Opinions from Others.
Page 17
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Are Tractors Too Powerful?
The Editor, THE COMMERCIAL MOTOR.
[1258] Sir,—Re the drawbar bracket. The higher tins is the better, for level pulling and climbing. For instance, chaining your load up a bank answers when you can't pull it attached direct to the drawbar. This answers the same. as a higher bracket would do. [Winding from the tractor at rest is not comparable with pulling by its tractive effort. —En.] Cooing down a bank, the high bracket would be a disadvantage, because your load would tend to lift the engine up and lessen the weight on the driving wheels, and you would have to use less brake power. In going down some bad banks with a very heavy load, or on setts, a practical man will turn his engine and attach the load to the front pulling bracket, so that., when the load tends to lift the front end tip, he gets more weight on the driving wheels, and the engine is then less liable to skid. Of course, it is not. necessary to turn on every
"
bank.—Yours faithfully, TR-AHO."
South Shields.
The Editor, THE COMMERCIAL MOTOR.
[1259] Sir,—The question has now drifted into other channels, such as the causes of the front wheels of a tractor "lifting." The problematic answer advanced by your correspondent Mr. T. C. Aveling is questionable, as a solvent to the solution of the causes of the front wheels lifting by tractive efforts. If your correspondent's hypothesis is real in fact, why do the wheels lift when the engine is started suddenly with no load behind the tender 1
The factor causing the wheels to lift is one of design, which is distinct in a four-shaft engine, and nonexistent in one with three shafts. The four-shaft engine ilis the propensity of winding itself up when pulling heavily ; the three-shaft type to wind itself down, and no alteration in the position of drawbar pull will counteract it, or the result of its objectionable functioning. But the redeeming virtue is that it diffuses strain in a very telling manner, and the action is not detrimental to the tractive. force of the. four-shaft engine. If it were so, it would not enjoy the popularity it has over the three-shaft engine.—Yours faithfully, Weston-super-Mare. Wieerem T. LA,LONDE.
The Editor, THE COMMERCIAL MOTOR.
[12601 Sir,—Mr. T. C. Aveling takes lee to task, and suggests that my previous reference to the Broom and Wade tractor was caatradictory, insomuch as I said that the Broom and Wade tractor did not slip its driving wheels so much as the Thornycroft, because it had not the power to do so. As a matter of fact, when this tractor was running on the road, there was no slip at all, but slip occurred when the tractor was passing through the bog without its trailer behind it, preparatory to hauling its trailer across with the winding cable, and under such conditions it is not surprising that the wheels did slip. I still hold to my point, however, that 40 h.p. on a steam tractor for all ordinary commercial use is more than is really neeessary ; the Broom and Wade showed that with its 25 h.p. it was quite capable of dealing with a commercial load under commercial conditions, and the fact that it did not make a better showing in the trials of .1909 was not the result of its having insufficient power, but due to its construction and workmanship.
Mr. Aveling raises a point concerning the lifting of the smoke-box end of traction engines. I have experienced this myself on many occasions, and it is due, as Mr. Aveling states, to the unequal balance of the smoke-box end as compared with drawbar pull, the result being that the final-drive pinion tends to climb round the final-drive wheel on the axle.
I should be greatly interested to have the diagram which Mr. Aveling promises, showing how he proposes to attach the drawbar to the axle. With a tractor with 5 it. wheels, which is about the average size on present-day tractors, the attachment would then only be 2 ft. 6 ins, from the ground, and this height is less than the height of the turn-table on many existing trailers, so that I fail to see how he is going to throw any of the trailer load on to the tractor axle as at present designed.
My point is, that by limiting boiler and engine sizes
to more reasonable dimensions, the weight thereby saved would enable builders to fit wheels of larger diameter,, thus raising the centre of the axle, and the method of attachment proposed by Mr. Aveling would then have the desired effect. I trust Mr. Aveling wilV forward to yoh the diagram which he promises, as I am sure that it. would be of great interest to many readers of your journal.
I quite agree with Mr. Aveling, that the use of a loaded tractor, of the La. France or any other type, in which part of the load is carried on the tractor, is entirely opposed to the experience of old road-engine men.---Yours faithfully, " VERAX"." A Challenge as to Resiliency.
The Editor, THE COMMERCIAL MOTOR
[1261] Sir,---We notice the letter from. Liga Tyres, Ltd., in your last issue, and would remind them that argument by analogy is as dangerous as that " little knowledge " referred to in the proverb. They are quite wrong in _saying that pure rubber has been discarded in the manufacture of electric cables. On the contrary, it is used as insulation on all rubber cables that we and other first-class cable makers manufacture, and there is nothing better known for this purpose. This, however, is by the way, as there is no parallel between the ease of an electric cable and that of a band tire.
A band tire is subjected to enormous disintegrating strains throughout its substance, due to the transmission of power and the partial absorption of road shocks. This is not so in the case of an electric: cable ; therefore, no useful comparison, can be drawn between them, and the analogy is useless. [We recall that it was merely sought to establish by analogy the ca-se for testing under conditions of use.—ED.]
With regard to the Liga Co.'s statement that " No
amount of nursing by leads of soft rubber or springs either in the wheels or chassis will in itself exclude the engine or load from the minimum shock," we do not know what this has to do with. the matter. We have not stated that our patent super-resilient tire will completely exclude the engine and load from shock : our claim exists particularly in the statement that it is more resilient than any ordinary band tire on the market to-day, by reason of its being fitted with a specially-shaped pad of soft resilient rubber, to absorb the vibration more completely, whereas the others are not.
The difficulties of heating and resistance to climatic conditions had already been fully guarded against, long before we put the first tire on the market. The patent super-resilient tire is fully guaranteed : if our claim for extra resiliency is not borne out, the user can have his money back, as per our published advertisement. Can Messrs. Liga Tyres say as much of their product/ They seem, by their intervention, anxious to bring this matter of resiliency into the daylight ; we are, therefore, quite prepared to extend our challenge regarding a resiliency test to them, on exactly the same terms as were expressed in our letter in your previous issue to Messrs. The De Nevers Tyre Co., to which, we are sorry to say, we have not as yet beau favoured with a reply.— Yours faithfully,
ST. HELENS CABLE AND RUBBER CO., LTD., WALTER BOND, Rubber Dept. Sales Manager. Warrington.