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 discussing epicyclic creep and potential modifications to forks, shafts, and pinions.
| Identifier | ExFiles\Box 6\4\ 04-page049 | |
| Date | 4th February 1925 guessed | |
| -2- epicyclic creep, but here again either we have not cured it or the fork was the cause. An idea has occurred to me that with the larger shaft (which is a definite improvement) we might try a taper bore on each end in turn i.e. more clearance to allow it to tilt first one way then another. If traitorous perhaps it would be better running on a stationary shaft which might prevent creep, but if O.K. at present and consistent, use present arrangement with the larger shaft. My impression is that it is not necessary, though perhaps advisable, to cut the forks as shewn in your letter. It certainly gets rid of the risk in one plane, but not in the other. I am aware that in one case the force makes the effect worse, while you leave would spring itself correct. I think however if gear stays still, and fork sufficiently slack for all errors of squareness, then no trouble will be found. You may be right in saying creeping caused the excessive collar friction. I thought this was due to wedging the gears. This is unimportant. I still think that in addition to the increased clearance between forks and collars, more clearance is needed between the actuating lever (hand lever in gate and pendulum lever ends and slider lugs) so that no obstructions are felt to sideways movements. In conclusion it is still possible that though torsional deflection of the shafts may have no effect of moving the wheels along the shafts, bending may have, and this could clear up the remaining mystery. At the same time I do not think this is so but it is our mutally agreed view that the double pinion creeps due to tooth pressure moving the wheel upon its keys, as I feared and telegraphed. The mystery is that we have done nothing to help this, but it may be that the movement was the combined action of the fork and the load, or it takes very little to resist this creeping, which I cannot believe. If there is still any doubt it would be wiser to increase the diameter of the double pinion and reverse pinion slightly, and if possible use the 14° teeth so that the pressures tending to disturb the pinion on its shaft are less. But if the reverse shaft increased in diameter and the forks made free, makes the job perfect, I am content. R.{Sir Henry Royce} | ||