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).
Fault with the 20/25 HP carburetter, its symptoms, and cause.
| Identifier | ExFiles\Box 102\1\ scan0218 | |
| Date | 8th October 1934 | |
| To E.{Mr Elliott - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By c. to Mx.{John H Maddocks - Chief Proving Officer} Carburetter (20/25 HP.) The new carburetter to LOP. E.60092 went into production on 18.7.34, starting on D.2 series, 1st chassis, commencing CYD-22. From the above date until 22.9.34 10% of the carburetters made suffered from a definite fault which was shown up on road test. From 22.9.34 up to 6.10.34 the percentage of faulty carburetters shown up on test increased to 20%. The symptoms of the trouble are recognised in the following way :- Driving a car along a level road and in top gear at a steady 30 M.P.H. the throttle is suddenly snapped open to the full position, and instead of the engine immediately responding, a momentary hesitation is felt. In severe cases, the engine will pop back before picking up. N.B. It was found impossible to reproduce this fault on the test bed. Cause of trouble. Considering the attached sketch, when the throttle is suddenly snapped open (under the conditions previously described), the high depression in the induction pipe (by virtue of the fact that the throttle was previously partially closed) is released and a sudden suction is caused in the carburetter. In the case of a faulty carburetter, the resultant depression is transmitted through the hole at the throttle edge (C) down the passage (2) and by way of the L.S. choke (P) to the passage (3), which leads into the float chamber. In effect, the sudden suction which should draw petrol from the main jet, is actually momentarily holding it back in the float chamber. | ||