Opinions from Others.
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The Claims of Coke.
The Editor, THE COMMERCIAL MOTOR.
(15591 Sir,-With reference to my previous letter on this subject, I was considering the chemical constituents of various fuels, and worked my theory out as follows : The percentages given for the mixture show a fuel higher in carbon than any coal but Welsh, the same sulphur as Lancashire, less ash than Leicestershire, and a theoretical heat value (formula Cornut) on dry fuel of 14,500 B.T.U.s. Having done this, I experimented, with the results already shown, and proved my theory.
It is natural that Mr. Hilton should in effect ask "How it was done l" Permit me first to mention how it is generally done, and the ideal.
It is a well-known fact that the chief source of loss in boilers is due to rushes of cold air through thin places in the fire ; the ideal, then, would appear to be some form of furnace to diffuse the air for combustion evenly through the fire, on the same principle that a spray is better than a jet for watering a lawn.
The furnace used consists of fivc troughs 5e ft. long by 6 ins, wide, on which are placed transverse bars, the undersides of which project forwardly to intercept the air for combustion, which air is forced into the trough by a small steam jet through a 21m. trumpet-shaped neck. The firebars in plan are 6 ins. by l in., with two air-spaces '4ins, by in.-a ratio of air-space to grate-area of 1-10, even if the fire does get thin in one place. The air-spaces are too small to allow of any rush of a volume of cold air. The air is forced in the form of fine sprays over a comparatively large area.
The available chimney draught was .75 in. in the side flue, but., to minimize the losses from faulty brickwork, etc., the dampers were only open to allow .3 in. The air-pressure under the bars was .6 in., a total draught pressure and vacuum of .9 in.
The flue gas temperature was nearly constant-a variation of less than 30 degrees in four hours. With the mixture of three parts coke-breeze and one part slack, 37 lb. per ,sq. ft. per hour were burned. Working on coke alone, the fires were cleaned at 6 p.m., and. they ran until midnight without again being cleaned. During this time, three tons of coke were burned. There Were 10-12 ins, of clinker On the bars, but, even through this, it Was possible to get a good draught, and a bright steam-raising fire. Mr. Lalonde no doubt knows, and all steam-wagon drivers will tell him, that their " thermometric or pyrometric indicator" is the " old clock "-meaning, of course, the pressure-gauge. On small wagons, where there is small reserve heat, the pressure-gauge Is very susceptible to variations in temperature. As temperatures vary directly in proportion to the rate of combustion, there is more variation in temperature in loco. (including road-wagon) boilers than any other type. The steam is generated automatically 'by the action of the blast-pipe, to suit the varying requirement, and this cannot be altered, but it is possible
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to restrict rushes of air through thin parts of the fire, and that the furnace described does do so is proved by the fact that a locomotive 4-4-0 type, fitted with this furnace, went six months " without a hammer on the tube-plate." The bars have been in use 12 months without any appreciable trace of burning ;the amount of smoke-box ashes and sparks from chimney have been considerably reduced ; it has done main-line express work on slack, and done a day's work of 205 miles without touching the fire with pricker or slice, or to clean out.
The traction engine I referred to is in the centre of Ireland, and I have not had an opportunity of observing the performance over any period, although the reports of the same are highly satisfactory. I am hoping, later, to carry out some tests with a mixture of coke-breeze and slack on this particular furnace, and I shall be pleased to furnish you with the results
obtained.---Yours faithfully, V. R. CuAnwicK. Caxton House, S.W.
[Our correspondent will woe, we think, that be has yet a long way to go in adapting his bars and sys:em to road conditions. We suggest the expediency of his getting into touch with the fuel expert of the
London Coke Committee.-ED.1
The Editor, THE COMMERCIAL MOTOR.
[1560] have read with much interest the Editorial article re "A Campaign to Popularize Coke." As to enlargement of fire-boxes, increased grate area and what not, might I suggest that it would serve a useful purpose to set forth also, in detail, if thought necessary, a few simple arrangements rendering possible the utilization of forced draught. I have on occasion surmounted difficulties in this way. It often happens that one can persuade users along these lines in preference to any important structural alterations.-Yours faithfully,
Anglesey. WILLIAM H. BURTONSHAW.
That Lamented 35] % The Editor, THE COMMERCIAL MOTOR [1561] Sir,-I should like to associate myself with " W.H.W." in the matter of the dropping of the 33i per cent. My own experience of the views of several importers of considerable standing bears out that. of your correspondent ; they are willing to pay, why deprive them of the privilege? Our heavy-vehicle manufacturers, notwithstanding the recent release, are still handicapped in their competition with the American for the custom of the user.-Yours faithfully, A. BIMSON. Cardiff.