OPINIONS FROM OTHERS.
Page 20
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The Editor invites correspondence on all subjects connected with the use of commercial motors, Letters should be 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, Gas Firing for Steam Wagon Boilers.
The Editor, THE COMMERCIAL MOTOR.
[1616] Sir,—With reference to the two articles which appeared in your issue of the 11th July, Lhave read these with interest, as this is a question which has appealed to me for some time past.
. On going into the matter, however, it is quite apparent to me that the figures you give are somewhat misleading. For instance, one ton of coal distilled in a retort yields approximately 10,000 cubic ft. of gas with a calorific value of about 550 B.T.U. per cubic ft. Amongst the many products of distillation there is 13 cwt. of coke with a calorific value of a.pproximately'12,000 WT.U. per lb.
Therefore the B.T.U. contained in one ton of coal is [Considering only that obtained from the coke of 10,000 x 550 + 13 X 112 x 12,000 = a total of .22,972,000 B.T.U. • Taking the coal consumption as given in your article, i.e., 200 lb. per half-day and coal with a calorifto value of 14,000 B,T.U. per lb., the total'heat in the coal burnt per half-day is 14,000 x 200 2,800,000 B.T.U„ and as coal-gas has 550 B.T.U. per cubic ft. we should need 2,800,000 5100 cubic ft. of gas.
. Approaching the question in another direction, wo will. assume that the average horse-power developed by a Steam wagon' engine is in the neighbourhood of 20 h.p., and the steam consumption at the rate of 25 lb. per b.h.p., we would then require 500 lb. of steam per hour. The total heat in, the steam is about 1200 B.T.U. per lb., so that the heat actually carried by the steam per hour is • .
1200 x 500 = 600,000 B.T.IT, = 1100 550 cubic ft. of gas. • Adding 25 per cent. to this for boiler losses, we have 1375 cubic ft. per hour. A four hours supply would mean 5500 cubic ft., which, even if compressed to 1000 lb. per sq. in., would need 81 cubic ft.—Yours faithfully, H.W.Y. Shrewsbury. Lts we stated in our last issue, page 444, we realized on further consideration of the subject that Molesworth's figures must be interpreted to mean gas produced' in a producer 'plant, and that the same efficiency could not. be expected from town gas.—En.
Steel versus Rubber Tyres.
The Editor, THE COMMERCIAL MOTOR.
[1617] Sir,—I have read with great interest the subject matter in your issue .of the 11th inst. on .. rubber or steel tyres. There is one point on which I think it necessary to correct the writer. He states that a 5-ton (meaning, of course, a 5-tun steam wagon) on rubb-er tyres is permitted to travel 12 miles per hour. As •a -matter -of fact it is not so; -.a 5-ton :vehicle on rubber tyres is only allowed -to travel at eight.miles per, hour. -If -the load on neither axle exceeds six' Jens then possibly he would be right in his 12 miles per hour as Stated, but as a 5-ton wagonwhen loaded, has a heels axle load of. eight tons eight miles per houris then (Ally Perinissible.
This being so, his relative figures will of course be altered, and it might be advisable to state 60 against 41 miles per day would be the rate instead of the 70 6 he states. This, of course, will rather alter all the ot-her figures to the worse side. Still,'" quite agree that the rubber tyre will be an enormous factor in the increased utility of the steam wagon, and .I am in favour of seeing. all vehicles so fitted even although the cost pei. mile will not be quite as rosy as your contributor makes out.
Thereis one fact he has overlooked, and that is while the highest speed on the steam wagons allowed by rubber tyres will undoubtedly save considerable -wear and tear, the owner of the wagon is likely, however, to be faced with the driver using this advantage excessively. I maintain therefore, that although wagons may go from five miles per hour on steel tyres tO eight miles per hour on rubber tyres, the driver will be tempted to travel at 12-15 miles per hour, which on a given gear ratio will mean a much higher engine speed, which causes wear and tear of a serious nature and if misused probably is as had. as running on steel tyres.
I have found that the writer does not make very prominent another point, and that is .that rubbers have this great advantage of acting in the winter months as a " winterwheel." If for no other reason than this I.would recommend with a trailer rubbers on the rear wheels only.—Yours faithfully, " UNPREJUDICED." our correspondent is quite -correct in his main, contention, and. the majority of steam wagons on rubber tyres are legally limited to 8 m.p.h. when running on rubber tyres, he has himself evidently overlooked one type of steamer, of which the Sentinel is.an outstanding example, which is-so constructed that its rear-axle weight, -when the wagon is evenly loaded, does not exceed a Maximum, of 6 tons. In such a, case, of course, a speed of 12 m.p.h. is permissilole, and the Chassis is designed for it. We have no doubt that the writer of the article had this in mind when he gave the figures to Which reference is macle.—En.]
Proposed Motor Trade Travellers' Association.
The Editor, THE COMMERCIAL MOTOR.
[1618] Sir,—It has long been a matter of intense surprise to me that no effective organization for gentlemen engaged in travelling for those firms connected with the motor trade industries exists.
Such an association is not a combination to " tilt " at employers, nor would it in any way form a "ring." There are hundreds of motor travellers in the U.K., very -few of whom 'areknown to each other, and to whom I am persuaded such an association would be of , material benefit in. various, directions. The prin ciples of co-operation are invaluable, and in these days of keen competition friendship -and association frequently make co-operative trading a pleasure, for there are a thousand-and-one Ways in which travellers. may help each other. The . objects' might include means of promoting, assisting and -defending the interests of members; nravision of a• Benevolent Fund and an. Accumulative Benefit Fund;. securing concessions from railways,. hotels, ete. ; arranging for 'the. formation . of pro-' 1:riucial.auxiliary committees -or branches ; . arranging' for, socialmeetings, forinationof a Guarantee 'Fund and .arranging about -insurance.. . . : tven,ture to ask the favour of all your readers who are interested in -the proposalto communicate With me.—Yeurs faithfully, JAB. V. rikEBOTT. 15-19, Great Titchfield Street,.London, W. 1