Class IX. ]
THRESHING-MACHINES ; MR. THOMPSONS REPORT OX THEM.
235
2. Threshing-machine.
Tliis is tlie most complicated agricultural machine ingeneral use; but, though it has also been long in use, andthough repeated trials have been made of competingthreshing-machines at our great agricultural show, it wasnot till the Norwich Meeting in 1849 that a very singular jdiscovery was made of their great imperfection. It oc- jcurred to the consulting engineer, Mr. Amos, that the !draught of the common threshing-machine worked by ihorses, should be tested when empty; and it was ascer- |tained that some of the best 4-horse machines required noless than three horses, putting out their strength as whenat plough, to keep the machinery in motion withoutthreshing at all. In other words, of the four horsesdragging round in their weary circle, three were over-coming the resistance of the machinery; one only wasthreshing the corn. Technically speaking, the duty per-formed was 25 per cent. only. So little, too, had themakers studied the principle of construction, that thisenormous waste of power was capriciously divided be-tween the barn-works and horse-works. To quote Mr.Thompson, of Moat Hall, whose reports always show thathe has mastered his subject—“The machines of Messrs.Garrett and Woods furnish an excellent illustration ofthis point, the whole friction being in these cases 2*78and 2*81—all but identical; the friction of the barn-works being, however, 2*07 and *40, while that of thehorse-works was *71 and 2*35.” Thus the makers wereworking so much in the dark, that, if the two best of thecorrelative parts had been put together, one horse in thefour would have overcome the resistance, and the duty ot75 per cent, would have been achieved; but if unfortu-nately the two worst had been mated, the resistance of the4-horse machine would have amounted to four horses anda half before any corn was put in for threshing, and therewould have been no duty at all.
The same rigid trial was applied to the threshing-ma-chines shown at Exeter in the following year. It thenappeared 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 difference in thepower required by the competing machines. For thresh-ing 100 sheaves in a minute, the two extremes of powerrequired were as 14^ and 36; and the work of the ma-chine which required triple power was inferior to that of
the machine which required least power. This shortsummary of what has been done already seemed necessaryin order to show the interest attaching to the followingreport by Mr. Thompson of the trial in the third year forthe present occasion:—
1. Threshing-machines may he divided into two classes—those adapted for steam or water power, and those intendedto be worked by horses. In the trial of the latter it isclearly desirable that the horse-works should be tested, andon this occasion, in the absence of the ingenious apparatusinvented by Mr. C. E. Amos, of the Grove, Southwark, forthis purpose, repeated attempts were made to obtain a satis-factory trial by the use of the dynamometer or draughtgauge. But after various methods had been fairly tried, itbecame evident that tire results obtained were not suf-ficiently accurate to warrant their being made public, andthe trial of the horse-works was abandoned, and the wholeattention of those who conducted the trials devoted to themore important part of the machines, known as the barn-works. The accompanying tabular form shows the resultsobtained, which were arrived at in the following way :—•
The steam-engine selected to drive the threshing-machineswas itself tested to ascertain the net pressure of steam whichrepresented one-horse power. An apparatus was then at-tached to it, which registered on a counter the revolutions ofthe driving-pulley. As each machine was brought up fortrial, the maker was asked how many horse-power herequired, what number of revolutions per minute he wishedthe drum to make, and the exact dimensions of the driving-pulley. From these data a calculation was made of thepressure of steam required in each case, and the supply ofsteam in the boiler of the driving-engine was so adjustedthat the calculated pressure was maintained during thetrial.
On reference to the tabular statement, it will be observedthat col. 1 gives the “ nominal horse-power,” as stated bythe makers; col. 2 gives the horse-power corresponding tothe power of steam actually employed during the trial. Thefigures in these columns are for the most part identical, itbeing wished that the machines should be tried in accord-ance with their designation— i. that a 4-liorsc machineshould be worked by steam of 4-horse power, kc. Some ofthe machines, however, could not be worked without addi-tional power, which is recorded against them in col. 2. Incol. 3 are given the revolutions made by the driving-enginewhilst threshing the allotted quantity of wheatsheaves, viz.,2j ewt. Col. 4 shows tile net pressure of steam at whicheach machine was worked, and which had been previouslycalculated from the data above mentioned. Col. 5 shows
and clumsy; and cast iron used freely in the place ofwrought. The coal consumed for duty done was three timesthat of the best engines.
Messrs. Kansomes and May brought an engine to thetrial-yard, but from some cause it could not be made towork. It was a trunk engine, which, in so small a power as5-horse, would give rise to much extra friction.
At the close of the trials, two engines, viz., Messrs. Gar-rett’s and Messrs. Clayton’s, were put through a second trial,to test the difference in steam-generating power between theLlangenneck coal used in these trials and the best New-castle, when the difference in favour of the former was foundto be as 8*63 to 1T3 lbs. of coal burnt per horse-power perhour.
Tabular Statement or Results.
Names of Manufacturers.
Nominal
Horse-power.
Timegeiting upSteam.
Coalused ingetting up8team.
Coal
IJornt perHorsepowerper Hour.
Minutes.
lbs.
lbs.
Tuxford and Sons, No. 1 -
- -
-
6
53
56*68
7*46
Ditto ditto, No. 2 -
- -
-
4
41J
35*60
10*80
Hensman and Son - - -
4
33
29*00
18*75
Hornsby and Sons — - -
6
49
35*23
6*79
Butlin _ - - - -
4J-
50
42*00
14-71
Garrett and Son* - - -
5
42
26*50
11*65
Caborn -----
9
44
52*00
12*48
Clayton, Shuttleworth. and Co.
No. 1
-
6
32
35*40
8*63
Ditto ditto,
No. 2
-
6
42
Withdrawn.
Barrett, Exall, and AndrewsBurrell -----
- —
-
26
25*56
9*20
6
28
35*00
13*10
Kansomes and May - -
- -
-
5 ;
70
Withdrawn.
Roc and Hanson - - -
- -
4 i
83
75*20
25*80
* Garrett and Son’s slide was wrongment, tried with Newcastle coal,equal ------
in this trial, but in a second expcri-\this engine worked out what would l
8*63
Charles John Carr, Bclper.