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#1
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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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#2
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Re: pic: Team 973 2009 Robot - RAPTOR
Wow, thanks for the detailed response! Seems like you were fortunate to have that machine shop with tubing capabilities, probably not something a lot of teams could pull of with a basic lathe. In any case, thanks a lot for the insight! Good luck at Las Vegas and Champs!
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#3
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Re: pic: Team 973 2009 Robot - RAPTOR
Quote:
As long as you have the travel it's not too hard to do it manually. Takes a long time though. |
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#4
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Re: pic: Team 973 2009 Robot - RAPTOR
it looks amazing i wish i got to see it work in person
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#5
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Re: pic: Team 973 2009 Robot - RAPTOR
Making the grooves wasn't too hard for us, I was referring more to putting a 1" ID through the entire 26" tube, is there a way to do that too? I'm not a very skilled machinist at all, I just know enough to get by. Does 254 drill out the middle of their rollers?
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#6
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Re: pic: Team 973 2009 Robot - RAPTOR
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The problem with them was that PVC is extremely heavy, and each roller would have weighed around 7-8 lbs. We ended up having to get a shop to remake them out of ABS for the weight savings. It's possible to drill a 1" through hole in the roller, if you drilled from both sides with a series of varying length drills, but that's obviously not an ideal solution. |
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#7
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Re: pic: Team 973 2009 Robot - RAPTOR
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#8
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Re: pic: Team 973 2009 Robot - RAPTOR
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They did the boring in two different operations. They stood them up on end in a very large CNC mill and used a series of drills of increasing length to bore all the way through. After they had the through hole they put them in another CNC mill and contoured the larger counterbore for bearings/plugs on each end. That's just one way of doing them. They can easily be done on the lathe with enough travel, or very accurately by someone who specializes in gundrilling. Our rollers this year were made for us by another sponsor who did everything on the lathe but the hexes on the ends, which they milled. |
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#9
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Re: pic: Team 973 2009 Robot - RAPTOR
The sponsor who made them specializes in all sorts of "tubing" and this really wasn't an issue at all for them. The lathes had several times the travel required, and there are all sorts of "accessories" that will stabilize parts will being turned (like a follow rest). Pretty much, I walked into their shop expecting them to say no as I was asking for too much, and they laughed like what I had given them was no challenge at all.
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#10
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Re: pic: Team 973 2009 Robot - RAPTOR
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