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 memorandum discussing failures and issues with speedometers, particularly the trip gear.
| Identifier | ExFiles\Box 59\2\ Scan086 | |
| Date | 1st November 1930 | |
| Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer} c to Hs{Lord Ernest Hives - Chair}/GWH{George W. Hancock - Head Chateauroux} c to WSRH from Mr Archer. X4308. RECEIVED LA{L. A. Archer}2/T1.11.30. SPEEDOMETERS. Hv5/T28.10.30. The majority of complaints about speedometers 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 a number of cases of our test speedometers 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 speedometer 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 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. We have had some cases of speedometer trouble due to oil going up the drive from gear box, and to overcome this a modification has been carried out in the gear box to carry away the oil. Since this modification was incorporated, we have had no further complaints of this trouble. LA{L. A. Archer} C. Daykin | ||