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Riveting up a frame
(I searched "rivet" and didn't find anything, so here goes.)
So I know that there are those of the riveting school of thought, at least when it comes to your frame. I'm looking at the option of riveting up the kit frame next year (assuming it's the same and blah blah blah), as it seems to be an easy way to both drop some weight (albeit less than welding, but with the advantage of easier repair) and cut out the issue of locknuts backing out. This leads to a few questions in my mind: 1) Are rivets a viable option for an average FIRST robot frame? 2) What kind of rivets are best for this? Aluminum is the cheapest option, but stainless steel rivets have higher strength by orders of magnitude. 3) If you've riveted the kit frame, is it best to just put rivets everywhere the bolts should go, or can you do well with less? 4) Is there anything in particular to look for in the way of damage after the robot has taken a few hits? |
Re: Riveting up a frame
That actually is a good idea in the beginning, however, from personal experience rivets break easily especially under strain, also if you use rivets you have to use washers to allow the rivet to grab and hold the metal together. Once again they are very weak and in a match if someone hits you your frame might break apart.
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Re: Riveting up a frame
Don't do it, unless you find some really large rivets.
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Re: Riveting up a frame
Rivets are weak in shock load, but great for static loads.
A loose bolt is much weaker under cylical loads than a properly tightened one (ask the Mech Engineering guys why). A rivet (of the type you are considering) cannot be 'tightened' - the tightest you can get it is not very tight. (Rivets for big steel, like the GW Bridge, are installed hot, so they shrink and 'tighten'). So, loose rivets and cylical loads equals premature failure. Also, the rivet starts to get loose quickly, and it's ability to be strong* drops significantly. That means instead of tightening up nuts and bolts, you get out the hammer and tighten up the rivets. *Strength doesn't actually change, but a loose member has a little bit of distance available to allow it to build up some momentum before it hits the end of the rivet...and that isn't good. Don [Edit: The above refers primarily to standard peen-over rivets, not Pop Rivets mentioned by Deepwater] |
Re: Riveting up a frame
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Any other questions just let me know. I have to give two thumbs up to a properly riveted KitBot! |
Re: Riveting up a frame
In one of the prototypes, I believe team 1114 used quarter inch steel rivets and it worked great for them. See this thread.
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Re: Riveting up a frame
I know that 1126 rivets their aluminum frame together instead of welding it. Right Dylan?
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Re: Riveting up a frame
We riveted our upper frame last year (1/8" aluminum riveted w/ 1/8" aluminum rivets) and it worked pretty well, but as someone already mentioned, rivets don't take heavy shock well.
Also, repairs can be a bit tricky. We found that in most cases it's easier and faster to add more rivets than to replace the old ones, which is fine if you're using small rivets, but on the kit frame, you'd need some big ones. (We didn't rivet our drive base.) |
Re: Riveting up a frame
Team 104 has used 1/4" steel rivets with back up washers since 2001 except the stack attack when we tried a 8020 frame. We have never had a riveted joint fail. For 2006 we bolted the kit chaise together and when the design became fixed backed up the bolts with rivets. We built up the kit frame with 1" 6061-t6 angle. The frame worked just fine.
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Re: Riveting up a frame
Team 1501 uses a frame completely made from sheet aluminum and pop rivets. You will not find a stronger frame.
http://www.huntingtonrobotics.org/ |
Re: Riveting up a frame
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As for rivets, I would use them in the less vital area's, but not for heavy frame rails. They dont react to shock very well, and could also reak havok on the field with wheels and drivetrains if some were to come loose. Just my 2 cents. :) If you can make it work you get a High 5. |
Re: Riveting up a frame
I am from a team where we usually only rivet our robot no welding. We have never had rivets break if you use the aircraft quality. these can take up to 26,000 lbs of shear force, only cost a couple dollars for a 1/4 lbs of them, and come in varying sizes. We find it is also safer than welding because we the students do almost all of the work. These are not pop-rivets though if that was what you were referring to.
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Re: Riveting up a frame
Why cant students weld?
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Re: Riveting up a frame
Most students we can trust to do work like that but there is those few who don't know when joking around should not be done. Also riveting is a lot easier to learn how to do rather than welding.
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