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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 memorandum on manifolding and torsional vibrations, with comparative engine performance data.

Identifier  ExFiles\Box 173\1\  img429
Date  10th February 1934
  
-7-
He/Rm.{William Robotham - Chief Engineer}9/KW.10.2.34.

MANIFOLDING.

There is now almost a standardised treatment of the straight eight induction system in which the exhaust and inlet are taken out on the same side and a simple hot spot arranged, with a thermostat controlled butterfly which by-passes the heat when once warmed up. By developing the materials the Americans have made this work every time, siamesed induction ports, four branch pipe for 8 cyls.

This is not bad for M.E.P. because on the Cadillac 16, with a short duration camshaft having accelerations only 80% of ours, a carb. for each 4 cyls, expanding type, induction ports in no way more streamlined than the Bentley and 6.5 C/R, they have the following M.E.P. curve -

R.P.M. 400 800 1200 1600 2000 2400 3600
B.M.E.P. 106 116 120.5 121 122 121 97

For a Rolls-Royce, as opposed to a Bentley, I think this is pretty good. Steaman should be able to show if a siamesed port fundamentally loses any volumetric efficiency.

The M.E.P. for Cadillacs new La{L. A. Archer} Salle side valve eight is definitely down, partly because it is a side valve engine and again partly because it is using a fixed choke carburetter.

La{L. A. Archer} Salle 240 Cu.Inch 6.5-1 C/R.{Sir Henry Royce}

R.P.M. 500 1000 1500 2000 2500 3000 3600
B.M.E.P. 97 103 106 109 105 97 84

TORSIONAL VIBRATIONS. VEE 8 & A LINE 8.

I saw the torsional vibration diagrams of the 8 shaft, particulars of which I have given. The 4 per rev. was at 3,300, the 8/rev. at 1600. I also saw the diagrams of the Vee 8. Curiously enough the 4/rev. period on this shaft was little higher than on the line 8, being about 3,300. There was a 3 per rev. period, presumably caused by inertia and not explosion, at about 4300 and at this speed they fractured several crankshafts.

He/Rm.{William Robotham - Chief Engineer}
  
  


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