• PNEUMATICS IN FARM TRANSPORTATION
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The Factor of the Fields—A War Weakness—The Problem of Power—Designing for the Farm—Pneumatics and Perishable Produce.
THE SUCCESS of the lorry on the farm depends on its ability to negotiate soft ground. Any vehicle whiub. cannot venture off a made road is useless from the fiti'mer's point of view. The work of the farm lorry is mainly the transportation of farm produce from the fields to the farm or to the market, and it is essential that the lorry should be able to get into those fields in which the produce grows. Can the solid-tyred lorry do so ? Under the most favourable conditions, yes: Under unfavourable conditions., decidedly DO. In:is partly a question. of pressure per square inch on the area of tyre contact., partly the difficulty of securing sufficient adhesion-fur tractive purposes on muddy ground, and partly a question of providing sufficient engine power and suitable gear ratio to. enable the vehicle to extricate itgell froth. a difficult position, when the necessary adhesion has been obtaineds,by resort to non-skid chains or other similar devices.
Limitations in War Service.
• This was one of the difficulties of the war. It was the weak link in the chain of road transport. It is the whole reason for the adoption of the caterpillar track in whatever applieatien it may be used. The fourwheel drive system is also an attempt. to overcome the drawback, but, when all four wheels of a vehicle are on soft ground, the system can avail but little, and, inevitably, the problem conies back to one of load per square inch on the-area of tyre contact. Thus, the problem which limited war transportation will limit the extension of lorry use in peace, in all circumstances wnere the conditionsiof useapproximate in any way to was conditions, Unless.a new development takes, plate.
. And the preblem of farm transportation is very much the same. It does not matter that your load consists of turnips and not shells; so long as you have field surfaced with mother earth co traverse, a similar problem confronts you.
Power and Pneumatics.
The. advocates of the pneumatic tyre claim great things for it in use on soft grdund. If their claims are justified, this means that the pneumatic tyre gives a greater area of contact with the ground surface than the solid does. It is only what would be expected, but figures on the subject would be interesting.
But, on very soft ground, even the pneumatic must sink in a little, and theifa,ct that it does so automatically increases the area of contact, so that the whole of the tread comes into use and is available for tractive purposes. A pneumatic that is fairly new and pro D48.
vided with a well-designed tread pattern should give a decidedly good grip, almost equally good, on would imagine, as that of a twin-solid Provided with &chain. But, this very, fact brings in another problem. The engine power and gear ratio that will propel a, laden vehicle, on a road may quite well prove unsuitable for soft surface work -and, with the pneumatic, the problem of power is introduced. First of all, most pneumatic tyres are larger in external diameter than the solids they replace and,. therefore, they increase . autoinatieally the gear ratio of the -vehicle to which they are fitted. On road work this is not very important., as higher speeds are thereby made possible, without. risk of engine:damage.
Designing for the Farm.
Dot, for a, vehicle to be used on soft ground,. the gear ratio, if anything, needs lowering ; so it .appears probable that, if the pneumaticstyred lorry is to make good on farm service, a special gear ratio will have to be provideisl. This is all part of the power problem. If pneumatics are going to enable the farmer to take his lorry on to surfaces and into places where lorries have not. been used before, the farm lorry will have to be sufficiently powerful to propel itself under these conditions.
The gear ratio must not he reduced to an extent which prejudices the speed of the lorry on the road, and, so, it may be necessary to provide the farmer's vehicle with a more powerful engine than would be 'necessary under other conditions. In short, it may become necessary to design. a special vehicle for the farm,
Tiansporting Perishable Produce.
Two factors are of great importance to the farmer in transporting his produce, namely, speed and ims niunit,.• from mock and damage. That the imetho.ds.at tran.sporsravailable to him in the past have not usually been good in these respects is no argument against their desirability.
In moving livestock from place to place, speed and freedom from shock are all to the good., The writer is not a farmer, but he is given to understand that in moving livestock shrinkage invariably takes place. An American tyre manufacturer tells us that, in hauling hogs ten miles to market in ordinary wagons there is 6 tier oenf. Shrinkage, whieh.means presumably 6 per cent. less rashers from any given porker ! It is a consideration. But, in the case of crushable and perishable produce—like that ot the market gardener —both speed in delivery and freedom from jolts and jars.are conditions of really successful transportation. The pneumatic tyre should go a, long way tow.4rds solving the perishable produce problem.