Half car – half motorcycle

A regular swap meet follower, Ray Morgan recently told me about his wife’s long deceased relative, Jim McMahon who was killed racing a Kurtis-Kraft midget speedcar at Carpinteria Thunder Bowl near Santa Barbara, California in 1948. He initially indicated the top portion of this engine was twin Triumph, hence I thought this should make an interesting story. Ray was able to later provide me with some written material which has allowed me to convey part thereof to readers to give insight into this man and an exceptional V8 race engine. Born 1912 in Sydney, McMahon was apparently a ‘good style” of a bloke and starred in seven Australian -made films commencing at the young age of 12. The film studios were at Bondi and Pagewood. On seeing a photo of McMahon, Neville Doyle told me that he has a strong resemblance to Victorian Scrambles rider Ray Fisher. A copy of McMahon’s marriage certificate dated 27 October 1934 shows that both he and his father, also named James McMahon, listed their occupation as Motorcycle Dealer. Ray tells that the dealership was based at Bondi. He initially raced solo motorcycles on Speedway before competing in speedcars to win the NSW Championship in 1941 and came second in the same year in the “World Titles”. McMahon obviously possessed a good deal of engineering skills. He built two lightweight aluminium bodied midgets which were powered by Douglas V twin aero engines. This engine at 2,000cc capacity was twice the capacity of his opponents but he was unable to extract the high revolutions that these engines usually produced. He also built at least one midget powered by the 880 V twin JAP. McMahon also built a prototype all-Australian aluminium sports car which he hoped to mass produce when he returned to Australia. This car, called the MCM, was initially fitted with a 600cc DKW two stroke engine which he entered at Bathurst in 1946 but did not start in the race. It was rumoured that midget car racer Ray Revell was going to participate in this venture with McMahon. I have not been able to find any reference to McMahon having any formal engineering qualifications, however back in those days that was often the case with people who possessed exceptional engineering skills in the making of outstanding motorcycles or cars. US race car historian and illustrator Joe Henning remembers McMahon as a bit of a loner and being capable of not only thinking up a complex engineering concept, but also being able to machine it into reality. He left Australia in mid-1947 but did not have too many wins to collect any great amount of prize money. The material claims that the engine in the midget car he was racing at the time he was killed was of his own design and construction. It is claimed that it was two litres. What happened to McMahon’s car after he was killed is unknown. Fortunately years later the engine was found in a junk yard in Los Angeles, destined to be sent to Japan for scrap. It was saved by someone who realised that it was unusual, in fact believed initially that it was some form of compressor. It was later sent to the Museum of American Speed in Lincoln, Nebraska, and remained there for several years before the proprietor, Bill “Speedy” Smith had a chance conversation and was able to connect this engine to McMahon. Later a restoration process was commenced; Smith remarked that the inside was the best machining he had ever seen. The normal Triumph set up is that the pistons are running parallel. In a V8 the conrods sharing the same big-end journal not only connect to pistons in opposite banks, but to pistons that are in different positions. It would be impossible to connect two rods travelling in the same direction off the same journal to the same bank, because they would be too close to meet the pistons. So using a V8/60 crankshaft, the Triumph system had to have been reconfigured to a one up, one down piston per cylinder. This would have been the key to making it all possible.