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 Ferodo Limited discussing the results of tests on a brake servo motor with different linings, RAD.13 and Ferodo Fibre 239A.
| Identifier | ExFiles\Box 141\3\ scan0207 | |
| Date | 30th August 1933 | |
| x719. All Communications to be addressed to the Company. FERODO LIMITED BRAKE & CLUTCH LININGS CHAPEL-EN-LE-FRITH, VIA STOCKPORT, ENGLAND. TELEPHONE: 19 CHAPEL-EN-LE-FRITH (4 LINES) TELEGRAMS: FRICTION, PHONE, CHAPEL-EN-LE-FRITH. CODES: WESTERN UNION FIVE LETTER EDITION, BENTLEY'S COMPLETE & 2ND PHRASE, MARCONI INTERNATIONAL, LIEBER'S CODE, LIEBER'S LATEST CODE, A.B.C. 5TH & 6TH EDITIONS. Depots:- LONDON 222, TOTTENHAM COURT RD W. 1. ABERDEEN 26, GUILD STREET. BELFAST 8, 10 & 12, MONTGOMERY ST BIRMINGHAM 202, CORPORATION ST BRIGHTON 84, QUEEN'S ROAD. BRISTOL 19, PARK STREET. CARDIFF 39, CHARLES ST DUBLIN 120, UPPER ABBEY ST GLASGOW 70, WATERLOO ST LEEDS 25, HUNSLET RD LIVERPOOL 1-3, BERRY STREET. MANCHESTER 32, CATHEDRAL ST NEWCASTLE-ON-TYNE WORSWICK CHAMBERS, 10, WORSWICK ST OFF PILGRIM ST August 30th 1933 YOUR REF. OUR REF. FJF/WAC. Messrs. Rolls-Royce Ltd., DERBY. Dear Sirs, BRAKE SERVO MOTOR. We have pleasure in confirming that your Mr. Grylls called here yesterday and witnessed a number of tests of the servo motor with linings RAD.13 and Ferodo Fibre 239A. As expected, the last named erected higher torques than RAD.13 and in this regard we are quite at a loss to account for the substantial difference that was observed, for with F.F. 239A the ratio out-put to in-put was 2.2 : 1, 2.3 : 1, 2.4 : 1 with approximate pulls of 120, 240 and 360 lbs respectively - whereas with Ferodo RAD.13 the ratio was reduced to 0.8 : 1. Assuming in the case of Ferodo Fibre 239 A µ = 0.46 then the lowest value of Ferodo RAD.13 was µ= 0.19 and this is difficult to appreciate in view of substantially higher values of similar material in other applications. For example, in the direct torque test µ equalled 0.3. Reference may also be made to two peculiar features evidenced during the test with Ferodo RAD.13, namely the two facts - 1. torque did not appear proportional to pressure. 2. torque did not fall appreciably with operating pull reduced by some 33% and the retrograde movement was only observed when nearly two-thirds of the weight had been removed. Nothing of this kind occurred with Ferodo Fibre 239A. Referring to the clutch linings mentioned in your letter of the 22nd instant, Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}3/MA, there can be no question in regard to the presence of oil in each of the four discs, for we were able to extract all the lubricant and gave the product to Mr. Grylls. The amount collected represents just half the total content of oil or grease and would, of course, be effective in substantially reducing the friction value. | ||