Re: Ribbit Rivet...
 

We did something similar with our robot this year. We used rivets (McMaster-Carr #97526A434) and I splurged and got a decent rivet gun (McMaster-Carr #90239A510). We wanted to paint the frame red and then throw on yellow rivets, but we ran out of time.

The gun worked great. The rivets held when our robot dropped off the 3 foot table we were working on. Rivets are very forgiving. We had no experience with them and all but 2 of the rivets were tight on the first application. The two that were loose were easily drilled and replaced. Those little guys saved us about 1 lbs over the bolts. We shall see how they do in competition, but right now, i'm sold.

Re: Ribbit Rivet...
 

We used 1/4 this year a step up from 3/16 and 1/8" rivets. We seemed to cut the amount of rivets we used in half this year by just switching to 1/4" They are gods (small g) among meer mortals in the fastener kingdom. But there are a few criterion that I like to follow when using them.

First, the ultimate importante is to have a pneumatic riveter, its much nicer/cleaner if you do and your kids don't end up walking around like popeye with one massive fore arm. Make sure you buy the right size riveter, and you get what you pay for. This year we used harbor freight riveter ran us around $95 but we had some issues, worked out the kinks and got it going pretty well. Don't waste your time with the HF hand riveter, it literally broke on the second rivet we popped.

For 1/4" aluminum is good, don't really need steel, we popped a few in the highest stress parts of our bot, but ehh it was probably overkill.

If you use 1/4" make sure you have plenty available, they are somewhat hard to find at a local hardware stores, we tried somewhere in the neighborhood of 6-10 stores before we tracked them down. Order them with the other parts, its cheaper and easier. ( I just happend to mis count )

When drilling out rivets be careful, this is kind of why I cringed when Paul said the challenge. Its true, rivets can stack up speed wise with most of FIRST style bolt construction, but hopefully you really won't have to drill out most rivets. Often times when drilling them out, you can open the hole a bit more, if you do this overtime the rivets aren't as snug... I know its like a few thousandths thing each time but if you come in at an angle I just hope your safety factors are high. Which with rivets, they usually are higher than you even know.

Use them everywhere and anywhere, sheet metal construction is one of the strongest available options if you want to put the engineering into it. One of the greatest parts is its amazingly cheap, to cut out entire robots worth of sheet on a water jet it can be a couple hundred dollars worth of labor. When all you have to do is place shafts and pop some rivets, its an amazing building experience.

If you don't for some reason think the rivets are strong enough, there is also the rivet/apoxy route. Adding structural apoxy like loctite E-20NS or the E-20HP which IF YOU NEVER WANT TO TAKE IT APART is amazingly strong.

So what have I learned with rivets over the last two years,

strong as heck, easy to use, have a good pneumatic riveter, apoxies are awesome if you don't want to take it apart, rivet where possible, don't drill them out too often, marvel at how cool they look and how light they are. Play count the rivet games with other teams that come by.

Happy Riveting.

Re: Ribbit Rivet...
 

Don,

When some of the students and mentors had this difficulty with our HF riveter, it was often due to using the wrong mandrel on the front and improperly setting the length of the jaw assembly. The 1/4" mandrel is, in fact, big and sloppy on a 1/4" rivet. The smaller mandrel is for 3/16" rivets and it allows the jaws to push too far forward, preventing the popped rivet mandrel from releasing. Similarly, the jaw assembly can be screwed in and out to set the unclenched grip of the jaws. The closer this assembly is to the body of the riveter, the stronger the grip when pooping and the stronger the grip when unclenched. Moving the assembly out from the body loosens the grip.

As mentioned, you get what you pay for. We paid $50-ish for our HF rivet gun. So we've acquired a dirt cheap rivet gun to get comfortable with, at the cost of it needing some TLC.

Re: Ribbit Rivet...
 

We use as many rivets as possible every year and have riveted the KitBot for the last three years with ZERO problems. We, of course, riveted it again this year. For the KitBot we have always used ¼” aluminum rivets with aluminum mandrels specifically either:
MSC #04045431 ($7.42/100 - Marson Brand)
McMaster #97447A651($12.75/100 - POP Brand).

As far as our experience with manual ¼” rivet tools here is what I can tell you:

It 2005 we purchased a “NuLine” ¼” rivet tool from MSC (#74327552 - $99.62). It has worked well for us but after 4 build seasons we have literally worn it out. It is made in China (or Taiwan?) and it shows. The main problem is the insert for the ¼” size rivet partially cracked and broke last year and then completely broke this year. The arms are linked by tiny E-clips that have continued to fall off since the beginning. After one too may times of crawling around on the floor looking for the E-clip that fell off we just replaced the pin with a 10-32 bolt this year. We have managed to keep it working but it is time for a new one. After our various modification and fixes the spent mandrels now come shooting out the back of the tool at a rather unsafe velocity. The handles are also very bent and battered from repeated use. Bottom line: I would rate it 3 of 5 stars. It has been a good friend but I think we pushed it a season or two past its useful life. If you are looking to invest is a quality tool that will last a lifetime this is NOT it your tool. It works for a while (~2-3 build seasons) but then literally starts falling apart.

As a replacement I decided to give the Harbor Freight 41291 ($13.99) rivet tool a try. I had a couple of $10 HF gift cards so it was free and good thing because if I had paid $1.00 for it it would have been a waste of money. It will grip and set the rivet fine but then you have to disassemble the thing to get the spent mandrel out before you can set another rivet. After reading through this thread I see that we aren’t the only ones with this problem and others have fixed it with liberal amounts of lubrication. I may give that a try but after the frustration that thing has given I really dread even messing with it any more!

Yesterday I broke down and ordered us a Marson “Big Daddy” rivet tool from McMaster (#90239A510 - $96.92) in preparation for competition. It should be here tomorrow and I am expecting great things after the reviews I have read of the “Big Daddy”. I was a bit hesitant because the McMaster image looks suspiciously like the piece of junk Harbor Freight 41291 but hopefully the HF 41291 is a cheap and poorly executed imitation of the superior Marson “Big Daddy”. The Marson “Big Daddy” from McMaster was the least expensive and best quality (from what I have read online) I could find. An added bonus is that replacement parts for the Marson “Big Daddy” are readily available from McMaster which is NOT the case for the import tools from HF and MSC. I will update this post with my review of the “Big Daddy” after we have received it and had a chance to break it in and see if it lives up to my expectations.

Re: Ribbit Rivet...
 

Another problem when drilling them out is that they can spin. IF you're drilling one out and the bit all of the sudden does not seem to be cutting, STOP! Spin the rivet for a minute with the drill bit and it'll be too hot to touch. Do that in plastic and it will have already melted.

Thanks Kevin & Chuck, for the good info. Next year we'll put a real riveter in the budget.

As for the HF hand riveter, I agree it's not worth a dollar, but with some careful work we did manage to get it to work OK. Indeed, mandrels do not come out until you lube the tips of the jaws liberally. I'm not going to waste anyone's time explaining how to fix that (PM me if you need it), my advice is buy something else.

Don

Re: Ribbit Rivet...
 

correct i find it faster scene we always have some kind of drill bit in the drill but we didn't use rivets

Re: Ribbit Rivet...
 

Agreed if the heads off already and the bottoms showing we usually just hammer out the rest with a 1/4" transfer punch :-)

Re: Ribbit Rivet...
 

Alright, time for a bit of hard data from us:

Perfection.

We ran eight rounds at Chesapeake, ignoring practice. For the most part, these were pure lapping, but we made our fair share of hard hits along the way. (The zip ties on the lane divider feared us, and we had our fun with low gear as well in a few matches, perhaps most notably the Great Pileup of Q56.) Through it all, the riveter stayed in the bottom of our tool cart.

Granted, all of this was with bumpers on our front and sides; we left them out of the corners and the back for various reasons. It would be nice to give this robot a few more events before declaring it a total success, but I'm quite satisfied right now.

Re: Ribbit Rivet...
 

2106's gun stayed in the bottom of the chest as well. not a single loose rivet. Now if we could find a way of riveting chains to the sprockets...

Re: Ribbit Rivet...
 

We got to use our rivet gun...something about trying out new treads, and then we finally got around to reinforcing an arm bracket that had needed it for a while. But we didn't have any failed riveted joints.