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).
Proposal to test stiffer springs in the Wraith III timing gears to address excessive wear on the camshaft driving wheel.
| Identifier | ExFiles\Box 136\1\ scan0293 | |
| Date | 13th April 1938 | |
| Giles 1155 DA.{Bernard Day - Chassis Design}18/G.13.4.38. Swell - I want you to examine the Spring drive off the 15,000 miles engine to see if it has been hitting the stops. Rm{William Robotham - Chief Engineer} WRAITH III. TIMING GEARS. It is suggested that a possible cause of the excessive wear on the camshaft driving wheel, experienced on the 15,000 miles test car, may be due to the spring drive thumping on the stops due to the torsional oscillations of the crankshaft and causing hammering on the gear teeth at six places on the gear and in order to test this theory it is proposed to stiffen up the driving springs of the spring drive. It would be necessary to alter a number of parts in the spring drive and damper, to obtain a large increase of driving spring load. We therefore suggest using the stiffest springs possible in the existing spring drive as a preliminary test to see if any improvement results. The present springs E.58239 and E.57758 have a total load when the spring drive is solid on its stops of 284 lbs. giving a torque of 33.2 lbs. ft. The outer spring E.58239 is already at a maximum for the space available, the inner spring we propose to stiffen to its limit, and by doing this we can increase the driving load to 33.6 lbs. giving a torque of 39.3 lbs. ft. which is an increase of 18.2 % Following are the particulars of the new inner spring :- Inner Springs (soft). 7 working coils of 17 SWG. (.056) dia. wire. Inside diameter of spring = .225" Free length = .775" Load to compress to .512" = .25 lbs. Choc-a-bloc length = .486" Uncorrected stress = 100,000 lbs. per sq.in. Rate = 94.5 lbs. per inch. Will you please detail and instruct this new spring for the experiment. DA.{Bernard Day - Chassis Design} | ||