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373.—Building Up Broken Teeth by Welding.

15th May 1923, Page 28
15th May 1923
Page 28
Page 29
Page 28, 15th May 1923 — 373.—Building Up Broken Teeth by Welding.
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Which of the following most accurately describes the problem?

One of the most awkward jobs which the garage hand or maintenance engineer is sometimes called upon to tackle is to repair a broken tooth in a gearwheel. Of course, this is a job which is not often andertaken except in an emergency, when it is necessary to get the vehicle on the road and no spare is available.

There are many ways which can be adopted, but most of them either take too much time or give teeth which are not sufficiently strong. One method is to dovetail a ne-w piece of metal into the wheel and to recut the teeth, hut this is a task of some magnitude Repairs have been made by drilling and tapping the wheel and screwing in studs, afterwards shaping these with a file, but, in some cases, these studs work loose and cause far more trouble than was previously saved.

The only objection to welding the new teeth in position or of building up teeth by the same process is that eoneiderable redressing is usually necessary

before a gearwheel can be .used. The following method is one which overcomes this objection and makes a cheap and efficient repair.

First, it is necessary to obtain some pieces of ordinary carbon, such as those used in are lamps. These must be shaped to fit on each side of the broken tooth, the space between. them giving the shape of the tooth required. The pieces should overlap the gearwheel at each side in (order to allow for the insertion of wedges, also made of 'carbon, and the whole can be locked together by means of wire.

These pieces of carbon control the flow of the metal by confining it between them.

It may be found more convenient before fitting these pieces of carbon, first to build up a semblance of the ends of the new teeth to act as a guide for the carbon forms, and then the metal can easily be run into the vacant space.

The building up should be commenced at the centre of the cavity, the rod of welding metal being pushed down as fast as it is fused. Care should be taken to ensure a perfect weld between the built-up ends of the metal and the centre. Finally, the teeth can be trimmed up with a file.'

ti42 To obtain a perfect weld it is advisable to play the flame into the tooth cavity until the metal of the rim also begins to fuse. Also the space should be filled a little above the level of the finished tooth to make allowance for finishing the tooth top.

374.—A Silencer Trouble on a 2i-ton Guy.

A short time r..r+go one of our readers who makes use of a 2i-ton Guy in his work experienced trouble With the silencer of this vehicle, the front end of the silencer being blown out. On examining the-component, it was found that ths front cone of the baffle plate had been forced from its original position and had come to rest against the second cone, the inner side of the small dome-shaped top resting on the outer edge of the small dome on the second cone in such a manner as practically to form a valve and valve seat, which caused a complete blockage of the

exhaust gases. .

The silencer casing and cones were riveted together, and it was apparently not intended that the parts should be taken to pieces for cleaning or repair. However, as the front of the silencer had already been blown out, it was found possible securely to hold the loose cone by using a split ring tapped for /-in, setscrews, in the manner illustrated.

375.—Replacing Rear Spring Bolts on a Maudslay.

In order to replace the rear spring holding-down bolts on a Maudslay vehicle, it is necessary to remove the spring holding-down plate and the torque mechanism. Four long collar bolts are used to anchor the spring to the axle easing, and as they have two nuts each and a long thread which is almost invariably rusted, one or more of the bolts will certainly twist off when unscrewing the nuts, in which case, the re

placement becomes rather a lengthy process. To shorten it as much as possible, it should be carried out as follows : Remove the upper portion of the broken bolt by cutting it off 1w two pieces with a chisel. The lower part, which passes through the axle casing, is usually rusted into position. To remove this piece, take off the two bottom nuts, place a jack underneath the bolt and. screw up the head, thus bringing a part of the weight of the lorry on the bolt, which will most probably be forced up and can then be removed. Should the offending piece require forcing the whole of the way, it will be necessary to use a punch. Such a tool can quickly be made from an old Ford spigot or valve.

Having removed the broken bolt it will be found that the new one cannot, in the ordinary way, be placed in position without removing the spring holding-down plate, which is a procedure taking some considerable time. To avoid this, put the bolt into a lathe and turn off its collar, then slide it up through the axle casing and spring prate and secure the ends in the usual way. This will be found to make quite a good job, and one which can be effected very much more rapidly than if performed in the normal manner.

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