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The Robey Lubricator

Fig. 156 is a sectional elevation, and fig. 157 a plan of the Robey lubricator. The revolving shaft A, which may be worked from any convenient part of the engine, but preferably from the cross shaft by an endless belt, is fitted with cranks B C, having depending wires DE. One depending wire, D, dips into the main oil reservoir F, and in rotating wipes off the oil carried by means of the fixed pin G into a smaller upper reservoir H, and the

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other wire, E, carries oil from this upper reservoir H to a fixed pin J and to the recess I, which leads it to the cylinder. The wire D lifting the oil from the main reservoir is proportioned so that excess of oil is always raised to the upper reservoir.

Fielding Lubricator

The lubricator shown at fig. 158 is on the principle of the bird-cage drinking fountain.

This lubricator consists of a closed air-tight chamber for

containing the oil supply, having a trough outside formed in the same casting, and at the base of this chamber a hole is drilled through the wall of the chamber, leading from its lower

FIG. 158.-CYLINDER LUBRICATOR (FIELDING)

port into the tray; through this aperture the oil escapes, maintaining a constant level in the trough, and the oil is delivered from the tray by a wiper or wick. A removable plug is provided for filling the oil chamber.

CHAPTER XXI

CAMS

THE usual practice in designing the air and exhaust cams is to use cast iron. The gas cam, whilst also of cast iron, has a tool steel piece inserted to ensure a good edge for the gas roller.

Cast iron of good quality gives good results when the striking position of the cam to the roller on the lever is suitably arranged.

Figs. 159, 160, and 161 show various methods of constructing cams, and their respective openings of the valves.

Fig. 159, where a lifting lever of equal centres is used, the

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lift of cam is shown at A, and the rate of valve opening and closing at B.

Fig. 160 shows the lift of lever of equal centres when using a parabolic cam. The lift of the cam is shown at C, and the rate of valve opening and closing at D.

In fig. 161 a quick opening and closing cam is shown, with a lever of unequal centres, the lift of the cam being shown at E, and the rate of valve opening and closing at F. The position of the crank at the commencement of exhausting stroke is shown at G.

CHAPTER XXII

EXHAUST SILENCING CHAMBERS

EXHAUST silencers are made in a variety of forms, all based upon the principle of allowing the exhaust products (at the high pressure of 30 to 40 lbs. per square inch) to expand into a much larger area than that of the exhaust pipe, thence to the atmosphere at a reduced pressure. The area of silencing chamber should be at least five times the volume of the cylinder.

Some makers use baffle plates, and though the advantage of a quiet exhaust is in many instances indispensable, great trouble is often experienced with the exhaust products through excessive baffling.

To expel the whole of the products of combustion would undoubtedly be a step in the right direction for high economy and hard continuous running.

This is somewhat difficult to accomplish without serious complications, yet the nearer this can be approached the better the results will be.

Fig. 162 is a sectional elevation, and fig. 163 a sectional plan of a very common design of exhaust silencing chamber. The exhaust gas from the engine may be arranged to enter at the side and out at the top, or to enter at the side and out again at right angles. In some cases two boxes are coupled together by a bridge piece pipe on top, the exhaust entering at the side

of the first box and out again to atmosphere from the side of the second box, or coupled at the side and the escape arranged from the top of the second box.

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Fig. 164 is a sectional elevation of two Justice' silencers, and fig. 165 a sectional plan. This type of silencer is usually placed

FIGS. 162, 163.-EXHAUST SILENCER

at the end of the exhaust pipe and partially filled with shingle, and there are cases where shingle is used as a silencer when placed in a pit arranged to receive the end of exhaust pipe.

Fig. 166 is a section of divisional silencer, and fig. 167 a cross section. In this form the exhaust inlet may be arranged

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