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 memo discussing the causes and potential solutions for transmission vibration on the 20/25 model.
| Identifier | ExFiles\Box 178\3\ img141 | |
| Date | 18th April 1932 | |
| HS.{Lord Ernest Hives - Chair} E.{Mr Elliott - Chief Engineer}) FROM R.{Sir Henry Royce} DA{Bernard Day - Chassis Design} ) (At Le CanadelHenry Royce's French residence.) C. to SC. WOR.{Arthur Wormald - General Works Manager} RG.{Mr Rowledge} C. to PN.{Mr Northey} HP. ORIGINAL. R1/M14.4.32. Sent from WW. 18.4.32. x5310. y u 20/25 - TRANSMISSION VIBRATION. You send a design of a friction damper to be mounted on the universal joint behind the gearbox. We must not however fit such a device unless we cannot possibly do without it. There are several reasons for not doing so. If after a struggle it is inevitable, the designers must work at it until we get the best design possible. One first imagined it was Mr. Platford's old pre-war friend known 20 yrs. ago as "Coronation Rattles", but I am not sure that it comes from the same source (piston inertia variation - 6 cyl. engine). This car has now been on the road say 12 yrs., and personally I have never noticed anything that one could put down to a torsional vibration of the transmission causing rattles in the gears etc, but I am not saying this does not happen on older cars. If however it does happen we ought to find or prove the cause. I am suspicious that it may come from the universal joints being out of line. Could HS{Lord Ernest Hives - Chair}/GRY.{Shadwell Grylls} find if it is 2. 3. or 4. per rev. of the propeller shaft. If 3. its source is in the engine, and asks for a more effective flywheel. If 2. or 4. it is in the couplings. Are the cars complained of fairly straight in both universals? It probably occurs on the over-run when the transmission is unloaded. Anyway find the source, if unknown or unproved. If the source is in the pistons it shews we need 8 cyls. One good idea is to fit a rubber coupling behind the gearbox (or between the engine and gearbox as on P. 2.) It would be fairly easy to substitute a Hardy coupling for the Mechanic's joint just behind the gearbox. In spite of its imperfections I believe this would be a great improvement, and to a small extent help the gear change. I should much prefer it to a damper, outside the extra cost, weight, etc, of the damper. When we had a somewhat similar trouble, (R.{Sir Henry Royce} away ill) the Works increased the flywheel dia. until the road clearance was too small. I removed the brake drum from behind the gearbox and fitted the foot brakes on to the rear axle. This was making the transmission have less torsional inertia, which is good if possible. Has anything happened to alter the prop: shaft or couplings, or spoil the alignment. One imagines we have not altered the inertia of the pistons or the flywheel, so the percentage variation of turning is the same. The importance of this will be realised when we consider that such a heavy, costly and undesirable fitting as this proposed damper would have to go on P.2., J.3., models per. Bensport - ie. all our models - terrible. R.{Sir Henry Royce} | ||