TRANSMISSION TROUBLES.
Page 27
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Difficulties Encountered and Overcome by Our Driver and Mechanic Readers.
WE SHOULD think that the difficulty which was encountered, by " A.W.R," of Canterbury, is a most unusual one. The gearbox of his lorry, which was by a well-known maker, had cracked at a point., close to the first-speed gear. It, had been patched, but evidently the patch was not sufficient to hold the box up to its work, foe, on engagement of the, first speed under heavy -load, the stress was sufficient to open the box so much as to cause the
gears to disengage. However, if the trouble is likely to be an unusual one, it is also true that the method of repair is equally unorthodox.
On reference to the sketch it will be apparent that the cracks were disposed in close proximity to a bearing holding one of the shafts. A hole was drilled in the gearbox at a point immediately opposite to and in line with, one .of the cap bolts of this bearing. A piece of halfinch steel bar was then procured, long enough to project through the box, whilst one end was practically touching the inner extremity of the aferesaid bearing bolt. Tres piece of steel bar was screwed at both ends. Two deep half' inchnuts were then made from a piece of hexagon bar Of the right dimensions; judging by the sketch, each nut was from ILins, to 2 ins. long. One of these deep nuts was used in place of the ordinary one which secured' the cap in place.
The long rod was then screwed into the upstanding part, of this milt, and When so located it projected through the wall of the box, as may be seen by reference ta one of the accompanying sketches,, sufficiently to allow of a, deep, specially 'shaped washer being slipped over it into close contact With the outside wall of the box, to be secured by the other deep nut. This was long enoughto leave room when screwed up on this long bolt, to allow of the, entry of yet another such bolt, which;' when in position, projected somewhat beyond the caster channel of the chassis.
A. piece of 2-in. by-in. fiat bar was drilled.and bolted to the frame, so that it would accommodate this second projecting bolt, which was secured to it by means of a nut as shown. We are not afforded any explanation of this unueual repair, and, while it seems reasonable that the long bolt would hoidithe two sides of the gearbox together and prevent the springing to which reference has been made, the reason for the second exterior stud, holding the box up to.the outside of the frame, is not so Obvious. Perhaps " A.W.R." will explain in a subsequent letter.
ft often happens, in the course of repair work, that a shaft, otherwise 'rite sound, is so deeply worn in its journals that, unless same special measures be taken, it has to be scrapped.
Something of the kind appears to have happened in connection with the repair job which " T.H.W.," of Wigan, had in hand. One of the gearbox shafts, be tells us, was worn so badly, in one of the main journals,, that by the time the grooves had been turned out of -it, the diameter at that. paint was less than, the main diameter of the shaft over the splines. This was unfortunate, as the shaft itself, as will be gathered by reference to the sketch, was rather an expensive item, being not only splined for nearly alI its length, but also . formed with a jaw end as part, Of a universal joint.
It was, therefore, necessary-to try to devise some means of saving it, and this " T.H.W." did in what is clearly now a very simple manner. He simply made ae new bearing in halves, one which would slip over the reduced journal, when both:shaft and bearing could be slipped in place together, making a sound repair at -but little expense.
Amongst several hints which have reached us in a letter from " W.C.S.," of Sunderland, is one in which he shows how a universal-joint spider can be pressed home on its shaft while the latter is in place on the chassis without there being any need for ;excessive use of the hammer. His Method is almost sufficiently apparent from one of the accompanying sketches. It will be seen that he ranges use of a, screw-jack in order
to be able to apply his own strength most effectively. The base of the jack is placed against a convenient member of the. frame, suitable wood packing being used if necessary.
On the top of the table of the jack a short, stiff piece of tubing is placed, large enough, as to its inside diameter,
to allow of its passing Over the.screwed end of the shaft on to which the spider is to be forced., Manipulation of the jack in the ordinary way, with, perhaps, the substitution, as the work proceeds, of thicker packings, will enable the spider to be forced into place ; without anyerisk of damage either to it or to-the shaft, damage which might very easily oceur if; as us so frequently the case, a heavy .hammer were to be used .for4the PulPose. •
. The other ,hints which come from this source have not, as a matter.of fact, ally.
thing to do with transmission, although they are, of course, none the less useful on that account. He tells us, for example, that he has replaced the ordinary holding-down bolts for the radiator brackets on his Thorriycroft lorries by long ones, each equipped with a couple of Washers and a, pair of substantial coil springs, all erected, as shown in' the sketch, so as to,allow the radiator to move slightly on the frame, and thus relieve it of the stresses which it would otherwise have to suffer asvthe result of the lorry being driven over bad ground, causing the frame to weave.