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).
Engine bore wear, material testing methods, and the development and use of cylinder inserts.
| Identifier | ExFiles\Box 132\5\ scan0056 | |
| Date | 11th March 1939 | |
| -4- Further to Helmore's machine. This consists of an aluminium rotor running inside a pot in which is situated our sample of material in the form of a ring about 1.00" wide. The vessel is electrically heated. The rotor is hollow and the same width as our test piece, but there is no metallic contact between the two; actually there is a lateral clearance of .010". Oil is supplied under pressure to feed through holes in the rotor to the space between the rotor and the test piece. In this way Helmore has shown that, by dividing up running time and stopping time, with suitable temperature differences, corrosion takes place to such an extent that it is possible to evaluate various materials in their order of merit re their resistance to corrosive losses. POSITION OF WEAR IN BORE. We know definitely, that about 75% of the total wear in the bore takes place just below the lip at the top of the bore, actually at the point of change over of the top compression ring. Most other firms have the same characteristic, and as a result of this a short insert has been developed which is pressed into the top end of each bore prior to final machining and honing. This insert is about 2" long, and advantages are as follows:- (1) It covers the portion of the bore where max. wear takes place. (2) A high grade of wear resisting material can be used. (3) Advantage can be taken of using centrifugally cast material in conjunction with a sand cast block. We have carried out a mechanical proof test on a test bed engine, and after running 20 hours no ill-effects are evident due to rings passing backwards and forwards over the join. Oil consumption is normal. Actually there are a number of firms already in production with this same insert. There is one snag, and that is cost. The British Piston Ring Co. of Coventry hold patent rights for the manufacture of this sleeve, which is thus known as the "Brico" Short Cylinder Insert. The price they have been charging for trial sets is prohibitive from a production standpoint. This is undoubtedly due to the fact that they have heavy royalties to pay. An investigation is at present being carried out regarding this patent, and patent rights. In the meantime, we are producing our own inserts in | ||