Opinions from Others.
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The Editor invites correspondence on all subjects connected with the use of commercial motors. Letters should he on one side of the paper only and typewritten by preference. The right of abbreviation is reserved, and no responsibility for views expressed is accepted.
Types ol Two-fuel Carburetters.
The Editor, THE COMMERCIAL MOTOR.
[1375] Sir,—I was greatly astonished to see your report of the Smith-King paraffin carburetter, and that this invention is being described by you as "novel." The main feature of the Smith-King invention seems to be that they use petrol on one jet, and paraffin on a second or third, or even a fourth, jet. This idea was patented by me in 1912, and. it has been constantly manufactured since ; in fact, from what I can see from the description of the apparatus, it is, except for detail construction, an exact copy of my invention.—
Yours faithiully, C. )INKS, LTD., C. SINES, Managing Director. Pheenix Works, Eccles, Lanes.
Paraffin Fuel and Lubrication Efficiency. The Editor, THE COMMERCIAL MOTOR.
[1376] Sir,—I have recently been carefully perusing the articles which have appeared in THE COMMERCIAL MOTOR relating to the numerous road tests and demonstrations that the various makers of paraffin caburetters have been giving to their prospective customers, and to members of the Press. You have, in certain of your editorial notes, made mention of the condition of the interior of an engine after the use of paraffin, but the amounts of engine oil that are used with that fuel, and the condition of the oil remaining in the base after being cooled down, seem to me to he points that want more ventilation.
I have had some little experience of running a fleet of commercial motors on paraffin, and I found that in eery case eventually paraffin got through to the engine oil. Very careful watch had to be kept to see that the oil was not allowed to get too thin.
It is all very well to test these .paraffin carburet , tens. on a new vehicle where the cylinders and pistonrings ha vf3 had very little wear. They will always give good results during a short run, the engine, of course, being tuned up previous to the demonstration, but, from the user's point of view, in my opinion, any test under the before-mentioned conditions is not good enough. I would suggest that, to have a really-efficient test of the capabilities of paraffin carburetters, the device should be fitted to a 2-ton or 3-ton vehicle that has already been in service a eouplel of years ; the engine should be opened out previous to the test, all carbon deposits removed, valves put in ordinary good condition, the base chamber cleaned out, and the required quantity of engine oil put in. When this has been done, a run of at least 100 miles under ordinary working conditions should be made, on petrol. At the completion of the run, the engine having cooled down, it should be opened out again and the amount of carbon deposits carefully noted, also the amount of engine oil used and the condition of the oil remaining in the base chamber, the oil being put into a glass jar for later comparison. The engine should then be cleaned and closed up, fresh engine oil of the same kind and amount put in, and the vehicle should do the same run on paraffin. Then, for the test to be conclusive, the cylinders shonld be taken off, after the run, carbon denosita carefully noted, also whether any paraffin still remains upon'the walls of the cylinders, or behind the piston-rings and valves (should this be the case. it would be detrimental to the engine if it stood for any length of time withont working), and whether the pistons and cylinder walls appear to have the same amoimt of lubricating oil remaining upon
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them under the paraffin test as they had under the petrol test, as if this is not the ease undue wear will take place owing to want of lubrication. The oil remaining in the base chamber should be carefully examined, to see if there are any signs of paraffin having been able to creep down the walls of the cylinders and get intermixed with the engine oil. The trial having been held under these conditions, I think one would be in a better position to judge as to whether it would be advantageous to change from petrol fuel and use paraffin.—Yours faithfully,
London. M. V. AMBLER.
[Users of paraffin fuel in internal-combustion engines are again invited by 119 to send any "bins" ox "tips" such as the foregoing.—En.] Mechanical Aids to Farming.
The Editor, TEE COMMERCIAL MOTOR.
[1377] Sir,—The contributor of this most interesting series of articles, when referring to chain-track tractors (page 429), states "it is impossible to lubricate the chains of these tractors in a satisfactory manner." We beg to differ. So far as the "Caterpillar" tractor is concerned, we provide a drip feed for the case-hardened steel space-blocks and the case-hardened steel pins forming the joints of the track-shoes, such drip feed supplying oil whenever required. We find, however, that this oil feed is absolutely necessary only when the machine is proceeding across sandy soil such as desert lands.
Later, your contributor states "it would almost appear that the most efficient type of tractor for general farm work is that fitted with ordinary driving wheels, and not that utilizing a track-laying chain." Now, the ordinary wheel tractor is designed for road use, and is capable under suitable conditions of being employed on the land. The chain-track machine, on the other hand, is especially designed for use on the land, and to meet all the conditions required in cross-country work. The difference is most apparent when manteuvring at headlands.
If a farm tractor is to be employed for ploughing, it must be of such a nature that (1) it will not compress or pack the soil, and (2) its adherence to the soil will prevent it from slipping on soft ,ground. These two attributes are found only in the chain-track tractor. An ordinary wheel, tractor depends for its adherence upon the weight of the machine, which is distributed along the transverse line-contact of the wheel with the ground. Thus, as loads increased, the width of the driving wheel had also to be increased, until wheels of 36 ft. in width were employed. Even that was ineffective for soft or marshy lands, such as reclaimed lands or clayey soil. The softer the soil, the more the wheel sank in, so that, while the line-contact was increased, the wheel was always rising out of the depression, i.e., going up bill.
Our " Caterpillar " distributes the weight of the machine along the whole surface of the chain track which is in contact with the ground. For this reason, it does not compress the soil, and, on any reasonable surface, ranging from swamp lands to ice-bound tracks, it does not slip. •
We would refer Your Contributor to the very excellent article on the " Caterpillar " published by you in your issue dated the 27th January, 1916.
May we also draw your attention to the fact that "Caterpillar " is ipur registered trade mark in this country for chain-track traction engines, and should not be used as referring to a type of machine ?—Youra faithfully, CATERPILLAR TRACTORS, LTD., VICTOR F. FERNY, Director.
60, Queen Victoria Street, London, E.C.