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).
Calculation of the moment of inertia and centre of gravity for vehicle 9.B.V.
| Identifier | ExFiles\Box 100\1\ scan0259 | |
| Date | 20th July 1939 | |
| 446 450d. Rm{William Robotham - Chief Engineer}/HFP.3/MH.{M. Huckerby}20.7.39. 6'1/2 2.S.W 4.9 11. C.V. MOMENT OF INERTIA OF 9.B.V. Experiments were carried out to determine the Moment of Inertia of 9.B.V. and the height of the centre of gravity above the line of the wheels. The following figures were obtained:- Weight on front wheels - 1893 Weight on rear wheels - 2029 Total weight - 3922 Wheelbase - 124" This gives centre of gravity 59 3/4" from rear axle. The car was made to pivot about a point 7" below the centre line of the wheels and 33" in front of the rear axle. The front of the car was supported on a spring having a rate of 270 lbs/inch and acting on the frame 97 1/4" from the point about which it was made to pivot. The periodic time under these conditions was .748 secs. This gives a moment of inertia about the axis of the pivots of 97,100 lbs.ft2. The front of the car was placed on the scales and weighed, the back of the car was then raised through 23° 16' giving a weight transference of 110.5 lbs. This was repeated with the rear of the car on the scales giving a weight transference of 114 lbs. for an angular movement of 23° 30'. The mean of these results gives the height of the C of G above the centre line of the wheels as 8.35". This gives the moment of inertia of the car about its C of G as 71,300 lbs.ft2. All these figures are indicated on the accompanying sketch. Additional data - Inertia of wheels - 41.85 lbs.ft2. Unsprung mass including wheels - front 260 lbs. total rear 410 lbs. total Spring rates at wheels - Front N.S. 130 lb/in. O.S. 135 lbs/inch. Rear N.S. 150 lb/in. O.S. 155 lbs/inch. Rm{William Robotham - Chief Engineer}/HFP. | ||