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).
Report investigating gear change resistance and oil friction on the Phantom II synchromesh gearbox.
| Identifier | ExFiles\Box 15\5\ Scan280 | |
| Date | 7th May 1932 | |
| X7310 To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} c. Sg.{Arthur F. Sidgreaves - MD} c. Wor.{Arthur Wormald - General Works Manager} E.{Mr Elliott - Chief Engineer} c. Da.{Bernard Day - Chassis Design} EV.{Ivan Evernden - coachwork} Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}1/AD7.5.32. P.II SYNCHROMESH. We suggested in our Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}13/MA25.4.32 that the resistance met when changing gear on this gear box was due to the torque required to keep the speeds synchronised against the oil friction in the gear box. We therefore ran the car with both side shaft helical gears absent. That is to say, we could do changes into top from a stationary clutch member. It proved to be very easy to do so, the cones being entirely adequate for speeding up the clutch inertia. With oil in the box this operation requires a very large effort on the gear lever. To measure the effect of the oil, we drove electrically the first motion shaft of the gear box, the third motion shaft being held stationary. By measuring the power in full we were able to find the losses due to oil friction and core drag in the gear box. We attach herewith figures for both the P.II and 25 HP. gear boxes. Providing there exists a torque on the bronze cone it will require a corresponding effort to push the cam out of the vee notch up the 45° angle. Instead of this torque becoming nothing when the studs are synchronised (i.e. when no torque is required to accelerate the steel cone) we still find a very considerable torque on the bronze cone required to keep the helical gears turning against the oil friction. Consequently however slowly the change is made a large effort is required on the gear lever. This suggested that one should eliminate the cam action from the synchromesh and rely on the plungers only to engage the cones. We started, therefore, with no cam but plunger springs three times standard load. This achieved the required result in that the cam resistance had vanished but brought up a new fault. When the plungers have left the grooves in the core member, they exert sufficient frictional force on the plain surface to continue pressing the cones together. This causes the second part of the gear change to be very hard work since the teeth do not enter easily. Similarly, getting out of gear was difficult. When disengaging, say third gear, the cones move immediately (i.e. in the first half inch travel of the lever) into the top gear position. This puts a load on the third gear teeth making it difficult to move the gear lever. | ||