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 test results and performance issues of brake linings for a servo motor.
| Identifier | ExFiles\Box 141\3\ scan0214 | |
| Date | 27th September 1933 | |
| All Communications to be addressed to the Company. x719. 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, BENTLEYS 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 72, 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 September 27th 1933 YOUR REF. Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}5/KT. OUR REF. FJF/WAC. Messrs. Rolls-Royce Ltd., Derby. Dear Sirs, We duly received your letter of the 13th instant and should have replied earlier but we thought it desirable to run a further series of tests before doing so. This, we trust, will explain our omission. Referring to the second paragraph of your letter, we found when we were testing Ferodo Fibre H.D. discs, that µ rose substantially at comparatively high temperatures accompanied by noise more of the nature of a groan than of squealing. This, unfortunately, appears to be a common feature when µ is of the order of 0.6/0.7 and where relatively heavy torques are produced. In the course of our further investigations we have tried six different types of lining but find that, for some reason not easy to explain, µ always appears to have a lower value than obtains in any other application and always substantially higher values are given at the maximum temperature reached. This may be attributed to the increased pressure produced by the expansion of the fabric, since in other applications the tendency is for µ to fall at the temperature reached, i.e. about 500° F.{Mr Friese} The best results so far obtained, apart from material Ferodo Fibre H.D., is given by one of our special types of lining, S. 3914. With this, µ cold is 0.3 rising to 0.33 at approximately 400° F.{Mr Friese} These values are probably on the low side since there must be some considerable loss of power in the levers connected to the end of your ball crank lever. Taking direct readings, we find with S.3914 that, with a weight giving a steady pull of 300 lbs on the end of the lever connected to the cam lever, the servo erected a torque of 810 lbs-ins, but when the weight was operated in the same manner as when one applies the brake pedal, the torque increased to 1350 lbs-ins, giving approximately 654 lbs circumferential resistance at the mean radius of the servo discs. This was the best figure we could get from any of the materials tested. Actually, we are at a loss to suggest any type of material other than Ferodo Fibre H.D. that will give a consistent µ of approximately 0.4 in connection with your servo motor. Yours faithfully, FERODO LIMITED. (Signature) H.{Arthur M. Hanbury - Head Complaints} J.{Mr Johnson W.M.} Field / wab CHIEF ENGINEER. | ||