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).
On the automatic brake adjustment for an epicyclic third-speed gearbox.
| Identifier | ExFiles\Box 15\5\ Scan232 | |
| Date | 1st January 1932 | |
| HS.{Lord Ernest Hives - Chair} ) FROM DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} ) E.{Mr Elliott - Chief Engineer} ) X7310 DA{Bernard Day - Chassis Design}1/118.1.32. X.7310 X.7360 C. TO SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} EPICYCLIC 3rd. SPEED GEARBOX. AUTOMATIC BRAKE ADJUSTMENT. The cotton duck appears to be upsetting the operation of this scheme. The number of teeth in the ratchet sets the clearance for the brake when off, and will maintain it within very narrow limits, unless the wear of the fabric is more than the amount replaced by the drawing in of the pawls. In this case the pawl gains on the ratchet wheel until the pawl gives a stroke of two teeth, when the clearance is maintained at twice the original intention. As drawn, the clearance called for is .020 all round, the same as provided on the road wheel brakes, and for a band brake may be considered not excessive. We cannot increase the number of teeth in the ratchet without reducing this clearance. We therefore suggest that the first move is to replace the cotton duck by Ferodo of the kind used on the Daimler epicyclic brakes, without altering the rest of the mechanism at all. But with a given number of teeth in the ratchet setting the clearance it does not matter within wide limits what is the gear ratio between the ratchet and the end of the band. All that would happen if the ratio were very high is that the clearance would for a time be reduced .001 or so below the normal, after each movement of the ratchet wheel, when it would gradually return to normal. The second suggestion then is that Derby should in the meanwhile be preparing a worm and wheel having respectively four starts and twenty three starts, with a view to increasing the ratio if the present is found too low, though with Ferodo we do not think this will be so. DA.{Bernard Day - Chassis Design} | ||