60 TRENCHING AND SUBSOILING 



The working of the machine is satisfactory. The anchor- 

 ing of the two fixed pulleys, which are not carried by anchor- 

 trucks, is the only difficulty. Anchoring-plates, as already 

 described, give the best results. 



MECHANICAL YIELD OF STEAM WINDING DRUMS. 



There is no definite record published on the mechanical 

 yield of steam capstans. However, we may estimate it 

 approximately by comparison with ordinary horse-gins. 

 The only mechanism interposed between the motive power 

 and the resistance is one or two pairs of cog-wheels, as in 

 the case of horse-gins. 



Numerous dynamometric trials made on horse-gins have 

 shown that the yield varies between 70 and 80 per cent., 

 and that in the case of a gin provided with two pairs of cog- 

 wheels the yield is 75 per cent. This figure can be regarded 

 as the yield of steam winding drums. 



AREA PLOUGHED. 



As in the case of horse-gins, the area ploughed daily varies 

 greatly, and depends on the length of the farrow, the size of 

 the block, the motive power, the experience and skill of the 

 workmen, also according to whether it is a simple or double 

 effect capstan. If we assume an average rate of travelling 

 of the cable of 65ft. 7in. per minute, and a sod 19'7 inches 

 wide, the area ploughed in one minute is 107-6 square feet. 

 Seven hours are required to plough 1 acre, assuming that 

 there is no interruption. But the hauling back of the plough 

 (simple-effect capstan), unforeseen accidents, ploughing of 

 the headlands, reduce this area to half. Therefore 14 hours 

 are required to plough 1 acre, that is to say, about one day 

 and a half, assuming that we work ten hours a day. 



With a displacement capstan, Gruyot or Pecard, for 

 instance, and with a powerful engine it is possible to work 

 one acre per day. But it is safer to reckon on one and a 

 quarter days. 



With a double-effect capstan, Pelous or Pineau, for 

 instance, the work is more rapid. The cable travels at the 

 rate of 88ft. 6in. per minute, ploughs 145 square feet per 

 minute, or 966 square yards per hour. Assuming that 

 one-third of the time is wasted, this means an area of 240 

 poles per day of ten hours. One acre may therefore be 

 worked in 6 hours 40 minutes. 



