THE RALLS SUSPENSION SYSTEM.
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A Sample Set in Use on a London General Omnibus.
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'G the past year, a considerable amount of correspondence has appeared in both the daily and the technical Press concerning the deplorable condition of the present-day roads. There is little doubt that, in the majority of eases, this is partly duo to the anfortunately necessary neglect, of the roads during the period of the war, but at the same time, it must be conceded that tho ever-increasing amount of heavy traffic in daily use at the present time is, to some extent, responsible for the uneven
ness of road surfaces. This fact is clearly proven by the rapid deterioration of largely used roads which have been relaid as recently as during the last twelve months.
In using the term "heavy traffic" it is not suggested that weight alone is the responsiblet factor. That is obviously not the case, but it is certainly true that the heavy lorries carrying big loads are comparativeli less well sprung than the lighter vehie_es of tho pleasure car type. This lino of thought obviously suggests the need for improvement in suspension systems, not only as a preventive for worn roads„ but also as a means of reducing running costs and increasing the longevity of the vehicles.
Giant pneumatic tyres are finding increasing favour for this reason, but, this is not, in everyone's opinion, the hest or only way of solving what is really a mechanical problem. A problem it
certainly is, and one not easy to solve on commercial vehicles, when loads vary from the empty wagon weight to the same weight plus as much as four, five, or six tons of merchandise, and over which range of loads tile springs—to be theoretically perfect--shoold function equally well at all times.
The Rails suspension system—whiali has previously been described in The Commercial Motor, but which is now further improved,—undoubtedly marks an improvement over the more usual types, and gaini additional interest by reason of its application to a L.G.O.C. " B " type chassis, on which it is undergoing exhaustive tests with a view to its ultimate adoption if successful by this .famous passenger transport concern.
In the majority of cases existing types of springs are so designed that the road shocks are absorbed in a vertical direction only, whereas many of the shocks received actually exert an influence which tends to push the wheel rearward.s in an aknost horizontal direction, as well as upwards. This fact has been duly considered and provided for in the Ralls system, which is designed to counteract both vertical and horizontal forces, and also to relieve the springs from doing duty for the torque drive thrust and tractive reaction which are now taken by spring drive radius rods.
It will be seen that the commonly used earns-elliptic springs are retained in the
Rails system, a point in its favour snice the conversion is thus possible at moderate cost. The actual principle of the springing is, however, entirely altered, as will be gathered from is careful study of the appended illustrations, which show that the usual semi-elliptic. spring is now shackled at its forward end and is free to move fore and aft instead of being anchored in the usual manner. The rear end of the spring is connected to a boll crank Lover, which is mounted on a substantial trunnion bolted to the main frame of the vehicle, and the upper arm of this lever ha& its movement controlled. by two powerful volute springs, through the centres of whioh is a long bolt having shoulders, between which the forked end of the bell crank lever registers.
The horizontal movement of the road wheel is, therefore, provided for and controlled by the forward shackle and the spring-loaded bell crank lever, and, further,by an extension of the crank, on • which is a roller which hem against two extra spring leaves when the road wheel is lifted beyond a. certain predetermined height. The object of this additional action is, of course, to increase the strength of the spring in relation to the shock to be absorbed, or the load carried.
It is obvious that, if this system is to have its full effect, the complete rear axle with its differential and casing must float both vertically and horizontally, and in order to allow this the special radius rods shown are employed. The one end of a radius rod is attached to the axle casing and the ether end is connected with a pivoted lever, the movement of which is controlled by means of volute springs in a similar manner to the bell crank levers employed on the springs. A torque beam is also used between the• centre of the rear 'axle Casing and a gess-member of the main frame, • whilst the propeller shaft slides In a universal joint in front of the driving werm. The front springing is similar in 'principle to the System employed at the rear, but in this case, of course, there are no 'torque strains with which to contend.
The Halls system has been very thoroughly tested over a considerable period, and the several claims made for it have been investigated by representatives of The Commercial Motor end other unbiased experts. The action of the •springs has been
closely observed under normal running -conditions, and also under abnormal conditions—such as driving, both slowly and fast, against and over such obstacles as railway sleepers. These tests clearly demonstrated she facts that this system relieves 'the clutch and
• transmission considerably When in the hands of a careless driver, and that the road -shocks are actually met in the tyre desired directions, viz., vertically and horizontally. A further important faet,wss noted, and that is that this system actually helps the progression of the vehicle, sinte, whilst the springs were compressed in one direction when the vehkla slowly meunted the sleepers, they returned the notion before the road wheels 'were at a standstill, and 'gave them a forward movement equal to the rearward movement imparted by the obstruction.
The•syitem should benefit the buses, and reduce the contingent ravages of vibration on 'roads and •property.