HINTS ON MAINTENANCE.
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Fitting Steam Valves. Bushes for Thornycroft Brake-cam Spindles. Removing Associated Daimler Pistons. A Peerless Safeguard.
Grinding-in Steam Valves.
GREAT many steam wagons, including the Sen-. tinel, make use of globe-type steam valves having enewable seatings and small valves the lower part of each of which is of hemispherical shape, whilst the upper part is fiat and has a screwdriver slot across it.
These valves •sometimes leak and require to be ground-in, but it is difficult to keep them properly seated while using an ordinary screwdriver for t1M work, as there is nothing to act as a steady, with the result that the valves tumble about and the contact maintained with the seats is irregular.
One of our readers makes use of a simple device for overcoming this difficulty. It consistsof a piece
of steam piping about in. internal diameter and 3 ins. or 4 ins. long. This fits inside the removable sleeve which ends in the valve seat. The actual grinding tool consists of a piece of mild steel bar in. diameter and of a length which will allow one end to be formed into a convenient handle, whilst the other is made into the shape of a screwdriver blade which can easily reach the slot in this • small valve.
To use the tool the hand wheel and valve spindle are removed • complete and the tube inserted and maromuvred around the top of the valve, after which the turning tool is inserted. The end of the pipe, which rests on the shoulder of the valve, should be carefully filed or turned perfectly square so that the pressure is equal all round.
Some Pointers on Early-model Thornycroft Vehicles.
IN some Thornycroft chassis the brake-cam-spindle brackets, which form parts of the rear-spring seats, are not bushed. In such cases it is advisable to bore them out to a size large enough to take a standard bush before the holes wear oval. With this done, new bushes can be kept in stock and tile old ones replaced at any time after wear has occurred. This will save considerable expense, as in some instances where bushes are not fitted it may be necessary to replace the camshafts.
• With regard to foot-brake shoes it will be found that the, fulcrum-pin holes and fulcrum pins also wear fairly. rapidly, allowing the shoes to chatter and causing unnecessary wear to take place in all parts of the footbrake gear.
Here, again, the holes in the brake shoes should be bored out and standard bushes fitted.
The guide paw which engages with the slotted collar on the foot-brake screw wears very rapidly, probably owing to vibration, and in many cases when a eV,
vehicle comes in for overhaul or dock inspection the flange on the collar will be found to be worn. away, making the guide paw useless.
To overcome this difficulty a small clip may be fitted to the brake screw and a light spring puoviderl between the top of the gearbox and the clip on the screw. This will keep the guide and slotted collar properly engaged and will increase the life of the fulcrum pins.
The lubricators of the bottom bushes of the swivel pins are often neglected, causing rapid wear.
' By removing the setscrew fitted at the bottom of each pin and replacing it by a good-quality greaser, lubrication is facilitated and the pins are more likely to be looked after.
Removing Connecting Rods and Pistons on an Associated Daimler.
IT does not appear to be -common knowledge that in the model 417 engine employed on the Associated Daimler Blenheim and Renown chassis the connecting rods and pistons can be withdrawn from underneath. In fact, according to one of our contributors, quite a number of engineers have said that this is impossible.
To carry out the job, first take off the big-end cap, then lift the connecting rod and let it hang down at the side of the crankshaft opposite the oil pipe, turn the crankshaft until it is at right angles with the connecting rod, and then pull the piston down until it is resting on the shaft. This will allow aboutin. between the top of the piston and the bottom of the cylinder, allowing the piston to be tilted towards the oil pipe. After this, the piston can be drawn down between the crankshaft and the side of the crank chamber. At the same time the crankshaft must be worked around very carefully in a -clockwise direction. The piston can be replaced in the same manner.
Breakage of Peerless Engine-bearer Bolts.
CONSIDERABLE trouble has been experienced through breakage of the front engine-hearer bolts on the Peerless lorry. It will be recollected that there are four bolts securing the engine to the bearer. Two pass through a lug on the crankcase outside the sump casting and two are fitted close up to the front main bearing. When one of the latter bolts breaks it drops into the sump.
As it is almost impossible to overcome breakage of the bolts, damage to the' sump can be prevented by drilling and tapping a hole near each inner bearer bolt. A short setscrew with a large plain washer should then be screwed into each hole so that the washer partly overlaps the bolt.