ROADSIDE AND GARAGE.
Page 67
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Interesting Contributions from Our Driver and Mechanic -Readers.
Overcoming Some Crank-pin Troubles.
TITE letters which we recently pubfished on the subject of big-end bearings appear to have touched on a point which is of great interest to all concerned in maintenance. One very practical repairer tells us that there is nothing he dreads more than the failure of a big-end immediately after overhaul of an engine, as such a failure is often used by the owner of the vehicle as an excuse for disputing the bill. In some cases he has known a failure of the kind to be used as an argument by a certain class of customer to dispute the whole bill, and to refuse to pay for work done on other parts of the vehicle, saying that the failure of the big-end was a proof that all the work was done in a careless manner, and even an appeal to a County Court has not had the result of uphoning the claim of the repairer. The summing-up Of the letters, which we Published on January 10th, deals with all the points which have been raised; we have, however, had many more letters on the subjeet, all of which go over the points already mentioned.
The correspondence, however, in now taking a new turn, as some letters point out that a bearing cannot be satisfactorily fitted to a crank-pin which is not round, the same applying to main bearings, but not to such a marked degree, as main bearings do not show xi:pis of wear so readily as crank-pins, A letter from " CH.M.," of Plumstead, points out the importance of bringing the crank-pin back to its true form, and says: "It is not fair to any fitter to expect him to bed in a set of big-end bearings to work satisfactorily on a crank-pin that is not round and smooth all along its length. The proper thing to do with a cinink that is worn is to send it to one of the firms who make a speciality of such work and have all journals ground, not turned up in a lathe. If time or circumstances will not permit of this, the next best thing is to use one of the tools that are made for the purpose. The work done by such tools, although good, is not quite equal to that done by a proper crankgrinding machine.
"In cases where neither of these methods is possible, the main hearings_ may be turned in an •ordinary lathe, but the crank-pins are difficult or almost impossible to get right by turning, so should be dealt with by some other means. I noticed in your issue of the 10th inst., page .1511, that a contrivance indescribed -which consists of two• blocks of wood, cut to fit the crank-Tin and held together by bolts; and used to grind the Pin true. • As an rid engineer who remembers the days v.vhen: there were no grindingmachines, find•Iapping had to be employed wherever a truly round shaft had to be produced, should say that the device shown would be little or no use to produce a perfectly round pin. The reason for "this is that the wood would yield, and so allow an oval pin to revolve within it without doing much more than act as a means for polishing the _pin. A proper lap should have pl.-antis:any no yield, and the way to make it is as shown, where. two pieces of I-in, by kinin._ iron are held together by baits and are forced apart by setscrews. Lead pieces are cast into holes drilled in the iron, The iron should be tinned so that the lead adheres, and water instead iof nil Nhould be used while grinding the journal.
"Emery powder of a -coarse grain should be pressed into the lead by rolling a piece of round _iron over it and not by merely sprinkling it on". The screws .should be adjusted no that the lap goes tight on the major axis of the oval and slack on the minor axis. Each piece of lead should only cover a quarter of the pin, so that the high parts can be lapped avilt5.' without touching the lower parts. Emery cloth should be dragged lengthwise along the pin so that the effect of the lap can be seen.
"By oscillating the lap on the high part and supplying fresh emery and water and moving the lap along the journal, a Very good job canbe made, which will compare favourably with the work of a grinding machine. For finishing a finer emery can be used. If the oval be very pronounced, a smooth file can be used to annist the action of the lap, as the effect of the lapping can be easily detected from the senntnhingof the emery cloth."
Useful Wheel Grips.
ONE of our correspondents, "F.L.W.," of Victoria Park, E., who has to do a lot of farm work, tells us of the troubles he has had with the wheels
of his vehicle either failing to grip on soft earth tracks or sinking deeply into the ground in wet weather. He has tried the usual chains made to go round a wheel, but finds that when the wheel has once sunk into the ground there-is great difficulty in getting the chain in place. So often did he have these difficulties that he thought that some better means of attaching grips might be devised—something that could be fixed up after the Wheel had imbedded itself.
With thin idea in view he procured
number of short pieces of gaspipe, the length of which was about equal to the width of the tyres. Through these he passed short lengths of chain, the ends of which he joined
with bolts. The chains were passed under • the rim and between the spokes. With this he can get out of any difficulty, as he has only -to put a number an the part of the wheel that is not on the ground, then put in his low gear, and partly rotate the wheels, and the rest of the chains and pieces of Pipe can he put in place. Where he is travelling over ground that is merely slimy on the surface, he uses the chains alone. He also says that if a fiirry be slipping to one side, and be likely to get into a ditch, he fits most of the pipe pieces% to the wheel that is on sound ground. About six per wheel is what he recommends.
Starling Large Engines in Cold Weather.
IF we may judge by the number of
letters we have received on the subject of easy starting, the matter in one that is of considerable interest, so we propose to deal very fully with all the suggestions we receive, The present correspondence was started by the letters of " W.G.B.," of Faringdon, and "E.G.," of Sheffield, both of which appeared in our issue of the 17th inst.
Some practical information is sent to us by " S.G.P.," of Winbeeh, whin has been driving heavy lorries for many years, and who has to be out punctually every morning, although he has to fill up with cold water from the mains and to keep his Vehicle in a garage that is not warm4d. His method is as follows. He sets the throttle of his Claudel carburetter a quarter open and the ignition lever abort three-quarters forward, when the vehicle is brought in at night, and before switching off he races the engine, and, quickly passing to the front end, closes the air shutter, turns off the petrol and switches "off:
On arriving in the morning he fills up the radiator, turns on the petrol, withdraws the clutch and. fixes the pedal in that position with a piece of wood. He then gives the engine about six turns with the switch off, opens the sir shutter about half-way and switches on, and be tally us that he rarely finds any difficulty in getting a start. He appears to be much in "favonit af holding the clutch out, as without that he often finds difficulty, probably' due to stiff lubricant in the gearbox.