Practical Hand Book of Gas, Oil and Steam Engines / Stationary, Marine, Traction; Gas Burners, Oil Burners, Etc.; Farm, Traction, Automobile, Locomotive; A simple, practical and comprehensive book on the construction, operation and repair of all kinds of engines. Dealing with the various parts in detail and the various types of engines and also the use of different kinds of fuel.

by John B. Rathbun

(145) The Rumely “Oil Pull” Tractor.

The Rumely oil-pull tractor is driven by a two cylinder, four stroke cycle oil engine, having a bore and stroke of 10 × 12 inches giving 30 tractive horse-power and 60 horse-power at the pulley. The cylinders are cast single and are provided with independent heads. The pistons are easily removed by unbolting the cylinder heads and the crank end of the connecting rod, after which operation they may be pulled out upon the platform. The exhaust and inlet valves are in easily removable cages placed on either side of the cylinder. The stems of the valves are at right angles to the bore of the cylinder and open directly into the combustion chamber without pockets or extensions to the chamber.

A bell crank rocker arm acts on the valve stems which in turn is actuated through a push rod that extends from the cam-shaft in the crank chamber. The cam-shaft, rocker arms, valves, and half time gears are clearly shown by Fig. 128. The housings of the inlet valves connect directly with the special kerosene carburetor made by the Rumely Company. The Higgins carburetor used on these engines is very simple and effective in vaporizing the heavier fuels and has no springs nor internal mechanism to get out of order. The carburetor is controlled directly from the governor which regulates the air, water and kerosene required for the combustion, and has no manual adjustments that need attention from the operator. A constant flow of kerosene and water is maintained through the carburetor by means of force pumps, the level in the device being kept constant by overflow pipes through which the excess returns to the supply tanks.

Fig. 128. Phantom View of the Rumely “Oil Pull” Engine.

As in nearly all types of low compression, or carbureting oil engines, the Rumely engine receives an injection of water in the cylinder to aid the combustion and cooling, and to reduce the initial pressure of the explosion. While the initial pressure is reduced by the water vapor, and with it the strain on the engine, the mean effective pressure is increased because of the absorption of heat from the walls and the more perfect combustion. The only moving part in the carburetor is a single plate controlled by the governor which is produced with one or more air passages. The governor that operates this valve is driven by gears and regulates the speed by throttling the charge. The speed of the engine can be varied from 300 to 400 revolutions per minute while the engine is running.

Fig. 129. Higgins Oil Carburetor.

In this engine it is a very simple matter to remove the crank-case cover and the cylinder heads and expose the whole of the working mechanism of the engine.

After removing the cylinder heads and without changing his position, the operator can examine, clean, and, if necessary, regrind the valves. Also without changing position the operator can control his reverse transmission gears, friction clutch for starting the tractor. He is also in reach of the ignition apparatus, governor carburetor and oiler.

The crank case is cast in one piece. The bearings are cast integral with the crank case, and are fitted with interchangeable, adjustable, babbitted shells. Binder caps hold the bearings together and keep the babbitted shells securely in position. The design permits removal of binder caps for examination of crank shaft bearings without distributing the adjustment. The crank case is secured to tractor frame by well fitted bolts, thereby avoiding annoyance from loose bolts and nuts.

The crank case is covered with a sheet steel lid that shuts out all dust and dirt. This cover can easily be removed at any time by simply unscrewing the bolts that hold it in place. It is constructed with this cover on top instead of on the side or end, which permits of easy access to any working parts in the crank case.

Fig. 130. Rumely Oil Pull Tractor.

To further facilitate the accessibility to working parts in the crank case, a secondary cover is provided which can be removed in a couple of minutes. This opening is large enough to allow the operator to reach any point within the crank case.

All cams are key-seated upon the cam shaft with double key-seats, which absolutely prevent any possibility of slipping or alteration in the timing of the engine. The exhaust and intake valves are mechanically operated. The valves are constructed with steel stem, nickel-steel heads, the whole being highly finished.

Valve cages are oil cooled, thereby eliminating all possibility of the valves overheating or warping. The valves themselves can be removed by simply unscrewing the connection. The engine is provided with a set of relief cams by which the compression can be relieved—this greatly facilitates the starting of the engine.

The piston is equipped with five self-expanding rings. Connecting rod is of drop-forged steel construction. Crank-pin bearings are made in halves and lined with shells of special metal.

A combination of mechanical force feed and splash lubrication is employed. Six force feed tubes enter the crank case, on to each bearing, and two tubes force oil into the cylinder. The crank case contains two gallons of oil and is arranged so that any surplus may be drawn off immediately. The lubricator has a gauge glass that shows the quantity of oil supplied at all times, and which is always in view of the operator.

A make and break system (low tension) furnishes the ignition spark, which is supplied with current by a Bosch low tension magneto under normal running conditions, and a battery for starting and for use when the magneto fails. The magneto is of course gear driven so that its armature has a fixed relation with the piston position. The igniters of either cylinder may be easily removed for examination by simply unscrewing two nuts.

Oil is used as a medium for carrying heat from the cylinder walls to the radiator. In the construction of the cooler the company have followed new principles, thus accomplishing the desired result with a minimum amount of metal and liquid. There is no surplus of liquid, just enough oil being used to fill the cylinder jackets, radiator and circulation pipes. The oil is kept in a constant flow from the cylinders to the radiator and back to the cylinders by a large pump which is driven by a chain direct from the crank shaft. The radiator is self-contained and will hold the oil for an indefinite period.

The radiator is composed of a number of sections of pressed galvanized steel. Oil circulates freely within the sections and the air is drawn round the outside. There is a constant flow of oil inside and a constant current of air outside.

The engine is provided with a smooth-working, efficient friction clutch, which is easily handled by a platform lever and with little exertion on the part of the operator. The toggle bolts are adjustable so that any wear in the blocks can be taken up.

The clutch and brake are so connected that when the clutch is thrown out the brake is immediately applied and when thrown in the brake is released.

The various movements of the valves and the ignition mechanism on the face of the flywheel, are marked so that one can check up the timing of the engine. By bringing any one of these marks to coincide with the stationary pointer attached to the side of the crank case, one can easily ascertain whether the adjustments and the timing are exact.

The crank shaft is supported by two end, and one intermediate bearing, the latter bearing being placed between the two throws of the crank shaft. As the two cylinders are placed on the same side of the crank shaft, the two throws are also on the same side of the shaft and to balance these throws cast iron counter weights are bolted on the bottom of the crank arms. The bearings are exceptionally long, the total length of the three bearings amounting to more than half the length between the outer ends of the bearings.

The frame of the tractor consists of four twelve inch “I” beams securely riveted together with intermediate channel stiffeners. The cast steel bearings are riveted to the frame so that the whole construction is one unyielding mass. The bearings are in halves which makes the removal of the shafts an easy task.

With the exception of the differential and master gears all of the gears are cut out of semi steel blanks. The fly wheel has a face of 11 inches, and a diameter of 36 inches.