USEFUL HINTS AND TIPS.
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Interesting • Contributions Mechanic from Our Driver' and Readers.
MHE subject of the easier starting of large engines still appears to interest our readers, if we can judge by the number of letters we are still receiving suggesting remedies that drivers themselves can apply and calling attention to what might be done in future designs to minimize the trouble. • A typical letter pointing out what might be done and how at a trifling cost drivers could be relieved of this unfair strain is that of " F.S.," of Swanky, which we publish in its entirety.
"Your easy-starting tips given lately in The Conint,reial Motor have been very interesting to me as a repairer. ' When we get a lorry in, it is often out of order, and has to be started and run to see what is wrong with it. You can imagine we are in for a hard grind when we are strangers to the vehicle and do not know the best position to Set the levers for easy starting. Since engines have become so large (and especially the big sixes), to start them up on a cold morning is now more than a
man should be expected to do. The main fault is with the designer—he may get all the kicks, but he is really to blame for this condition of affairs—and ant sure that if a lorry designer had to start one of his own lorries every cold winter morning there would soon be something doing, and we should see makers each claiming to start lorries easier than their competitors.
"-All the following suggestions could be incorporated in a vehicle without making more than a slight difference in the cost. The clutch pedal could be held down by a catch when necessary. A starting handle could be made which would accommodate two men for turn
ing. As regard impulse starters for magnetos; the writer has had a good deal of experience with these on American tractors fitted with indifferent American magnetos. These tractors would not start without the impulse fitting—with a good magneto they would be ideal. Why is it not possible to slide the camshaft to give half-compression as was done in the case of the old big-bore 40 h.p. touring car engines? These often had a keyed camshaft sliding in its gearwheel, which was a bad method ; it is quite easy to make a wider gearwheel and slide the teeth through those on its neighbour ; there is then no more backlash than is normal to gearwheels. Lastly, a really decently made large tap with handle, which will take a pail underneath so that the radiator can be drained without using a spanner, should be incorporated. This tap should be inside the bonnet, er some bright boy might turn it on while the driver was absent.
'I have advised many an owner to have a gas geyser fitted so that the driver can fill up straightaway with hot water on cold mornings ; I have never seen one do it yet, however, and it is a mystery to me why they will not do so. The gas companies fit these free at a quarterly rate, and one can get a bathful of scalding hot water for 2d., and Yet the owners prefer to see a man get up extra early on cold mornings and waste the best part of an hour, getting hot and exhausted. It is not a good start either for a day's work or a cold drive."
Mysterious Failures with Taper-roller Bearings.
ALL who have had experience with
bearings of the taper-roller type have at times stem mysterious failures for which it is not easy to account. A correspondent, " F.W.W.," of Hendon, recently showed us an example of such a bearing. In this case the bearing was on a road axle of the type in which the wheel is secured to the axle by a cone, the axle revolving. The failure occurred in the bearing near the road wheel.
A close examination of the outer and inner rings showed that very great pressure had been brought to bear on the rollers. There was no sign of want of oil, of a seizure, or of the rollers refusing to revolve. The appearance of the rings was that of steel in perfectly good condition, well lubricated, but having received a pressure that no ordinary cireumstances could account for ; the bearing at the other end of the axle, which must share equally any end pressure due to the running up of a nut, showed no signs whatever of distress. The load which the vehicle carried could not possibly account for the pressure which must have been brought to bear and which had discoloured both rings and had burst the outer one, enlarging the housing in which it was mounted.
We have on other occasions seen similar failures of one of a pair of bearings, both of which have been under the same load. Our correspondent, " F.W.W.," has recently been investigating the Humfrey-Sandberg free-wheel device, in which rollers somewhat akin to those used on bearings, but placed askew with the axis of the shaft, are employed. He suggests that the cause of these mysterious failures may be due to the cage of a roller bearing becoming damaged or breaking up and the rollers getting askew so that they are turned for the moment into a Humfrey-Sandberg clutch, as it is now known that such a clutch will transmit almost an unlimited torque without slipping, so, if the rollers take up this position in the direction which tends to wind them inwards, the discolouring of the metal, the bursting of the outer ring and the enlarging of the housing can easily be accounted for.
Should this surmise be a coerect diagnosis of the trouble, we would suggest that the makers of such bearings should investigate the matter, as a stronger cage might provide a remedy.
A Tool for Grinding-in Overhead Valves.
A READER, " C.A,B.," of Ipswich,
tells us that he has found in some engines of the overhead-valve type there is no provision, suchas a screwdriver cut, for the grinding-in of the valves. In such cases be has made a simple tool which he tells us answers very well.
The tool consists of a piece of mild steel drilled up to take the valve stem, and provided with a setscrew and a cross-piece for a handle. With this tool he can get hold' of the valve stem, and by pulling the head down on its seating he can grind it in with ease.
He also suggests that a small drill chuck might be fitted to the stem of the tool so that it could be used for any size of valve stem.
To Prevent Wheel-wobble.
WHEEL-WOBBLE is not often a trouble with the heavier classes of vehicle, but among many fleets the are often light vans, which are practically private cars, and travellers' cars which fall under the care of maintenance engineers.
A simple suggestion to prevent this trouble is given by " R.S.," of Herne Hill, SE., who fixes an ordinary shock absorber or damper to the steering as shown in his sketch. We take it that the class of damper he suggests is one that causes friction in both directions, and not one that goes stiffly in one direction and freely in the other direction. He tells us that he has known this device to have cured the trouble in four cases besides his own.
It is well known that in many cases a very slight friction will remove the tendency to wobble, as we have known instances of the removal of ball thrusts and the replacement of them by fibre washers to prove a cure.