Trackers, this sort of thing...
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Take a normal bike, remove any extraneous weight such as lights, mudguards, and often the front brake, fit cyclo cross or chunky touring tyres and cowhorn bars and you're away. Very similar to the cycle speedway bikes that were popular in the 50's.
Geoff Apps took the tracker bike one step further, fitting 27 wheels into a 26 frame, thus raising ground clearance and break over angle.