MODEL ENGINE DESIGNER AND MANUFACTURING PROFILES
DC Tornado Twin
No. 34 in a series compiled by David R. Janson,
SAM #273, AMA #78416 and MECA #210-04.

 

British model engine developments during 1960 were mainly confined to improvements and modifications to existing designs. The two "big" events that year were the Merco designs which rapidly came to the forefront in radio control and the unique Davies-Charlton "Tornado" twin of 5cc displacement. Among continental manufacturers D-C had one of the most modern and expensively equipped factories at the time. D-C had joined with Allbon and moved to the Isle of Man in the Irish Sea in the middle 1950s. (In later years, 1960s, D-C also manufactured the Frog line). And while production at the D-C plant concentrated on mostly small sport diesels, in 1960 manufacture of one of the most ambitious power plants ever unveiled by a British firm, the precision made, horizontally opposed twin cylinder glow engine with dual rotary valves, fed from a single cast in carburetor was a gem. Since a one piece crankshaft was used the connecting rods had detachable caps-per full scale practice-each secured with two screws. In the definitive test article in Aeromodeler, Sept. 1960, R. H. Warring noted, "The real advantage of a twin is smoother running. Even the simplest "multi"-a twin- means more complication, more friction and real production headaches. But in radio control models, in particular, excessive vibration can cause skipping relays and control response troubles. The much higher production costs of a "twin" delegates it as a specialized engine, with most obvious appeal to R/C'ers and large stunt control models. Its commercial life will depend largely on how it succeeds in this respect." The design of the "Tornado" is essentially orthodox.

Induction is via crankshaft ports fed from a centrally mounted choke tube opening into a horizontal passage connected with down tubes in each endplate casting to machined in passages in the cylinder jacket overlapping the diametrically opposed exhaust ports. The crankcase unit is a relatively complex casting faced to take the fixing screws. The horizontal intake passage is machined out. The investment casting is aluminum and very light. Both front and rear covers are removable (secured by four screws each) and the intake is cast in topside, with full brass seated needle attached. The cast rear cover has a nicely machined radial aluminum mount attached. "DCL Ltd" is cast on the right side and "made in England" cast on the left side of the crankcase. No serialization was done. The cylinders and heads are machined aluminum, polished, heads secured by six screws, three of which hold them to the crankcase. Glow plugs are centered, head fins are low and flat and attached to the exhaust stubs are down draft exhausts, neatly silver soldered and polished. The prop drive washer is turned and polished aluminum, and the steel nut is covered by a screw on solid aluminum spinner with nose hole for tightening.

Internally the crankshaft (one piece as noted before) has very finely finished and polished bearing surfaces. The shaft is carried in plain (unbushed) bronze bearings in each end cover and machined from the solid. The "split ends" connecting rods of high tensile steel are attached to hardened steel pistons, ringless, by silver steel pins. Cylinder liners are of conventional pattern, machined from Leadloy but not hardened. Judging from the amount of machining from the solid, the "Tornado" was intended for limited production (estimated at less than 500) very expensive but avoided the tool cost in die castings and also left the design open for change.

Reaching the market at around $40-50 it was very expensive for the times. This 5cc (.303 cid) twin is rated at .4bhp and weighs a mere 10 oz. It is a very attractive small model engine. On the market for a mere 5 years (1960-65) it was put to "rest." The great collector interest in model engines causes this engine to be a "must" for any multi-cylinder collection. Not yet rare, but exceedingly difficult to locate, all serious collectors are after this beauty, paying big "bucks" to get one.

See also: Adrian Duncan review.

 

This page reprinted from "Model Engine Designer and Manufacturing Profiles" by permission of the author, Mr David R. Janson.

 


 

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