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Bletchley · 26 November 2007, 01:44 PM

Andrew Nahum, 'The rotary aero engine' (HMSO,1987) states that the BR2 was rated at a nominal 200 hp, normal max. power was 230 hp at 1300 rpm, but it had a "maximum output of over 230 hp". So, I would guess the answer is:

Nominally 200 hp at 1250
Normal maximum 230 hp at 1300
Full maximum (a few minutes only) 234 hp at 1350

Bletchley

The BR1 was nominally 150 hp at 1250 rpm (Air Board figure, but Nahum has 158 hp at 1250 although I think this may have been the high compression version of this engine), but it could reach 1300 rpm 'for a few minutes only' (Air Board), although I have no figure for the hp at this engine speed. In his memoirs W.O. Bentley stated that a further 11 hp was gained by drilling a small hole in one of the induction pipes of the BR1, and "We sent the word round and fitters on every B.R. squadron were soon busy with little 2-mm drills" (Bentley, W.O. The autobiography of W O Bentley, Hutchinson, 1958).

The Clerget 9BF that Bentley was associated with also produced more power than it's nominal 130 hp. Gwynnes rated it at 150 hp, although it appears to have produced 'only' 140 hp at normal max. speed, 1250 rpm, 160 hp for 'a few minutes only' (compared to 134 or 135 hp at normal max. speed, 150 hp for a few minutes only, for the original French built Clerget 9B). Gwynnes Ltd, Clerget patent aero engines, 9b & 9BF, 1917 (reprinted by Camden Miniatures, 2001).

Graham Mottram, Director of the Fleet Air Arm Museum, has written a useful pamphlet 'W.O. Bentley's aero-engines' (W.O. Bentley Memorial Foundation, publication no.3, 2003), that has a lot of very useful information on the BR1 and BR2 and Clerget 9BF.

26 November 2007, 01:44 PM	#4
Bletchley Forum Ace Join Date: Feb 2005 Location: Cowes, England Posts: 634	Andrew Nahum, 'The rotary aero engine' (HMSO,1987) states that the BR2 was rated at a nominal 200 hp, normal max. power was 230 hp at 1300 rpm, but it had a "maximum output of over 230 hp". So, I would guess the answer is: Nominally 200 hp at 1250 Normal maximum 230 hp at 1300 Full maximum (a few minutes only) 234 hp at 1350 Bletchley The BR1 was nominally 150 hp at 1250 rpm (Air Board figure, but Nahum has 158 hp at 1250 although I think this may have been the high compression version of this engine), but it could reach 1300 rpm 'for a few minutes only' (Air Board), although I have no figure for the hp at this engine speed. In his memoirs W.O. Bentley stated that a further 11 hp was gained by drilling a small hole in one of the induction pipes of the BR1, and "We sent the word round and fitters on every B.R. squadron were soon busy with little 2-mm drills" (Bentley, W.O. The autobiography of W O Bentley, Hutchinson, 1958). The Clerget 9BF that Bentley was associated with also produced more power than it's nominal 130 hp. Gwynnes rated it at 150 hp, although it appears to have produced 'only' 140 hp at normal max. speed, 1250 rpm, 160 hp for 'a few minutes only' (compared to 134 or 135 hp at normal max. speed, 150 hp for a few minutes only, for the original French built Clerget 9B). Gwynnes Ltd, Clerget patent aero engines, 9b & 9BF, 1917 (reprinted by Camden Miniatures, 2001). Graham Mottram, Director of the Fleet Air Arm Museum, has written a useful pamphlet 'W.O. Bentley's aero-engines' (W.O. Bentley Memorial Foundation, publication no.3, 2003), that has a lot of very useful information on the BR1 and BR2 and Clerget 9BF. Last edited by Bletchley; 26 November 2007 at 02:14 PM.