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).
Technical page discussing and illustrating torsional deflection tests on automobile chassis and complete cars.
| Identifier | ExFiles\Box 154a\2\ scan0005 | |
| Date | 1st January 1939 | |
| January, 1939 HARSHNESS IN THE AUTOMOBILE 5 Fig. 3 - To obtain the deflection characteristics of the chassis so that they would be comparable with those of the complete car, the frame was loaded as shown for the twist test. DIAGRAMS: [Top Diagram - Frame Twist Test] ANGLES ARE TOTALS OF TWIST, BOTH DIRECTIONS FROM ZERO AND ARE DIRECTLY COMPARABLE WITH COMPLETE CAR TEST FRAME-PROOF LOAD DIAGRAM of TORSIONAL DEFLECTION ORIGINAL POSITION ---- DEFLECTED POSITION -- -- OVERALL LENGTH-166 IN. (A-O) STATIONS SPACED AT 12 IN. TOTAL TWIST-7º28' TOTAL WEIGHT OF FRAME, FIXTURES AND LOAD - ONE-HALF WEIGHT OF COMPLETE CAR AND PASSENGERS SUPPORT REMOVED CAR TREAD FRONT REACTION (1/4 OF FRONT AXLE) - ONE-HALF FRONT REACTION OF COMPLETE CAR AND PASSENGERS [Bottom Diagrams - Beam Loading] THE FRAME - BEAM LOADING THE COMPLETE CAR DEFLECTION CURVES BEAM LOADING CHASSIS FRAME ONLY THE COMPLETE CAR - IDENTICAL LOADING TO THAT FOR FRAME Fig. 5 - The X-brace type chassis frame contributes as little as 25 per cent to the resistance to either twisting or beam deflection of a complete car. MAIN TEXT: carries the entire load is seriously in error. It may have been that, several years ago, the rigidity and strength contributed by the body to the complete assembly were accidental but, in recent years, this function of the body has been recognized and structural principles have been applied in its design. Calling upon the body to carry its share of the load is sound in principle and permits economical design. Depth of the body can be utilized to attain a structure that is far more rigid than that which any frame alone, within reasonable proportions, can provide. Test methods have been set up, designed to establish the contributions of body and frame units to complete car rigidity. The complete car has been used as the test specimen because many makes and models thereby are made readily available, and deflection characteristics can be obtained without injury to the car. The chassis frame is compared with it. Car tests and frame tests must be identical if the results are to be given credence. For test purposes, the car is brought up to road weight plus passengers by adding lead weights on the seats. The car is raised onto wheel blocks and, for the twist test, diagonally opposite wheels are lowered until one wheel hangs free. This is a front wheel on conventional cars where the center of gravity is to the rear of the wheelbase midpoint. It can be shown easily that this set-up introduces into the car structure a couple equal to one front-wheel reaction times the tread. Reference points are established at 12-in. increments along the frame rails, and measurements from these points are taken to the floor for both the unloaded and the twist positions. Fig. 2 shows the test method and results given as angles of twist at the 12-in. increments along the car. For comparable tests of chassis frame, the test frame is fitted with dummy springs and axles and supported at the wheel locations. The section is brought up to one-half of road weight plus passengers by adding lead weights distributed along the span and the front reaction is checked against one-half the reaction of the actual car. Twisting is introduced by removing one support. Similar measurements are taken and the results, multiplied by 2 to bring them up to full weight, are shown on Fig. 3. The one-half road weight is used because, in some cases, the full load is too severe for tests of the frame alone. Fig. 4 compares elevation diagrams (side views of the structures as distorted by twist load) of the frame and complete car. For normal symmetrical beam load (a test condition to which has been applied the term “equal wheel”), lead weights are added to the complete car duplicating all the sprung weights. motor, body, frame, seats, passengers, and so on. The deflection curve due to these weights is established. Exactly the same weights with exactly the same distribution | ||