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CONVERTING PRIVATE CHASSIS TO VANS.

10th April 1919, Page 16
10th April 1919
Page 16
Page 17
Page 16, 10th April 1919 — CONVERTING PRIVATE CHASSIS TO VANS.
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Which of the following most accurately describes the problem?

Dangers of Overloading. One-tonners in Demand.

THERE IS a tendency to associate the word " lorry " with the heavier type of commercial vehicle, of which the load capacity may be 3 tons or upwards. Yet, it is a matter of fact, as was pointed out in The Commercial Motor of February 20th, that quite half of the industrial motor vehicles in America are designed for loads of 1 ton or less. In. this country, where the Statistics are not so accessible, probably the same holds good; and evidence accumulates on all hands of the demand for 1-tonners. Delivery vans continue to be sought by distributing concerns, and the field for the light lorry is very wide indeed.

This demand has often been met by the expedient of converting a touring chassis to commercial work through the substitution of a lorry or van body for the original touring body. Naturally enough, makers of industrial vehicles do not view this movement with enthusiasm ; nor, for different reasons, do the privatecar manufacturers. On the one band, the reputation of industrial vehicles generally tends to suffer as a consequence of the unsatisfactory results arising from an ill-considered conversion; and, on the other hand, such results are unlikely to enhance the prestige of the maker of the converted vehicle, even though the latter has been subjected to condition k for which the designer never intended it .

• At the present time, this question of converting touring ebassis"is not so-much to the fore, because at the prevailing prices of comparatively new British vehicles, for example, it will not pay to convert them. Unfortunately it is usually the older types of chassis that are so converted, vehicles that are handicapped from the start by the facts that spares are not easy to obtain, and that their worn-out condition does not give them a proper chance to do justice to their corn mercial application. After all, the success or nonsuccess of the conversion is going to depend almost entirely on the load the vehicle will have to carry. Merely to remove the touring body and substitute -a lorry body is not to increase the load eapacity of the vehicle. Assuming for the moment that the original and substituted bodies weigh the same, it is -evident that the load capacity of the adapted chassis—in the absence of any reinforcement in the design—is the same as the load of passengers and their luggage that it originally carried. It is true that, by a _reduction

• of the gear, the engine power may be made to suffice for a greater load ; but the fact is that the frames a-nd•sprinrrs of a touring car are necessarily made as light, as the deadweight they may have to carry will permit.

Taking the rather extreme ease of a touring chassis carrying five passengers averaging 10 stone each, with luggage amounting in all to 2 cwt., the load is' well under 9 cwt. ; moieover, it is distributed about as favourably as it °quid be. Inquiries made by The Commercial Motor among manufacturers of those private cars which are commonly to be found in the converted state tended to establish an average net load' of 10 cwt. for chassis of 12 bp. or thereabouts, and of 15 cwt. for those of about 20 bp. Overloading is one of the bugbears of commercial vehicle practice, and, although it is not possible to give a loading factor constant for any horse-power, as, after all, strength of frame and working.parts constitute factors .of greater importance in this regartt than horse-power, there is always one 'way of arriving at the desired result—to write to the makers of the vehicle.

Where the conversion is decided upon, and where it i deemed worth while to spend money on struc tural changes, the chassis should be given a greater reduction of gear in the back axle. Under conditionsof lorry work, the vehicle does not need to attain the high road speeds that it was expected to give in touring-car work ; and everyone knows that the danger of fractures due to road shocks increases with the speed. Moreover, the tractive effort of the vehicle is greater at the lower speed. In the case of a chaindriven vehicle it is not a difficult proposition to reduce the gear, and this may be accomplished by fitting larger sprockets on the rear wheels. At the same time be it pointed out that such an operation is to be undertaken only by an engineer. It involves the manufacture of entirely new sprockets and, of course longer chains are necessary. Substantially to alter the gear of a live axle chassis, however, is usually impracticable, except by the method of fitting an entirely new rear axle. In the case of a worm gear, for example, the bottom of the worm thread is usually of about the same diameter' as the tail-shaft; more over, the fixed distance between the tailshaft and rear axle centres allows no latitude in working Usually, the diameter of any .crownwheel, whethe worm or bevel, is very little less than that of th adjacent casing, the clearance being so small as to preclude increase in the size of the wheel. e When it has happened, in the past, that establishe and reputable firms have taken up the conversion of private chassis to commercial work, they have generally done .the job as thoroughly as possible, . equipping the vehicle with new, and more robust, frame members ; with new rear axles, having a greater reduction of gear ; and with stronger springs. In this way, touring chassis may be adapted even to loads of as much as 30 cwt. ; but the policy is, at best, a makeshift, and instances could be quoted where manufacturers have abandoned this-practice in favour of constructing 30-cwt. lorries designed expressly for commercial work.

Treatment of this subject would be incomplete without reference to the various Ford adaptations that arc now on the market. Some of these attachments are better than others, but for the better ones the demand' continues to exceed the supply. This policy has something to commend it it is cheap, it appears to work satisfactorily, and, above all, spares are readily to be had. It is hardly likely, however, that this policy represents finality, any more than does the expedient of converting touring ears, and the light commercial vehicle of 1 ton capacity is a proposition worth careful consideration by manufacturers. Such a vehicle would make a wide appeal to small tradesmen and others whose purses are not too long. Hence the necessity for keeping the price down as low as possible.

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