8 Jan., 1907.] Farm Engines and their Care. 7 



gzs, and then a proper proportion of atmospheric air drawn in by piston is 

 mixed with it. The piston on the backward stroke compresses the mixture, 

 which is ignited by the heat of the vaporizer, by a red hot ignition tube, 

 or occasionally by an electric spark. The ensuing explosion sends the 

 piston forward. 



If the engine is running well, the exhaust should be practically colour-- 

 less ; the piston should keep clean ,; there should be no knocking, and the 

 speed, i.e., the number of revolutions per minute, should be practically 

 constant, whether running light or with full load. The explosions should 

 be regular and uniform, and without a coughing sound. Smoky exhaust, 

 with black sticky piston is a sign of incomplete combu.stion, due to too 

 much oil, or too little air. In such a case, have a look at the oil-feed 

 valve, and also see that exhaust and air valves are working freely. The 

 exhaust valve is always worth looking at. The next likely source of 

 trouble is the ignition. If a tube, see that it is clean internally, and 

 that it is kept red hot. In the case of the hot wall igniter, there will be 

 trouble unless the compression is correct. This may vary for different 

 brands of oil, so that a change should not be made withO'Ut a trial run. 

 An incorrect proportion of air will also interfere with the ignition. Per- 

 haps the cause is that the supply of oil is blocked. The vaporizer has 

 to be brought up to the right heat in the first place. 



There may be leakage in the rings or piston itself, or in the valves. 

 This will interfere with the air supply. Try if tight by turning engine 

 backward. 



Blocking of the oil supply may be due to leakage in pipes or in pump 

 (if supply is raised). The filter in the tank (overhead supply) is a probable 

 source of trouble. 



Look out for hot bearings. Lubricate well, and use a good oil. A 

 light oil with high flash and fire tests is the best. 



Knocking means worn or loose bearings in the connecting-rod, piston 

 or crank pin end ; loose keys ; or igniting at wrong part of stroke. The 

 last cause of trouble needs an expert to remedy. For the first, take up 

 bearings by filing; be careful not to make too tight when screwing up. 



Draw out the piston occasionally by uncoupling the connecting-rod 

 crank and bearings. Be careful not to break the rings ; let piston slide 

 out on to a Avooden bed. If necessan^, clean well with kerosene both 

 piston and cylinder. 



Complete instructions are supplied by the various makers, and can 

 be obtained from them or their agents. They should be carefully fol- 

 lowed, and then, with cleanliness and good lubrication, there should 

 seldom be any cause for complaint. 



Battery troubles in case of electric ignition need too much space. 

 Broken connexions, dirty terminals, bad insulation of plug, are the chief 

 causes, while the battery may be run down altogether. 



MANURE INVOICE CERTIFICATES. 



Farmers are advised to retain, for a reasonable time, the invoice 

 certificates supplied to them by vendors when purchasing manures, with 

 the object of assisting officers in the work of protecting farmers from 

 possible imposition. 



