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).
Hispano cylinder construction, detailing their nitriding process, materials, and design features.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan039 | |
| Date | 20th December 1930 | |
| -9- Hispano Cylinder Construction. The Hispano liners are all nitro hardened and a really excellent job. They say they passed through a lot of trouble with the nitriding of cylinders due to distortion before they reached the present perfection. The correct temperature during the nitriding is very important and they operate at about 500°C. The surface is afterwards ground producing a surface like a mirror. I have not previously seen such an excellent finish to cylinder liners. We examined the surface through a magnifying glass just as a liner came off the machine and failed to see the slightest scratch mark. They experienced considerable trouble at first in obtaining suitable stones for grinding the hardened surface due to their quickly wearing before completing the job. Only a very small amount is ground away - the process resulted in more of a burnished finish than a ground finish. I examined the cylinder liners taken from the engine with which Costes and Bellonte flew to New York in the Breguet and did numerous other flights in America. They were in excellent condition and not a single score, scratch or hard mark was visible. They also say that no wear was detected. The Hispano liners were of a much thicker section than ours - 50% thicker at least I should judge - and the same thick section was continued right down to the end of the skirt. The outside was ribbed very closely about every 3/8" right down to the rubber ring. The top of the liner screws into the cylinder head for somewhere about 1" and pulls up on a shoulder at the base of the thread. Two soft rectangular black rubber rings forms the seal at the base of the liner. These rubber rings appear of similar material to the familiar square rubber strands used for catapults. The width looked about .10" and depth about .25". One ring is above the other and pressed up by a plain non-split steel ring which is pushed up by a screwed gland ring which screws on the liner. The bridge pieces between the bores in the cylinder block appeared no thicker than in our blocks. There was appreciable clearance between the metal of the liner and alum block - I should judge about .020. The liners we saw from engines which had run were quite free from any distortion marks in the bedding which we associate with ours. We have appended a print of the construction. | ||