NEARLY thirty years ago, back in 1922, a keen youngster named George Rogers started in the Australian dirt-track game, not so much as a rider as a mechanic and tuner. And because George had a thick crop of blonde hair he quickly became known as Snowy Rogers. Those were the days of mile dirt-tracks, when machines raced were anything the lads could lay hands on, including 250cc two-strokes. Small-track racing on third and quarter-milers came later, in 1925.
Already Snowy was making a name for himself in Australia as a specialist in restoring broken and battered frames and a miracle-man in engine knottery. So much so that when, a year or two later, Californian hill-climb champion Sprouts Elder went to Australia to try his hand at small-track racing, it was Snowy who had charge of Sprouts machines. When Sprouts came to England in 1928, Snowy remained behind, he had so much business on hand he could not leave Australia. In April, 1949, Snowy came to England for a holiday, and he is still here, in the speedway game all his life, he cannot break away.
After watching racing on Britain's (for the most part, tiny speedways with their small-radius bends), Rogers was quick to note certain peculiarities in the behaviour of machines in a slide, and the extremely narrow margin between conditions giving good traction, on the one hand, and those resulting in overslide, lost traction and, often, a flat spin, on the other hand.
The Rogers brain reasoned as follows.
With a normal motor cycle steering layout, when the handlebar is turned
on lock, the front wheel centre describes an arc, and moves to one side
or the other relative to the line of the frame. When a speedway machine
is sliding a turn (anti-clockwise), the machine is banked to the left,
the back wheel is sliding to the right and the steering is turned to the
right to counteract the slide. The front wheel centre, therefore, moves
to the right of the frame line, thus running across the radius of the turn.
The effect is a tendency for the front wheel to drift to the right, out
of the slide, so that the back wheel has to be made to slide out farther
to achieve a given radius of turn at a given speed. This necessitates a
greater degree of right lock, moving the wheel centre farther out of line
with the frame.
Now, if the front wheel centre could remain in dine with the frame regardless of the degree of lock, the wheel should thereby be held into the slide instead of trying to drift. The effect should be less difficult in holding a desired course, and a lesser angle of bank for the machine should be required to negotiate a given radius at a given speed. As, a result, there should be improved traction and greater safety.
Knowing what he wanted, Rogers set out to find a way of achieving it. The result is a new steering layout which he has now patented As the patent has only recently come through, the new layout has yet to be proved in racing, although two or three famous speedway stars have given it a provisional tryout. However, the design is theoretically sound and is interesting technically from that view- point In a nutshell, when the front wheel is turned on right lock, the fork moves bodily to the left and vice versa. The amount of sideways movement of the fork is such that the wheel centre is constantly in line with the frame.
Behind the fork cross-members are through-bolts and distance tubes extending between plates welded to the fork legs. These distance tubes are a sliding fit in cross-sleeves welded to the top and bottom lugs of the steering stem. The fork, therefore, is capable of sliding sideways through the sleeves. When the handlebar is turned either way the sleeves, being forward of the steering stem, describe an arc. Although the fork turns at the same time, its movement is pivotal (about its own axis) rather than accurate. This is achieved by a roller, extending between the fork cross-members, acting in slotted members which are welded to the steering head and which are, therefore, an integral part of the frame. Turning the fork lengthens the wheelbase fractionally. Maximum lock available is 45 degrees. Trail is normal, in this case 2 7/8ins. Self-centring action is fairly marked. Rubber sleeves are fitted to exclude dust from the cross-members, and a metal shield, attached by the fork cross-bolts, passes in front of the fork legs to ward off heavy cinder streams.
Fork deflection is a little over 1in, which is normal for speedway work. The deflection is not however, controlled by springs alone. Progressive friction dampers are incorporated within the legs and consist of cork sleeves surrounding upward extensions of the wheel sliders. Mating faces of the corks are cut somewhat to the shape of face-cams employed for engine-shaft shock-absorbers. The arrangement is such that fork-spring pressure expands the corks; hence the degree of damping increases as the fork is deflected upward. Rogers has, of course, patented this device also.
Another Rogers patent is an overslide throttle control, a device which automatically part-closes the throttle when the steering is locked over too far. Star riders sliding a bend do not use more than about 20 degrees steering lock. More lock spells the beginning of an overslide. In such circumstances (which can arise in an instant, such as from a soft patch on the track) the rider may have his hands too full for niceties of throttle control to correct matters. The overslide control does it for him. In consists of a small cylinder attached to the frame top-tube and containing a spring loaded slide, which is linked to the steering by a rod.
The cylinder is closed at both ends except for throttle cable entry and exit. The cable outer casing enters a stop screwed into the front plate of the device, and the casing starts again in the slide, to which it is firmly attached. The cable passes without a break straight through barrel and slide. When the steering is locked over too far it pulls on the rod, which, in turn, pulls the slide forward. This, of course, shortens the " break " in the cable outer casing, thus, in effect, lengthening the cable relative to its casing, hence the throttle starts to close. Adjustable internally, the device can be set to suit individual needs.
Normal adjustment is for the device to begin to operate at, or just over, 20 degrees steering lock and achieve approximately half-closure of the throttle at full lock (45 degrees). The remaining throttle movement at any juncture is still fully controllable by operation of the twistgrip in the usual way. As the overslide is corrected and steering lock decreased, the device automatically opens the throttle again to the extent determined by the position of the twistgrip. The new steering layout and other gadgets were inspected on a machine which Rogers has just completed for Pat Clark, last year's Third Division Champion. With the exception of engine, wheel, transmission and controls, the entire machine was built by Rogers and, the frame, of T45 chrome molybdenum tubing and bronze-welded construction, is a masterpiece of triangulation.
A vertical steady plate from cylinder head to top-tube results in the engine being a common side to two triangles formed with the saddle and front-down tubes, top tube and lower tank tube. A triangle supports the steering head and another, a stiff one, the rear wheel. The object is that no power shall be wasted in flexing the frame. The drive is so positive when the power is turned on that, to quote Rogers, "This machine cannot be ridden by a lazy rider". Except for the bright chromium plated parts, the entire machine is copper plated and lacquered. A real showpiece. And the total weight? Just 1821b.
Has the new steering layout any useful application to ordinary road riding or road racing? Only actual test could show. However, three motor cycle designs of the past, the" Ner-a-Car" O.E.C. and Wallis which achieved constant alignment of the front wheel centre with the frame-were noted for their outstanding stability.
About the Speedway Workshop Archive