MORE MISCELLANEOUS TIPS.
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Further Helpful Contributions From Our Driver and Mechanic Readers.
AMANCHESTER correspondent, " A.E.," to whom we are this week awarding the 15s. prize, sends some
useful tips for testing lubricants. The " body " of several oils may be compared, he says, in a simple manner. 'fake a piece of glass strip and place it with its surface in a slanting position. Put a few drops of the oils, which are to be tested, on the glass, at its highest point. The oil which runs the farthest has the least " body."
To test for " gumminess " allow a small quantity of the oil to remain on the top of a piece of glass for a few hours. Then proceed to rub it off. If it is sticky, then the oil has been mixed with some gummy substance, and is the worse for it.
The presence of acids may easily be discovered, Put a little of the oil in a test tube with some het water. Shake, and leave to settle for a few minutes. Then pour off the oil and test the remaining water with litmus paper, which will turn red if acids are present. The flash test is important, especially in connection with cylinder oils. Place the oil in an evaporating dish, and heat A method adopted by "A. E." for test. ing the relative consistency of grease.
gently with a Bunsen. Suspend a thermometer in the oil, When the temperature reaches 150 degrees Fehr. bring a small flame near the surface of the oil. If nothing happens, continue the heating process slowly, applying the flame, in the same way, at every rise of temperature of 2 degrees. At last a small blue flame will be noticed flashing across the surface of the oil. When this happens the temperature should be recorded, for that is the flashpoint.
The accompanying sketch shows a simple apparatus by means of which the ... consistency Qf a lubricating grease may be tested. A sheet-iron bracket mounted 1011 a wooden base is drilled to accomanodate a brass peg or pin, the hole being so large that the pin is an easy fit therein. A small weight is attached to the blunt end of the pin as shown. The pin must be long enough to touch the board without the weight coming into contact with the bracket. A receptacle for the grease is then procured which will go under the bracket. This should be filled with grease, and the pin allowed to rest on the top, sinking into the grease on its own accord, under the influence of the weight. The time taken for the pin to sink until its point reaches the bottom of the grease is a measure of the consis
tency of the grease. This test is, of course, only a comparative one, that is to say, it is only useful for testing a new grease against an old one, the satisfactory nature of which is thoroughly well known.
" H.A.B.," of Rotherham, in the course of a repair job, found that some 1i-in studs had stripped in the holes in the housing. To get them out he had to drill them, and, subsequently, to open out the holes and tap them in. Whitworth. He made new studs in the manner indicated in the accompanying sketch, by turning down the heads of bolts, and screwing them I in. " H,H.," of Highgate, reminds us that a bolt which frequently breaks may sometimes be strengthened, paradoxical How "H. H." strengthened a bolt by reducing its diameter.
as it may seem, by turning it down in the middle, as shown in one of the accompanying sketches. The diameter at the reduced portion must be the same as that at the bottom of the thread of the bolt, and the step from one diameter to the other must be well filleted or radiused as shown. This also applies under the bolt head. The reason for this curious phenomenon is that when the bolt is stressed, that stress, in the ordinary way, is must felt at the weakeat part of the bolt, namely, at the bottom of the thread. As a slight stretching here is sufficient to break the bolt, the mischief is soon done. Turning the bolt down as shown allows of the stress being taken over a much longer piece of bolt, which distribution of effort allows the bolt to give slightly without. breaking.
" H.B.," of Stockton-on-Tees, drives a lorry the accelerator pedal of which operates the throttle valve through the medium of a Bowden cable, with which, he tells us, he has had a lot of trouble, from one cause and another.. The wire is sweated into two nipples, which screw into ball pins in sockets on the operating gear. It frequently happens, on using the accelerator, that the wire buckles, and, after a time, as the result of this buckling, strands begin to break, and eventually the cable itself gives way. Having at last got tired of this trouble, "H.B." got over it by removing the Bowden cable altogether, and substituting a pair of motorcycle-wheel spokes. He removed-the Bowden cable from the nipples and the nipples from the ball sockets. The wheel spokes were then fitted in place of the cable, and were connected by a piece of cycle chain, round the end links of which the free ends of the spokes were bent. The result was quite satisfactory.
" E.J.," of Sandbach, Cheshire, sends us a tip which may be useful to those readers who may have to rebore some of Reboring an old bracket on the lines adopted by "E. J."
the odd-shaped brackets from which no motor vehicle chassis is free. The sketch is almost self-explanatory. It is shown applied to an ordinary drill, and can be se applied to any machine which is capable of taking a 1-in. drill. The two strips shown are needed to allow clearance for the tool as it emerges through the hole at the underside of the bracket. The latter, if it has a face parallel to the hole, should be located by that face, holding it to an angle plate as shown. If no such facing exists, hold the bracket down with split plates as usual. The cotter (D) holds the tool, and by easing it off the tool can be set to give the desired cut.