Brake system adjustments, testing of Tee lever offsets, and suggestions for redesign.
| Identifier | ExFiles\Box 12\5\ 05-page123 | |
| Date | 12th July 1929 guessed | |
| (3) Since this time (the Fall of 1927) we have succeeded pretty well in keeping clank out of the mechanism by keeping the front brakes set up fairly close and the rear brakes fairly slack (i.e. not less than .700 movement at the ends of the actuating levers on the rear axle.) (4) But the depots tell us this setting will not always stay put, and also some owners insist on a very close setting of the brake pedal which is not possible under above conditions. We have now just concluded a test in which the pivot of the Tee lever was offset 1.175 upwards so that the vertical arms, instead of being each 3.925 long, were 5.100 long at the bottom and 2.750 at the top. This makes it possible to operate the brakes without clank when the front brakes are adjusted one notch "loose" and the rear brakes set normally. (5) That is to say that with above brake adjustments the actual center of rotation of the Tee lever is about 1" above the standard pivot center and about .175 below our new pivot center. We think it would be well to go further and make the pivot center 1" higher i.e. make the two vertical arms 1.750 at top and 6.100 at bottom. (6) In this case we believe it will be found that the actual center of rotation of the Tee lever, with the worst condition of brake adjustment which would ever be met in practice, will be slightly below the pivot center, and therefore no clank will occur. It will be noted that the position of the pivot center in the Tee lever has no effect on the proportion of braking front and rear, except a very slight difference in the effect of the damping friction at the upper end of the Tee lever suspension link. So that in case of any redesign it would seem preferable to have this lever in the form of an inverted "L" with the pivot center coinciding with the jaw at the front end of the rear brake pull rod. See SK-846 attached. Very truly yours, ROLLS ROYCE OF AMERICA, INC. | ||
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).