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).
The testing of a boxed cross member and a Rover frame stabilizing bumper bar.
| Identifier | ExFiles\Box 3\6\ 06-page252 | |
| Date | 11th October 1934 | |
| -2- (b) Boxed Cross Member between the Headlamps. When the front of the frame vibrates torsionally the headlamps try to move with a similar frequency. As they are supported on relatively long tubes they succeed in twisting the side channel of the frame locally below their point of attachment, and by doing so actually move further than they would if the frame channel section was boxed in. The object of the dropped front cross member was to prevent this local deflection, at the same time it was made torsionally stiff so that it might brace the whole frame to some extent. From the results on our own cars we think that this cross member might be worth standardising, but we were able to try it on the worst customer's car with which we have come in contact, and from the results of this test came to the conclusion that it was too heavy and expensive for the amount of advantage obtained, actually, in conjunction with the stabilising bumper, the torsional stiffness which it adds to the frame appears to be a disadvantage, and we therefore think that we can reduce its weight to about one third of the present figure, 7 lbs., and at the same time increase its effectiveness. This we are doing, and it will be run on the next 10,000 miles test. (c) Rover Frame Stabilizing Bumper Bar. This device was actually invented by Packards about 6 years ago, but the latest in this Country are held by the Rover Company. It consists of a bumper bar at the two outward extremities of which weights are located. These weights are mounted on springs, which springs have a damped movement. By a careful choice of weights, springs and damping it is possible to make this bumper bar oppose the torsional movement of the frame, and in actual practice it does this remarkably well. Several makes of bumper bar are made and originally Messrs. Wilmot-Breeden, the Manufacturers of the bumper under licence, supplied us with one for the 25/30 which weighed over 60 lbs. Since the 20/25 frame movement was not very bad we turned this down on the grounds that it was too heavy. We have been using the Rover stabilizer on the Bentley, however, and this only weighs about 30 lbs. The lightest standard type of bumper obtainable for the Bentley weighs about 16 lbs. | ||