Well problem already solved.
Had the same issue and welded it with silicon bronze. Been so long ago I do not even remember what caused it to break; slamming it up, slamming it down, or looking at it cross-eyed. Bought in the mid-nineteen eighties when these imports started flooding the market here in the States. It broke within the first five years. Whatever the cause, it has held since.
You might notice the drive wheel is not a cast spoke type. Found that tended to slip too much and made a steel drive wheel, double flanged, so it would hold a rubber drive tire (or tyre). In hindsight might have been able to have used the original drive wheel as the rubber tire does not seem prone to move about. The tire is just a sliver of inner tube. That needs replacing about every twenty years.
-Doug