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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).
Page of calculations and design considerations for vehicle leaf springs.

Identifier  ExFiles\Box 43\2\  Scan203
Date  28th September 1937 guessed
  
- 8 -

.218 plates. stress - 81,420 lbs/in²
Modulus - .0158
Bending Moment - 970 lbs.ins.
Overhang - 970/615 = 1.580"

.187 plates. stress - 63,030 lbs/in²
Modulus - .0117
Bending moment - 738 lbs.ins.
Overhang - 738/615 = 1.200"

The overhangs are marked on the above spring diagram.

The rear of the spring is then treated in the same way.

To reduce this to practice:-

(a). Half an inch is added to the nominal length of each plate-end to represent the occurrence of the bedding point ½" from the tip.

(b). The plate lengths are approximated to the nearest ⅛"

(c). The second plate is made longer than theory to bring the support under the eye as close as possible.

(d). On the plates where rebound clips are required, these plates are lengthened the minimum amount which will provide clearance for the clip. (with the present English type of clip, using forged ears, this is unnecessary, and the spring is undoubtedly improved by omitting all such excess metal.)

It will be found that the shorter plates become much shorter than conventional practice, for example the 14th plate above will be only about 6" long overall, whereas common practice would make it 9" to 13" long.
We have found that plate lengths proportioned this way do make the spring lie flat.

Bedding.

With our almost square tips as compared with the old pointed and tapered ends it was found that the circular curve had to be modified to prevent separation of the leaves as below at the ends when spring was flat.
  
  


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