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).
Proposal to have the top of the piston eccentric with the skirt to keep the piston head axial with the cylinder centre line.
| Identifier | ExFiles\Box 66\1\ scan0182 | |
| Date | 19th October 1928 | |
| E c. Hs.{Lord Ernest Hives - Chair} X8040 BY5/G.19.10.28. PISTONS. RE.R'S PROPOSAL TO HAVE TOP OF PISTON ECCENTRIC WITH SKIRT. -------------------------------------------------------- In the above suggestion it is evident that R.{Sir Henry Royce} is aiming at keeping the head of the piston axial coincident with the cylinder centre line. I have gone carefully into the whole matter and attach hereto a sketch showing the relation of the skirt to the head in order to attain this result. You will notice that the axial centre line of the head for the Phantom lies .0025" on the opposite side of the centre line of the top of the skirt from the split, and that the axis of the skirt is inclined to the axis of the head. This result has been arrived at by starting with the cylinder wall on the unsplit side of the piston as a datum and working outwards from this point gives us the above figure. It is evident from going fully into the figures that our present piston head is roughly .0025" out of centre with the cylinder centre line under normal working conditions, and the displacement is towards the side of the piston which is split. In arriving at this figure the water in the cylinder jacket is taken at 90°C, the temperature of the piston at the top of the skirt by experiment has been determined at 135°C, and at the bottom of the skirt at 124°C. With this information at your disposal you can if you wish, check my results. You will observe that the amount is as I suggested before, small, and that further it is somewhat complicated by the fact that the axes of the skirt and the head are inclined to one another. I ought to add that on a properly bedded piston the dimension for the top of the skirt is 4.245" and for the bottom of the skirt 4.250". The 20 HP. piston will be pro rata to the above on cylinder diameter ratios. BY.{R.W. Bailey - Chief Engineer} By [Sideways Stamp: COPY NUMBER 10] | ||