The wheel is a greatest invention of the mankind. Let us try to restore the process of its invention and improvement.
We do not know and it looks as if we will never learn who invented the first wheel. But we can restore the process of its “devising” with a great degree of credibility. When ancient people were hauling a heavy object, for instance, a carcass of a mammoth or a block, something round –
a stone or a smooth log –
got under it by chance. And suddenly it became quite easy to haul. People noticed that and began putting such round objects on the way of load hauling. Hauling became easier. But putting such rollers was a vexatious business.
In effect, the first law of ES evolution was satisfied. In TRIZ it is called “the law of completeness of system parts”. But that was not enough. Wouldn't it be great if the roller rotated under a load! Dictum-factum. The middle part of the roller was made thin and was attached to a platform through a primitive bearing. The platform served to hold a load. A cart appeared that was a sort of an engineering system the elements of which had a link. Thus, the law of “through passing of energy” was satisfied.
However, such a cart could only go straight, it was difficult to turn. The operation of such a cart did not properly match its working conditions. The third law of ES existence was not fully satisfied.
The situation was easier if there was only one axle. But in that case a new problem occurred –
when turning, the outer wheel traveled a longer path than the inner one.
The cart wheels had to be dynamized. They were made separate from the axle and then put on it from two sides. In that case nothing prevented the wheels from traveling different paths when turning. A two-wheeled (uniaxial) cart became easy to control.
The “Dynamization” principle implies an increase in mobility degree and a change in some parameters of an object.
Paradoxical as it may appear, providing a brake was the dynamization of the wheel. A simple board pressed to a wheel by a lever evolved into a high-precision, efficient and clever mechanism. But at the moment it is important for us that a wheel with a brake has variable mobility –
from zero (the wheel is blocked) to full (the wheel is free to rotate).
But what can we do with a heavier four-wheeled cart? By that time, such animals as a horse, cow, camel, etc. had already been domesticated, so there was a lot of draft-cattle. To achieve better controllability, it was necessary to increase the dynamization of the controllable elements of ES. The mobility of wheels and their mountings improved. An axle with two wheels was beginning to be attached to a platform by means of a vertical hinge. A pole was attached to that turning axle and draft-cattle was fastened to the pole. The result was good!
That construction carried by an unfailing horse successfully lived to see the advent of automobiles. The “iron horse”, or, rather, its driver did not master the turning front axle, because the load on the control organs was too high.
This is how one of the most curious constructions appeared –
a steam engine vehicle with a horse harnessed to it. It is clear that the horse could not draw the heavy vehicle, the rear drive wheels were driven by the steam engine. What was the horse for? It performed an important function of turning the front wheels of the cart.
The construction of the pole steering device turned out to have a great disadvantage when an attempt was made to use it in automobiles. To move wheels while turning, the space was needed which was already occupied by the engine and other parts of the automobile. Our old acquaintance –
came in useful again. The axle was divided into two parts and only two little pieces of it were left. Each piece of the axle with a wheel put on it was attached by a vertical hinge to the automobile body. The pieces were connected with each other by a tie-rod. Now it was enough to turn the steering wheel and a special rack mechanism moved the tie-rod to the right or to the left and turned both wheels simultaneously.
The next step along the axis of dynamization is adjustments. Practice made it evident that to achieve optimal wearing of tires and easy control of an automobile, the controlled wheels must be skillfully installed. They must slightly diverge in the upper part and converge ahead, the way the automobile is going: the well-known camber and toe-in. The wheel position must be adjusted depending on the tire type, road conditions, driving style, etc. For this purpose, the mounting of half-axles to the body was made mobile, dynamic. But that was a kind of stepped mobility when we could move the wheel mounting only while adjusting, it being reliably fixed in a state of operation.
This scheme of mounting the controllable wheels is widely used today as well. But at the same time the “dynamization” invention principle also works.
For instance, why not to make controllable not only front wheels, but also rear ones? One of the schemes of such control does not include controllable wheels at all. Both the front and the rear axle are rigidly attached to the body that consists of two parts –
front and rear –
connected by a vertical hinge in the middle part of an automobile. When turning, the body seems to be broken or bent with the aid of the hydraulic cylinders and the vehicle makes a turn. This scheme is widely used in heavy-duty tractors.
The side scheme of turning, used in tractors, tanks and popular small six-wheeled off-road vehicles on low-pressure pneumatic tires, may also come into this group. In this case the wheels on one side are braked, while the wheels of the other side are rotated by the engine. In this manner, the vehicle can turn literally on the spot. But it is rather a step back along the dynamization axis, because the number of movable elements in the control system decreases. In addition, the straight motion of such a vehicle between two turns is somewhat awkward though energetic.
As for an automobile, the dynamization of its controllable wheels can be improved by making both front and rear wheels steerable. To make a turn, they deviate in opposite directions. An automobile with such wheels features a very high maneuverability.
Maneuverability in its turn would be improved if rear settable wheels could deviate both in the opposite direction with respect to front wheels (for making a turn) and in the same direction. In the latter case, the automobile will be able to move sideways, which is extremely convenient while parking.
Our wheels have become too complex%2