202 Miscellaneous Tmj^lements Exhibited at Doncaster, 1912. 



manufacture and to maintain in use. The temperature of the 

 cylinder quickly attains that of boiling water, and it is a well 

 known fact that this class of engine works to most advantage 

 when fairly hot. There is also less chance of freezing of pipes 

 in winter. A good example of these engines was seen at 

 Stand 339, The Eagle Engineering Company, Warwick. 



Some other engines were noticed with a water cooling 

 arrangement consisting of a cone of wire gauze on to the apex 

 of which the water was pumped after passing through the 

 jacket ; the gauze exposing a large surface to the air while the 

 water trickled over it. This arrangement is not nearly so 

 simple as the one mentioned above, nor in any degree more 

 efficient. It is possible that the "American Invasion," so 

 prominent on Stand 346 of the Associated Manufacturers' Co., 

 London, N.W., is responsible for this innovation. The engines 

 displayed on this Stand are remarkably clieaj^, ranging from 

 161. is. 6d. for 2^ H.P. to 3Sl. for 6 H.P., but as regard finish 

 and design our makers have no need to fear comparison. 



One looks in vain for a great extension of the Diesel or 

 Semi-Diesel system from the engines shown last year. There 

 are a few such engines which claim to work with heavy crude 

 oil. It is well to bear in mind that Semi-Diesel is somewhat 

 of a misnomer. Dr. Diesel's system works with a very high 

 compression necessitating extremely accurate and sound work- 

 manship, the cost of which militates against its employment 

 for purely agricultural work. An air compressor also is 

 necessary for compressing the air to start the engine and inject 

 the oil in the form of a spray. The cycle of the Diesel engine 

 is as follows : — The shaft having been turned till the piston 

 is just commencing its working stroke, air, previously com- 

 pressed by a compressor attached to the engine itself, to some 

 500 lb. a square inch, is admitted, giving an impulse and start- 

 ing the engine. On the compression stroke the air enclosed in 

 the cylinder i^ heated to a high temperature, and at the top of 

 the stroke the oil is sprayed into the cylinder by means of 

 compressed air, and burns, being ignited by the hot air itself. 

 In the so-called Semi-Diesel the compression does not usually 

 go above 120 to 150 lb., and the oil alone is squirted into a 

 bulb at the head of the cylinder previously heated by a lamp 

 but which afterwards is kept hot by the subsequent explosions. 



It will thus be seen that it is unlikely the Diesel proper 

 will come into general use for agricultural purposes owing 

 to higher cost and greater complication. The Semi-Diesel 

 must always suffer from the necessity of having to heat the 

 bulb with a lamp or of starting on petrol with electric ignition. 



A good example of a simple engine is seen on Stand 304, 

 Messrs. Robey & Co., driving a dynamo. It is of a vertical two 



