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).
Letter discussing a sample four-speed transmission with Maybach clutches and instructions on its operation.
| Identifier | ExFiles\Box 137\5\ scan0106 | |
| Date | 25th October 1930 | |
| X3720. P. O.{Mr Oldham} Box 109, Detroit, October 25, 1930. Messrs. Rolls Royce, Inc., Derby, England. Gentlemen: Attention of Mr. E.{Mr Elliott - Chief Engineer} W. Hives. Some time since you received word from Mr. Olley that you woud be sent the prints of some four-speed internal gearing transmissions made by Chrysler Corporation for their new lines of eight cylinder cars, and that you woud also receive a sample transmission made from one of the designs shown by the prints. The sample transmission which we had made up for you differed in one particular from the print. Insted of having the interrupted tooth clutches between the third and fourth speeds, it has the clutches invented by Dr. Maybach of Maybach Motorenbau of Friederichshaven, Germany, whom you undoubtedly know as the builders of the Zeppelin engines and the Maybach car. These Maybach clutches have the peculiarity that they will not engage, as they are used in our transmission, until the two jaws are in synchronism. The clutch has no effect in producing synchronism, which must be done by the driver by means of controlling the engine speed, but the clutch will select the instant of synchronism and then instantly engage. In driving the car, one accelerates very gradually to go into third speed and takes the foot off the accelerator pedal to go into fourth; in both cases after shifting the clutches into neutral position and then pressing the jaws to be engaged very lightly together to catch the slight buzzing noise of the overtraveling jaws in contact. We have provided a weak spring interposed between the shift rail and the clutch fork to give this gentle buzzing sound and so indicate that the jaws are in position for engagement as soon as this is made possible by the proper change in engine speed. If one accelerates the engine first and then tries to go into third, the engagement occurs with a bang, while if one accelerates before trying to engage fourth speed, the soft buzz continues until the engine speed has been allowed to come down to synchronism with the propeller shaft. You will soon get on to the operation of the job by driving it and will discover that the best shifts can be made by neglecting the operating clutch of the car entirely and making engagements only with the Maybach clutches between third and fourth speeds. These may be disengaged very redily by operating the accelerator while pulling gently on the shift lever and disengaging at the instant of tork reversal in the clutch jaws. If the engine is pulling the car, release the accelerator pedal; if the car is pulling the engine, touch the accelerator - either way will release the clutch, depending on the direction of applied tork, and the clutch may be disengaged without using the operating clutch of the car at all. | ||