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).
Tests on engine vibration, focusing on damping friction and the effect of piston position and weight.
Identifier | ExFiles\Box 25\3\ Scan143 | |
Date | 20th September 1926 guessed | |
contd :- -5- which vibration was then at a max. but less severe than at 3300 RPM. (5) The damping friction used in case (3) (200 to 300 lbs.ins.) seemed too high to effectively damp out the vibrations due to the explosion pressure harmonics at the lower speeds. As in the case of the Phantom the same applies to the 20 HP. with regard to the erratic torque experienced when the pressure on the friction wheel surface is high. The total inertia of the slipper wheels - apart from the spring drive parts - is .0163 units and a calculation shews us that with this effectively solid on the shaft would account for the critical speed being lowered to 2450 r.p.m. EFFECT OF POSITION AND WEIGHT OF PISTONS ON AMPLITUDE OF VIBRATION. A test was made to compare the effect on the amplitude of the vibration of the whole six pistons and the three rear pistons - 4. 5. and 6. - only. The engine was motored for this test and after taking a diagram the three front pistons were removed. In the latter case the vibration was practically non-existent as will be seen from the appended print. The maximum total amplitude recorded with all six pistons was 8 3/4º while the three rear pistons gave 2 3/4º. This is proof that the pistons farthest from the flywheel are the most effective in the promotion of torsional oscillations. The effect of piston weights on the amplitude was next investigated. For this purpose the tops of the pistons carrying the rings were removed which reduced the reciprocating weight from 1.75 lbs. to 1.187 lbs. Vibration diagrams shewed that this only only reduced the amplitude from 8 3/4º to 7º. contd :- | ||