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).
The wear of Wraith timing gears.
| Identifier | ExFiles\Box 107\2\ scan0161 | |
| Date | 11th April 1938 | |
| To Ms. from RM{William Robotham - Chief Engineer}/PJH. G.{Mr Griffiths - Chief Accountant / Mr Gnapp} Fry. C. Riv. C. H.{Arthur M. Hanbury - Head Complaints} C. EX. C. Oli. C. Da{Bernard Day - Chassis Design}/Ins. C. RM{William Robotham - Chief Engineer}/MyB. WRAITH TIMING GEARS. We give below the information we have obtained so far on the wear of Wraith timing gears. At the completion of 21,000 miles the gears of 26.G.VI had developed backlash varying from 0.012 to 0.025 on the pitch line resulting in very bad gear rattle. The gears were to the following particulars:- Camwheel. Moulded Coarse mesh Fabroil. Crankpinion and dynamo pinion. Soft Steel. Helix angle 41°. Camshaft balancing cam plungers removed. Original backlash 0.000 - 0.001. Judged by visual examination the steel gears appeared to be unworn. All the wear is on the camwheel and the maximum wear occurs in six patches round the gear. The attached table shows the approximate wear of all Wraith units together with particulars of the gears and running to date. Apart from the recent French test unit the three units Nos. 1, 2 and 5 have an outstanding amount of wear. These have all had more high speed running than the remaining units. From this we conclude that the serious wear of the Fabroil gear occurs at high speeds. Units 1 and 5 have had the camshaft balancer fitted throughout their running, so that results do not appear to confirm that the balancer is of assistance to wear. The irregular nature of the wear indicates alternating loads. These can arise from - (1) Camshaft torque variations due to valve inertia. (2) Crankshaft torsional vibration. (3) An oscillation in the timing train itself, including the dynamo. By/B. has produced curves of camshaft torque due to inertia of valves plus gas pressure on exhaust valves and inertia | ||