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).
Instructions on machining and fitting bearing shells, shims, and connecting rods.
| Identifier | ExFiles\Box 115\3\ scan0032 | |
| Date | 11th August 1937 guessed | |
| -2- "Give + 1/2 thou. limit to the diameter of the shell. Machine the outside diameter by grinding to the same dead size as the housing of the rod. Machine the bearing flange to suit your own dimensions then saw the bearing in two halves. Both the joint face of the rod and the face of the cap to be machined by .050 so that when .100 thickness of shims are fitted, the rod comes back to the original diameter. This operation should of course be carried out very exactly and checked by gauge before commencing to fit the actual bearing shell. When this is done the bearing halves are 'topped' respectively to the rod and the cap and left to stand proud by 1/2 thou. (.0005), no more. This allows for a definite nip of the actual shells which is important, but must not be overdone by any more than the above figure, otherwise the bearing will be overcrushed and distort. When assembled in the rod [REDACTED] the bedding between the back of the bearing and the rod housing to be checked over to see if O.K. In its finally assembled form the bearing is diamond bored to give a diametrical clearance of .002 on the crankpin. For this diameter of bearing, the clearance limit should be between .002 and .0025. If for any reason you cannot adopt our method of shims then we send this precaution. The outside dia. of the shells we are sending you is only .040 in excess of your final detail drawing, so that when you sawcut this should be as fine as possible in order that the outside diameter of the shells is still in excess of your required diameter for machining. Your letter of the 10th inst. has now come to hand and seeing that we cannot carry out the final machining, all the details of fitting and clearance etc. have been covered by our letter. Regarding your bolt centres, this is O.K. and the grooves can be machined as shewn on your drawing, as in conjunction with the shims this is our standard practice. The shims will be despatched tomorrow and may be .001 or .002 over the .100 which can be carefully fetched down to match up exactly with the .050 you will machine off the rod face and the same amount off the cap face. They will require drilling for your bolts and conforming to the external shape of your rod. These are diamond bored in position with the bearing shell. Yours faithfully, FOR ROLLS-ROYCE LTD. | ||