Opinions from Others.
Page 19
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Turbine v. Reciprocating Pumps.
The Editor, THE COMMERCIAL MOTOR.
L16011 Sir,—Re the recent correspondence on the above subject, I wish to suggest that the mostimportant advantages of the turbine type of pump have not been made clear, and, writing as an officer running two Dennis fire-engines in the fire service, I are quite convinced of the superiority IA the turbine type, after carefully carrying out comparative tests. Some of the points which have led me to this decision are as follow:— With the turbine, the wide range of capacity, i.e., the ability to deal with small or large quantities of water, at high or low pressures, as may be required. For instance, a, nominal 350-gallon turbine fire-engine, in actual tests, has proved that up to 450 gallons and over can be delivered at a useful pressure, the efficiency keeping reasonably high, whereas, with the reciprocating pump, the range is much smaller, and, should an attempt be made to obtain an increase over the nominal output as stipulated by the manufacturer, say, by runninir elittra,or larger jets, the effi ciency drops rapidly kid the jets as fire jets would be useless. Thus, if the average efficiency is taken over such a range of duty as a fire-engine may be required to undertake, from a small jet at very high pressure to a "damping down" job where large volumes of water would be required at low pressure, a distinct advantage is shown with the turbine.
Another very important point is the total absence of the vibration and " wriggling" which are so noticeable with the reciprocating pump—especially when working at a deep lift. There is much attendant wear on suction and delivery hose, in spite of the elaborate precautions taken to protect them with chafing leathers etc., and, as we all know, the failure of a length Of hose may be attended with very disastrous results. No risk of this kind should be taken that can be possibly avoided, and the slightest continued movement of the hose when laid out on a stony or rugged surface will very soon cause a "burst."
There is also a great advantage in the capability of the turbine pump to deal with muddy or otherwise contaminated water, without any fear of injury to the pump ; this is a most-important point to be considered, especially when attending country fires where a duck pond in the yard may be the only available water supply.
Another point is the regularity with which these turbine pumps—possibly due to their separate starting apparatus— are able to obtain water from deep lifts, with ease and certainty. In the olden days, 25 ft. was looked on as much as could be expected ; now, it is quite common for officers to get 28 ft. or 29 ft. of vertical lift (in as many seconds) with the turbine pump. Further, these pumps will take advantage of the pressure in the main, whereas the reciprocating pump, although it will work direct from the main,. only does so without any increase of pressure overand above that which it can give when working from a 2 ft. lift.
I would also advise any officer, in selecting a fireengine for his town's use, to give attention to other details of the chassis, and not to confine his investigations to the pump only. The appliance must be sure of getting to a job, when turned out in answer to a call. In my opinion, the facility for constructing a fire-brigade chassis on interchangeable and standardized lines, also the works facilities for turning out first-class and accurate work, choice of materials, experience in building similar chassis, and obtainable records of machines in commission by the best makers, should have equal attention.—Yours, faithfully, " SunnEv."
Checking Repairers Charges.
The Editor, TEE COMMERCIAL MOTOR.
[1602] Sir,—May I draw your attention to the practice which exists among the managers of certain re pair garages of charging excessive amounts for repairs: to commercial vehicles. The owners of many such vehicles, although experienced business men, have no knowledge of engineering prices, and unfair advantage of that fact, unfortunately, is often taken by some garage owners. Manufacturers and vehicle owners should do all in. their power to check this practice' as the imposition. of excessive charges is calculated to scare off a user and to make him think his motors are not such economic necessities as he had been led to believe. Such a man becomes the worst possible advertisement the movement can have. Some few weeks ago, a most-flagrant case of imposition came under my notice : an owner obtained_ a quotation for an overhaul, and, being a cautious man, he submitted it for the examination and report of an experienced engineer. The estimate was laid out in very minute detail, and was well calculated to impress a user with the idea that the total amount was low in relation to the amount of work involved,.
but the engineer discovered that for such replacements as ball bearings, bolts and nuts, Stauffers,. chain links, copper tubing, insulated wire, white metal, etc., from 30 per cent. to 50 per cent, had been. added to the ordinary retail prices! In addition to the charges being high, in many cases the amounts of material were also excessive ; for instance, for the re-metalling of four big-ends on. a 24 h.p. engine 25 lb. of white metal at 2s. 3d, was specified. The labour charges, too, were very high,, and amounted to 2 times the actual costs.
The engineer was authorized to interview the repairer on the owners behalf, with the result that a. revised estimate was submitted and accepted. The; work was carried out satisfactorily, and on its completion was examined and passed by the engineer. The owner, after deducting the engineer's fee, saved 20 per cent. on the original estimate, and had the, satisfaction of knowing that he had got good value for money. My advice to all owners who lack the necessary knowledge of engineering prices is to take the adviceof an engineer whose practical experience in the design, construction and operation of commerciaL vehicles enables him at once to decide whether the charges are reasonable.—Your faithfully, Richmond. GEOFFRY WALLACE..