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MODERN IDEAS ABOUT STEAM WAGONS.

17th April 1923, Page 12
17th April 1923
Page 12
Page 13
Page 12, 17th April 1923 — MODERN IDEAS ABOUT STEAM WAGONS.
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Which of the following most accurately describes the problem?

Recent Developments in its Design Raise the Question Whether the Steamer can be Ousted by the Accepted Type of Petrol Vehicle.

DEALING with the steam wagon from the designer's point of view, at the meeting last Wednesday of the Institution of Automobile Engineers, Mr. F. J. Bretherton said that had the brains and money been spent on the steam vehicle that have been spent on internal-combustionengined vehicles some wonderful machines would now be on the road. It has.yet to be seen whether the accepted type of petrol vehicle chassis will oust the present type of steam wagon, but, at the same time, it must be said, that the last few months have seen great advances in the overtype wagon.

Dealing with the two types of steam wagon the overtype and the undertype, the former, he said, had been evolved by various makers of traction engines, Messrs. Manns being the pioneers. The undertype was of French origin and had been designed and not really evolved from any previous type, the credit for the construction of the type being due to Count De Dion, Messrs. Thornycroft being the first • to build it in this country on any commercial scale. From 1900 to 1905 there was a leaning towards the undertype, from 1905 to 1919 the preference was for the overtype, whilst from 1019 to within the last few months the undertype again returned to favotir, but now once more ssattention was being directed to the overtype wagon.

For long-distance hard road work, and where a short wheelbase was necessary, the undertype scored, but for hard, dirty work, such as the transport of stones or brick, and the numerous kinds of haulage where bad roads and soft ground were likely to be encountered, the overtype was the better. Three-point suspension saved many a broken spring on bad ground.

The older type of traction-engine driver always preferred the overtype on account of its accessibility, as he could undertake his own adjustments, a thing to which he has been used all his life, but the comfort and ease of driving of the undertype rendered that class of vehicle very popular with the drivers, and allowed a greater mileage to be accomplished with less fatigue. The tendency, however, is for engineers of big fleests to prefer the unit system of the undertype and to employ'rnen who are drivers only, keeping complete units, at home for replacements. Mr. Brethcrton thinks the advantage of the adjustment system is proved by the fact that there are a large number of' overtype wagons running to-day which are about 20 years old, whilst it would be difficult to find many undertype wagons of this age.

In the course of his paper he went on to describe the various ideas that underlie design. He dealt with the locomotive boiler, with the typical square firebox and the type used in the Robey wagon, the firebox of which is so shaped as to resist pressure in every direction.

The water-tube boilers used on undertype wagons have a large grate area, but comparatively small heating surface, and it is essential with this type to have an efficient superheater, as the steam given off is very wet. He pointed to the advantages of the Hopwood type of boiler, with sloping water tubes accessible through two manholes, as this allows the use of a fixed fire hole. He thought that a central fire chute had its objections, whilst space for it was obtained at the expense of tubes, and it also left a large unstayed flat face on the firebox sides.

In Mr. Bretherton's opinion, the exhaust should break at the base of the chimney. The tendency now was to increase the heating surface, to lessen the exhaust, and to make the draught as natural as possible, this being imperative if the proposed regulations are passed with regard to spark catching.

He pointed to the need for care in positioning the pump feed-water inlet, as, being at a low temperature' it must be kept away from the hot firebox plate. The point was not of such great importance when an injector was used, as the temperature of the water was then little below that of the boiler plates.

It was the custom to fit blowers, but they might be regarded as the boiler repairer's friend.

He dealt with many points in connection with engine design to secure ease and economy of maintenance.

Underty.pe engines were nearly always non-compound, and, in Mr. Bretherton's opinion, the economy of these engines cannot be compared with that of the compound high-speed type, as he has never come across a better consumption than 1 cwt. of coal for a 10i, mile journey with a 10-ton loadowhereas there is an authentic case of the overtype engine having done 17 miles per cwt. of coal under the same conditions.

The chain type of steering was simple and cheap to manufacture and maintain, whilst the chains acted as a sort of safety valve in which breakages could occur and very quickly be made good by a split link, but, now that speeds have increased, this type of steering has been dropped, and either Ackerman or the worm and quadrant type has been substituted. Some makers use the ordinary swing arm steering, and others the central pivot, type, but he considers that there is not much in this, as, in the former case, the wheels can be set at such an angle as to bring the tread of the wheel in line with the pivot centre. He considered the dished wheel was not a pretty job, and it prohibited the use of the hollow spoke. Caststeel wheels are the only practice now. The worm and quadrant type steering can be made nearly as quick in action as the Ackerman and is cheap to manufacture.

Dealing with transmission details, Mr. Bretherton stated that attempts had lately been made to use a standard type petrol lorry rear axle, but it remained to be seen how it held up in practice.

The author dealt with many other technical details which had best be considered with the paper as a whole, and he concluded with an expression of opinion that :there were great possibilities with regard to the six-wheeled steam wagon, because the increased weights allowed will render it possible to make a very powerful tractor. The backing of the six-wheeled steamer is simple, on account of the quick reverse, and, in fact, it can be made more handy to .operate than a petrol-driven wagon. The steam wagon lends itself to economically operated tipping, the simplest form being the hydraulic ram directly operated from the boiler feed pump, so that no extra pump is required. Simple cranes can also be operated in the same way.

The steam wagon will always be the -showman's favourite, on account of the simplicity of the drive for a dynamo; and the closeness with which its speed can be governed. As a rule, large flywheels are fltt?t1 to. get a more even turning moment ; this also makes it possible to run the engine at a lower speed to give about 16 h.p., which is sufficient to light the average show.

The discussion which followed the reading of this paper and that an " The Use and Limitations of Steam Wagons," by Mr, 0: Le M. Gosselin, was very animated, many well-known engineers and designers participating, among them being Messrs. G. W. Watson, Thomas Clarkson, F. Ayton,F. G. Bristow, Lt.-Col. A. E. Davidson Major Worby Beaumont, and the president, Lt.-Col. D. J. Smith.

Unfortunately the space at our disposal does not permit us to deal with the many points raised. Mr. Watsen, the first participant, alone dealt with phases which, if examined in detail, would cover pages.

The dominating factor was stated to he that of carrying the largest quantity of goods at the smallest cost per ton-mile, and the main difference between the steam wagon and the petrol vehicle is that the former is more suitable for the hauling of a trailer, and it is by this means that the costs per ton-mile are reduced.

Much. of the discus-ion concerned the comparative advantages or otherwise of the undertype and overtype. It was pointed out that the latter will stand snore knocking about, chiefly because of the very sturdy construction of the boiler.


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