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 Cresswell's Limited discussing the co-efficient of friction for their 'Chekko' asbestos brake linings.
| Identifier | ExFiles\Box 26\4\ Scan148 | |
| Date | 1st December 1921 | |
| CONTRACTORS TO THE LORDS COMMISSIONERS OF THE ADMIRALTY, THE INDIA OFFICE & WAR OFFICE. ALL COMMUNICATIONS TO BE ADDRESSED TO THE COMPANY. Cresswell's Limited SPINNERS & MANUFACTURERS OF PURE ASBESTOS, OIL BLENDERS AND CHEMICAL MANUFACTURERS. SOLE MAKERS OF CHEKKO PURE ASBESTOS BRAKE & CLUTCH LININGS. WELLINGTON MILLS, BRADFORD. ALSO AT 11 BOTHWELL STREET, GLASGOW. BALTIC BUILDINGS, GLOUCESTER PLACE, SWANSEA. 44 & 45, EXCHANGE BUILDINGS, NEW ST.{Capt. P. R. Strong} BIRMINGHAM. IN YOUR REPLY LG. GAB 11221 REFER TO STENOGRAPHICAL & CLERICAL ERRORS SUBJECT TO CORRECTION. PRICES SUBJECT TO CHANGE WITHOUT NOTICE, SALES SUBJECT TO STRIKES AND CAUSES BEYOND OUR CONTROL. ORDERS OR QUOTATIONS IN THIS LETTER OR CONTRACT WRITTEN HEREON ARE NOT BINDING UNTIL ACCEPTED AT THIS OFFICE. TELEGRAPHIC ADDRESS: "ASBESTOS," BRADFORD. A.B.C. CODE 4TH & 5TH EDITIONS. TELEPHONE No. 950. Messrs. Rolls-Royce Ltd., Nightingale Road, Derby. December 1st, 1921. Dear Sirs, We thank you for your letter of the 30th ult and also for your order No. 6865 which shall have our best attention. With reference to the question of the Co-efficient of friction of Chekko, we may say that as the result of a considerable number of tests conducted during the last two years, we find that the value of 0.35 - 0.40 may be accepted as a safe working value. When Chekko is first fitted the co-efficient may be as high as 0.6 but this is only quite temporary and it's value rapidly drops to a remarkable constant quantity. We have our Chekko fabric working on differential brakes on a certain drop forge plant and the makers of this plant, who have done a lot of experimental work, confirm our statement about the constant value of the co-efficient of friction of our fabric. Our method of testing the fabric varies but we generally test for co-efficient of friction on a special machine fitted with an un-anchored band brake. The ratio of the tensions on the ends of the band is noted and also the angle of embrace between the band and the drum. We then calculate the co-efficient as follows:- T₂ = T₁ ε^µα or nat log T₂/T₁ = µα P.T.O. | ||