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Originally Posted by sidewinder
We are big fans of the 1" extrusion but in my pit scouting for the last few years i have noticed something, The robots built for first don;t have enough power to bend 1" extrusion with any kind of blow.
I beleive that 20 mm extrusion, very light by comparison to its big brothers, has more than enough strength for our purposes.
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20mm extrusion is something that we've looked into too, and I think that's definitely a possibility to reduce weight, though rough calculations would show the moment of intertia would drop to about HALF that of 1" 80-20 just by reducing the overall width and height (and presumably weight) to roughly 80% (20 mm / 25.4 mm/in) . That's the one reason that we haven't made that switch. Has 20 mm been used by your team in the past?
To keep with the thread:
In the past two years we're always using 80/20, 1010 (1" x 1")... and here's why:
The moment of inertia of 80/20 1010, which is 1" x 1", is .04413 in^4
The moment of interia of 1" x 1" x 1/8 thick box is 0.0570 in^4
The weight of 80/20 1010 is 0.495 lbs / ft
The weight of 1" x 1" x 1/8 aluminum box is 0.511 lbs / ft
So.. for those of you trying to save weight, look again!
Check it out at:
http://www.8020.net/pdf/Fractional/0...%20(31-62).pdf
Obviously though, it's more expensive than box aluminum. We were purchasing it at around $2.50 a foot. Box aluminum is about $1.50 a foot off of
www.onlinemetals.com
People tend to make assumptions... crunch some numbers and you'll be surprised what you find!
In addition, the ability to actually CHANGE your frame around makes 80-20 great stuff. You can buy a 100 pack of t-nuts for $.08 each and go to town. Where 80-20 makes all their money is on those brackets and corner squares at $18 each. We make our own and come out just fine.
Matt