I've used a few and the best by far is three 4X8 hot rolled plates leveled, grouted, and bolted to the floor. Leave two gaps between the plates and lay them width wise on the floor.
Of course who can afford that so the next best and probably the cheapest is two angle irons strips 20 feet long (or as long as your car) with one leg imbedded in a slot cut by a diamond saw, 6"X 1/2" flat head allen head capscrews with washer/shims beneath levelling it. You should get/borrow an engineers level for dialing it in.
A few good straight I beams make up the parallels and they can be clamped or bolted to the angle iron or with beam clamps if you shim it high enough (2" is lots). It looks not bad and can be grouted in later for a professional look. For detail cut the angle for entrance ramps at the ends. Square tubing or any other straight piece of material can be used as a spacer block for jigging the frame and accessories etc. 4"X4" angle is a nice size, the heavier the web the better. The same could be done with square tubing but it costs more. <img src="graemlins/pimp.gif" border="0" alt="[pimp]" />
[ September 25, 2002: Message edited by: 4 Jaw Chuck ]</p>
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