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).
Letter from Boulton & Paul discussing motor horsepower, velocity, and the power factor formula for a jet.
Identifier | ExFiles\Box 27a\3\ Scan182 | |
Date | 31th March 1931 | |
X45161 BY APPOINTMENT BOULTON & PAUL LIMITED. NORWICH. FOUNDED 1797. WIRE NETTING DEPARTMENT 139, QUEEN VICTORIA STREET, LONDON, E.C.4 TELEGRAMS: 'BOUTIQUE, CENT, LONDON' TELEPHONE: CENTRAL 4642. 16, BATH ROW, BIRMINGHAM. TELEGRAMS: 'BOULTON, BIRMINGHAM' TELEPHONE: MIDLAND 3381. 8-11, PAVILION BUILDINGS, BRIGHTON. TELEGRAMS: 'BOUTIQUE, BRIGHTON' TELEPHONE: BRIGHTON 3284. G.{Mr Griffiths - Chief Accountant / Mr Gnapp} P. O.{Mr Oldham} BOX 3799T, SYDNEY, N.S.W. TELEGRAMS: 'BOUTIQUE, SYDNEY' P. O.{Mr Oldham} BOX 904, JOHANNESBURG. TELEGRAMS: 'PROSTEEL, JOHANNESBURG' TELEPHONE: CENTRAL 7500. CODES:- A B C (5TH & 6TH EDITIONS) BENTLEY'S COMPLETE PHRASE CODE BENTLEY'S SECOND PHRASE CODE MARCONI, Etc and PRIVATE. TELEGRAMS: 'BOULTON, NORWICH' TELEPHONE: NORWICH 851. DIRECTORS: CAPT. J.{Mr Johnson W.M.} D.{John DeLooze - Company Secretary} PAUL. W. H.{Arthur M. Hanbury - Head Complaints} FFISKE. O.{Mr Oldham} E.{Mr Elliott - Chief Engineer} FFISKE. R.{Sir Henry Royce} SNOWDEN. J.{Mr Johnson W.M.} D.{John DeLooze - Company Secretary} NORTH, F.R.AE.S., Etc. ALL QUOTATIONS SUBJECT TO USUAL STRIKE AND ACCIDENT CLAUSES TO WITHDRAWAL OR ALTERATION WITHOUT NOTICE TO APPROVED QUANTITIES AND SPECIFICATION. ALL COMMUNICATIONS TO BE ADDRESSED TO THE COMPANY AND NOT TO INDIVIDUALS. Our Reference M.8608 Telephone Extension 78 Your Reference HS{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/KT Date 31st March, 1931. [STAMP: RECEIVED 1 APR 1931 HS{Lord Ernest Hives - Chair}] Messrs. Rolls-Royce, Ltd., DERBY. For the attention of Mr. Robotham. Dear Sirs, In reply to your letter of the 26th instant, we repeat that we should expect a 30 h.p. motor to give in the jet we drew for you with the right propellor, a velocity of 64-65 m.p.h., and you ought by a safe overloading of the motor to get 75 m.p.h. which you desire. We cannot agree that 130 h.p., or anything approaching it, would be necessary. I have taken a figure of .68 for what Wind Channel experts all over the world call the power factor, and it may be of interest to you to know that a recent open jet 5-ft.wind channel installed at Farnborough had actually a power factor as low as .38 and giving a speed of 100 m.p.h. with a 50 h.p.motor. The power factor is defined as - HP x 550 / (1/2 p A V³) where A = area of jet in sq. feet V = jet speed in feet per second p = air density = 0.00237 slugs so you will see that the smaller the power factor the higher is the efficiency of the outfit. With regard to falls in velocity along the jet, experience shows that you will not have a drop of more than one or 2 per cent in 10 feet travelling along the 5 ft. square jet. Yours faithfully, for BOULTON & PAUL LIMITED. A.G. ODGERS. AGO/BC. | ||