Has the Low Level - Frame Come to
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PROBABLY the don of .the forthcoming Commercial. Motor Show will be the low framelevel chassis, for the simple reason that it will be a new type of which almost every leading manufaCturer will show an example, although it will be found that there is considerable divergence of opinion upon the extent to which a frame should be lowered, some makers being content with two or three inches below the standard frame level, whilst some will have gone to extremes. , The development, in our opinion, is one which calls for careful consideration, and we do not wish users to act precipitately and to rush in and order low-level chassis just because a fashion has apparently set in. If there is a real advantage to be gained for every inch a chassis can be lowered, then lowering should be encouraged, but first let it be proved that this advantage can be secured. A great deal is made of the fact that, with a low frame but a single step is necessary between road and bus platform, with a furthe step to the lower deck level, but on the bus with the lowest deck level yet put into extensive service, the step up to the platform is 13 ins, high, and the step into the bus' a further 9 ins., both of Which heights compare very unfavourably with the hei5tt of the average stair riser to which, in their homes and offices, ordinary bus users are accustomed. We believe that eventually the idea of a "single step up" (as it is inaccurately described, because there are always two steps) will be abandoned and a return will be made to two steps betwMa road and platform.
With regard to the claim of increased safety because of the lowering of the centre of gravity, we doubt whether this claim could be substantiated. The determining factor is the top of the back axle casing which, in rising through any road irregularity, must not bump the underside of the. floor of the vehicle. A double-reduction gear here shows to advantage, but it is not generally favoured, the worm and worm-wheel being the type of final drive most commonly employed for passenger work. But if the worm shaft is above the worm wheel it is useless to • lower the frame because the top of the worm casing would then come above the level of the frame. Hence, the worm shaft must be placed below the axle and this, unfortunately, involves raking the shaft dine, so that the engine shall be lifted high enough to clear the front axle. The effect of this seems to be to raise the le_vel of the mass of the engine, thus nullifying the effect of lowering the frame and restoring the centre of gravity to its former height or thereabouts: In other words, the advantage 'sought is not in reality gained. Whilst the centre of gravity must be kept low, we doubt If any Instance could be brought forward to shOw that a bus had turned over because the centre of gravity was not low enough. In every case of a bus overturn, there hasalways been some exceptional circumstance—the bus has run up a bank or into a ditch, or it has been swung sharply off its course when travelling at an unduly high speed, but buses have even been struck by a very high wind without overturning.
We put it in this way—the low frame should only be adopted if public safety and convenience are 'enhanced and provided that there is no sacrifice of strength of chassia frame, no reduction in wheel -size, no awkward internal structure such as a cumbersome wheel arch and no loss of clearance under the vehicle.
Saving Part of the Cost of the Spare Tyre.
IN the course of our description in this week's issue of a new 30-cwt. chassis by one of Britain's leading manufacturers, we refer to a very curious tyre equipment which has been adopted, one which seems to us on mature reflection to call for consideration by other manufacturers and by,psers of pneumatic-tyred vehicles.
The chassis in question is equipped either with cushion tyres or pneuthatic tyres, at the customer's option, the difference in price being £25, this extra charge covering a spare wheel and tyre. When pneumatics are fitted, the vehicle is equipped with 34-in. by 7-in. tyres on the rear wheels, and 33-in, by 5-in. tyres on the front wheels. One size of tyre all round would make for convenience, but would be impracticable, as a smaller size tyre on the rear wheels would not oarry the load and a larger tyre on the front wheels would make the steering heavy.
The spare wheel, however (and here is the curiosity), is shod with a 34-in. cushion tyre, the argument being that this course gives greater reliability _ and effects definite economy. Nowadays, a life of 20,000 miles may be relied upon for pneumatic tyres, and if this is the case, it is highly probable that a spare tyre would not be brought into use for a couple, of years and might hot be touched for months at a time, the result inevitably being that, when the hour of trouble came, the spare tyre would be found to have deteriorated or, at least, to be deflated. A heavy capital cost would be locked up in a spare pneumatic tyre.
By using a cushion as the spare tyre equipment, the capital outlay would be materially reduced, and there would be no risk of deterioration, whilst when a defect occurred in one of the pneumatic tyres, the cushion tyre would adequately serve the purpose of enabling the vehicle to complete its day's journey and to return to garage for the defect to be repaired.
The idea is distinctly novel, and certainly valuable, and we-think that it should be generally adopted. Many a pneurnatic-tyred vehicle is running to-day with no spare wheel and tyre because of the capital outlay involved in such equipment, which perforce is lying idle all the time, but the use of a cushion tyre as a spare so largely overcomes the objection that we shall not be surprised to find it taken up first of all by owners of these now spare-less vehicles el8 Trailways still command that extremely 2valuable item of business, the transport of milk, and, so far, the motor vehicle has made little or no headway in Its competition with them. Milk is brought from the West of England to a London terminus for lid. per gallon, so that a full milk churn weighing about 210 lb. is carried for 1s. 9id., whilst the 35 lb. empty churn is returned free of further charge: The railway companies provide milk vans and loading and ualoading. facilities, and if there is one objection to the scheme, it is to be found in the fact that in the handling of the full churns, -particularly at suburban stations without lifts from the platform to a higher level, more Men are permanently injured in the course of a year than in any other form of employment.
Milk weighs a little over 10 lb. to the gallon, so that a thousand gallons of milk, which would be a practicable load for a five-ton lorry, bearing in mind that the glass-lined tank and fittings would weigh about 2,500 lb., would bring to the haulier, if he accepted Pre railway companies' rate of lid. per gallon, the sum of £5 4s. For this he would have to do one journey empty and one journey full, and at the end of the inward journey would have to cleanse the tank thoroughly. This return would beettuite inadequate but actually he ought to be entitled to a higher freight because he would collect at the .farm centre where the milk would be cleaned, cooled and tested, thus saying perhaps a long haul to the station, and he would deliver direct to the factory, thus cutting out all the handling after the railway journey, whilst the capital outlay in churns would be avoided. In America there have been extensive developments in motor haulage-of milk, and Chicago milk dealers, as we show in a special article this week, have reached the point of beating the railways on freight charges. With better roads and a more equable climate, we ought in this country to be able to do quite as well, and it is our hope that the information which we give concerning the accomplishments of the milk hauliers of the American city will encourage the large wholesale milk dealers to look further into the question of road haulage of some proportion of the carriage of the millions of gallons of milk -which are annually conveyed between farm and populous centres.
The Passenger Chassis Breaks Away.
DURING the past few months there have been -1--0 many surprising and almost startling developments in connection with the design of chassis for passenger transport, and it wOuld appear that in certain models the complete break-away from the goods vehicle has come at last. No longer will it be advisable for those who cater for both markets to offer certain machines as being entirely suitable for both classes of work—at least, where the loads are heavy or passenger capacities large. In the case of smaller vehicles the speeds are more nearly akin and pneumatic tyres are almost always employed, so that the divergence need not be so great, but it is practically -impossible to compare, say, a 5-ton goods vehicle running on solid tyres at moderate speeds with a modern bus or coach which is built particularly for pneumatic-tyre equipment and is capable of speeds up to 40 m.p.h. Apart from speed there is also the consideration of differences in load between running light and laden. Even in the largest bus the difference is seldom greater than 3 tons, and the springing is often graduated to render it more supple when not under full load. It is certain that many improvements will also be made in goods vehicles and that pneumatic tyres will be employed more freely, but such progress must necessarily be slower.