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).
Promotional leaflet for the 'Dobie-McInnes' 'Farnboro' Electric Indicator, detailing its use with time-base diagrams for high-speed engines.
| Identifier | ExFiles\Box 165\4\ img378 | |
| Date | 14th December 1934 | |
| CIRC. 16 A.{Mr Adams} "DOBBIE-McINNES" 'FARN'BORO' ELECTRIC INDICATOR FOR HIGH SPEED AUTO AND AERO ENGINES EXTREMELY LARGE TIME BASE DIAGRAMS The invaluable services of this indicator, so frequently commented upon by Consulting Engineers, Engine Designers and other authorities—see references in our Catalogue—are once again emphasized in the Technical Press. The ‘Farnboro’ Indicator diagrams and extracts reproduced below from “The Characteristics and Performance of Oil Engines of Lanova Design,” by Dr. S. J.{Mr Johnson W.M.} Davies, “Engineering,” vol. cxxxvii, p. 559 et seq., 30 Nov. and 14 Dec., 1934, illustrate some of the many important uses of the instrument, the sensitivity and accuracy of its recording and the valuable information obtainable. Under the heading “Special Tests,” the author states :— “A claim which the designers make is that the pressures in the main combustion chambers, and thus on the running gear, are “relatively low at all loads. This matter is obviously of the greatest possible importance . . . and the “author considered it essential to investigate the matter with the aid of ‘Farnboro’ Indicator Diagrams.” Fig 10. DIAGRAMS UNDER VARYING LOAD. CONSTANT SPEED: 1400 R.P.M. [Diagrams Section] Top-left diagram: NO LOAD B.M.E.P.= 0 Lb. per Sq. In. Bottom-left diagram: FULL LOAD B.M.E.P.=89.0 Lb. per Sq. In. Top-right diagram: HALF LOAD B.M.E.P.=44.5 Lb. per Sq. In. Bottom-right diagram: OVERLOAD B.M.E.P.=109.2 Lb. per Sq. In. [Second set of diagrams] Main Combustion Chamber - FULL LOAD B.M.E.P. = 89.0 Lb. per Sq. In. (Peak at 570) - OVERLOAD B.M.E.P. = 109.2 Lb. per Sq. In. (Peak at 624) Air Chamber - HALF LOAD B.M.E.P. = 44.5 Lb. per Sq. In. (Peak at 788) - OVERLOAD B.M.E.P. = 109.2 Lb. per Sq. In. (Peak at 1062) Y-Axis for all diagrams: Lb. per Sq. In. Fig. 10 shows four pairs of ‘Farnboro’ diagrams taken by the author with varying load at constant speed; for reproduction purposes the scale has been greatly reduced since the indicator is actually capable of records 7¾ in. high × 14½ in. long. He continues:— “These diagrams are extremely interesting. They show that the pressure even with overload reaches “the low value of 624 lb./sq. in. Apart from the values of the pressures reached in the auxiliary chambers, it is | ||