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 to the A.T. Speedometer Co. regarding failures with speedometer trip gears.
| Identifier | ExFiles\Box 59\2\ Scan088 | |
| Date | 17th November 1930 | |
| 84308. Expl. Dept. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} 3/MJ. November 17th.1930. The A.T.Speedometer Co., Chronos Works, North Circular Road., London.N.W.2. Dear Sir, The majority of complaints about speed-ometers appear to be due to the failure of the trip gear. We have not been able to get hold of any actual cases of this failure, but we have been able to examine several of the older type speedometers used by us for test purposes, also some of the latest type now being delivered with chassis. In both cases, in our opinion, the drive of the trip gear is not a very satisfactory job judging from the number of cases of our test speed-ometers which have done considerable mileage. We consider there is not sufficient provision made for thrust on the vertical shaft which drives the trip, in consequence of this the end play which develops in this shaft allows the fibre worm gear to partly run out of mesh with the driving worm, and in some cases less than 50% of the tooth is engaged, this leads to very rapid wear and the trip then goes out of action. Another trouble with the later type of speed-ometer is that owing to poor provision for thrust when the speedometer is run in the reverse direction, it is possible for the worm wheel fitted to the end of the trip gear shaft to jump and mount the top of worm gear on vertical shaft. This has the effect of jamming the whole speedometer, and if the speedometer flex does not give way, the fibre wheel on top of vertical shaft must do so. Contd......... | ||