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).
Discussion with Dr. Maybach concerning the design and operation of Maybach-type dog gearboxes.
| Identifier | Morton\M19\ img129 | |
| Date | 2nd March 1931 | |
| ORIGINAL To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Hn.{F. C. Honeyman - Retail orders} c. to Da{Bernard Day - Chassis Design}/Hdy.{William Hardy} Sg.{Arthur F. Sidgreaves - MD} c. to wor.{Arthur Wormald - General Works Manager} E.{Mr Elliott - Chief Engineer} Ev.{Ivan Evernden - coachwork} Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}9/KT.2.3.31. X3S31 X2200 MAYBACH DOGS. With reference to your Da{Bernard Day - Chassis Design}/Hdy.{William Hardy}1/20.2.31. We discussed with Dr. Maybach in Berlin the points you raise in your memo. He gave us the following information - (1) The Maybach type of dog was apparently tried before he recently took an interest in it. It failed because the troubles which were encountered, and which we have recently encountered, with the neutral position, defeated those who were experimenting with it. Dr. Maybach's patent is apparently entirely the elimination of the neutral position. He states quite definitely that he knows no way of making the change work satisfactorily with a neutral position; he knows of the Chrysler attempt and considers it was fore doomed to failure. The Chrysler Co. have not, we believe, ever fitted a box of the type they sent us as standard. Dr. Maybach does not consider that rounding the teeth as you suggest would give any good results. He has tried it out. (2) Maybach's are now using a very small face angle which apparently depends exactly on what is found most desirable by experiment but looks less than 5°. It is certainly very quiet when a one ratio change is made but naturally becomes less silent when changing from top to bottom. However this is not of great importance being a freak condition. The dog can always be made to click if a bad change is purposely made, but it is inconceivable that anyone could for long persist in doing the wrong thing as the necessary operation is so simple. (3) We agree that increasing the number of dog teeth would reduce the jar of which you complain, but we think this jar mainly occurs when the clutch is used, as in the true Maybach scheme it is very difficult to reproduce the trouble (7 teeth). We did not, during our tests, observe any evidence that the dogs were not fully engaging. The low inertia of the 12 cyl. unit may assist in reducing any shock of engagement. (4) One would assume that Maybach's could use a lighter spring pressure for engagement than we can because there is no neutral position. In practice the clicking is not very noticeable and the clonk when the dogs go home is actually negligible. (5) As the clutch is never used with the true Maybach change, the question of a clutch stop does not arise. | ||