For the past two seasons we’ve used good ol’ fashioned nuts and bolts to keep the bot together. After the second regional, our bot got pretty roughed up and nuts start coming off or becoming loose.
I was wondering how many teams have been using rivets to keep their bot together and if so, did you use them for the whole bot? Did they perform well?
Also, is it really final when you fasten the bot together with rivets or is it relatively easy to remove them if mistakes were made or adjustments are needed?
We haven’t used rivets, but a quick search of the forums for “rivet frame” comes up with many related threads, such as this one http://www.chiefdelphi.com/forums/showthread.php?t=59567&highlight=rivet+frame
I can say that welding the kitbot frame significantly increases frame stiffness relative to bolts, and saves probably one or two pounds of bolts in the process. Rivets offer a signficant weight savings, too, I understand, and in this game saving a few ounces can make a big difference.
Jason
We’ve riveted large numbers of joints since 2007 and are very happy with how they’ve held up in competition. We use 1/4" aluminum or steel rivets as necessary. Steel rivets are much harder to drill out, so we use them sparingly, and otherwise avoid using rivets at points where whole mechanisms couple to the robot so that we can more easily remove them should that need arise.
1/4" rivets require a special tool that is about $150. Ours is called the Big Daddy - by its manufacturer – and we bought it at a local supplier of hardware and tools. You can also order them through McMaster-Carr or similar, I’m sure.
The past few years we’ve used a lot of rivets, mostly on the mechanism, but our 2008 chassis was riveted together (fiberglass channel and sheet aluminum). We prefer smaller rivets, mostly 5/32", we also use some 1/16" and 3/16" rivets where appropriate. Sometimes the rivets get loose…that generally means the joint was not designed properly.
See if you can find pictures of some past 1501 robots 
217 and 148 are my favorites for riveting. Search CD-Media for their bots.
-RC
In one word to answer your question… yes. If you have specific questions, feel free to send me a private message. The past examples of different teams have led me to believe that rivets do a great job; as well as led me to use rivets for my teams.
Our basic frame is welded, but we use a lot of rivets for attachments and lexan. They are easy to drill out and remove when needed and are great for quick fixes. The mechanical team has a large assortment of diameters and lengths as well as aluminum and steel.
In 2008, our grabber completely snapped off (hit a wall head on) and were scheduled for a back to back match. A hand full of rivets, hand drill, and a manual rivet gun; we had the grabber back together before the staff had the field reset:cool:
I’m guessing we are mostly talking about steel and aluminum ‘pop-rivets’.
Does anyone use solid rivets ? They are used on with a riveting tool that vibration hammers the rivet against a bucking bar.
If you are riding down the road look at the side of a common tractor trailer made of aluminum structural framing. A zillion of the rivets. Used on aircraft too !!
177 has been known to buck solid rivets in our robots. We have the full aircraft builder’s set up in our shop with pnuematic hammer, a variety of bucking bars, and plenty of kleckos.
Former mentors on our team built their own aircraft and taught us how to dimpel the sheet metal and everything. We usually only use this in applications were we need higher shear strength or the rivet needs to be counter sunk, or we make a monocoque structure out of sheetmetal
I believe 1501 Thrust uses some solid rivets in their robots as well because they build their robots almost exclusively in a monocoque aircraft fashion.
Any recommendations on pneumatic hammers ? Bars ?
We have done projects where it would have been really nice to do it that way but we didn’t have the tools or knowledge at the time.
I’ll take a look at what we have this weekend and let you know.
Instead of “Is riveting that much better?”, a better question would be “what are the pros and cons of riveting?” Just like everything else in this world, there are advantages and disadvantages. I’ll post some of each below, but I’m sure there are more that other people can think of.
(btw, I’m referring to pop rivets here)
Pros:
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light weight. We once weight all of our fasteners on a robot and it came out to nearly 20 lb. An aluminum pop rivet weights about one tenth of the steel nut/bolt combo it replaces, so you can save 5 lb pretty easily with good use of rivets.
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Fast and easy removal and replacement. You don’t need to track down the 7/16" wrenches and unscrew a bunch of nuts. Grab a drill and the proper drill bit, and two seconds worth of drilling will remove each rivet. You can easily remove 10 rivets in less than a minute, and that includes searching for the drill. Likewise for attachment. It takes about 10 seconds to load a rivet into the gun and do the fastening - no need to figure out how to hold a nut still in a hard to reach location.
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thread locker not necessary
Cons:
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Not as strong as a nut and bolt. They’re much lighter and sometimes rely on a bit of friction to do their thing. If it needs to bear a lot of load, you should probably stick with the nut and bolt.
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Special equipment necessary. You have to buy a rivet gun and make sure you have the right drill bit to remove the rivet if you need to.
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Drilling out rivets can sometimes leave rivet remnants in place where you may not want them (like inside of tubes). Usually not a big deal, but something you might want to think about.
I’m sure other people can expand on this, but this should at least get you started.
…or design the assembly so it can use several rivets. Usually the stuff we rivet is made with sheet aluminum brackets riveted to aluminum tubing.
That was my thought too. You say they weigh 1/10th of a steel bolt/nut combo. So throw 5 of them on to replace a bolt/nut and you are still under.
If you’re trying to join two pieces of 1" aluminum at a 90 degree angle, you may not be able to do that (you would have a 1" x 1" overlap). You could use a 90 degree plate to do the joint and then use lots of rivets, but I would argue that a nut and bolt would be simpler and lighter at that point. I guess my point is, do whatever is simplest (KISS).
Glue it, screw it, bolt it, rivet it, weld it. If the design is flawed it will fail.
Case in point, for any large pieces of sheet metal (like many of the bots I have seen riveted) more rivets is probably better but I suppose its easier sometimes to bolt things like that together as sheet metal gussets would make it non KISS.
Last year we made this super awesome looking shooter guard for our turret wheel and it took us well into the morning, needless to say we forgot about rivets…
If you can’t get a screw in there make sure not to forget about the rivets.
Yes, yes it is.
For one thing, as awesome as welding is you are usually going to have two problems:
- Frame distortion- Every frame I have designed that has been welded has warped to some degree (especially aluminium), this is not a happy thing to deal with (wheel contact, conveyor alignment… ).
- Skill- My team was lucky to have a veteran welder around, but I have seen what happens when a new student tries to weld aluminium. It becomes more like modern art, and less like robot frame :rolleyes:.
Bolts lose in the weight and remaining tight categories.
Rivets are light, easily installed and uninstalled, and create pretty solid joints when done correctly. I think every FRC robot has at least one application where rivets would be the most useful of all fasteners.