Failure of a Wraith speedometer drive due to seizure, corrosion, and lack of lubrication.
| Identifier | ExFiles\Box 8\11\ 11-page129 | |
| Date | 15th October 1938 | |
| 628 To By & Rm. {William Robotham - Chief Engineer} ..from RHC. {R. H. Coverley - Production Engineer} c. HS. {Lord Ernest Hives - Chair} c. IA. c. HFB. RHC. {R. H. Coverley - Production Engineer} 2/MD.15.10.38. SPEEDOMETER DRIVE - WRAITH. We are informed by JLE. {J. Lee Evans - Chassis Test Manager} that a Wraith Speedometer drive has failed, due, it is understood to seizure occurring between the driven gear and its bearing. The Gearbox in question is being removed and returned to Derby, and after examination it will be possible to give a more detailed report of the trouble. We have however removed the speedometer gears and bearings from a number of Wraith cars in the Test Department, and find these parts to be badly corroded due to condensation, whilst in addition the outer bearing has apparently received no lubrication since initial assembly. Although we have heard of no actual seizures at Derby, it is quite understandable that failure could occur under these conditions. The speedo drive is of generally similar design to PH.III but incorporates aluminium bearings for the gear spindle as compared with bronze on PH.III, and it may be considered that aluminium bearings are more likely to seize in the circumstances, especially since the bearing in question has only .0005 diametral clearance. An oil trough is provided in the bearing but this is masked in almost every case by the gearbox casting bore, and in any case there are no signs that lubricant has reached the area in which this trough lies. It is thought that a solution may be provided by incorporating slots in the gear adjusting washer bore which will enable lubricant to pass along the shaft and reach the bearing, whilst in addition it appears that a more adequate breather is required to combat condensation. RHC {R. H. Coverley - Production Engineer} , | ||
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).