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Some Pointers for Post-war Designers

21st July 1944, Page 22
21st July 1944
Page 22
Page 23
Page 22, 21st July 1944 — Some Pointers for Post-war Designers
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A Few Practical Suggestions Put Forward by Road Transport Engineers Which Would Tend Towards Easing Repair and Maintenance Work

'THOSE whose business it is to super-1 vise the servicing and maintenance generally of road motors are able to collate, over a period of years, many ideas which, if applied to the vehicles under their charge, would make for increased efficiency and simplification of the many tasks involved.

It is, of course, true that suggestions that appeal to some may not be viewed with the same degree of enthusiasm by others, but this will always besso, as it has usually been difficult .to' obtain unanimity concerning any individual feature in vehicle design.

A transport-engineer reader of this journal, who wishes to remain, anonymous, recently sent us some observations on a varied number of features and these, together with some received from other sources, should provide .material for some constructive criticism.

Fixed Handle to Relieve Battery

Should the starting handle be removable or a fixture? It is contended that if it be removable -then a suitable tunnel representing an extension of the crankcase should be brought forward beyond the radiator. If fixed and convenient for use there would be more relief for an already stressed battery.

A plea for a radiator with bottom and top tanks of more robust construction is made and, coupled, with this, the need for a drain cock that will ensure that all the water is drained off from the engine.

An improvement in the normal type of fare would be to provide a ring to encompass the blades or, in other words, to build the fan after the style of a wheel. This, our correspondent says, would prevent the blades from a20 • flying off. He'quotes, as an example of this practice, the fan as fitted to Whtte lorries nearly 30 years ago.

As the process of decarbonizing is really necessary only at long intervalS, it is suggested that exhaust valves should be made more accessible. Our correspondent says': " It is very annoying to have to undress the engine and, in some cases, to have to remove the radiator, to obtain access to one valve."

Overhead valves are favoured, one reason being that they can be taken to the bench complete with the head assembly. A heavy one-piece cylinder head—where the vehicle is of the forward-control type—entails the purchase of a special crane, is a comment of this engineer.

He then goes on to ignition equipment and mentions a magneto with impulse starter as being his preference. Complaint is made against the quality of condensers and the fact that they are usually fixed in an awkward position, whereas they could be housed in a clip on the dash.

The method of mounting some types of carburetter is considered to be wrong, in that the two-bolt flange fitting is not sufficiently robust to withstand the continuous " lamming " of the accelerator pedal. With the aboli

tion of the float chamber "tickler " there is no ready means for knowing the quantity of petrol in the float chamber. The orthodox type of strangler'a criticized on the ground that it is so readily abused and something different is wanted.

Still dealing with fuel matters, our correspondent wants to know where the Autovac failed. He quotes a Dennis 6-tanner, made in 1931, that still runs on the original Antovac and has never called for a replacement part. The same story cannot be told of petrol pumps. A new kind of diaphragm material might be experimented with, says this transport engineer, from which it may be gathered that trouble in this direction has been experienced.

• Longer Leads and . Easier Inspection

Dealing with the wiring of the electrical system, the main criticism here is that the leads connecting components are too short and do not permit of a unit being released and inspected. If the leads be longer, adjustments could, in many cases, be carried out without breaking connections.

Is a water pump really necessary? If it be, then arrange it so that it can be removed as easily as the average dynamo. An instance is quoted where, to fit a seal costing ,2d., the radiator had first to be removed in order to gain access to the water-pump impeller.

The servo air-pressure brakes as fitted to the Scammell 15-tonner are selected as being ideal from the point of view of easy a'djustment. Having to get underneath the vehicle to carry ouf such an operation is both inconvenient and means a waste of time.

. Servo-hydraulic braking systems are considered to be good, but the need for

bleeding the line, on occasions, is not looked upon with favour. Servo only is preferred to only hydraulic, as there are not so many tubes to break, apart from the fact that it is considered more reliable.

Our correspondent, in summing up the question of brakes, says, " Surely it is possible to have a layout which is efficient withoutassistance and ultra, efficient with. If this be sO it would be possible to keep the vehicle in use while the assistance unit was being serviced."

Chassis extensions and other major alterations of a similar character should be subject to the approval of the vehicle maker, a remark which would -seem to point to the fact that such alterations, in some cases, cannot be looked upon as being highly satisfactory.

Engine Speed Should be Governed There always has been considerable controversy on the matter of engine governors, so the suggestion made in the present instance that suitable means for keeping engine speed within sensible limits are highly desirable, will, no doubt, not be universally applauded.

Forward control comes in for trenchant condemnation. It is stated to be the main cause of inaccessibility, and, as our correspondent puts it, "the accumulation of filth is disgusting." On some forward-control machines the driver's view from the seat is such that "a woman could push a pram across the front without the driver's knowledge."

• He goes on to say that " speed and tax are not the all in all." He doubts the sense of the policy of trying to put 6-tonner in the 30 m.p.h. class. Strength and service, he comments, are better than a flimsy body and weak chassis.

Dealing with the question of dopes in engine oil, he says that, "if a Dennis 6-tonner will run 82,000 miles with the original pistons and rings undisturVed, why use dope in the oil? The same is true of a Bedford 3-tonner, which covered 71,730" .miles on the original pistons and rings, whilst a Scammell 12-tonner has topped the 75,000-miles mark and is still carrying_ on," He suggests that, before dopes are put on to the market, they should be submitted to the National Physical Laboratory, or be recommended by the vehicle makers.

Our correspondent is evidently not in favour of using reclaimed oil, for on this subject he says, "it is open to question as to whether there is any economy, When, you consider the bother of filling the filter and the electricity it consumes in return for the small amount of oil reclaimed. Take a half pint of reclaimed oil, put it with, say, a pint of new oil, stir it and note that it will not mix. Surely, if the oil be changed at 5,000-mile intervals, new oil is a small enough expense-rather like paying an insurance premium."

Another correspondent who has sent us a few ideas on post-war vehicle design, also favours magneto ignition with what he refers to as " a trip coupling for easy starting." He advocates the adoption of a pressure-fed carburetter as this would prevent air locks and one would not be troubled with faulty petrol-pump valves. He says that 90 per cent, of the troubles experienced to-day can be attributed either to the ignition or the petrol pump. He also is in favour of push-rodoperated overhead valves, as this design makes for easier replacement and adjustment. As in some cases it is necessary to remove the rear a,xle,in order to replace a clutch disc, it is suggested that " the driven meinber should he removable without taking the lorry to bits."

Improvements in Rear-axle Design

Synchromesh on all ratios, and a gearbox that can be removed without daturbing the rear axle, engine, brakes or clutch gear, are two further postwar suggestions. Dealing with rearaxle design, this correspondent's suggestion is for fully floating half shafts, with the weakest shearing resistance at the hub end. This would avoid dismantling the axle should the broken end not be readily removable from the

differ6ntial. A flexible-drive hub, he says, would save hundreds of half shafts.

With regard to. the braking system, the shoes should be wedge or hydraulically operated at both ends, with mechanical servo action, If mechanically operated there should be a minimum of yoke and pin joints between the pedal and the hub. A case is quoted of one make of machine in which there are no fewer than 24 pin joints, and the brakes have to be adjusted by feeler gauge. .

The foregoing are but just a few of the directions in which the lot of the maintenance staff might be eased with considerable advantage to the efficiency of the fleet and there is no doubt, that when the Institute of Road Transport Engineers gets into its stride, it will be able to do a considerable amount of most useful work in this particular direction.


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