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).
The development and testing of Armstrong dampers, detailing issues and modifications.
| Identifier | ExFiles\Box 152\2\ scan0003 | |
| Date | 6th July 1937 | |
| -2- At the moment we see no basic fault in the Armstrong damper and if development continues at the present rate of progress we should be in a position to order production quantities at the end of this year As up to this year Gordon Armstrong has only had damper experience in production quantities of a smaller inferior damper which is standard equipment on Ford and Morris 8 HP. and, 10 HP. cars, a large amount of development work has been necessary in order to make this new damper stand up to our very high loads. Originally we had intended that the Armstrong damper should be used for Bentley only, however, in view of the advantages gained by the customer (such as the reduction of knocks) with such a saving in cost, the damper has been developed to be suitable for all our chassis. In order to reduce development time, the specification for the latest Armstrong dampers has been made generous rather than run the risk of experiencing trouble for additional saving of 5/- per damper. This further saving can easily be made at a later date. DEVELOPMENT The following development work was done in order to get 50 hrs. life on the bumper using 300 lbs. ball pin load and 3" cams. (1) The first pair of dampers as Fig.A. were fitted to the bumper chassis. The main shafts broke after 4 mins. and 4 1/2 mins. (2) The new pair of dampers had:- (a) Nickel steel shafts replacing mild steel. (b) Hobbed serrations to avoid the undercut which is necessary with broached serrations. (c) Spring loaded valves to replace orifice restriction. Fig.1. The outer valves were slightly noisy on the rig. New valves with a longer taper gave no improvement. Finally the inner valve seats cracked on the bumper. (3) Spring loaded valves having half the effective area were tried. These were less noisy on the rig, but the inner valve seat cracked on the bumper. (4) The rear dampers on 3.B.LV. for 15,000 miles in France had the following specification:- (a) Mazak die cast casings. (b) 2 bolt fixing. continued | ||