regarding opposite ends of the spectrum, Coasby built a neat little 12 inch wingspan stunter for a K Hawk Mk II, which he used to display (and demonstrate) at model meets alongside the 67 inch span "Icarus"!

The Hawk Mk II appears to have been fairly quickly supplemented by a further variant known as the Hawk Mk II "Special", which first appeared in a June 1949 advertisement placed by the "K" Model Engineering Co This retained the FRV induction of the original Mk II and apparently used the same cylinder design. However, it employed a revised crankcase casting which featured an Arden-style tankless radial mount and updraft intake located beneath the main bearing to feed the crankshaft rotary valve. Overall, it displayed strong influences from the contemporary 1.96 cc K Falcon and other K designs as well as the radial-mount Elfins.

I've been unable to locate an actual example of this mega-rare engine, and there is in fact some question as to whether or not it was ever actually produced in commercial quantities. Under these circumstances, the image from the June 1949 advertisement will have to suffice for the present. I assume that the Mk II Special retained the bore and stroke measurements of the original MK. II, but cannot confirm this in the absence of an actual example to check.

The FRV versions of the Hawk don't seem to have stayed around long enough to make much of an impression on the consciousness of the modelling world. Many people today appear unaware that they ever existed, although the sideport Mk I model seems to be quite well-known. Even Aeromodeller magazine blinked on this one—the list of British engines in the early 1958 first edition of their compilation "Model Aero Engine Encyclopaedia" made no mention of the FRV Hawks, although the Mk I sideport version which had then been out of production for nine years was still included! One can only wonder why? The Hawk Mk II's were great little engines which richly deserved to be better remembered!

Serial Numbers and Production Figures

How many examples of the various Hawk models were made? Well, we can make a reasonable attempt to develop a working estimate by considering the serial numbers which are encountered for the various designs. This exercise is greatly helped by the fact that the numbering sequence for the Mk I Hawks appears to have been uninterrupted by the various design changes which were periodically introduced.

Serial numbers for the original Mk I Series I variant are in short supply since that appears to be the least common survivor among the sideport Hawk models. It seems likely that the vulnerable carburettor mounting and unbraced main bearing played a role here! The latter factor certainly explains why the later examples of the Series I Hawk featured the revised case with three bracing webs for the main bearing. We may also expect to find examples of the Mk I Hawk fitted with later cases as replacements for broken originals.

One of the Mk I Series I serial numbers that we do have seems at first sight to give rise to another anomaly, since my own previously-illustrated Mk I Series I example bears the number 1106, considerably higher than numbers found on the Series II variant! However, I think this is easily explained. The poor little engine appears to have suffered some major abuse at the hands of a previous owner or owners. For one thing, the twinned exhaust port openings on each side have been joined by grinding—why, one can only wonder! In addition, the venturi tube had broken at the mounting thread, and this had to be restored, as did the needle valve mounting.

It appears that some previous owner had managed to break the original crankcase (among other things!) and had come up with a case from a Series III model from somewhere, likely a "bones" motor. The lugs are the giveaway—they are of the thick variety with four mounting holes, a combination found only on the Series III engines.

A very careful examination reveals unmistakeable evidence that both the four webs and the "K in a circle" trade-mark have been filed off this engine to restore the case to the appearance of an original Mk I Series I engine. The work has been very carefully and competently done and the result is a nice-looking representative example of the original Mk I Series I Hawk, but the serial number clearly belongs in the Series III sequence.

I also have three-webbed case number 514 which is fitted with a Series I cylinder with internal bypass. We have seen that some of the later Series I engines undoubtedly featured the three-web case, and this seems to be such an engine. It thus appears that at least 514 examples of the Hawk were produced in 0.2 cc form with the internal bypass cylinder. This engine also has a modified Series III plastic tank, fitted either by an owner who understandably wanted to be able to see the fuel level or by a later collector simply wanting to complete the engine. All that was required was to thread the delivery end of the venturi tube—an easy task. The tank itself is a somewhat inaccurate but highly serviceable repro.

By the time we get to serial number 581, owned by Brian Cox, we find that the Series II variant with the revised "big bore" cylinder with external bypass has appeared. This implies that the switch in bore sizes and bypass designs must have been made at some point between numbers 514 and 581 - exactly where remains unclear, but the limits are close enough for our purposes. The clear indication is that perhaps 550 examples of the Hawk were made in 0.2 cc form before the change was made to the larger-bored cylinder of the Series II variant.

I own Series II engine number 701, while Eric Offen has number 830 in his possession. Clanford had number 991 of the same series, Les Stone’s Series II variant bears the serial number 1013 and the one tested by Charlie Bruce in issue no. 59 of SAM Speaks is number 1033, which is the highest serial number of my acquaintance for that variant.

When it comes to the Series III model, we seem to be on somewhat firmer ground. Engine number 1094 of this type sold on eBay in 2011. Since we have confirmation of the existence of Series II engine number 1033, we have quite a narrow range for the introduction of the Series III model - somewhere between numbers 1033 and 1094. Given the fact that we know that the Series II numbering sequence started at some point between 514 and 581, the implication is that perhaps some 530 or so examples of the Series II variant were made.

David Owen has reported the existence of Series III engine number 1401 and Eric Offen has consecutive engine number 1402 to back this up. On page 35 of his Collector's Guide to Model Aero Engines, OFW Fisher stated that his example of the Series III variant bore the serial number 1601. David Owen has a shot of Series III engine number 1709, and the highest reported number to date is 1901, of which David also has an image.

Summarizing the above evidence, we appear to have confirmation that over 500 examples of the Series I Hawk were made, with the later examples featuring the revised case with three webs on the main bearing. We also have evidence for the manufacture of 500 or more examples of the Series II variant and a minimum of 800 examples of the Series III model. Certainly, the combined total number of sideport Hawks was in excess of 1900.

The production of at least 1900 engines over an approximately 15 month period (January 1948—March 1949) represents a minimum average output of around 125 engines per month over the production life of the Mk I Hawk. Not all that impressive by industry standards—ED are known to have produced well over 2000 examples of a single model in certain months! However, much of this production took place at 7 Bank Street prior to the take-over by the "K" Model Engineering Co, and this is remarkably good going for a small "cottage industry" manufacturing operation.

In fact, when we consider the situation objectively, it's actually very much to the original Kemp company's credit that a full-time staff of only three-and-a-half men could manage production figures of this magnitude while also meeting the demand for the other models in the range (the Eagle and K4 sideport models) as well as handling the business affairs of the firm! No wonder that production figures for those other models were reportedly quite low—after December 1947 they were too busy making Hawks!

Turning now to the FRV Hawk models, it's clear from their relative rarity today that these were produced in far smaller numbers than the better-known sideport Mk I models. The serial number sequence was definitely restarted for this model, but a letter H was added (at least for the earlier examples) to distinguish this sequence from its predecessors. The numbers with the H prefix seem to have been applied on the left side of the case.

I've been able to uncover only six confirmed serial numbers for the Mk II Hawk, two of which have passed through my own hands. These numbers range from H 202 through H 276 (which I still own) to 476, the latter without the letter H attached. This latter number appears on the right side of the case, and it seems that they dropped the H after a time, also switching sides. This seems to be confirmed by a rather fuzzy image of one of these engines which bears a three-digit serial number over which there is considerable doubt due to the image's lack of clarity. I think it's 353, but I could be wrong. Regardless, this one also shows no sign of the letter H, and it too appears on the right side of the engine. I’m also aware of similarly-identified engine number 388. Clearly the company dropped the H prefix at some point in the H 3xx numbering sequence.

So at present it looks as if perhaps 500 or so of these engines may have been produced over a period of only four or five months. This may seem rather paltry, but it's more or less comparable to the rate at which the sideport Hawks were produced. We also have to remember that the attention of modellers in Britain was becoming increasingly focused on control-line at this time, and the Hawk really had little practical application to that field, John Coasby's efforts notwithstanding! So demand may have been considerably less than it had been for the earlier Mk I model.

When it comes to the Hawk Mk II Special, we enter the twilight zone since I am presently unaware of any surviving example(s) of this model. Further information will have to await the uncovering of some hard evidence in the form of a surviving engine or two.

The End of the Line

We mentioned previously that the "K" Model Engineering Co Ltd had been very active in developing new models over the course of the 18 months or so following its take-over of the Kemp operation in mid 1948. During that period, the reorganized company developed an ever-widening range of updated FRV diesel designs including the 2 cc K Falcon, the 5 cc K Vulture (in several variants), the 2 cc K Kestrel (an "economy" version of the Falcon), the 1 cc K Eagle Mk II and the 0.2 cc K Hawk Mk II and Mk II Special, as well as the 2 cc K Tornado FRV glow model (a direct derivative of the Falcon) which was apparently the company's final offering to actually see production. Quite an active programme.

It's clear that production volumes remained relatively small by comparison with those of, say, ED and IMA with their Frog range. However, this was not all bad news. While limitations on their production capacity would in turn have limited the company's financial growth potential, it would have had the benefit of easing the marketing challenges involved since there would be far fewer engines for which to find buyers. The prevailing challenge in fact would far more likely have been keeping up with demand.

Despite this, the company was quite active in promoting its products, continuing to advertise in the British modelling media throughout this period. The K engines also received favorable coverage in widely-read books such as the second edition of Col. Bowden's "Diesel Model Engines". Furthermore, such tests as were published for a few of the K models were generally positive. Consequently the range continued to be well publicized, and to all appearances the company's marketing potential should have matched or exceed their production capacity.

However, it's clear from the record that the momentum with which the "K" Model Engineering Co seemingly headed into the 1950's was quickly dissipated, and indications are that the company ceased development of new designs soon after the turn of the decade—their last new model which is definitely known to have entered production was the 2 cc K Tornado glow model which was first advertised in February of 1950. Even this was not really a "new" design, being in effect a glow conversion of the Falcon diesel. A further model called the Falcon Mk II having a displacement of 2.5 cc appeared in several advertisements a little later in 1950, but there is currently no evidence in the form of surviving examples that this was ever actually manufactured.

Production apparently ended altogether at some later point during 1950, and by the end of the year the company had ceased advertising. The possible reasons for this rather abrupt departure deserve closer examination.

One contributing factor to the apparent erosion of the "K" Model Engineering Co's market position may well have been the rather chequered career of the company's flagship 5 cc Vulture design. We plan shortly to publish a detailed account of that model's somewhat unhappy history, but suffice it for now to say that the Vulture suffered from a number of significant design shortcomings as of its introduction in October of 1948 and never really recovered from the consequent blow to its reputation. In addition, it was a notoriously difficult engine to start (still is!), which certainly can't have helped.

The company made a sincere attempt to rectify the above issues with the Vulture through the issuance of several improved variants, but these efforts appear to have been insufficient to rehabilitate the engine in the eyes of the modelling public. It's an inevitable conclusion that the reputation of the company itself must have suffered as a result of this situation. This is a great pity, since the firm's other offerings such as the Falcon, the Mk II Hawk and the Kestrel were excellent engines which fully deserved the support of the marketplace. But their merits may have been insufficient to overcome the erosion of the company's reputation arising from the generally negative perception of the Vulture.

As we've already seen, the Hawk FRV models don't appear to have survived long in production, but the company continued its efforts to promote its other products into 1950. As of February of 1950 they were still promoting the Mk II and Mk III Vulture, the Falcon and the Kestrel along with the newly-introduced Tornado glow model.

However, the Tornado fell well short of matching the performance of its diesel progenitor, and this can't have helped the cause. By May of 1950 the company was no longer advertising the Falcon or the Mk II Vulture and had significantly reduced the size of its monthly advertising placement in Aeromodeller. It seems highly likely that production of even the Mk III Vulture had ceased by this time and that the company was simply selling off existing stocks of that model. This may in fact have been true of all the K models by this time.

The emerging picture here is one of a company struggling and failing to maintain its position in the marketplace in the face of a negative perception resulting from the failure of several of its offerings to live up to their billing. The final Aeromodeller advertisement to be placed by the "K" Model Engineering Co appeared in the November 1950 issue at which time the price of the Mk III Vulture had been dropped from its former £4 15s 0d to a mere £2 19s 6d. This is about as clear an indication as one could wish that the company had ceased production and was simply liquidating its assets by this time.

However, the above issues may not have been the sole cause of the company's demise. The timing of their departure makes it appear entirely possible that the final crisis may have been precipitated by the financial impact of the hefty purchase tax imposed on model engines in September 1948 by the Government of the day. We have mentioned this decision in an earlier section of this article, but for convenience we'll re-state here that its effect was to bring model aircraft parts and accessories, including "power units of all kinds" under Group 20 ("amusements") of the Purchase Tax Schedules. The immediate result was the imposition of a crushing 33-1/3% increase in over-the-counter domestic prices of model engines.

Naturally, this Government decision struck hard at the very foundations of the British model industry. An argument presented by the Model Traders' Association (MTA) was successful in reversing the decision as far as kits were concerned, but the Commissioners of Taxation continued to insist that all parts and accessories, including engines, propellers, spinners, wheels, and in fact every identifiable accessory that could be used in conjunction with a model kit should be subject to tax. The Purchase Tax was calculated not on the retail price but on the manufacturer's wholesale price, thus presumably making the manufacturers responsible for collection, reporting and payment. Generously, nuts and bolts were exempt!

To fight this decision, the MTA formed a sub-committee comprising Eddie Keil (KeilKraft), Jack Ballard (ED Ltd), Arnold L. Hardinge (Mills Bros) and Henry J Nicholls (Mercury Models Ltd). Legal advice to them indicated that the best strategy would be for MTA members to refrain from paying Purchase Tax, thus allowing a test case to be raised. It was anticipated that the challenge would be successful and that a favorable decision would be backdated to January 1, 1949. Nevertheless, prudence would seem to have dictated that a contingency provision be made by those concerned, simply to guard against the possibility of an adverse decision. Some apparently failed to do this.

The test case dragged on for almost two years, ending in late 1950 with a decision which upheld the Government position. This meant not only that manufacturers thenceforth had to pay tax on their ongoing production but that the unpaid taxes on production dating back to September 1948 were also now due (with interest). Ouch!

It appears that a number of participants in the model trade had failed to take the prudent step of establishing and maintaining an adequate contingency fund to cover the possibility that the test case might fail. We know that ED were one of these firms, and it appears that the drain on their financial resources resulting from the need to pay their back taxes, coupled with the erosion in profitability relating to their then-current production, created significant financial problems for them. Among other things, their research and development program seems to have suffered to some degree and there was considerable upheaval among the members of the Board, including the resignation of Jack Ballard.

Another victim was Mercury Model Aircraft Supplies Ltd, who were unable to weather the storm and were wound up in 1953, although the assets and name remained "in the family" by being acquired by "H J Nicholls Wholesale Ltd". It's also possible that the North Downs Engineering Co, makers of the Nordec racing engines, also ceased model engine production in late 1950 at least partially as a result of this decision.

ED probably only survived because they were a very large concern by this time and had the underlying resources and sales volume to carry them through the crisis. Although it took time, they eventually rebounded quite strongly, to the extent that they were able to move into new and modernized premises in 1956.

However, the "K" Model Engineering Co apparently remained a relatively small-scale operation throughout its existence. If they had been among those companies which did not make an adequate contingency provision against the possible failure of the Purchase Tax case, it seems obvious that the loss of the case and the consequent need to pay two year's worth of back taxes as well as absorb an erosion of profits due to the application of tax to current production might well have been sufficient to drive them out of business. The fall of this blow and the departure from the scene of the "K" Model Engineering Co at one and the same time may well be more than coincidental!

Regardless of the reason, the loss of the "K" Model Engineering Co was a blow to British modelling. One can only wish that they had been able to continue—we might have seen some very interesting new engines if they had done so!



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