1922.] The Shrawardine Tractor Trials, 1921. 975 



tractor hauling a separate implement. Crude oil was used as 

 fuel and the engine appeared to be operating satisfactorily. 

 Garden tractors were represented by the Service and Simar 

 machines. The Service is a miniature tractor controlled by an 

 operator walking behind, and the Simar is operated in the same 

 way. The latter is made in two sizes but the smaller one only 

 was entered. The special feature of this machine is the rotary 

 spring-mounted tines of round section steel which till the land 

 and produce a fine tilth in one operation as though plough and 

 harrow had been used. 



The implements submitted for test included eleven ploughs, 

 nine cultivators, two harrows, one disc harrow and three exca- 

 vators. Among the ploughs were to be found a skim plough, a 

 stubble breaker and specially designed sub -soiling ploughs. 



Performance and Tests. — A pleasing and noteworthy fact was 

 that of the 38 machines tested and demonstrated there was not 

 one single failure. It was clearly demonstrated that machines 

 of different types can work steadily for a week without one of 

 them being held up for any mechanical defect other than some 

 unimportant detail easily remedied. 



The tractor drivers did not attempt to give exhibition perform- 

 ances, but ran their machines as if under normal conditions, 

 and this was reflected in both the regularity of running and 

 absence of stops due to mechanical defects. In previous trials 

 breakdowns have been frequent, and it is apparent therefore that 

 manufacturers have recognised and remedied defects which 

 showed themselves in past years, while the experience gained 

 has not been lost upon the organisers of the trial as the 

 machines were set to do work well within the limit of their 

 powers. 



With regard to the performance of individual machines, any 

 attempt to deal with each one, judging from mere observation 

 of the work done, w r ould be mere repetition, the uniformity of 

 excellence being notable. 



The power tests that were carried out were of very great 

 interest. The engines were all submitted to a belt power test 

 by means of a Froude dynamometer, and in addition underwent 

 a draw-bar test by which the overall mechanical efficiency was 

 observed. A point made clear during these tests was that in the 

 majority of cases only a fraction of the total power developed was 

 available for useful work, due to the lack of adhesion or gripping 

 power in the driving wheels. Frequently the draw-bar horse- 

 power did not represent more than one -third of the power which 



