Opinions from Others.
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A Sprag-cum-brake Fitting for Heavy Lorries.
The Editor, THE COMMERCIAL MOTOR.
[1393] Sir,—I have pleasure in submitting a tracing of my scotch-brake and a small black and white sketch showing an alternative method of fixing the side plates to the chassis side members.
In this latter connection I might explain that the construction shown on the tracing happened to be one that was best suited to the particular vehicle to which we fitted the brake, namely, a Yorkshire sixton steamer. In both methods the construction permits of the whole device being moved about 3 ins: in the horizontal plane, facilitating fitting in the first place and subsequently allowing the sprag to be adjusted at the same time as the radius rods. I may say that owing to the acute shortage of labour we have so far only been able to get one of our fleet fitted with the device, and are awaiting a suitable opportunity to fit up the remaining five wagons, all the fittings being ready for attachment. I had hoped to get it taken up by the makers of heavy motor vehicles, but there seems to be a prejudice against a device whose existence appears to cast a reflection upon the efficiency of the ordinary service brakes.
The fitting was designed in consequence of a sequence of unhappy experiences we have had with heavy vehicres on the severe local gradients. We use wagons of six tons capacity built by the Yorkshire Commercial Co., and I wish to make it quite clear that I should not like this letter to imply in any way that these vehicles meet with more than an ordinary share of trouble. We have had several cases of wagons running backwards as the result of (I) wheels skidding on a steep gradient, (2) chain breaking whilst ascending a steep gradient, (3) joint in main steam supply pipe blowing out whilst ascending steep gradient, and in each of these three cases the service brakes failed to hold and the wagon ran back. The brake is applicable to any type of chassis, and where such vital issues as the safety of the public and human life are at stake I do not think the argument that it cannot be lifted from the driver's footplate need carry much weight. As regards the objection that it will only act in one direction, I would point out that a duplicate set could be fitted to act in front of the driving wheels and could be operated by the same control as that one by which the back-run sprag is dropped.
The device is essentially for use in very hilly districts, and our tests have shown that with a loaded wagon, 13-14 tons gross weight, running back at a speed of 8-10 miles per hour, it can be trusted to bring the vehicle to a standstill.
A man who would let his vehicle attain such a speed on a back run without dropping the sprag has no right to be in a position of responsibility.
We have not tried it beyond this speed for obvious reasons.
In the case of a. forward runaway there seems no reason why this sprag should not be used, but, as I have pointed out, it was primarily designed for stopping a run back. In the case of the wagon getting out of hand whilst travelling forward, the driver at least can see where he is going and has a chance to put his wagon "into something" to stop it.
In order to be on the safe side, and in view of the heavy cumbersome vehicles for which it was designed, I made it comparatively heavy, but I have since come to the conclusion that the wedging action is so perfect that a much smaller sprag might be used I do not know what your experience is with these heavy steamers, but I have always held to the belief that the engine is really the brake. The ease with which an engine can be thrown into mid gear or reversed and the sweet braking effect so obtained is, to my mind, a subtle menace to the efficient condition of the regulation brakes, as drivers become so accustomed to checking their speed by "linking up" that they are apt to neglect their other brakes and to allow them to fall into a state of inefficiency. Ever
in such circumstances the vehicle is under. perfect control until a chain breaks, a key shears, or a gear strips, and then the trouble commences.
This particular design has its faults, but it fulfils that duty for which it was designed, and that's the main thing. So long as wagons run, so long will chains snap, gears strip, and keys shear at the very moment they should not do these things, and so long will careless drivers, neglect their regulation brakes, but with a wagon fitted with this device a driver can face the steepest gradient in the busiest part of a town without the haunting dread that should his driving gear fail he is going to make a shambles of the traffic coming up behind him. The most striking fact in connection with a run back, consequent upon a chain breaking, is the incredible speed a wagon will attain in a short dis
tance.—Yours faithfully, H. C. WIDLAKE. 5, Chester Place, Mutley, Plymouth.
Typical Forms of Hiring Contract for Long-term Haulage.
The Editor, THE COMMERCIAL MOTOR.
[1394] Sir,—I have perused with interest the form of hiring contract appearing in THE COMMERCIAL MOTOR of tbe 21st ult., and, whilst I am not, of course, competent to express an opinion as regards the general terms of same, it appears to me as an insurance man that Clause IX might be very much strengthened by the insertion of a few words providing that the hirers shall give to the contractors notice of any accident so soon as it shall come to their knowledge.
I have not lost sight of the fact that the contractors' own employees would be driving, but it sometimes happens that the notice of claim would be sent direct to the hirers, and, if they omit to advise the contractors, the latter might have some trouble ,s ith their insurance company. This may be only the super-criticism of an insurance man; if so, I have no doubt you will know how to deal with this letter. --Yours faithfully,
24, Moorgate Street, E.C. S. WOOD. [Mr. Wood's point is one of practical importance and value.—ED.]
No More Tramways.
The Editor, THE COMMERCIAL MOTOR.
[1395] Sir,—The articles on "The Tramway's Decay," recently published in your journal although interesting to most of your readers, must have been somewhat amusing to many tramway men. How a man who as you tell us has invariably been an enthusiastic champion of the commercial-motor vehicle can make a dispassionate study of the relative claims of the two types of passenger conveyance is a trifle beyond me. However the subject is one of the most debatable of modern times, but I venture to think there are many who will agree with me that each has its own particular sphere of action, and that there is plenty of room for both. Neither you nor I have time to go into many details, but I should 'like to draw your attention to the official returns for 44 of the principal tramway undertakings in the United Kingdom, for the week ended 30th September, giving total receipts of £198,009, or 224,160 more than the corresponding week of last year. If this is decay it is a form I think that many of us would like to be.
associated with.—Yours faithfully, "BOTH."