626 



Report to II. II. 11. the President 



To quote Mr. Thompson, of Moat Hall, whose Reports always 

 show that he has mastered his subject — " The machines of 

 Messrs. Garrett and Woods furnish an excellent illustration of 

 this point, the whole friction being in these cases 2-78 and 2*8 1 — 

 all but identical ; the friction of the barn-works being, however, 

 2*07 and -46, while that of the horse-works was 71 "and 2-35," 

 Thus the makers were working so much in the dark, that, if the 

 two best of the correlative parts had been put together, one horse 

 in the four would have overcome the resistance, and a duty of 75 

 per cent, would have been achieved ; but if unfortunately the two 

 worst had been mated, the resistance of the 4-horse machine 

 would have amounted to four horses and a half before any corn 

 was put in for threshing, and there would have been no duty 

 at all. 



The same rigid trial was applied to the threshing-machines 

 shown at Exeter in the following year. It then appeared that 

 Messrs. Garrett had profited by the lesson, and reduced their 

 dead resistance from 2|- to 1^, or one-half. Yet there was still 

 found a vast diflerence in the power required by the competing 

 machines. For threshing 100 sheaves in a minute, the two 

 extremes of power required were as 14^ and 36; and the work 

 of the machine which required triple power was inferior to 

 that of the machine which required least power. This short 

 summary of what has been done already seemed necessary in 

 order to show the interest attaching to the following Report 

 by Mr. Thompson of the trial in the third year for the present 

 occasion : — 



1. Threshing-machines may be divided into two classes — those adapted 

 for steam or water power, and those intended to be worked by horses. 

 In the trial of the latter it is clearly desirable that the horse-works should 

 be tested, and on this occasion, in the absence of the ingenious apparatus 

 invented by Mr. C. E. Amos, of the Grove, Southwark, for this purpose, 

 repeated attempts were made to obtain a satisfactory trial by the use of 

 the dynamometer or draught gauge. But after various methods had been 

 fairly tried, it became evident that the results obtained were not sufficiently 

 accurate to warrant their being made public, and the trial of the horse- 

 works was abandoned, and the whole attention of those who conducted 

 the trials devoted to the more important part of the machines, known as 

 the barn-works. The accompanying tabular form shows the results obtained, 

 which were arrived at in the following way. 



The steam-engine selected to drive the threshing-machines was itself 

 tested to ascertain the net pressure of steam which represented one- 

 horse power. An apparatus was then attached to it, which registered 

 on a counter the revolutions of the driving-pulley. As each machine 

 was brought up for trial, the maker was asked how many horse-power he 

 required, what number of revolutions per minute he wished the drum to 

 make, and the exact dimensions of the driving-pulley. From these data a 

 calculation was made of the pressure of steam required in each case, and 



