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).
Engineering test procedure outlining the method for conducting a skid pad test on a chassis and analyzing the collected data.
| Identifier | ExFiles\Box 155\4\ scan0060 | |
| Date | 1st March 1939 guessed | |
| E.R. 51. VAUXHALL MOTORS LIMITED ENGINEERING TEST PROCEDURE CHASSIS SCHEDULE No. H.1. SHEET No. 4. Handwritten: 2/6 SUBJECT SKID PAD TEST PROCEDURE ( Contd.) As it is very difficult to read the theodolite scales when the car is running, the car is stopped after each run. Readings of the speed, front wheel indicator, steering wheel indicator, horizontal and vertical angles of the theodolite are made for each run and entered on the data sheet. Runs are made at approximately 2 1/2 mile increments of speed starting at five miles per hour and increasing to as high a speed as possible consistent with holding the car on the circle and taking readings. TREATMENT OF TEST DATA. Speed in miles per hour is obtained from (T) the stop watch time for driving one lap of the 108 ft. radius circle. Miles per hour = (5280 x 60) / (2 x 108 x 3.14 x T) = 463 / T Both front wheel indicator readings should be tabulated and the average readings plotted. Steering wheel angle should be divided by the overall steering ratio in the straight ahead position and plotted. The roll angle indicated on the theodolite vertical scale should be correct as read but may need slight zero correction, although the initial outward roll and return ( see page 2) should help to avoid this. Too much reliance should not be put into readings taken at low values of side thrust, due to friction in spring bearings and between leaves. The roll angle will be greater when driving in left hand turns than in right, due to the engine torque in cars with rear axles. In cars with independent rear suspension, the roll angle in right and left turns should be equal. The attitude of the car in the horizontal angle as read by the theodolite and may require slight zero correction. FRONT SLIP ANGLE ( Sheet 13) Front slip angle Ø1, equals the sum of the steering angle Z and the attitude angle A minus the ackermann angle X. Ø1 = Z + A - X The steering angle Z has been found from the test runs. The ackermann angle X is the acute angle of a right angle triangle with the radius of the driven circle ( 108 ft.) as the adjacent side and the wheelbase (w.b.) of the car as the opposite side. Tan X = w.b. ( inches) / 1296 Signed __________ Dated __________ Approved __________ | ||