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).
Recommendations for a fifth wheel speedometer.
| Identifier | ExFiles\Box 165\2\ img289 | |
| Date | 15th November 1940 | |
| To Rm{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/GB. R H Hyman Please have this Completed. Rm{William Robotham - Chief Engineer} tire Speedometer 6065 Completed. Y Goad 26-11-40 5th Wheel Speedometer. As requested, here are recommendations for a fifth wheel speedometer. This instrument consists of three parts:- 1. The trailing wheel and its associated equipment. 2. The driving cable. 3. The speedo-head and distance measuring counter. These are briefly described below:- 1. A 26" trailing wheel and forks from a brake test rig can be used for this instrument. Since the running boards are disappearing, the wheel and forks could be fixed to the rear bumper, as shown in sketch. It is usual to fit a spring to hold the wheel on the road. This does not prevent excessive bouncing. Damping is usually provided by running the tyre under-inflated. A small Armstrong shock absorber should reduce bounce to a minimum and enable the tyre to be run fully inflated (A small Armstrong shock absorber is available). There is a chain and gears to take the drive to the front end of the forks. 2. A long speedo cable of the heavy type (as recommended by Rm{William Robotham - Chief Engineer}/RC{R. Childs}) would be used to take the drive from the wheel forks to a speedo head situated conveniently for the driver. A fifteen foot cable would be long enough for any car but a Limousine. 3. The speedo cable would be arranged to drive a 5" dia R.R. speedo supplied by Rm{William Robotham - Chief Engineer}/RC.{R. Childs} and a counter supplied by Rm{William Robotham - Chief Engineer}/Clm.{D. D. Clapham} The counter would be fixed in guides and arranged so that it could be slid into mesh as the petrol passed the top mark of the .1 gallon test tank, and out again as the 2nd mark was passed. By this method, there would be no distance readings to take until after the test run. Rm{William Robotham - Chief Engineer}/GB. G.B. | ||