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).
Letter comparing Bentley and Packard dampers, American vs. European car characteristics, and Girling brakes.
| Identifier | ExFiles\Box 127\1\ scan0231 | |
| Date | 10th July 1935 | |
| -2- Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}10/KW.10.7.35. If we compare our Bentley damper with the figures of the Packard damper which you sent to me, we have a rating of flexibility whereby the inertia is driven by the crankshaft at 79 lbs.in./degree as against 1000 lbs/in./degree of the Packard. The damping load on the Bentley is 310 lbs.in. against 180 lbs.in. on the Packard. The inertias of the two dampers are much the same. From these figures it would appear that we are using much more damping than you are to kill our crankshaft period. Nevertheless, we are going to get one of your dampers and put it on one of our engines, and then we shall be able to give you more information. With regard to brakes, when we have our own 120 Packard we shall be able to give you some first-hand information. If you come over here, however, I think we shall have no difficulty in convincing you why our rate of wear is so much higher than you get in the States. My brief period of "sub-zero" motoring in America left me with the feeling that American cars are exactly right for American conditions, but that on the whole they are not suitable for European roads with regard to steering, road holding and brakes. Their merits with regard to smoothness, silence, roominess and comfort, however, are such that American cars are sold over here in quantities. The reverse is certainly true, that English cars are totally unsuitable for American conditions. I am sending you some particulars of the Girling brakes. I am more in favour of the layout from the pedal to the operating cam than I am of the operation from the cam to the shoes. Being a floating fulcrum brake, one shoe is self-energising. We always try and avoid this because self-energising means that any variation in 'u' due to oil, or brakes fading, is more noticable than with a shoe which has a minimum wrapping tendency. I do hope that you will manage to get over to Europe this Summer. I am sure that if you want to sell Packards over here, your visit will pay a good dividend! Yours sincerely, Natural period of damper of 100 lbs in^2 at 1000 lbs in / degree is 75~/sec | ||