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).
Analysis of throttle spring direction and its effect on bearing loads and throttle spindle wear.
| Identifier | ExFiles\Box 13\4\ 04-page147 | |
| Date | 29th April 1933 | |
| x7080 To E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} c. to BY.{R.W. Bailey - Chief Engineer} c. to MX.{John H Maddocks - Chief Proving Officer} Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}1/KT. 29.4.33. THROTTLE SPRING. P.II. Referring to E.6/HP.29.3.33. The geometry shewn on Lec.3412 is without question what is desirable. The point as to whether the closing spring should pull in the same direction as the throttle suction or not is very interesting, and we have carried out the attached experiments to analyse the results obtained by each arrangement. It will be seen that to have the same certainty of closing the throttle, a 50% stronger spring is required when pulling in the same direction as the induction pipe depression as when pulling against it. With regard to the bearing loads, allowing for the stronger spring required when fitted pulling upwards, we have under idling conditions and full throttle conditions - | Conditions. | Approx. Total Bearing Loads. lbs. | |---|---| | | Full Throttle. | Idling. | | Closing Spring pulling up. | 6.5 | 33.8 | | Closing Spring pulling down | 12.0 | 23.45 | Since full throttle is used for only a small percentage of the running time, certainly not much more than the fully closed position, the gain in bearing wear due to the upward spring load cannot be very much if anything. The leakage in the throttle spindle due to wear is only of significance when idling and whatever the direction of the spring pull, the throttle will be hard against the top surface of the bearing under these conditions due to suction. Considering the three points, therefore, the evidence seems slightly in favour of the downward spring where two carburetters are used, and the accelerator load | ||