177 Uses POP rivets in similar ways to what Paul said above for 217. We also use solid aircraft rivets installed with a pnuematic hammer and bucking bar in application where higher shear strength is needed or if we need the rivet to be flat headed. We have made arms capable of lifting a robot of the ground this way using aircraft construction methods. Needless to say we believe the strength is there.
A word of advice if you plan on using big diameter rivets is to get a pneumatic tool for installation. Particularly if you use a lot of them.
Just a general comment, we find a mixture of joining using welding, rivets, rivnuts, and nut/bolt fastening depending on the application gives us the best solution for the problem. Don’t rule out any of these methods unless you are not properly equipped to do them.
Interesting discussion - good question Billfred. I’m surprised to hear the amount of success using rivets and the kitbot, especially using backing washers. Normal design practice for rivets - at least in my work experience - is to avoid tensile loading and just use them for shear loading (obviously they have some amount of tensile capability, but they aren’t designed for it) Installation involves match drilling close fit holes - I would think that the kitbot standard clearance holes are nowhere near adequate to get a good interference fit after bucking or popping. Has anyone run any calcs or tested tensile load capacity?
S.P.A.M. (I can’t say ‘we’ anymore) has used rivets very successfully on some structural components, but not the chassis. Definitely the lightweight solution if you can make it work.
Back in the days when Northrop Grumman was just plain Northrop, we built the fuselage for 747s. We also installed 3/4 of those million rivets. (Actually I think it was 995,000 but at that point who’s counting?)
In modern aircraft structure rivets are often used for joints that are never intended to come apart. Just walk down the F-18 line with me sometime and listen to all the rivet guns, and just why do you suppose hearing protection is required in all the assembly areas?
Used properly, rivets are a very practical fastening method, but they have to be done right to work. That means matching the rivet diameter and length to the hole, countersinking to the correct depth for flush rivets, and using the proper mandrels and riveting tools. But if it is good enough for a modern fighter aircraft if ought to be good enough for a FIRST robot.
The whole frame is “ribbed” and “skinned”. Just like an airplane is made. No need for welded steel. It does get “dented”, but it never has “failed” on us yet. Even the wheels are riveted with bulkheads and quite strong.
What is this pick on chakorules day? LOL ;-). I didn’t get a chance to respond to myself in that post. I meant, kitbot and rivets don’t mix well because we don’t normally use the kitbot frame, we make our own frame. I didn’t mean it as it “reads” like we used rivets on the kitbot frame. We have never tried that to my knowledge. We always use the bolts and normally we use the kitbot to build a proto-type frame to the programming team, that’s where I come in. I don’t think I’ve ever even used the pop-rivet gun yet in three years on the team, woooo…I am gunna get it for saying that…
Nah, I didn’t mean it that way. I guess my sense of humor didn’t come through on that one. I guess I was trying to point out that I tried to start this very discussion about riveting KitBot frames back then but nobody seemed to take the bait at the time.
We have aluminum pop riveted some assemblies with excellent results.
A good design practice is to use a splice plate or gusset plate at connections between two structural members & install multiple rivets in each member.
For instance at a right angle connection between two tubes, put a triangular gusset top & bottom with 4 rivets thru the gusset plates into each tube.
This also spreads the load over a larger area of the frame tubes, reducing the likelyhood of exceeding material yield at a single concentrated point if using one rivet.
A 3/16 rivet is the same size as a #10 screw. Holes are easy to drill and they are plenty strong for anything on a FIRST robot if using multiple rivets at a joint.
1/8 rivet are great for adding small plates for limit switches etc. or reinforcing structures after it’s all bolted together.