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 effects of a bent shaft or worn bearing on engine timing in Bentley distributor heads.
| Identifier | ExFiles\Box 61b\2\ scan0272 | |
| Date | 30th October 1935 | |
| Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Wst. Hs{Lord Ernest Hives - Chair}/Wst.6/MA.30.10.35. AFFECT OF BENT SHAFT OR BADLY WORN BEARING IN BENTLEY DISTRIBUTOR HEADS. According to a test carried out on the bench rig, a difference in the contact gap of .015" would alter the engine timing by 10°, and for a difference of .010" an alteration of 7° was obtained. In the case of a badly worn bearing, no difference in timing would be noted because the spring loading of the contact finger would take up the play equally on each cam lobe. If the shaft was bent from the bottom of the cam, by approx. calculation 1° shaft bend would give a maximum alteration in the gap of .00275" on say, 6 and 1 cylinders less on 3 and 4 cylinders and practically none on 2 and 5 cylinders depending on the position of the bend, so that a severe bend would alter the engine timing. For a 1° shaft bend, the rotor blade spark tip would move a distance of .022" and as only .005" clearance is allowed, between the rotor blade and H.T. points in the distributor, it will be seen that before any difference could be noted in the engine timing, the rotor blade would be fouling the H.T. points. We do not consider therefore that the bent shaft would seriously affect engine timing if no evidence of damage to the H.T. rotor was noticeable. Hs{Lord Ernest Hives - Chair}/Wst. | ||