From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Technical analysis of competitor synchro-mesh gearboxes and steering systems, including those from Buick and General Motors.
| Identifier | ExFiles\Box 170\2\ img039 | |
| Date | 12th May 1931 guessed | |
| Messrs. Hives and Robotham - #2 Synchro Mesh Gear Box. The Buick scheme we all agree is good and simple. It achieves a very high standard of consistency in the production line. Our scheme being partly on the box and partly on the shaft tends to be more variable, but when correctly done we think it has a less mechanical "feel". General Motors holds all the patents which are in various names principally Thompson and Tenny. There would be no difficulty about reasonable royalties. The Warner synchro-mesh is not a General Motors patent and is probably not patentable as there are some English patents of about 1910 calling for such a simple device. It is only effective in conjunction with a free-wheel where a free tailshaft is synchronised with the engine. Without a free wheel where the spinning clutch plates, etc., have to be synchronised with the driven mass of the car, more power is needed. Steering. Buick uses the Gemmer-Marles steering, which is like the original Marles but improved by the use of Timken bearings, etc., which permit the partial "self-locking" tendency without damage. Other divisions use the plain Gemmer with the hourglass worm except Yellow Coach who seem to favor the Timken bearing Ross. Buick seems to be the only one who use plain pivot thrusts, and therefore need the high efficiency (about 75%) of the Marles. Their layout is therefore similar to Rolls Royce in many respects with the important addition of the shimmy shackle and with the difference of a steep pivot angle and nearly center point kingpin. The shimmy shackle of between 7,000 and 10,000 lbs. per inch at the spring eye is undoubtedly one of life's little compensations. All American tires (complete) are now in static balance within 30 oz.-inches. Front 7 1/2" tires for the "16" are selected to come within 15 oz.-inches. Nearly all side steering tubes are solid. (I believe all are solid on General Motors cars.) The shimmy shackle does more than the side steering tube springs in permitting the axle to walk to and fro and lowering the frequency of wobble, at the same time dissipating energy in tire friction. (I think this is a correct rough description.) Too soft a shimmy shackle will promote low speed wobble. | ||