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 adaptation of a 3-pen chronograph for the measurement of braking performance.
| Identifier | ExFiles\Box 29\1\ Scan235 | |
| Date | 22th July 1926 | |
| Contd. -2- Hs{Lord Ernest Hives - Chair}/RmL/T22.7.26. Adaptation of the 3-Pen Chronograph to the Measurement of Braking Performance. The adaptation of the three-pen chronograph for making braking tests entirely eliminates all personal errors. Normally, when measuring the distance to rest, after the application of the brakes, a number of personal factors are liable to cause errors. Some of these are - (1) The difficulty of determining the exact moment when brake pedal is depressed. (2) The difficulty of reading the speedometer correctly. (3) The difficulty of determining exactly where the test started on the road. In addition actual measurement of distances to rest is a laborious proceeding. Before the electrical measurement of braking, the contact on the wheel actuates one chronograph pen once per wheel revolution. If the front wheel is likely to be locked a small independent wheel is fixed to the axle. A second contact operates another pen when the brake pedal is depressed. A third pen indicates 1/10 seconds. The instrument is switched on some two seconds before the brakes are applied. The number of wheel contacts made after the brake pedal has been depressed, gives the distance to rest, the front tyre being pumped hard, (to eliminate centrifugal errors) and its effective dia, being known. The fraction of a revolution which the wheel makes past the contact on stopping can be measured when the car is at rest. Contd. | ||