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Opinions from Others.

1st August 1912, Page 18
1st August 1912
Page 18
Page 18, 1st August 1912 — Opinions from Others.
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Which of the following most accurately describes the problem?

The Editor invites correspondence (pi all subjects connected with the use of commer:ial motors. Letters should be on one side of the paper only, and type.written by preference. The right of abbreviation is reserved, and so responsibility for views expressed is accepted. In the case of experiences, names of towns or localities may be withheld.

Speed of Chars-a-bancs.

The Editor, THE COMMERCIAL MOTOR.

[1589] Sir,—In reply to the lefter from the manager of the Llandudno _Motor and Carriage Co, which appears in the current issue of your journal, I would remind this gentleman that my previous letter was intended to show the danger of excessive speed at which certain motor chars-asbancs running in North Wales are driven—not to show the seating capacity or the special design—and my contention was amply borne out by the editorial which appeared in your journal of 13th June.

If the Llandudno Motor and Carriage Co. consider my remarks apply to their vehicles, all I have to say is, that, if the cap fits. they are entitled to wear it.

As a matter of fact, their letter supports my original statements, as they remark that their machines average a speed of about 18 m.p.h. They further state that, if necessary, the vehicles can reach a speed of 25 m.p.h. without undue risk.

An average speed of 18 m.p.h. is excessive on the roads in North Wales. I consider a maximum speed of 18 m.p.h. on the level is ample for chars-à-banes seating 15 to 20 passengers.

It. would be interesting to know the maximum speed of the Llandudno Co.'s vehicles—Yours faithfully, 26th July, 1912.

Turbine versus Reciprocating Pumps:

an Official Test Wanted.

The Editor, TEE COMMERCIAL Moms.

[1590] Sir,—I have read your leading article on turbine versus reciprocating pumps in your issue of the 18th July, and Messrs. Merryweather's letter in the following issue, with considerable interest. So much has been claimed by the makers of both types of pumps, especially for fire-brigade purposes, that I think it, is quite time we had irrefutable figures placed before us of tests made by independent engineers. Such tests, if made under fire-brigade conditions, would be of inestimable value to many advisory engineers who, like myself, are on occasion called in to adjudicate upon tenders and specifications for motor fire-engines ; we should thus be able to give our clients the best possible advice, and our clients could see the published results of the tests.

Fortunately, the class of pump is not always, er even often, the deciding factor ; it. is far preferable to have an engine and transmission mechanism which can be relied upon to give satisfactory working at all times than to have a pump •which is a little more efficient than the average, and a chassis of indifferent design and build. To put the matter in another form. it is better to have a pump which gives an efficiency of 68 per cent. all the time than one which may give a higher efficiency for perhaps a few minutes only.

The turbine pump has, in my opinion, many points to recommend its use. for fire-brigade purposes beside its consistently-efficient working ; it has its low weight as compared with a plunger pump of the same capacity, and the fewness of its parts. If Messrs. Merryweather do not admit these advantages why do they build fire-engines equipped with turbine pumps? Surely their position in the trade is strong enough to warrant their saying, "No ! we will not build a machine which we do not believe is good enough for the purpose."

I have looked in vain for independent confirmation of such abnormally-high efficiencies as those claimed by .Messrs. Merryweather for their Hatfield single acting pumps. I have found records of 82 per cent. efficiency for a double-acting pump delivering to a height of 200 ft. for a few minutes only, but Prof. Perry states that " 40 per cent. would be regarded as a reasonable efficiency for reciprocating pumps of low lift, whereas it would be regarded as rather poor for pumps of high lift." I suggest that if Prot, Perry had been convinced that for high lifts anything in the region of 70 to 80 per cent, might reasonably be expected he would have used the word very instead of 'rather. The italics are mine.

However, there is not much to be gained by quoting figures of tests made under conditions which have not been made public, and I suggest that, in order to back Ill) their claims for 90 per cent., Messrs. 1Vierryweather should submit one of their pumps to independent tests by a committee of engineers, to the Institution of Mechanical Engineers, or to the Royal Automobile Club, and that one or two makers of turbine pumps, say Messrs. Gwynne or Mather and Platt, also submit pumps of their makes for tests under the same conditions and at the same time.

The tests, if carried out by a committee of independent engineers, need not cost much, for I am sure that, there are many engineers who would give the necessary time for the pure love of the research_

Will the makers I have named come forward and voluntarily submit their pumps for independent. tests, or must a fund be raised with which to purchase the pumps necessary for the making of independent tests of pumps for fire-brigade purposes ?—Yours faithfully,

GEo. W. WaTsoN, M.I.Mech.E., Woodford Green.

A Criticism of the W.O. Specification: preference for Chains and Large Wheels.

The Editor, THE COMMERCIAL MOTOR.

[1591] Sir,—In your issue dated 9th May, you published the draft, of the " War Department Subsidy Scheme, 1912 " specification. I note therein that chain drive to hind axle will not be permitted."

I should be interested to know why this is so. During my four years of experience on these rough roads of Patagonia, I have found the driving chains to be very reliable. They are, in fact, the only part of the whole transmission that has given no trouble.

Chains serve as a very accessible and economical. "safety valve" for the whole transmission, if something must go, which would often be the case in active war service when everything is strained to the utmost. Another advantage of the chain is the increased road clearance which it gives, as compared with the live axle ; this, too, is surely an important point? From experience gained on rough roads and nature's surface, I am of opinion that the diameter of road wheels in general is to small. Even for good average roads the diameter should not be less than 4 ft. for driving wheels. The increased smoothness of running is a revelation and adds to the life of the car by reducing vibration. There are two serious objections, however, to wheels of larger diameter, namely, difficulty of manufacture and consequent expense. Hence the smaller wheel is very tempting in these days of close competition, hut, if British firms wish to succeed in Colonial and foreign markets, they will require to study the wheeldiameter question. At present the Americans appear to be the only makers who have attended to this matter.—Yours faithfully,F. A. EDDIE.

Chubut. Argentina.


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