Welded Frame Horror Stories

Ok, our team is considering a welded frame and cantilevered drivetrain for next year, but I’ve heard many horror stories regarding broken welds, permanently bent frames and destroyed drivetrains because of a dent in a frame member. Tell me your horror stories, what happened, and if it can be avoided. Are welds prone to break in a certain style of game and can less-than-aerospace quality welds withstand tough play, especially if braced properly? Is 1/8" tube capable of an aggressively defensive style of play, and how badly do drivetrains suffer when you’re somewhat out of square?

As long as you design your fram right with welded members, you won’t have any issues. The materials we use is 1/8th inch wall 1x1 box extrusion. It’s never let us down.

The only time we broke it was when the bot tipped over and got rammed 8 timed by a tank tread bot. But that was a whole different issue.

So design it smart, and you’ll never go back.

116 has welded our frame for longer than I can recall, and we’ve never really had any problems with it. The closest thing to anything you’re describing we’ve encountered, that I know of, would be taking about a 1" dent after a vicious ram (while we didnt have bumpers attached). But that didn’t really effect us in the long run, as the dent didn’t effect our chain. Plus, had we been using bumpers, it would have been a non-issue.

We’ve used 1"x2" 1/8" wall aluminum tubing the last few years, with great success.

Put a couple cross braces in the center, and you’re good to go. We got the heck bashed out of us all year long, and the frame is just as square as the day we had it welded. Haven’t had a single issue.

I suppose it helped that a professional welder did all the welds on our frame, but as long as you design the frame properly, you shouldn’t have a problem.

We had a similar frame this year and the fame itself never had any problems. Some other welds on the upper part of the robot broke, but they were from tipping probably.

How to stop deformation from game use? Simple, decent welding and GUSSETS. So many teams never reinforce their joints, and sure that may work for a non stress application, but whenever you get two or more robots colliding, gussets prevent the welds from damaging forces.

Just my $.02

MAKE SURE IT’S NOT TOO BIG!

Ours wasn’t welded, persay. The main frame, we desighned and got it cast.
When we got it back it was a half inch too long.

We hade to take a grinder to it. (UGH)

Fusion has been using welded frames and custom transmissions at least since 2003 on Squid bot, the years before that I cannot be sure about except for Flash, Fusion’s first robot, that has a welded frame if I remember correctly. We have not had any trouble with the frame, but at IRI in 2005 with Arm-N-Ra our arm was welded to a gear, and the weld broke and our arm came crashing down, but that was a weak point in the design of the robot. 5 more ounces of aluminum would have saved us. Also at IRI 2006, a chain in our transmission lost its master link lock and fell apart. Those are the only two problems Fusion has had with the robots in the past 2 years.

We use welded frames and we have had no problems, except when we pre-drilled the bearing holes and they warped :ahh: . The frame was put to the test when we were auto programming and the robot was setup backwards then went forwards at full speed into the cement curb; lets just say the curb lost.

6063 Aluminum 1/8" wall box tubing TIG welded for past 3 years never had any problem worth doing something about.

Can you elaborate on how bad of a problem this was? Did they warp a few thousanths, or turned into ellipses? I’m trying to compile as much info on problems as possible so we may avoid them should we decide to move to welded.

Additionally, if you pop a weld in competition, whats the best way to fix it? Carrying a TIG welder in with us is not especially convienient.

Bandage it, use a piece of aluminum plt and lots of pop rivets. No harder than fixing a broken gusset if you don’t weld.

Here are a few lessions learned from the ONE year we welded…

  • Don’t let you welder learn on the robot frame
  • Don’t let you welder learn TIG welding as his first kind of welding
  • Don’t let you welder learn on aluminum
  • Don’t let you welder learn on 1/16" thick aluminum
  • Don’t let someone grind off all the “ugly bumps” on the surface after you are done welding.

We made some mistakes. Huge mistakes. But if you have a skilled weldor on the team, you should be OK.

And here is my thinking on bent frames. “Assume” that your frame will bend. Now how does your robot work? Try to think of ways to design so that it will work WITH damage. Because if you are anything like our team… you are going to eventually run it into a wall at top speed, fall over, or drive it off a cart at some point.

Get some practice! Especially if you want to use aluminum, we have had a professional machinist do some of our welding, and the first time he did it it broke (luckily before it got out of the shop) and he’s been welding for at least 40 years…and small mistakes happen a lot with aluminum, any one will tell you that. Anyway, he hasn’t had a problem since then, but he always does a test run with the same alloy before you weld.

If your looking for an alternative to welding thats still light and easy to fix, my team has been very happy and slightly fascinated by the latest rage in the facing industry, Screw Rivets! (Look up Rivet Nuts on McMasterfor more info)

Kind or works like this

/off topicness

I thought the fastening 306 did this year was a neat idea just really machine work intensive, I talked to one of your mentors about it at Philly.

We use 1"x1"x1/16" AL 6061 box for our frame and had no issues with breaking anything. We planned for a high impact game last year and built a properly reinforced ladder frame to handle the load. The only damage that our frame showed after 2 regionals, the championship and Battlecry was on the front where there is a slight indent (~1/8").

I don’t believe cantelievering will be an issue if you support it right but I don’t reccomend unless you protect you wheels well.

A couple other comments:
Don’t pre-drill your mounting holes before welding. Assume you will have some misalignment/warping from the heat of welding.
TIG!
Drill vent hole to allow hot gas to escape when closing a box.
Bolt to the frame properly. I.E. don’t put a bolt all the way through the box and crush it, use rivnuts.
1x1x1/8 angle weighs the same as 1x1x1/16 box. Sounds stupid, but people forget. Also 1x1x1/8 weighs almost the same as 1010 8020 extrusion.

#1 Rule: only have an experienced welder weld your robot frame.

Our robot is welded by a grad student who is on Northeastern’s Mini-Baja team. He’s been welding for years and is very proficient in welding aluminum because of aluminum tubing being used in their vehicles frame.

We were mentoring a rookie team and they had an inexperienced person weld their frame. It was disastrous and the frame broke apart before the build season was over. Our Mini-Baja guy cut all the old welds away and did it correctly. They never had another problem.

I would say if you don’t know of anyone who is experienced on your team then you should call up local machine shops. Even if they won’t do it for free the last thing you want to happen in competition is a broken weld.

We welded (or had it done, rather) our frame for the first time this year, and I was personally pleased, for it helped us cut down on weight (not too many steel bolts), but here’s the thing- we built our robot for defense (remember our drivetrain? :smiley: ), and we made the HUGE mistake of building our gearboxes into the frame as structural members (very bad idea, in my experience). In addition, we didn’t use the ever-so-wonderful gussets to reinforce the corners, so after the first day we were doing some massive tweaking jobs just to get the frame square enough to keep our gearboxes from binding up.
As for fixing the welds that broke (all but five or six by the time season was over*), that was simple enough. When we first designed our frame, we had aluminum angle in all the corners and such, and it was welded with those on (we took them off after the weld job), and thankfully someone had the presence of mind to bring them along to the competitions, so when a weld broke, we told one of the newb’s to find the right piece and fix it. No big deal, but sort of time consuming.
So I would make these suggestions:
-USE GUSSETS! they would have saved us literally hours of repairs
-make sure there aren’t any “vital weakpoints” like our gearboxes
-have the materials and equipment to make quick repairs if you would have to, this saved us several times (all you really need are some flathead bolt, angle, and a drill and bits.)
I think a welded frame, when properly done, has a lot of advantages over a bolted one (like weight and bolts coming loose), so I’d go for it. I think we’re going to stick with it, just making some adjustments
Good luck, y’all.

*this was not because of faulty welds, the guy that did them knew what he was doing and the welds were great, but we hadn’t engineered our frame to take the kind of beating that it did. (remember our infamous defense? :yikes: )

Here’s a welded frame done right. Here’s a welded frame done light. The front 1x1x1/8" box tube in the second pic bowed in slightly after a lot of bashing but never caused any problems. Professionally TIGed, only one weld ever so slightly cracked ever.

one of the design criteria you should be using to evaluate different design approaches is servicability / repairability, or MTR (Mean Time to Repair)

simply put, if your frame is damaged, how easy will it be to repair? how long will it take on average?

dont paint yourself into a corner thinking there is no way your frame could be damaged. Bad things happen, crates get dropped off trucks and forklifts from 8 feet up, Robots fall off tables and carts, or down stairs. When something bad happens to good robots you will need to repair it, then the question is: will it take 8 people 4 hours, or 40 hours?

If the only approach to fixing a welded frame is to bring a complete spare frame, then thats what you must do. How long will it take you to transfer everything on your robot to the spare frame? Or it might be better to fasten the frame members together some other way. or maybe have welded subframes that bolt together?

Team 829 has done welded frames for three years. Here is this year’s frame. This frame was welded by our welding class. No breaks or bends and we were a very aggressive player this year. In the background you will see last years robot made from the KOP. We welded it too.

http://www.warrenrobotics.org/Picture%20097.jpg