Pedal Dozer Project

Track Conversion Kit for Bicycles

Article from the Star describes a conversion kit that turns any mountain bike into a snow capable mode of transportation.

And another image (via autobloggreen)of the conversion kit that also includes a from ski to replace the front wheel.

What I like about this design is that it demonstrates an efficient pedal powered track system is possible -- specifically the narrow flexible rubber track seems to be the key here.

Notice the design doesn't force the track into a sharp radius bends at the rear idler cogs like the previous post. And I notice that the drive wheel seems to be solid plactic (not an air-filled tire) with sprocket style nubs that enmesh with the track to ensure positive alignment and drive characteristics. Both of these characteristics seems to optimize efficiency.

Lastly, I notice a detail that is obvious only when comparing the two photos: The rear idler assembly (3 cogs located behind the main drive wheel) pivot under power. The bottom photo (bike stationary) shows the rear idler down. The small idler in the middle seems to be touching the ground and the larger idler at the rear is actually raised off the ground slightly. I think this is to shorten the track contact patch and facilitate turning (A point Greg has mentioned previously).

On the top photo, the rear cog assembly seems to have rotated and raised off the ground a considerable amount under the power of the rider. I'm guessing this is for the purpose of some built-in suspension qualities, or terrain following capability for the track, or perhaps it is a variable mechanism to improve the handling characteristics depending on power output.

It looks like additional power from the rider turns the track and induces a secondary effect of driving the little idler down to make the track have a longer contact patch with the ground. I imagine that under hard pedaling the track bites down to provide more straight-line traction. And under less power, the rear cogs rotate back up to reduce the contact patch and increase maneuverability.

So based on this I'm thinking a narrow rubber-based track -- using v-belts? -- with solid cog style wheels may be a good way to optimize efficiency for our bulldozer application. Not sure if the variable rear cog system for handling is useful for our two-track application yet.

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