Axles with independent twin wheels.
Heavy good vehicles represent the ideal field of application for the concept of axles with independently suspended twin wheels.
Construction principle :
Based on the original orbital wheel concept, the idea is to double up the wheels using a pair of tilt arms set parallel to the axle axis. The central swivel point of the tilt arms is integral with the axle end.
When one of the wheels moves vertically (due to a bump or hole), it transmits the opposite vertical movement to its twin.
The four wheels along the axle are constantly in contact with the ground, however uneven it may be. If an obstacle such as a stone or a pothole causes one wheel to move vertically, the axle receives only half the shock, the rest being absorbed by the vertical movement of the other wheel.
The figure opposite represents a preliminary model in which the traditional axle has been retained. Among other advantages, this makes it possible to keep most of the tried and tested components and to experiment more easily with the new suspension principle. The traction and braking forces are transmitted via articulated connecting rods which link the axle end to the outer rim, and also the two rims to each other. Future configurations, still based on the same principle, will be aimed at developing more powerful braking systems on the basis of multiple brake rings.
Axles with independent twin wheels provide significant advantages:
As each tyre is subjected to the same load, the subsequent wear is greatly reduced and more evenly spread: no more abnormal wear due to the cambered surface of most roads.
The tyre carcass is no longer subjected to sharp shocks (stones, various obstacles) and so its useful life is increased.
As the overall load per axle is evenly distributed over the four tyres, the load per wheel is reduced. This should lead to the development of a new cheaper type of tyre with an equal performance level.
A hydraulically-powered lift system can be used to reduce tyre wear by raising either the inner or the outer wheel when the vehicle is not heavily loaded (Lorries run empty 40% of the time).
Maximum adherency is constantly maintained for all four wheels on a single axle. The effect of vertical oscillation on the axle is reduced by half, thereby improving shock absorption capacity and decreasing structural vibration.
Low-profile tyres can be used to steer a more accurate course.
The resulting increase in comfort becomes a safety factor, as long-distance drivers will suffer less fatigue.
As vibration and jarring are reduced by 50%, the driver is much more comfortable and therefore tires less easily.
Goods are also carried in better conditions as they undergo less vibration. There is less strain on the straps used for fastening the goods down and holding them securely in place, so road safety is also increased.