Riding Comfort a Priority Claim in Post-war Construction
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Our Contributor Discusses Some of the Features Which Will Undoubtedly Call for Attention in the Design and
• Appointment of Post-war Passenger Vehicles
By J. Pickles
T, HE general opinion seems to be that, with the cessa tion . of hostilities, a tremendous drive for markets will commence. If this is to be the case, then one May be sure that the road-transport industry will be well
to the fore. .
In extensive efforts to bring "even More besiness to the roads, more development and publicity are certain to be in evidence, and not the ieast,important feature to receive attention will he the appeal to bodily comfort. which passenger-service vehicles, and coaches in particular, are able to give_
.0ne ot the majoi factors in maintaining riding Comfort is the suspension of the passenger, through the agency of the tyres, toad springs and the seat. 01 these, the road springs are the most important, and their satisfactory design represents a large percentage of the Work put in by vehicle designers.
The major property, of all types of -spring is that of periodicity, which is a function of deflection; any type of spring, when deflected a given amount, will vibrate with a given number of cycles per minute: If this periodicity reaches too high a value, then high accelerations, will be caused which if, of sufficient magnitude, will result in the passenger being bounced off his seat.or, if,the seat be hard, he will be subjected to uncomfortable jolting.
Springs of . low periodicity, on the other hand, will induce a sickness akin to mai-de-met. The number of cycles per minute :is, in practice, determined largely by mechanical. considerations, the periodicity employed being the neatest to the ideal that is compatible with other features, .
-The tendency is to make the springs too hard for comfort as the vehicle must be designed, to carry a wide range of loads; and as spring deflection . is a function of the /clad, it will be apparent that with light loads there will be higher periodicity than with heavy ones. A method of mitigating this, to some extent, is found in the use of progressive springs, although this system is by no means in simple an aebievernentwith laminated springs as with other types: The oliject of this scheme is to provide soft springing up to moderate deflections, and relatively hard suspension to cope with greater amplitude of movement of the wheels.
Elimination of Pitch Demands Careful Study Having decided on the ideal periodicity for each axle, the problem is by no means solved for, if oil passing over a road undulation the front springs be moving in an ' opposite direction to. the rear ones, pitch will occur and, to minimize this at all speeds, careful experiment is necessary. It is a task demanding infinite patience if the best results are to be obtained.
Rolling is another disturbing feature of the modern vehicle, and, in this country, but little attention seems to have been paid to its elimination. Torsion bars have been fitted, so that the movement of one wheel in relation to its neighbour results in the bar being set in torsion. When body roll occurs the resistance of the torsion bar is added to that ofthe springs, but when one wheel passes over a road undulation, the same stiffness occurs. This, then, is by no means the answer to increased passenger comfort.
Mechanisms which give a real advantage in this respect have, however, been produced, and one such device was the subject of a German patent. ,Although I cannot recall that it went into production, it had every appearance of being a simple and satisfactory device. Longitudinal torsion-bar springing was employa the torsion bars being
linked from axle to frame in such a 'manner that, although, the body rolled in the true sense, in that the centre of mass moved away from the turning centre, it inclined in such a waY that the sensation imparted to the pa.sengers was that of being thrust into their seats by a slightly greater downward pressure. '
Another mechanism, patented in America, was claimed to have a similar function, and here, again, a system of links was utilized to achieve, the required effect.
Modern transmission systems leave much to be desired— in this matter of passenger comfort, although the Fluid Flywheel is undoubtedly a Step in the right direction. The great development of this device in recent years, which has resulted in lower productipn costs, should go a long way towards its more extensive adoption, on a wider range of models.
The subject of passenger comfort embraces the amenities of the body interior and, although much has been done, there is stilt room for improvem.eiet; in some cases, a reduction, or the removal, of some fittings would be welconiA.
An example is found in the radio which was installed in many vehicles. As any group of people represents a variety of tastes, it follows that one type of broadcast item cannot please every passenger, so that it is, at best, a mixed blessing. The best proposition, if radio be essential, would be the use of headphones, which could be plugged-in at will.
Another Sphere for the Use of Plastics
Interior decoration offers much ,scope for improvement and the anticipated post-war availability of plastics, at
an economical price, promises at least one possibility.
Lighting may be concealed behind tastefully shaded translucent or transparent panels to give useful and attractive
illumination, whilst the tawdry chromium fripperies, with which pm-war vehicles were festooned, should suffer a belated demise.
Toilet accommodation,' although provided in a few coaches, was by no means universal, but must be so in the future on all long-distance vehicles. In this respect the railway companies have the lead and, although they have a certain advantage over road vehicles, this is by no means so marked as some people would have us believe.
Passenger seats are, at long last, receiving the close attention which their importance demands. In their development it has seen a gradual progression from a mobile version of the Victorian chair with its, pleats, buttons and horse-hair stuffing, to the expanded rubber, pneumatic and softly sprung components of the present day. Pre-war vehicles of the private-car type were announced as being
• fitted with " body conformity seating as developed -in conjunction with Harley Street specialists." . In some cases, such titles were more figments Of the imagination of publicity men than the products of scientific research, hut, nevertheless, good work in this direction has been done by some companies, to which every . 'credit is due.. There is no doubt that correct seating form greatly relieves one of much driving and riding. fatigue. The seat, besides forming a distance-piece between one's body andthe floor, mutt transmit all the vertical and horizontal kprces involved when the vehicle is in motion, although, fortunately, these do not seriously approach the
acceleration of gravity. The downward weight of the body is the greater force to be considered, and it was on this basis that a commission in America carefully studied the problems involved. American experiments have used a basis-of coil springs each separately adjustable, so that, by suitable, modification, the occupant could be made completely comfortable. When subjected to violent acceleration and deceleration some personal discomfort may be caused, and although these factors should obviously be limited to a degree which ,is compatible with passenger ease, their maximum comfortable magnitude is largely dependent on the seating arrangement. Suitable provision for be support of the passenger's back is obviously the answer, The seat-back which is designed in conjunction with the seat proper is essential for true " body conformity," that is, the correct support of the organ of the body so as to minimize the fatigue which would otherwise occur, Another less-evident cause of riding discomfort is the leakage of carbon-monoxide gas int!) the passenger compartment. When mixed with the obnoxious odours which frequently emanate from the internal-combustion engine, it is still more unpleasant, but there is this advantage that attention is called to its presence, whereas the existence of carbon-monoxide alone may go unsuspected.
A -frequent cause of this trouble is combustion " blow by " past the piston rings, 'a condition which is aggravated when sticking occurs. Gases thus pass into the crankcase and are expelled via the ventilator, or breather, from whence, by way of any aperture which may exist, they enter the body. The joint between the exhaust pipe and manifold is a frequent offender, and an air-tight seal is imperative.
Care Needed in Laying Out the Exhaust System
, Under-bonnet fumes frequently collect beneath the front wings and thereafter find access to the body. The remedy is obvious. Careful research into exhaust systems should be purstied to obtain fume-free running, and the practice whereby exhaust pipes are fitted by mechanias and then measured for record purposes by 'a member of the drawing office should be discouraged.
Chi the majority of passenger vehicles the whole problem of ventilation is treated in a very casual manner and the question would seem to tie one to be taken seriously.
Ventilatibn and air heating, or " air conditioning" as our transatlantic;, friends call it, divides itself into four categories—(l ) Heating by circulation with incidental ventilation system (termed by passengers " draught "), as largely employed at present; (2) heating of part of the air (inside) by circulation, augmented by the addition of heated air drawn in from outside; (3) complete heating of all air induced. (4) heating or refrigerating of all required air.
The last two systems are, obviously, the ideal at which to aim, with No, 3 as the most advantageous, for it is rarely that there is any need for artificial air-cooling in this country. Research, however, should be conducted so that an adequate system may be incorporated in our export models. With either of the two laet-named methods it is possible to control. the supply of air in respect bf volume and direction, as a proper air entry, or entries,. must be
employed so as to lead it to the heating plant. There would be no need for using windows that can 'be .opened and elosed'and, thus, there would be less expense, no irrita.ting.rattles and, what is of some importance, no wrangling between the passengers as to whether it is to befresh air or "lug."
Best MeanSfor Effecting Efficient Interior Ventilation _ The entry for this controlled flow of air may take the form of a large duct,or, several small ones,' distributed along-the walle, of the body and, in either case, they may be positioned at floor, waist, or roof-moulding level. Probably, the mos-. amenable position would leg just above the floor, so 'that the greatest heating effect would be directed on. to the feet of the passengethe as these are usually the first portion of the anatomy .to indicate discomfort. Another, point, too, is that the natural convection would raise the temperature of the interior of the body to a come fortalale level. , If the multiple-entry system be employed, then the -space between the inner and outer, skins,' if the body be ,so constructed, suggests itself as the logical pathtor the.air.
Heating mechanisms are .of several.types. Among those which have been, or are at present us'or.1, are those employing electricity, hot water, exhaust gas and, in America, petrol. The electrical energy .needed to heat all the air required in a large coachwould be such that extremely big batteries would be needed. Besides this; as the generator would be driven from the engine extra fuel would be consumed, and this applies also to the petrol-heated system. In the engineradiator we have an arrangement for dissipating about a third of the heat value of the fuel supplied to the engine. What more logical, then; than to employ this heat usefully, rather than to incur still more expense in a separate heating system?
If the radiator is to be utilized, then the present position occupied by this component is not permissible, for engine fumes would be induced into the vehicle interior. In any case, the orthodox location of the radiator is incompatible .with optimum engine efficiency, as heated air is inspired into the cylinders by passage through the radiator.