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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).
Fundamentals of body construction, including load distribution and bending moments.

Identifier  ExFiles\Box 14\8\  Scan290
Date  23th June 1930
  
( C O P Y )

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June 23, 1930.

To: Mr. Olley
From: Mr. Burton
Cc- Mr. Beck
Mr. Ainsworth

FUNDAMENTALS OF BODY CONSTRUCTION

We are now experimenting with some bodies supported only on two points each side -

Forward - 15" behind dash - using standard subframe mounting brackets.
Rear - as near as possible to axle - using the same brackets.

An investigation of the loads on the sill gives figures shown on SK-403 and SK-404.

We believe that our fundamental requirement is to produce a sill that under existing conditions of loading will take up when deflected a uniform curvature throughout its length, and that this condition will produce in general the least destructive strains on the coachwork structure. This condition is satisfied by keeping the factor -

M/EI

constant throughout the length of the sills, and this is the basis on which the following investigations were carried out.

Distribution of load.

As basic assumptions we take -

Body weight - 1500 lbs. } Total 2400 lbs.
Passengers - 900 lbs. }
Body base - 120"
Points of support - 15" and 91" from front end.

If we assume a uniformly distributed load, this will give us a rating of 20 lbs. per inch run. On this basis we have plotted on SK-403 -

(a) Bending Moments as shown in curve I reaching a max. +9400 lbs. ins. at 48" back - concave upward and -8400 lb. ins. at 91" back - concave downward, crossing the zero line at 0, 18-1/2, 79 and 120" from the front.

(b) The cube root of the bending moment - curve II - expressed as a percentage of the max. value of this - i.e. at 48" this curve is made to read 100 and all the other ordinates are in proportion, but at the same time making all values positive.

- continued -
  
  


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