We have been looking into using monobolt rivets on our high vibration and impact mechanisms like a drive train. We used all aluminum last year and had a terrible time with them popping, loosening, stretching, and a ton of shearing. We are testing steel rivets and the monobolts to see if we see improvement. Just wondered if anyone has seen/heard/used them.
-Ronnie
You can use Hugh strength rivet . Which should hold a lot better.
We have been looking into using monobolt rivets
Yes you want to use a structural or aircraft grade rivet (like the monobolt) that locks the stem into the body of the rivet. Not the big box store variety rivet.
If the rivets are stretching/loosening then they aren’t big enough or enough of them.
It really depends on how you’re using them.
There is nothing wrong with regular rivets, they just aren’t as strong… So design accordingly.
Use gussets with more rivets, etc…
It’s also nice in some ways to design for regular, knowing you can switch to the stronger rivets if you need to (or switch to steel).
Agreed. 3/16" aluminum rivets are rated for 310 pounds of shear strength and 500 pounds of tensile strength. Going to steel bumps those numbers up over 2x the aluminum rating. A few more well placed aluminum rivets can add a lot of strength.
One word of caution if going the steel rivet route, we used steel rivets in a high load application and they were a bugger to drill out. After they were out, they were replaced with aluminum rivets without failure during use.
Ty! We were using 5/32" aluminum rivets and gussets; filling every open hole on our gussets. I we are already for sure going with 3/16" rivets next season and hope that helps. We will be putting 3/16" steel rivets on our off season bot and see how they hold up.
We use 1/4" rivets for the main chassis, where the load will be for crashes etc. We use 1/8" rivets everywhere else. THe only place I saw a 1/4" rivet fail was on our catapult arm, where the gusstens on the arm began to pull off of the 2x1. Fortunately, we caught it and replaced the arm with a welded one post-season.
I am curious on the decision to go with 1/8" diameter rivets, is there a reason for going to that size?
It doesn’t have much of a weight savings and they are significantly weaker than larger diameters.
The main reason we go 1/8" whenever possible ise because we have a pneumatic riveter for 1/8" rivets and small hand riveters for 1/8" rivets.
Our only 1/4" riveter is a very large tool by comparison, so if something breaks it takes more time to rivet it. It’s almost impossible to use the 1/4" riveter on the robot.
Occasionally we use 3/16" rivets as the small hand riveters and pneumatic riveter work with those, like on our pickup arm this year.
Another one is that if a steel rivet fails, it will more likely elongate your hole because the rivet is stronger than the material it is in. That means that you’ll have more trouble putting a rivet back in. We use only aluminum rivets for that reason.
We found countersunk rivets a couple years ago, and have fallen in love.
What is the reason for welding and using rivets with gussets? I have noticed you guys do this in a few areas. I would assume for extra strength and rivets/gussets make alignment pretty good while welding?
-Ronnie
Any issues with corrosion when using a steel rivet on an aluminum frame? If so, how long does it take to become an issue? Just curious when to retire use of older robots from “playing defense” against newer robots.
I’ll note that the #1 reason our rivets have repeatedly failed in the past (2010 frame, 2012 arm, 2013 wheels) is due to an incorrect drill bit size when drilling the initial hole (less common) or when replacing a failed rivet at competition (more common).
I can’t speak for 254, but I would guess added strength. Some parts on their intakes, like the little machined hinges, had to be welded anyway so why not? It is very minimal effort. Additionally, you would want parts that go outside your frame to be as rigid as possible to be able to withstand impacts.
Speaking of stuff done in addition to riveting, one of our new mentors advocated using adhesive in addition to rivets on our tube-and-gusset constructions. We’re doing this now, as it should reduce wear on the rivets/holes during impacts.
Just wondering if any teams have done something similar, and, if so, how effective they found it to be.
Yes, those are countersunk 3/16 rivets.
The extra strength isn’t part of the reason. They are riveted before welding so that the parts are pre-jigged when they arrive for welding. That makes it easier to get a better result.
Got ya. I was wondering if that was the reason since we do the exact same thing.
We do this mainly for fixturing purposes. It makes the welders life much easier.
I am not a Mech Eng but I do want to point out the opposite of this thought. Rigid is great but there comes a point where you can’t make it rigid enough. At that point you should look into making it flexible. For example, the 16 beater bar intake is wonderful because it is nearly impossible to break. I’ve seen them rotate around 180 degrees without failure.
That was my second thought. *(http://www.chiefdelphi.com/forums/showthread.php?t=129789&page=3&highlight=welding+gussets)
I know my statement was pretty broad, but I think it greatly depends on the device. Some devices you would need rigid and some would benefit from added flexibility.*