Dynamo (Roller Replacement)

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Here's an old friction dynamo typical of those found on bicycles in the 1950's.  These are often referred to as "bottle generators" due to the resemblance in shape.  Like most parts on bicycles from the 1950's it is over-engineered and will, or may already have, outlived its original owner.  The entire casing is steel and completely chromed.  Note that the manufacturer MITSUBA is proudly displayed, not with a cheap paste on label, but with a badge that is riveted to the chrome case.  If one is going to go to that much trouble to put one's name on their product, you can be sure that it is good quality. 

As over-engineered as these old bottle gernerators were, one part requires replacement.  It may come as a surprise to some people but the metal roller on top, which makes contact with the sidewall of the tire to drive the generator, will actually wear away over time. 

The peaks on the ridges have worn down over the years and have become dull.

Note the sharp peaks on the ridges of the replacement roller.

In the old days the BE (Beaded Edge) tires had tracks molded into the rubber to improve traction for the dynamo roller.  Note the fine lined tracks in the photos below.
Click on photo to enlarge.

Replacing the roller is simple but it helps to have the right tool.
This is the T-spanner used to remover the nut which secures the roller to the dynamo's spindle.  The manufacturers included one spanner per case when shipped to shops.

A very thin walled socket might also work but this tool makes the job a snap.

In the photo below it is apparent how dulled  the original roller has become.

Simply slip the new roller on tighten down and the dynamo is ready for another quater of a century of maintenance free riding.