A 24-hours' Ploughing Test.
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Results with the Marshall 30h.p., Oil Tractor, near Gainsborough.
One of the most practical of the machines which have been exhibited in recent years is the 3oh.p. oil motor which Marshall, Sons, and Company, Limited, of Gainsborough, will stage, for the first time, at the coming Smithfield Show. This company has been steadily testing its new motor for over two years and during that time it has eliminated every weakness as it has been discovered. In our issue of the 17th of October last, we gave a few particulars of this tractor and we are now able to supplement these by a more detailed description and several interesting photographs.
The design of the engine is such that every working part is easily accessible. The diameter of each of the two cylinders is 61 inches and the piston stroke is 7 inches. The normal, engine speed is 85o r.p.m., at which speed 3oh.p. is developed. The general disposition of the parts of the engine is somewhat novel. Figs. i and 2 show the engine from the near-side and the off-side respectively, whilst Fig. 3 is a top view of the engine, showing the valves and the manner in which they are operated from the camshaft by bell-crank levers (A). The camshaft is situated, high up, at the back of the cylinders, and it is driven from the crankshaft by a double set of skew-gearing. The governor is mounted on the vertical shaft through which the drive to the upper set of skew-gearing is transmitted ; a bevel wheel which drives the circulating pump (B, .fig. 2) is also secured to this shaft. The pump is of the rotary, gear-driven type and has three wheels, the centre one of which is twice the width of each of the other two. The object of this arrangement is to get a double suction, and a double delivery, for the water.
Low-tension magneto ignition is ,fitted, and the magneto is mounted with, and driven by, the camshaft. The vaporiser (C) is of the hot-plate type and is kept at a sufficiently high temperature by the exhaust gases from the cylinders; the rate of feeding the fuel may be regulated by a valve (D) mounted directly over the top of the vaporiser. A small quantity only of the air is passed through the vaporiser, the main air supply being taken in at the " U " bend (E) of the inlet pipe (F). The fuel is fed to the vaporiser from the tank (G) by gravity ; the tank is divided into two compartments, one for petrol and one for paraffin. The paraffin is lifted from the main fuel tank, which is situated under the watertank at the rear of the tractor, by means of a small plunger pump (H) which is driven off the camshaft by means of an eccentric and rod (I).
A large -diameter, inverted cone, metal-to-metal clutch (J) transmits the power, through spur gearing (K), to a three-speed, gearbox which provides for speeds of z, 4, and 6 miles an hour in a forward direction, and a reverse speed of z miles an hour. The belt pulley (L) may be used for driving a full-sized, threshing machine or any other kind of farm machinery. The lamp bracket (M) swings out of the way when using the motor for driving machinery by a belt.
The water cooler resembles a watertower in miniature : it is divided into two portions and each receives water from one of the two delivery pipes (N), in a distributing chamber, from whence it passes through a large number of small holes, to a series of inclined, corrugated metal shelves ; the water is thus spread over a very large surface, and the cooling is further as
sisted by the draught induced by the exhaust gases passing up the funnel.
The final drive from the gearbox is by means of spur gearing to the live axle. The differential gear may be locked when necessary, and a slip-winding drum is fitted. There are two sets of brakes : one of these is actuated by a
foot lever, and the other is a screwdown brake acting directly on to the back axle.
Simplicity, strength, and durability are the principal characteristics of this machine. It has been designed especially for agricultural use, and it may be used for any purpose for which an 8h.p. (nominal) fraction engine may be used, and for many other uses to which the heavier machine cannot be put. Mr. H. W. &Amber, M.LMech.E., of 25, Ryder Street, St. James's, S.W., who is the designer of this machine, and who is acting as consulting engineer to this department of Marshall's immense works, and the makers, are to be congratulated on having produced such a useful and powerful motor for agricultural purposes. A most interesting experiment was made with the machine which we have
just described, in a 36-acre field of stubble, on Mr. Nicholson's farm, near Kirton, about 12 miles from Gainsborough. The object of the trial was to determine how much land the machine could plough within the space of 24 hours, and also to demonstrate the reliability of the motor. A member of our technical staff was the only representative of the Press who observed the test throughout. Petrol, paraffin, and water tanks were sealed, and all supplies were carefully measured. The figures which we are thus able to give are based upon the notes made by him on the spot, and may be taken as perfectly accurate.
Although thc total cost per acre is about one third, to one quarter, of the cost for horse ploughing, we are convinced that the cost would have been very much less had the ground been in a more friable state. For some days previous to the trial, rain had fallen continuously and, as might be expected, the ground was very heavy. At 10.40 on Friday morning last, the trial began, and the tractor continued to haul its two ploughs which, together, turned over, to a depth or from 5 to 6 inches, just over oneacre during each hour of daylight. The makers were unable to procure a 6-furrow plough so it was decided to use one 4-furrow, machine plough and one double-furrow, horse plough ; the result was a rather long equipment which required considerable skill and time in turning at the headlands. As darkness settled, that difficulty became more pronounced on account of the bad and uncertain lights which were carried on the engine and ploughs. Had the same attention been given to the efficient lighting of the field as was given to the comfort and feeding of the men, we have no doubt that the daylight average would have been maintained all
through the night, It was hoped that the trial would be completed on one tank of water, but, in this respect, the makers were disappointed. The perforated plate of one half of the cooler became choked with solid Matter from the dirty, ditch water which was used and the result was that half of the total cooling surface was rendered useless. The first stop for supplies was made about 7 p.m., when it was found that one of the drain cocks was open and water was leaking. Throughout the test, the motor ran remarkably well and there were only two involuntary stops, which together amounted to eight minutes. The total time lost for Ailing up the tanks, examining the mechanism in search of parts which might, but did not, require adjustment, and including the eight minutes already mentioned, amounted to 73 minutes-. The trial ended at 11./5 on Saturday morning and it had thus lasted for 24 hours and 35 minutes ; the 35 minutes over the 24 hours was allowed in order to make up for delays to that amount, which were requested by our representative for the purpose of sealing the tanks and taking photographs. The actual ploughing time was 22 hours, 47 minutes, and during that time 21 acres of land had been ploughed at an average rate of 63 minutes per acre. The quantities of fuel and lubricating 4)il which were used during the test are given in Table 1, where it will be seen that an allowance of 2S. od. has been made for carting the water from the nearest pond; this item is an outside estimate, as also is the amount allowed for grease and waste. The total cost under this head was 13.53d. per acre.
Cost for Fuel and Stores. s. d.
44 gallons of paraffin at 40. 16 6
2 gallons of petrol at is ... 2 0 _ I!.,' gallons of lubricating oil at is. 6d. ... ... ... 2 3 Grease, waste, etc. ... ... 1 6 Carting water from pond ... 2 0
Total fuel and stores cost for
2 I acres 4 The fuel and stores cost per acre is, therefore, /3.53d.
Cost of labour.
Two ploughmen for 26 hours, at 3s. per day of 91 hours... 16 One driver for 26 hours at 4s. 6d. per day of 91 hours 12 4 5 Total labour charges, for 26 hours ... ... i 8 9 The labour cost per acre is, therefore, 6d.
Turning, now, to Table II, the details of the labour cost will be seen to work out at 16d. per acre, but this item could be reduced by the employment of a six-furrow plough which could be operated by one man. In connection
with this charge, we have assumed that the men spent one hour before, and one hour after, the trial, in getting the equipment ready, and in clearing it away.
Table NI includes all the charges from the two previous tables, together with interest on capital at the rate of 5 per cent., and depreciation at 20 per cent.; the latter charge, we consider, might be placed as low as I2 or 15 per cent., but our object in placing it at 20 is to arrive at the maximum cost per acre, which, as seen in the table, works out to 2s. rod. No allowance has been made for repairs as none were found necessary, but, if we assume that the repairs would amount to ro per cent. of the total outlay, we must add JO. per acre to Table III, and the total ct. per acre even then is under 35.
TABLE Total cost for ploughing 21?1 acres.
Fuel, stores, etc. ... ... 4 Labour charges ... ... r 8 Interest on capital outlay at
5 per cent. ... ... ...
Depreciation at 20 per cent. 5 Total cost for 2I acres 2 19 1( The total cost per acte is, therefor just under 2s. rod.
Note :—The interest and depreciatk figures given in the above table a based on a total outlay of:..5oo f■ motor, ploughs, and tackle.