Letter discussing a 'chunking' noise in the transmission and its relation to slack in the high-speed dogs and rear spring types.
| Identifier | ExFiles\Box 156\4\ scan0004 | |
| Date | 19th August 1921 | |
| X/1511 CC Mr. Belnap Mr. Madison Oy6 - G 19821 August 19, 1921 Mr. Claude Johnson, Managing Director, Rolls-Royce Ltd., London, England. Attention: Mr. Royce & Works Committee. Dear Sir:- Re: "Chunking" in the Transmission COPY X1511 Replying to Mr. Royce's letter R10/G3/6/21, we find that on cars in which the high speed dogs are held to a slackness not exceeding .006", the amount of "chunking" is generally speaking negligible. This does not apply, however, to roadster bodies even when fitted with very light springs, because the rear weight is insufficient in these cases and the back axle is consequently more lively in its movement than in a heavy car. The first car which gave us an inkling of the necessity for tightening up the dogs was 24-TE, an imported car, which was found to be practically free from "chunking". The drawing stipulates a slack not exceeding .004", but it has apparently not been the practice to work to these dimensions and some of the early post-war cars had as much as .030" slack in the high speed dogs. The bedding-in of the rear springs has a very noticeable effect on "chunking" on rough roads, and very often a car which "chunks" when newly turned out, is found to be free from "chunking" after a few hundred miles running. A car with very slack high speed dogs will "chunk", in our experience, even when the springs are well bedded in. The above remarks regarding the state of the rear springs of course only apply to rough-road "chunking". For "chunk" which occurs in slow speed running, we find it absolutely necessary to hold the slack of the high speed dogs to a minimum of .005". | ||
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).