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 detailing the diagnosis and resolution of a persistent engine misfiring issue in a demonstrator vehicle.
| Identifier | ExFiles\Box 174\2\ img222 | |
| Date | 9th November 1937 | |
| NEW YORK SALES SALON 10 EAST 57TH STREET CABLE ADDRESS "ROLLIC" NEW YORK ELDORADO 5-2605 J.{Mr Johnson W.M.} S. INSKIP, INC. AUTHORIZED RETAILERS FOR THE UNITED STATES ROLLS-ROYCE & BENTLEY MOTOR CARS NEW YORK SERVICE DEPOT BY AUTHORITY OF ROLLS-ROYCE, LTD. ENGLAND BREWSTER BUILDING, LONG ISLAND CITY STILLWELL 4-3240 Long Island City November 9, 1937 Mr. E.{Mr Elliott - Chief Engineer} A.{Mr Adams} Robotham Rolls-Royce Ltd. Derby, England. Dear Mr. Robotham: You are no doubt aware from Lewis' report that we had a considerable amount of trouble with the demonstrator due to periodic misfiring and even changed all the rocker arms and bushings which were sent from England, but the trouble still persisted. After Lewis left we had a number of failures of the car on important demonstrations due to the fact it would run perfect for a while and then commence to misfire causing very unpleasant vibrations. Although we removed the cylinder head and ground in the valves and did everything possible, this trouble still recurred. Finally we came to the conclusion that evidently this was caused by the fact the oil pressure in the plungers operating the eccentric bushing built up to such an extent that it pushed the bushing too far ahead to enable it to recover. This would apparently occur when the valves were late in closing due to probably a tendency to stick on weakening of the valve springs. We finally overcame this trouble definitely with the demonstrator and have had no further recurrence of it by fitting a plate and a set screw, sketch of which is enclosed. This set screw does not interfere with the normal operation of the valve mechanism in any way. It is simply used for the purpose of a stop after a full movement of the eccentric has taken place. In other words, the valves with the plungers depressed are set with the usual .014 clearance and operate in the normal way. The adjusting screw on the plate is set to give additional .001 or .002 clearance after the .014 clearance has been taken up in the regular manner by the hydraulic plunger. This simply prevents the eccentric bushing from being pushed further up and over centre in an endeavor to follow the valve if it should be sticking and be late in closing. We had to carry out this work on several cars in New York including the Baker car, which customer I believe you met abroad. The fact that this seems to take place after the car has done a few thousand miles seems to indicate that it is due to sticky valves or weakening of the valve springs. It occurs mostly after the car has been run in New York at low speed and under heavy traffic conditions. On the open road where one is able to drive at high speed this is less likely to happen. -OVER- | ||