Quote:
Originally Posted by Bletchley
...I am fairly sure that the figures for rotary engine hp would have been without any losses for windage.
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I fear it's not so. Report No.448 by Technical Department at the Air Ministry, May 1918, it's not clear about; B.R.1 is credited with 150 HP at 1250 RPM and then are sperimented losses for windage, leaving to think 150 HP is "gross" power output. Do you think, or have evidence that B.R.1 could otherwise develop about 180 HP inclusive of windage? In addition (and again): why B.R.1 powered Camel should have same speed of Clerget powered one, with 24 HP more?
Frenchs, OTOH, seem to have the habit to give "net" horsepowers. I think the guys of Air Board used loosely a mix of "net" and "gross" power outputs, reporting french test bench results literally, without converting to british units and, as mentioned, "net" of windage, while B.R.1, perhaps the sole british-built original rotary and tested in britain, retained its "gross" horsepower.
And what about germans?
Quote:
Andrew Nahum ('The rotary aero engine', HMSO, 1987) quotes S D Heron, who was with the RAE/AID at Farnborough, as saying that the 'rotary engine builders objected strenuously to the power of their engines being determined on the dynamometer. They insisted that torque stands should be used. On a torque stand, the very considerable windage loss due to rotating the cylinders was recorded as useful horsepower'. I think this must have become the standard way of recording output from rotary engines.
Bletchley
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I would be explained what a "dynamometer" is intended in previous quote: as a mechanical engineer, I don't know any device to measure power different from "torque*RPM" system, where torque is measured by just a dynamometer (more precisely a brake, a water brake, I think, at that time).
Thanks as always for your big help.
GB