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).
Comparing the engine smoothness and crankshaft designs of Cadillac and Packard V-12s and V-8s, discussing issues like deflection and bearings.
| Identifier | ExFiles\Box 173\4\ img160 | |
| Date | 16th October 1935 | |
| To MG. c. to R.{Sir Henry Royce} c. to HY.{Tom Haldenby - Plant Engineer} c. to Ndy. c. to Rhu. c. to EV.{Ivan Evernden - coachwork} The following is a memo. received from A/Cry. dated November 1935 :- "By arguing with the Cadillac and Packard people about V-8 and 12's, and by trying the various cars, it seems that a 12 of any V angle will be smoother than the V-8 at low speeds full throttle and also at high speeds due to the lateral deflections in the V-shaft, all of which so far have only 3 bearings. As I wrote in an earlier letter, all the periods in the V-8 vanish with the EXP flywheel. Packards maintain that combustion roughness is due to deflection of the crankshaft at crankcase, and not by making either sufficiently stiff. The 4 bearing Packard 12 cyl. crankshaft weighs 125 lbs. They say that the increased number of bearings in a 7 brg. shaft does not necessarily give greater smoothness unless the bearings are sufficiently stiff. There doesn't seem any doubt that a cast-iron engine is smoother than an alum. construction of the same dimensions. The Cadillac is a smoother engine than the Packard, particularly when run on light water which condition the former is excellent and has none of the periods noticeable in a gearbox. The orthodox V-8 is bad under this test but not when the flywheel runs steadily. On the Cadillac V-12 the torsional period at axle antisqueak was also a lower period is detectable by moving the gear lever. There was too much ice on the road to log the Packard but full throttle low gear is very bad and in their opinion entirely due to the massive crankshaft. Packards were certain the engine is rough because the structure of crankcase and crankshaft is not up to the high compression requirements. | ||