Motorcycle 6

In the most simple form, the two-wheeler frame is made up of pressed steel segments (see picture 1). Although scooters appear to have these frames, they mostly have a strengthening construction which, e.g., may be a piece of thick tubing running in the center under the weather shields and up to the front. The tubular frame is always relatively light-weight (see picture 2). It can be partially added to the framework (see picture 3). The direct connection may be made of steel (see picture 4) or more often, aluminium (see picture 5).

In the meantime, and particularly the manufacturers of superbikes, have long since moved away from the steel-tubing-frame. Aluminium with a special profile is now 'in' and, it is so precisely balanced, that not even a small hole may be drilled in the frame, we won't even mention the possibility of repairing one after an accident. Indeed, they do look good and they fit in well with the design, which cannot be said about, e.g., certain box-swing-arms.

In the past, one had to pay special attention to the seat- and particularly, the leg position because of the unnecessarily wide framework. Nowadays, the frame, the engine and the tank are, more or less, merged into one unit, so that not the frame, but e.g., the tank or the width of the engine prevents having a satisfactory sitting position. In this vein, one could probably criticize the unnecessary height of the foot-pegs on some superbikes as well.

Because of the weight advantage, more and more aluminium is being used in the motorcycle frame. Steel however, does still have certain advantages. With steel, one may perhaps have a certain amount of 'advance warning' before it breaks, which is indeed, not much comfort for the motorcyclist. Particularly cast aluminium, will give no warning at all and unpleasant cracks may appear. However, because motorbike riders depend a great deal on an intact frame, the frame should always be closely examined after any accident, in fact, it's condition should be checked every now and then, before it's qualities suddenly change. These check-ups are even more important if magnesium has been used as an alloy.

Sections are created when aluminium, when still in a pasty stage, is pressed over a type of awl to afterwards form a hollow section. In modern motorcycles, these sections are cleverly inserted, e.g., between the engine and the tank. The steering head in the front, and a transition tube at the rear are then welded on. The welding of aluminium is still a technical challenge, whereby generally, no finishing work on the seams is needed. Indeed, a more complex quality-control must be made.

Looking at one of these frames, certain engine developments become apparent. In the front curvature, one of the cylinders of a diagonal V-2 seems to fit in well, however, not all the cylinders of an R-4. The revving ability and thus the performance, of a bike with (only) two cylinders is above all doubt. When air-cooled, the first cylinder slopes strongly to the front, this enables sufficient airstream to reach the second cylinder. The engine is mostly mounted on rubber-blocks, thus to a certain extent, also plays a supporting role. The vibrations however are almost completely absorbed before they reach the handle bars or the foot-pegs.

The only difficulties are the fuel- and above all, the air supply, particularly at high speeds when a certain amount of turbo-effect is desired. In the V-2, the inlet port is sometimes slanting to the side. Whatever the case may be, the V-2 is always better that the 'steam-engine' R-2, particularly then, when each cylinder has it's own crankpin. 12/13