Beautiful machinery. Any back story on the Riley?
The Riley belongs to an aircraft engineer (that is his Tiger it was parked beside) who restores cars as well. He wanted a vintage sporting car and a Bugatti was out of reach (although he has just restored a Type 59 for someone). His father who is also an expert car restorer with in interest in aviation built an early 1920's Sunbeam powered by a Sunbeam Maori V12 aero engine, as well as a re-creation of the 1906 Grand Prix Darracq based around the the original 4 cyl 14.25 litre engine which found it's way to New Zealand just after WW1.
Anyhow. Robert (the son) wanted some of the big engine action so he got the running gear of a 1931 Riley Nine saloon, a pretty useless 1100cc four cyl thing and a heap of time-expired Gypsy Major engine bits and set to work.
To make the engine work in a car it has to be turned upside down (crankshaft is at the top of the engine when mounted in an aircraft), swapped end for end so the prop. boss is at the back, and a flywheel and clutch added. What this means is the engine now spins in reverse to a car engine, so the thrusts in the gearbox needed to be modified (he used a Moss gearbox from a Mk1 Jaguar) to take the loads.
In order to avoid having four reverse gears and one forward the innards of the diff have to be in upside down as well. The aero engine runs at half the speed of the car so a much higher rear end needs to be fitted. An early 1920's International truck uses a 1.9/1 crownwheel and pinion with epicyclic gears to reduce the final drive. Robert used the crownwheel and pinion from the truck and fitted them inside the original Riley housing. The combined weight of the Gypsy engine and Moss gearbox is basically the same as the original cast iron lumps which came out of it sot the handling hasn't been effected at all.
It now does 100 km/h (60 mph for our British and American friends) at 1400rpm, 100 mph (160km/h) at 2100 rpm, and will rev to 2500 rpm.
The car is an absolute work of art, mechanically and aesthetically and is an amazing thing to ride in on the road. I didn't drive it but I have driven quite a few miles in a Grand Prix Bugatti and the Riley is faster, more comfortable and does not feel like it is about to fly into a million expensive little pieces which is always the impression the Bugatti gives.
