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Originally Posted by GeeTwo
Does that include cleanup? And did one, both, or neither of the two removers use a power tool?
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I'm guessing power drill and hand rivet tool, and probably ratchet and hand wrench for the threaded. But a power tool for the threaded will probably only get things down to even, so rivets still win on weight.
Quote:
Originally Posted by GeeTwo
As noted above, rivets can't be passed them through both thicknesses of channel or tubing to get resistance to torque.
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Teams that design primarily with gusseting+riveting in mind would probably tell you that you're designing your joint wrong if you have to run a fastener through both walls of the tube.
Quote:
Originally Posted by GeeTwo
When it comes down to it, we don't even use many threaded fasteners that are short enough to be effectively replaced by a rivet, and many of those go in blind so that we couldn't get a rivet in or out anyway.
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Okay, so this has me the most confused. We exclusively use blind rivets on our robot. It's right there in the name that they're meant for blind holes. They're just about the only way to attach something in the middle of a tube, short of drilling+tapping or bolting through the whole tube. Are you talking about blind holes into solid material? That's the only kind of blind hole I can think of that (most) blind rivets won't work in.
Anyways, we move to using lots of rivets on our robots. As others have mentions, we're only using threaded fasteners for things we're planning on removing occasionally and joints that are too awkward for a riveted solution.
We're pretty standardized on all aluminum 5/32" (thanks to Vex) and 3/16" structural rivets. When we're not using the premade Vex gusset plates, we typically use 1/16" for gussets on lightly loaded joints and 3/32" for heavier loaded joints. We've mostly been reserving the 3/16" rivets for the heavy duty joints. I'm afraid we're not super-scientific on the spacing and amount of rivets. The students and other mentors tend to throw a lot of rivets at a joint because they're light and easy to install.
The only time I see problems with riveted joints that I wouldn't with threaded fasteners is when there's poor fit up. Threaded fasteners will obviously let you pull together two sides of a joint that aren't already clamped together. Rivets (especially standard pop rivets) aren't nearly so good at pulling together two sides of a joint. If you have poor fit up, you'll see gaps between your gusset plate and the tube you're riveting to. That gives rooms for thing to shift and loosen and almost always results in wobbly joints after a short while.
We use rivets because they're typically lighter and faster than threaded fasteners. Yes, a threaded fastener of exactly the right length into a threaded hole is about the same weight. It's just a lot more tedious. Installing a rivet is as fast as drilling a hole (in place if necessary) and popping in a rivet. Your other options are drilling a hole, lining up a nut and bolt on either side, then tightening. Or drilling two different size holes, tapping one, and tightening down the bolt.
Other rivet advantages are they can't be cross-threaded and it's stupidly easy to add a few more to a joint if you need to for some reason.
If you're worried about getting the right hole sizes, holes wobbling out, strength, picking the right grip range, etc. then go with the
3/16" high grip range structual rivets. Also, no matter what rivets you need, buy them from Rivets Online. They're cheaper than McMaster for pretty much all your riveting needs.