I first bought my Unimat 3 nearly thirty years ago and took no time at all to become thoroughly disenchanted with the O-ring drive belt system. Although small, the lathe itself was quite evidently capable of some good work, but the irritation of disentangling the drive belt from itself, and all too frequently replacing them rapidly lead to the desire for changes. So around 25 years ago I built this toothed belt drive system. At the time I thought I should write it up for the benefit of others, but the difficulty of producing a useful set of drawings caused this idea to fall by the wayside. The drive itself has survived all these years, first being used with the original motor, then with one of the permanent magnet motors such as the current Unimat 4 is supplied with. A year or so back that too in its turn died, and so the motor was replaced with a jack shaft fitted to the existing drive plate. This is now driven via a poly V belt drive from a small three phase motor with an AC speed controller. The poly-V pulleys have two steps, so I have a total of 8 ratios plus the variable speed feature from the controller. The only downside is that I cannot fit that system to the milling attachment.
The drive I describe in MEW 168, does not include the poly-V belts and the speed controller. The special features of the arrangement described are that it all fits inside the original plastic cover and provides speed ratios similar to the original belt drive. It can work with either the original old Unimat motor, which was a series wound universal type, or with the later larger diameter permanent magnet type. It can be used on the milling attachment or the lathe. Speeds can be changed readily, the belt being able to be moved from one wheel to another as required. All machining for the original was done using the Unimat itself. The equipment available included the milling attachment and the simple direct dividing attachment.
You can read the full article in MEW 168, and download full drawings with this link:
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