Document QXaDxzrOQKoL1VDdxmXX8yrw6

Johns-Man vi iLE SALBS CORPORATION PACKINGS AND FRICTION MATERIALS DIVISION CHESTNUT STREET AT FOURTH PHILADELPHIA 6, PA. TELEPHONE: WALNUT 2-5000 The Mall Building July 17th 1962 General Electric Company Salem, Virginia ATT*i J. 0* Copland KE: JOHNS MfiHVlEEE STILE 1202 BRAKE BLOCKS BONDED TO STEEL BACKXSO PLATES Gentlemens- You -will -undoubtedly recall giving car Mr* 0, T Ghalloner during the latter part of June a bonded assembly taken from a get of blocks returned to you by one of your customers* The blocks in this set indicated that they -were starting to debond* The saaple assembly you gave to Mr* Ghalloner was forwarded to our Waukegan Factory for their observation and comments and the following is quoted from their report, "The sample block has been examined and it appears that high temperatures plus shock leads has caused a partial debonding* As to the maximum temperature the bond will withstand, it varies with the length of time at which it is subjected to that temperature* For example, to debond the brake blocks, 600F for 30 minutes is enough to destroy the cement* At *>.006F, it takes about 2 hours and at li*foF about 2h hours* At the lower temperature, -Die cement- is not actually destroyed, but it becomes brittle so that a sharp blow cad shatter it -and separata the brake bluuk frum1 the MBtftl J The temperature we are talking about Is the temperature at the bond, not the temperature at the surface of the block* To get such high temperatures at the bond in service would require extended or prolonged friction heat -that could be severe enough to destroy the binder in the brake block itself, especially -When one considers the mass of metal available in the brake assenfoly to absorb and dissipate the heat* The surface of the senile block is badly heat checked and does show evidence that it had been at a high temperature for a considerable time* Ws vo&ld assume that at that time the brake gave off considerable smoke which should hare been quite evident to the operator* lb. answer to your question as to what is the maximum safe operating temperature and still maintain a satisfactory bond. $ PLAINTIFF'S ( EXHIBIT I usV'fi2/6ZI PLAINTIFF'S EXHIBIT GEWVOCT04-011751 WV-21521 Page #2 we can only say that at any time the natal plate to which the brake block is bonded is over k50F, there will be a weakening of the bond. If this happens repeatedly or frequently, then there is a hazard of the block debonding completely. The ridge along one edge of fee brake block is an impression from the bonding jig cavity,, The mold is designed about l/fl" shallow so that there will not be any mstal-to-metal contact when the jig is under pressure, Very slight flow of the Untwg stock under the bonding pressure sometimes occurs into this unconfined space, leaving a small ridge such as was evident on this sample block. It is not a defect and in no way affects the performance of the material". life trust that the foregoing will provide you with the information you requested. Yery. truly yours 0. BOSCH, District Sales Manager Packings and Textiles Department GEWVOCT04-011752