The Danger of Limiting Six-wheeler Development.
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TIESPITE the progress which has already been made in the development of the rigid-frame six-wheeled vehicle, both as light or medium-capacity goods models for cross-country and rough-road work and as large-capacity vehicles for passenger work, our designers have by no means reached a• stage at which they can call a halt, or even a stage which justifies the framing of such regulations regarding their construction as might tend adversely to affect future enterprise and the production of new types of multi-wheeler.
We are prompted to issue this warning after studying certain of the proposed regulations of the Ministry of Transport concerning details of sixwheeler construction. These would appear to be based on existing models, whereas we know that certain makers, who have not already produced six-wheelers, are seriously contemplating the design and manufacture of types which Will embody many different features, some of possibly vital importance to the future success of the multi-wheeler.
So far, very few six-wheelers of British make have run many more than, say, 10,000 miles in regular service; consequently, it is as yet far too earlyto institute stringent regulations. In fact, the greatest possible scope for experiment should be given to the designer, otherwise we shall .be apt to fall into the fatal error of almost standardizing on a 'type of multi-wheeler which time may prove to be immature.
We do not wish in any way to decry the brave, pioneer and whole-hearted efforts of present producers, wbose vehicles may eventually prove the best types which can be built, but we fear for the possible effects of restrictions, which favour one type more than another.
Take, for instance/ the proposal to enforce the provision of two separate brake drums for each of the four rear wheels of a multi-wheeler when a differential gear is employed between the driving axles. Such a proviso might almost damn a form of construction which, in the qpinion of a number of prominent designers, both here and in America, should be tested out before arriving at any decision.
The matter would not have been such a serious one If cast-steel wheels and solid tyres were still to be employed, but now that the use of steel-disc wheels and pneumatic tyres has been rendered possible on the largest passenger vehicles by the advent of the multi-wheeler, the whole situation is changed, for it is both difficult and unsatisfactory to fit separate drums on such wheels. The rim diameters are small, unless the wheels are of abnormal diameter; consequently, a concentric inner drum becomes so little as to be inefficient, and what is perhaps of even greater importance, is so shielded that the cooling is most unsatisfactory. If mounted side by side the drums occupy such a width as to necessitate reducing the centres of the road-wheel springs, which would have a serious effect on the stability of the vehicle.
Apart from this point, the provision of double brakes for all four rear wheels must necessarily further complicate a brake lay-out, which, with a multi-wheeler, is already quite difficult enough, whilst correct adjustment will be rendered more difficult and call for more attention on the part of the driver.
The only feasible method of dealing with the problem would appear to be to employ two sets of shoes in a single drum, and even then this should not be necessary for each wheel. It would be quite possible to employ brakes on the front wheels, in which case one control could well be 'utilized for those on the rearmost wheels and the front wheels, and the other control for the middle wheels only. An alternative arrangement could be to have one control for the brakes on all six wheels and a second for those on the rear wheels only, of course acting through a second pair of shoes in each drum. Such brake arrangements will become illegal if the proposed regulations be brought into force, although they are manifestly sound and provide a high safety factor.
We commend the matter to the further attention of the Minister of Transport, and would also sug'gest that the question of providing compensation between front and rear brakes or between the brakes on individual axles should, at least for the present, be left to the discretion of the makers.
An Important Move on Behalf of Export Trade.
FURTHER information of an official character is now available concerning the delegation which the Council of the Society of Manufacturers and Traders is sending overseas next month, and to which reference was made in our pages of. Editorial Notes in last week's issue of this journal. We are, therefore, able to refer to the constitution of the delegation, which will consist of Major Sir A. Boyd-Carpenter (M.P. for Coventry), who has made a special study of overseas trading generally; Mr. Alan H. Fenn, whose technical knowledge of the motor vehicle rqnks high in the industry; and Lieut.-Col. A. Hacking, D.S.O., who, as secretary of the Society, has an intimate knowledge of the capacity, intentions, ability and wishes of the motor manufacturers in connection with the overseas markets.
The delegation is to visit not only Australia, but New Zealand and South Africa, and six months is to be devoted to the trip. That time is not too long for the task in hand, and some of It will be occupied in concluding arrangements with local motor trade institutions for affiliation to the Society, all of which will help to cement the bonds between the mother country and the Dominions. c16 We are glad to know, however, that the delegation, in the month at its disposal before its departure, will visit the leading commercial motor ami other factories in order to be well posted on British products and on all questions of trade policy, for it is sure to be faced, in each of the Dominions, with demands for concessions and charges of inconsiderateness on the part of British makers, to which a ready reply should be available.
" We still hope that the Council of the Society will think fit to add to the usefulness of the delegation by the inclusion of a man whose chief interest will be the commercial motor, for the field open to that type of vehicle is enormous, and we think that if the right man were chosen he could push propaganda on behalf of the type to a degree that would have a material influence upon our export trade and would further help this country to make full use of Empire produce.
Reducing the Labour of Driving.
THERE is no doubt that, in many instances, far -Itoo much effort is demanded from the drivers of commercial vehicles, and particularly of passenger types which may be operating all day in comparatively congested traffic and, consequently, make the utmost demand upon the care and strength of their drivers. With the advent of still larger buses running at higher speeds the matter has become one of vital importance, and everything possible should be done to alleviate the difficulties which exist at present. Last week we gave considerable space to the question of servo devices for facilitating brake control, and this in( itself is certainly a most important factor, but it is not the only one. Greater attention is 'required to steering gears. In some vehicles they are quite satisfactory; in others, steering requires a real effort. The gear, unless power-assisted, must always be a mean between a ratio which will give easy steering and that which will provide sufficiently rapid control. In general, it would seem preferable to give as Iowa ratio as is consistent with safety, for, in the majority of cases, even with the lowest ratios employed, the Most rapid steering is required only over a small angle of wheel lock. In certain types of gear it is possible to give a variable ratio which will afford either a quick steering fon the minor angles and a slow steering for full lock, or the reverse arrangement, according ta the requirements and the conditions of service. Gear changing is still often a matter of considexable difficulty, sometimes due to great differences between the respective ratios, whilst in certain gearboxes the teeth are not sufficiently backed off to facilitate entry, this, of course, applying only to the sliding type, although this difficulty is occasionally experienced with engagement dogs.
In gear changing much also depends upon the weight of the spinning parts, such as the clutch, and their freedom when disengaged. Carefully adjusted clutch stops will often help matters in this respect. When drivers are expected to attend to the whole lubrication of the vehicle, the tast should be rendered as simple as possible, for -it is not fair to add considerably to the labours of what may already have been a long day.