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).
Various methods of applying heat to engine manifolds and induction pipes.
| Identifier | ExFiles\Box 50\3\ Scan036 | |
| Date | 25th March 1921 | |
| Oy4 - G 25321 Mr. Claude Johnson - Sheet 2. (2) Methods of applying heat: (a) The Marmon - An early method of applying heat was one in which exhaust gases were taken from the exhaust manifold through a pipe about 1" diameter to a jacket round the throttle. This is seen on the Marmon. (b) The Hot Spot - The next method was the "Hot Spot" originating in the Chalmers, about 1915, and now extensively adopted. Several photographs of engines with pipes of this type have been sent to Mr. Royce. The Hup. is typical of this design. We are informed that on the later Hup engines the hot plate is covered with an asbestos sheet, on the exhaust side, having a small hole about 3/8" dia. at the centre, so that the temperature is highest in the centre and diminishes towards the edges. It is sometimes necessary, on individual cars, to alter the size of this hole to obtain the best results. Presumably the location of the hole is intended to be opposite the liquid petrol which is streaming up the centre of the pipe. We do not know whether the Hup we beat-over has the device in this form. As we have written to Mr. Hives, our attempts at obtaining a hot spot at the Tee junction were unsuccessful owing apparently to some stratification of gas in the manifold, which gave us preignition in cylinders 2 and 5, and at the same time liquid petrol into cylinders 1 and 6. (c) The Through Pipe: We have found that the 1" through pipe with interchange of exhaust heat between the two exhaust boxes has given us consistently good results and no pre-ignition. A print of this was sent to Mr. Hives on March 3rd. (d) Vee Engines: The method of heating the induction pipe by inter-change between the two exhausts is practiced on the 8 cylinder Vee engines. Mr. Royce will see the Lafayette design in the "Automobile Engineer" of March, and the similar scheme used on the Cadillac is shown on the Cadillac folder sent to Mr. Hives on Mar. 7th. | ||