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).
Wheel balancing tests for 33 x 6.75' tyres, focusing on inner tube joint positioning.
| Identifier | ExFiles\Box 4\3\ 03-page67 | |
| Date | 26th November 1926 | |
| To EY. from Hs{Lord Ernest Hives - Chair}/AJL. 4401 x401 x4565 4457 WHEEL BALANCING (33 X 6.75" tyres). We have carried out tests to investigate the advantages gained by using inner tubes in which the joint in the tube is opposite the valve, as compared with the previous type of inner tube in which the position of the joint was not definitely fixed in relation to the valve. It is possible to change the tube in a balanced wheel fitted with the former type of tube and only upset the balance by a maximum of 3 to 4 ozs., whereas, when changing the latter type of tube the consequent out-of-balance can be as much as 10 to 12 ozs. The outer cover of course in each case is replaced after changing the tube, in the same position relative to the wheel, as before changing tubes. The tubes with the joints opposite the valve therefore are a very definite advantage in this respect. Initial balancing. The use of tubes having the joint opposite the valve necessitates a different wheel balancing scheme. The present scheme embodies a plate fixed in the rim opposite the valve of a weight sufficient to balance the valve, in addition to three bolts for carrying balancing weights. It is almost impossible to balance a wheel fitted with a tube which has the joint opposite the valve, if the existing balancing scheme is used. The heaviest part of the tube (i.e. the joint) coincides with the plate fitted in the wheel to balance the valve, producing a large out-of-balance at a point where it cannot be counteracted by the application of an equal weight diametrically opposite owing to the disposition of the balance weight bolts and the large weight required. The following conditions are necessary for the easy balancing of wheels when fitted with tubes having the joint opposite the valve :- (a) Removal of the existing plate opposite the valve. (b) Addition of a plate weighing 7 ozs. at the valve. This balances up the wheels and tube to within one or two ozs., the remaining balancing necessary being very easily obtained (and with the use of very little weight) by the use of the existing balance weight bolts. ktx contd :- | ||