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).
Design notes and specifications for the 'Goshawk 11' rear road spring, including load calculations.
| Identifier | ExFiles\Box 49\3\ Scan022 | |
| Date | 2nd February 1921 | |
| To Da.{Bernard Day - Chassis Design} from E.{Mr Elliott - Chief Engineer} c. to CJ. c. to Wor.{Arthur Wormald - General Works Manager} c. to Hs.{Lord Ernest Hives - Chair} c. to By.{R.W. Bailey - Chief Engineer} c. to EFC. X4261 E2/G2.2.21. x.4263/4. RE "GOSHAWK 11" REAR ROAD SPRING. N. SCHEME 727. Referring to the above, Mr. Royce has, as you are aware, increased the length of the rear springs from 50" to 56". He has also increased the width from 2" to 2¼". We send you herewith drawing Lec.1341, which gives some notes on the rear spring, as follows:- (1) MAXIMUM SPRING FOR "GOSHAWK 11". The heaviest "Goshawk 11" spring required should be designed for a load equivalent to a four-seated landaulet having one or perhaps two occasional seats four people including drivers, petrol, oil, and one spare wheel on rear of car, and water. With the car thus loaded, it is expected that the load on the rear wheels will be twice that on the front. Weight of chassis------------- 18 cwt. " " body, wings etc.--- 9.2 " " " four people--------- 6.0 " (4 - 12 stoners) " " petrol, oil,& water 1.3 " (3 gals. water 2gals. oil, 12 gals petrola) " " spare wheel---------- 0.5 " Total for car loaded as above 35 cwts. Weight on one rear wheel = 35 / 3 = 11.66 cwt. = 1300 lbs. Half weight of rear axle, road wheels & springs etc. = 200 lbs. Weight carried by one rear road spring = 1100 lbs. (2) MOST EFFICIENT SPRING. To design the most efficient spring, i.e. the lightest spring that will do the work apart from damping effect, the stresses in the spring leaves should be identical from nothing up the maximum. This, it is thought, would be obtained if all the leaves were of equal thickness, other requirements being neglected. A spring that had leaves of greatly varying thicknesses or that is put together with great differences of set in the leaves will not have uniform stress and will be big and heavy for its work. (3) CURVATURE AND LEAF THICKNESS. The radius of curvature of the spring leaves in the bump position is not the same for each leaf and if Contd. | ||