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).
Procedure for the torsional stiffness testing of a vehicle frame.
| Identifier | ExFiles\Box 170\2\ img278 | |
| Date | 2nd July 1935 guessed | |
| -2- It is weighted sufficiently to give a twist of say 2½ to 3½ degrees either side of center without lifting at any corner. We start off by loading one scale with say 1250 lbs and the other with 50 lbs and using the jacks till the scale beams float. Then we take four deflection readings. Then we transfer 200 lbs from the one scale to the other and balance again. Read deflections again. Then another 200 lbs and so on till we have 50 lbs on the one scale and 1250 lbs on the other. Then we repeat the test backwards till we come back to the original loading. This job takes about 20 to 30 minutes. Then we work out the full hysteresis loop for the frame. The torque on the frame is the difference in load multiplied by half the distance between jacks, divided by 12, to give lbs feet. The deflection is the difference in reading in inches at either end of the measuring bar, and these are equal to degrees if the distance between measuring points is 57.3 inches. Actually it is only necessary to operate one jack. The other can just as well be a solid block. We plot the results on squared paper like enclosed sample sheet and thus obtain the torsional stiffness overall, from fr wheels to dash, and from dash to rear wheels. These three lines must check between themselves, ie, the deflection (.890 Degrees) of the overall curve must equal the sum of the two deflections (.475 Degrees and .415 Degrees) of the two parts. Any loose rivets or other loose joints show up as definite slips in the curves or as excessive hysteresis loops. The most important thing about all this is that a good frame for a roadster or any "soft-top" car, must be about:- Bet Wheel Planes Dash to R Whs Fr Wls to Dash 2640 4600 6200 344 2.7 Giving with a soft-top body about: 3100 6200 6200 In fact the most important single item is that a good car of any type which will stand up to 25,000 miles on the Proving Ground without cracking up, has to be about 3000 lbs feet per degree between wheel centers. | ||