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).
Technical specifications and procedures for clutch components.
| Identifier | ExFiles\Box 130\3\ scan0052 | |
| Date | 8th February 1939 | |
| -2- We think 1/- is a very reasonable sum for Bonderizing and Enamelling, especially as B. & B. have to send the cover out for this work. An alternative to consider is a blue-black finish, which is standard on all other B. & B. clutches, this appears to prevent rusting, at all events early in life, but the appearance is inclined to be patchy (see sample). ITEM 9. MACHINING OUTSIDE OF COVER PRESSING. 6d. We do not consider this is really necessary either for Long or B. & B. and the shape of the Long pressing does not lend itself to usefully machining the outside, because it would be too springy to use for accurate location. Since the standard practice of B. & B. is to locate off the holes when balancing the assembly, and also when fitted to the flywheel it is solely located by the holes, it appears the most logical thing to use the holes only, and omit the machining of the outside, this is standard practice throughout the world, and has been quite satisfactory on our experimental cars. We note that on the drawing (issued by B. & B.) of the American made Long clutch, the six holes are marked .3130 - .3145, so that if we use KB bolts which are .312 - ½ the minimum slack per bolt would be .001 and the maximum .003, but actually there would be no likelihood of .003 run out, because there are 6 holes all locating. With a clutch weighing 16½ lbs, the out of balance would be approx. ¼ ounce-inch for every .001 run-out, so it does not appear likely that out of balance from location would reach ½ ounce-inch, which is our present tolerance. We recommend the small dowel as at present used to ensure that the clutch is always replaced in the same position. ITEM 10. SELECTION OF COVER & PRESSURE PLATE - 2/6d. This, in the case of the B. & B. clutch, is to avoid the excessive drilling of balancing holes in the pressure plate casting, but in the case of the Long, there appears to be ample scope for drilling in the Long bosses inside the springs, without any risk of weakening the casting, we therefore think this item could be deleted. ITEM 11. SPECIAL METHOD OF BALANCING - 1/-d.{John DeLooze - Company Secretary} This automatically disappears if we agree to delete item 9. | ||