A Bentley eating Austin?
(UPDATE: a flood of gear ratios...!)

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John Barringer has a technical question about a most interesting automobile: "My son, Simon, has recently purchased a 1923 Austin 20 Sports dual cowl, dual windshield, phaeton (click dog's nose). The factory built about fifty of these in the early 1920's based on the standard 20 hp chassis. The Sports model varies from standard by having a high compression head, high lift cam, Claudel Hobson carb., water heated inlet manifold, close ratio gearbox, softer rear springs with snubbers, centre lock wire wheels and a high ratio rear axle. The standard Austin 20 produces 40 bhp but the sports model turns out nearer 90 from its 3.6 litre flat head four! One was timed on the Railway Straight at Brooklands at 104 MPH! Now here is the mystery: what is the rear axle ratio for this model? The rev. counter on the instrument panel tells us that the engine is turning at 1600 RPM at 60 MPH with 23 inch wheels (the car will do 90+) but as maths was never my strong suite I cannot calculate it from this. We have tried to roll the car forward while counting the prop shaft turns but this was inconclusive. We owned an Austin 20 Marlbrough landaulet some years ago and this was 3.9 : 1 but this car is much higher geared. Are there any experts out there on this model?" Contact Us
UPDATEs came in form John Hearne, Josef Kubista, Reg Harris, Dick Trenk & alain Gallego. All with meticulous explanations on how to solve the gear ratio mathematics. We want to thank you all, the messages moved on to John & Simon Barringer. See Read More for all the possibilities…

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