Not so long ago was invented the elliptical leading Cycling asterisk, allowing to increase the efficiency of holotransmit, faster to scroll through “dead spots”. One time they even went on sale, but then disappeared. To produce such a star yourself is very difficult and time consuming due to its configuration and the large number of teeth.
But if you look, it turns out that this number of teeth is not necessary, and the ellipse can be replaced… the rectangle with pulling teeth just at the corners. He will successfully perform the function of an elliptical sprocket.
The figure shows a rectangle with dimensions corresponding to a round sprocket with sixty teeth. To make it from steel sheet with a thickness of 2-3 mm depending on the type of bike lengths of the sides of rectangle can be reduced (or if you want to go faster — increase), remembering that the chain pitch of 12.7 mm. equal to multiples of him, it is necessary to subtract (or add) from the specified dimensions in the picture. For example, if there is a need for one revolution of the rod extends 48 of chain links (as in the standard star is the most optimal variant), then the dimensions of the rectangle will be 178×115 mm. the Rectangle is welded to the rod so that the angle between the axis of symmetry of the connecting rod and the short axis of symmetry of the rectangle was 30°.
1 — rectangle (45 steel, sheet s2—3); 2 — staff rod; 3 — tooth (4 pieces); 4 — Cirrus (wire Ø2 — 3,4 PCs.)
The height of the teeth and the radii of the curves should be taken the same as in regular stars. Each of the teeth is provided with antennae made from durable wire that is soldered (welded) to the rectangle They are needed in order to prevent chain jump off. Since in any position of the rectangle length of its perimeter covered by the circuit constant, a sagging chain almost will not, and antennae needed only for insurance.
Vladimir GAVRILOV, the item of Inozemtsevo, Stavropol Krai