Bearings for a Bicycle Generator

Some models of the bicycle electric generator, better known as a “dynamo,” have serious design flaws.

For example, the plain bearings in which the rotor shaft rotates need periodic lubrication. And their design is inconvenient to disassemble. Once the lubricant is depleted, increased friction appears, along with wear of the bearing bushings and of the rotor shaft itself. As a result, the clearance between the rotor and the stator becomes uneven and, consequently, the voltage fluctuates and the headlight light flickers.

A modification of the electric generator is proposed, consisting in replacing the plain-bearing bushings with two 60025 ball bearings with protective washers. It will be necessary to make a new roller and a bearing housing, two spacer bushings and a gasket, and in the electric generator to rework the housing and turn down the rotor shaft.

To do this, disassemble the electric generator, cut off the part of the housing with the bearing bushings, true up the cut on a cylindrical mandrel, and bore the hole to a diameter of 20—22 mm. Using a template, mark the centers of four holes on the electric generator housing and on the flange of the manufactured bearing housing. Then drill them: on the generator — to a diameter of 3.2 mm, and in the flange — for an M3 thread. Using the same template, make four holes 3.2 mm in diameter in the gasket as well.

Turn the worn rotor shaft with a nominal diameter of 6 mm down to a diameter of 5 mm, and cut an M5 thread 15 mm long on the end.

Before assembling the rotor, put the gasket on its shaft; the gasket will serve as a support for the outer race of the lower bearing in the axial direction. Then press the ball bearings onto the rotor shaft with the spacer bushings (the protective washers of the bearings should face outward). Place the shaft in the bearing housing, which you then connect with M3 screws through the gasket to the reworked electric generator housing. Reduce the height of the screw heads by half so that the electric generator cover can close. After installing the stator and the cover, check the quality of rotor rotation and screw on the roller. In doing so, the clearance between the end faces of the roller and the housing should be at least 0.5 mm.

Two years of operation, including winter, of a bicycle electric generator modified in this way have shown the reliability of its new design.

“Modelist-Konstruktor” No. 8’2000, V. KHOMENKO, Sumy Region, Ukraine