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 from Thos. Firth & Sons detailing the design of 20/25 HP Front Flexible Road Springs.
| Identifier | WestWitteringFiles\W\May1931-August1931\ Scan065 | |
| Date | 29th May 1931 | |
| COPY. THOS FIRTH & SONS LIMITED NORFOLK WORKS SHEFFIELD. Messrs. Rolls-Royce Ltd., Nightingale Road, D E R B Y. May 29th, 1931. 20/25 HP. Front Flexible Road Springs. For the attention of Mr. Harvey Bailey. Dear Sirs, We give below particulars of the further alternative design of these springs to your ideas contained in your letter of 21st inst., signed by Mr. Robotham. These springs are referred to in Mr. Stanfield's letter of even date. | Plate Nos. | Thickness Inches Finished | Lengths Inches | Ecc. Dist. Ins. | Trial Radii Ins. To Template | Remarks. | |---|---|---|---|---|---| | 1. | .30 | 38+2eyes | 1.0 | 180 | Span 38 ins. | | 2. | .16 | 36.0 | .95 | 20 | Width plate 1¾ ins | | 3.X. | .16 | 31.7/8 | .84 | 20 | Load 700 lbs | | 4. | .16 | 27.3/4 | .74 | 20 | Free camber 4.5 pos. | | 5. | .16 | 23.3/4 | .64 | 20 | Loaded " .5 pos. | | 6. | .16 | 19.7/8 | .54 | 20 | Deflection due to load 4 ins. | | 7.X. | .16 | 16.0 | .44 | 20 | | | 8. | .16 | 12.1/4 | .35 | 20 | Clip plates marked X. | | 9. | .16 | 8.1/2 | .25 | 20 | | | Totals | 1.58 | | | | | Please note that :- (1) Range of stress in Mainplate to the loaded position. = 43 Tons per sq.inch. (2) Range of stress in Mainplate to the maximum bump position = 69 Tons per sq.inch. P.S. Above mainplate thickness is ground flat. Other plate thicknesses are concave buffed. Yours faithfully, THOS. FIRTH & JOHN BROWN LTD | ||