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).
Gas leakage issues with non-gas-retaining split type pistons causing noise and fumes.
| Identifier | ExFiles\Box 35\2\ scan 198 | |
| Date | 6th February 1920 | |
| EH. from EP.{G. Eric Platford - Chief Quality Engineer} c. to Bn.{W.O. Bentley / Mr Barrington} c. to BY.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to E.{Mr Elliott - Chief Engineer} C.K. x 2448 EP{G. Eric Platford - Chief Quality Engineer}19/F6.2.20. X 3432 RE LEAKAGE PAST THE PISTONS. X.858 We have been concerned with the way in which the present split type pistons are not gas-retaining. The compressions by "feel" are not very good and we have had a number of cases in which, when the engine is running slow speed at full torque, there is a distinctly audible and objectionable noise of the gases, which we have demonstrated to you is caused by the gases blowing past the pistons. We have made a special test case of one engine and have made sure that the piston clearances are satisfactory, also that the rings are a good bed and fit correctly in the grooves, also that the stops are correctly fitted and that the piston ring clearance at the stops is to the minimum drawing dimension. We have also checked that the cylinder bore is correct as regards not being out of truth, etc. and is to the drawing limits. We still find, however, as demonstrated to you on the car this afternoon, that blowing past the pistons is still prevalent, and can be temporarily cured by injecting about half a syring of oil into the cylinder. As requested, I am holding up this car for a further test, in which it is proposed to fix a piston which you will supply, and which will not have the holes drilled under the bottom rings. I am anxious to bring this to your attention as I feel rather concerned, as the question of pistons being gas-retaining is a feature which has been brought to our attention as being a decided improvement with the present type of piston, which, according to the actual cars we have produced and tested, does not appear to be the case. We certainly know from past experience that if this is the case, the engine will be inefficient from the point of view of HP and consumption, and there is also a tendency to overheat, unsatisfactory piston lubrication, also the gases blowing past the pistons causes foul gases to get into the body, which on the present cars I consider is worse than on pre-war cars. On a covered body even though the floor boards may be well fitted, the fumes in the body, which we have traced to this source, are very objectionable, and I feel sure we shall sooner or later have complaints. Also could not larger vents be fixed (running out through the undershield) Gases now collect and as the passage is not so clean under the floorboards (starter and dynamo) are drawn through the floorboards. P.T.O. | ||