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 instruction on the formula for correcting Brake Horse Power (B.HP) for atmospheric temperature and pressure.
| Identifier | ExFiles\Box 37\3\ scan 115 | |
| Date | 3rd September 1917 | |
| E.S.1.Technical Instruction No.1. Issue No.1. Circular No. 676. To Officers i/c Districts. and Sections, Engine. Aeronautical Inspection Dir: 3-6, Clements Inn, Strand. W.C.2. 3rd Sept: 1917. H.P. CORRECTION FOR ATMOSPHERIC TEMPERATURE & PRESSURE. It is assumed that under ground level conditions, the B.H.P. of an engine varies directly with the density. Therefore the B.H.P. will vary directly with the barometric pressure and inversely with the absolute atmospheric temperature. The formula for correcting B.H.P. to Standard Density (dry air at 760 mm. and 16°C) will be as follows:- 1. H.P.= B.H.P. x 760/p x (273 + t)/289 where p = barometer pressure in m/m.{Mr Moon / Mr Moore} and t = temperature in °C. Reducing the equation we get H.P. = B.H.P. x 760/289 x (273 + t)/p 2. = B.H.P. x 2.63 x (273 + t)/p where p is in mm. and 3. = B.H.P. x .1035 x (273 + t)/p where p is in inches. To convert °F to °C the following formula may be used:- 4. Temp.°C = (t °F - 32) x 5/9 (contd) R.R. & A.{Mr Adams} 1770 (S.D. 147) P-1-17. G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 1965 | ||