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).
Engine 'chunking' issues, automatic chokes, and silent tappets, with comparisons to Packard, Buick, and Cadillac vehicles.
| Identifier | ExFiles\Box 173\4\ img162 | |
| Date | 16th January 1938 | |
| -3- and that automatic chokes are now electrically operated and take a continuous current from the battery. Under bonnet temperature but not exhaust heat is the other controlling feature. CHUNKING Packards say chunking, can sometimes be overcome by altering the engine mounting frequency. They cured a car some time ago by this method. On their 12 cyl. they go to extreme measures to have no backlash in top gear and reduce it in 2nd gear by the ball bearing mounting of the free pinions with no end play and an eccentrically adjustable side shaft for pitch line slack. The car we tried chunked loudly if the engine were switched on and off in 2nd gear, but due to the new pushpot throttle control, not at all under ordinary driving. This last method they lock on as the only cure and state that hypoids are worse than spiral bevels. So far Buicks are the only cars free from this trouble. They will not pass any car with more slack at one rear wheel than .750, the other wheel stationary. From the figures I took on our Buick the total slack in the axle was about 1/10way of our cars. Further information from Packards - (1) For excessive engine movement when idling they use on the 12 a soft main mounting and side feet of rapidly increasing rating. (2) The volumetric efficiency of the 12, at max. power is 62% the same as all the U.S. side valve engines. (3) Cadmium lasts no longer than white metal and has corrosion troubles. Silent Tappets Cadillac expect us to have trouble with the valves being held open on a cold morning unless we have at least 1.0 thou. plunger clearance. Their production test is by the rate of fall of the plunger under a given load based on the time of a satisfactorily operating unit. | ||