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).
Design suggestions for the 'SS' chassis, covering the starter motor, engine mounting, and length.
| Identifier | ExFiles\Box 14\5\ Scan038 | |
| Date | 25th December 1928 | |
| HS.{Lord Ernest Hives - Chair} DA.{Bernard Day - Chassis Design} } FROM R.{Sir Henry Royce} E.{Mr Elliott - Chief Engineer} BY.{R.W. Bailey - Chief Engineer} } (At Le CanadelHenry Royce's French residence.) Cp. to BJ. WOR.{Arthur Wormald - General Works Manager} SG.{Arthur F. Sidgreaves - MD} S. SECRET ORIGINAL R1/M25.12.28. REC'D AT WW. 31.12.28. X.762S/SS{S. Smith} X7005 "SS{S. Smith}" CHASSIS. My impression is that there is nothing to be anxious about in the design of this at present. STARTER MOTOR. I am sending Mr. Elliott some suggestions for a damper attachment to the rear end of the starter motor to enable the end motion to finish silently. The other features are only a matter of proportions of end pull and spring pressure. I repeat my suggestions of (1) returning to a parallel armature, (2) a hold out spring of lowest possible rating (even pull) of about 25% = a quarter of the weight of the armature, (3) a kick-back spring of very small initial pressure and fairly high rating - (these are only suggestions, and others should be tested.) The dashpot I have schemed allows say 75% of the stroke undamped that can be done quickly, and the remaining 25% allows for the slow coming to rest of the armature endways in each direction. The design only affects the rear end bearing, so is a small item of the starter equipment. (See sketch attached - sheet (3). E.{Mr Elliott - Chief Engineer} is quite right about the crossing of the teeth, but I think if they can get in 50% of the angular time they will do, so when the kick-back spring and torque is made more suitable perhaps a few more teeth in the pinion would do good to the gear - not much harm. In addition I suggest rather coarser teazer winding for greater vigour of end pull and torque - i.e. make it feeble enough and it will stick where-ever placed. ENGINE MOUNTING. I am hourly expecting to hear some results which will say what kind of fixing gives the best results. We believe that somewhere between rigid and the flexible we have at present should give results equal to anything we have ever had. My impression is that very little flexibility in the front feet is essential so that the frame cannot go without the engine. This should give slow period of engine and frame and not match tramping period (of about 800 per minute.) LENGTH. I have already written that if this proves excessive with 2 wheels on the back we ought to have 2 lengths of chassis, and only carry the 2 wheels at the back when we supply the shorter chassis. Personally I believe for ordinary work only one spare wheel is necessary and that has been my practice for several years, (1) | ||