474 



THE FARMER'S MAGAZINE. 



breadth ploughed at once 42 inches, we find that 14 

 journeys or half-bouts must have been made; and 

 allowing the observed time of i to ^ of a minute for 

 turning at each end, we arrive at the same time of 2| 

 minutes for the distance from end to end. This is at 

 the speed of 270 feet per minute. Now, 170 stones' 

 draught, at 270 feet per minute, is equivalent to 642,600 

 lbs. lifted one foot per minute; and as one horse- 

 power equals 33,000 lbs. raised one foot per minute, 

 the power represented must be 19J-horse power. As 

 the engine was nominally of 12-horse power— that is, 

 having two Ti inch cylinders of 12-inch stroke — though 

 worked up to 68 lbs. pressure per square-inch, instead 

 of its normal pressure of 45 lbs., there is no such very 

 great margin for increased percentage of duty actually 

 engaged iu the tilling. 



Let us now look at the amount of power applied to 

 the implement in the heavier-land trial up and down 

 a steep hill. Three furrows were taken up hill and four 

 down — that is, three-and-a-half furrows at once, an 

 average of the whole-time. The draught of Busby's 

 plough (average of up and down) wa&95| stones; and, 

 deducting 12 stones as the average draught empty 

 (the less draught in descending compensating for the 

 greater draught in ascending), we have 83i stones as 

 the resistance of the work itself. Thus, Fowler's 32^ 

 furrows took a draught of 83^ x 3i) about 292 stones 

 To this add — say, 23 stones as the average 

 draught of the implement empty, and there will be 

 314 stones total average draught of the plough up-hill 

 and down-hill. The length of furrow was 330 yards ; 

 the time occupied in the journey (as observed by our- 

 selves), was 6 minutes in going down hill and 6| 

 minutes in going up. The average pace, therefore, 

 was 156 feet per minute. Now 314 stones' draught at 

 156 feet per minute is equivalent to 685,776 pounds 

 lifted one foot per minute— thus representing 20|-horse 

 power. 



From this case, as from the other, it appears that 

 the engine applied about 30-horse power to the im- 

 plement. 



The speed affects the proportion of power employed 

 in simply moving the implement. In the first trial, 

 with a pace of 270 feet per minute, the total power 

 applied was 19|-horse power, of which 2|-horse power 

 was for moving weight of plough; leaving 17- 

 horse power effectively engaged^ in the actual cutting 

 and turning of the soil. In the next trial, with a pace 

 of 156 feet per minute, the total power was 20|-horse 

 power, of which only 1 J-horse power was engaged in 

 moving the weight of the plough, leaving 19J-horse 

 power for the actual tillage. So that for economizing 

 power, as well as for lessening the number of turnings 

 at the end in a day's work (thus securing a greater 

 number of hours in real work), the slower has an 

 advantage over the quicker speed. 



It will be observed, too, that the economy of working 

 is proportioned to the amount of resistance met with 

 in the operation. The implement may take li to 

 2J-horse powei", according to pace, merely to move its 

 own weight and the loss of power in working the rope ; 

 and the other parts of the apparatus also varies from a 

 fixed quantity, according to the speed travelled— what- 

 ever may be the nature of the tillage being performed. 

 That is, the power required to drive the whole 

 machinery empty is least when the pace is slowest, as 

 it is in doing the heaviest work. And hence, when 

 the full force of the steam-engine is engaged, a much 

 larger per-centage of the power is most effective in 

 actual tillage than when the engine is performing an 

 operation below her capability — such as ploughing 

 light land when it could do heavy, or driving three 

 furrows when it could manage four. 



The amount of power applied to the haulage of the 

 steam plough was about 20-horse power. What 

 was the full amount of power given out by the engine ? 

 The judges make a general statement that the engine, 

 with two 7|-inch cylinders 12-inch stroke, was driven 

 at the. rate of 140 revolutions per minute, with a pres- 

 sure of 68 lbs. on the square inch — equivalent to a 

 working.power of about 35i horses. This is the com- 

 puted power, allowing 3-lOths lbs. for friction, &c., 

 and supposing that the 68 lb. pressure per square inch 

 was maintained upon the pistons uniformly throughout 

 the whole stroke. But such calculations of the power 

 of engines from a few minutes' observations of their 

 speed, Sec, is liable to considerable error; and it is 

 not only unlikely that the 68 lbs. pressure was exerted 

 through the whole length of stroke, but also unlikely 

 that a pressure of fully 68 lbs. was maintained in the 

 boiler without flagging, all the time the engine was at 

 work. The gearing of the machine was so timed that 

 the engine crank-shaft should make 130 revolutions 

 for 264 feet advance of the plough ; and as the plough 

 travelled 270 feet per minute, the engine in the first 

 trial must have made about 132 revolutions per minute 

 on the average. From what we have said above, we 

 are therefore inclined to estimate the jiower given off 

 by the engine at that trial as under rather than over 

 thirty-horse power. There would appear, then, to have 

 been something like ten-horse power consumed in 

 working the apparatus itself, while at such an exces- 

 sively heavy task. In the farmer's hands, run at a 

 lower pressure, the twelve-horse engine would probably 

 give off about twenty-horse power effective, when, of 

 course, both the amount of ploughing done and the 

 deduction for the friction, &c., of the machinery and 

 tackle would be alike reduced. We believe that the 

 power consumed by the machinery itself has been 

 greatly lessened by means of the new clipping drum 

 and adoption of larger gearing ; so that a larger per- 

 centage of duty is now got out of the engine. 



