In the early years of the 20th century there was a fashion for simpler forms of transmission for motor cars than the rather brutal but nevertheless effective ‘crash’ gearbox. This was partly to make gear-changing easier for those who found it difficult to master the necessary double-declutching – but it was also a cheaper solution for light, lower-powered cars where there was less need for sturdy gears.
The most common form of this type of transmission was friction drive – and an example from America appeared in 1905: the Aurora. The remarkable aspect of this car, however, was its more substantial four-cylinder taxable 30 h.p. engine. The manufacturer, the former Aurora Carriage Top Company of Aurora, Illinois, must therefore have had high confidence in the efficacy of its system. The engine had, in fact, a claimed power output of 24 to 30bhp at 1,000rpm. It was a water-cooled four-cylinder side-valve Beaver unit of 108mm bore and 121mm stroke, giving a capacity of 4,434cc.
The transmission firstly comprised an extension of the crankshaft that extended right to the rear axle of the car. On this were mounted two paper friction wheels, the front one for reverse gear and the rear cone-like one for moving forwards. There was no clutch, but behind the flywheel was a coupling using a continuous belt running on bolts going backwards from a flange on the crankshaft and forwards from a flange on the transmission shaft. This allowed the transmission to take up any misalignment between crankshaft and transmission shaft.
The cast-iron main drive discs were reinforced on their outsides with radial and circular flanges, and their inner driving faces were parallel at their outer extremities and conical in the middle. Since the discs had to rotate in opposite directions, one drove the rear axle via a sprocket and chain and the other drove a gear engaging with another gear further back to reverse the drive direction. This then drove the rear axle via its sprocket and chain.
Forward drive required the action of two levers: one moved the conical paper friction wheel on the transmission shaft forwards and the other closed the two main drive discs together to achieve friction drive. Low gear was achieved with the paper friction wheel towards the rear; high gear was achieved with it forwards, thus engaging with the conical centre of the main drive discs.
All this complexity had apparently been extensively and successfully tested around Chicago in 1904, ready for a 1905 announcement and deliveries starting in 1906. Sadly, however, enthusiasm exceeded reality, and not many cars were built before the company closed in 1906.
Image courtesy of The Richard Roberts Archive: www.richardrobertsarchive.org.uk
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