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).
The difficulty of changing into 3rd gear in a gearbox, detailing issues with resistance and cone synchronisation.
| Identifier | ExFiles\Box 178\4\ img046 | |
| Date | 28th April 1932 | |
| R.{Sir Henry Royce} From RM{William Robotham - Chief Engineer}/Dry. c. to S.G. c. to Mr.F. c. to A.{Mr Adams} c. to JV. ORIGINAL X7310. RM{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}13/A.{Mr Adams} 28.4.32. P.11 of [illegible] The trouble we are having with this gearbox is the difficulty of changing into either top or 3rd gear. When changing into 3rd, for instance, one meets with a very considerable resistance to motion of the gear lever in both stages of the operation. The first resistance is caused by the cam and should exist until the speeds have synchronised, but in this case continues to exist because of the work required to keep the gear trains revving against the oil friction in the box and against the drag of the other half of cones. In the P.11 box the oil friction causes more resistance than that due to synchronising the speeds. We have demonstrated this by running the gear box with no oil when the crude gear is on more work than the 25/30 car that we have fitted with a heavy clutch member. Having overcome the cam action, one meets the second resistance when the teeth start to engage. This necessitates relative rotation of the cones that have just synchronised. That is to say the cones having done their work must free themselves and rotate easily one within the other. We have found that they do not do so. This is particularly noticeable when engaging 3rd gear from rest, the cones sticking together nearly every time. We lessened this effect by fitting springs between the two gears and this seemed to free them after the cam had ceased to press them together. This made the second part of the movement of the gear lever considerably easier, and gear could be engaged from rest with ease every time. We have also tried 40° cones as these should be more effective for a given effort at the gear lever. They however never freed themselves after synchronising and it was nearly always impossible to en-gage the teeth. | ||