DC Manxman


Name DC Manxman Designer Hefin Davies/ Alan Allbon
Type Compression Ignition Capacity 3.5cc (nom)
Production run unknown Country of Origin England
Photo by Ron C Year of manufacture 1956



The Manxman is 3.5cc "diesel" produced by Davies-Charlton Limited on the Isle of Man in the mid to late 1950's. It has the same bore, stroke and general appearance of the earlier DC "350", featuring the distinctive "up-draft" intake (or down-draft if you mount it upside down). Although described and advertised as 3.5cc, Ron Warring's test of the engine in the February 1957 Aeromodeller quotes the bore as .680" and stroke as .5625". He goes on to say this gives a displacement of 3.444 cc or 0.21 cuin (compare this with the manufacturer's figures of 3.5 cc and 0.21 cuin). My calculator says 3.348cc and 0.204 cuin. It was not uncommon for British manufacturers to purposly undersize an engine slightly for the competition event class it would be used in. For example, the ED 2.49cc "Racer" for A class team racing where the maximum permitted engine capacity was 2.5cc. The intent being to protect owners from the depredations of over-zealous scrutineers by ensuring that the engines would be under the limit despite any vaguries of manufacture. As seen here, it carries a plastic backplate mounted fuel tank for free flight use which the add quotes as being "crystal clear". The anodizing is original and in very good condition. The case has some rather unsavory marks, and the tank retaining stud/nut arrangement is almost certainly not original.

The first add I was able to locate for the Manxman was a full-page, two color, inside front cover placement in Aeromodeller of March 1956--the usual location for DC adds. The same add was repeated in different colors in April and May. In June, DC changed to a new montage of their engine range, now including the new Merlin, Super Merlin, and Manxman. The same full-page add appeared in Model Aircraft magazine of April and May. Note the line saying "Supplies will be at your model shop shortly..."  Normally, Aeromodeller and Model Aircraft would review new engines as they were first released. Eleven months passed from first add to Aeromodeller "Engine Analysis No 30" mentioned above. This may indicate that supplies were slower arriving than anticipated. I've searched Model Aircraft through to the end of 1957 and find no review for the engine. Terry McDonald's Index of Engine Reviews doesn't show a MA review date either, so we'll conclude that none exists.

The earlier DC "350", reviewed in Aeromodeller by LH Sparey in November 1950 and January 1952, used a mono-block case with cast-in fins and a head secured initially by 3, later 6, screws (after heads were observed to explosively and embarassingly depart from the case while running). The Manxman adopts the simpler, lighter and more robust design with separate cooling jacket and 4 bolts. Aeromodeller reports that the main crankcase journal size had also been increased--this being another noted weak-point of the "350". The Aeromodeller test figures for the Manxman stated RPM in the range 8000 to 14000 (the latter using a 7x5 prop--stand back and mind your fingers on a cold winter's morning!). The report observed that it was not possible to stop the engine by backing off the compression screw, right thru the RPM range. The comp screw is also rather short, perhaps to prevent it being over compressed (whether by the screw bottoming on the head top, or the operator burning his fingers on the head is uncertain). Although the DC 350 was most certainly designed by Hefin Davies, I'm tempted to credit the Manxman design (or redesign) to Alan Allbon as it bears more of his style. Incidentally, no-one seems to know who "Charlton" was, or if he even existed. Perhaps it was like the "Ashton" of early database vendor "Ashton-Tate"--a name made up to make it all sound grand (although George Tate did eventually buy a parrot and name it Ashton--but I digress...)

I'm uncertain regarding the color of the tank on my example. It is distinctly orange, though I don't know if this is original, a result of age, or a result of some strange fuel additive (DCO suggested someone had dumped "Redex" in the mix, but he's prone to the occasional leg-pull). Construction is quite conventional: Steel liner, cast iron conical-top pistons, plain bearing, 360 degree porting with a small but noticable amount of sub-piston induction at TDC. Although die-cast, the case is rough enough to be sand cast. This is odd as all other DC engines had quite elegant die-cast cases with fine, intricate, embossed lettering. These features are totally absent on the Manxman. At 6.5 onces, it's sure no light-weight, but most find it attractive and purposful looking.

Finally, why Manxman? According to the Archaeology of the Isle of Man, "Manx" means "of, relating to, or characteristic of the Isle of Man".  Manxman is also the name of two silent films telling the story of two men (from the Isle of Man naturally) in love with the same woman. The most recent of these (1929) was directed by Alfred Hitchcock, no less. Now apart from the obvious connection given DC's then recent move of manufacturing to the Isle of Man, there's subtle closeness of "manx" to "max", as in a free-flight max, and notice the closing line of the add: "A real man's motor".  Of course, I could be reading more into this than actually exists...




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