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Unread 23-03-2009, 02:44
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Re: pic: Team 973 2009 Robot - RAPTOR

After looking at all the material properties, we chose (guesstimated) that ABS was the best material to go with.

We actually bought 2.5" OD ABS and had it turned to 2" OD. A local machine shop specializes in tubing and it was no problem at all for them. They were turned to 2" OD, cut to length (they held 29.5 to 3 thou!), gundrilled at 1" thru, and finally bored to 1.125" for 1/2" on each end. After all that, a 1/4" round grooving tool was used to groove 3/16" deep. In hindsight 1/4" would be better, as we've had some small issues with belts jumping, but most jumping issues were solved when we used properly tensioned belts; I think I only saw 2-3 belts jump at LA.

In terms of price, it's not cheap stuff exactly, but we always do our homework and shop around. We think if you're buying massive amounts of material from mcmaster, you're doing something wrong. I think we ended up going with Interstate Plastics, who had it for somewhere around $16-19 a foot after haggling.

We weld our belts with a soldering gun with a spade tip and a jig we bought on ebay for specifically welding round belt. Works great. In terms of strength, there is no difference between that and a Jig would made that was basically two plates with matching slots, but it's certainly easier to use. We initially trimmed them with dykes that were custom ground to have no back angle, but while being lazy I found that a table belt sander works great (not sure if fine grit is required, it's what we used and it worked great for us).
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