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?

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

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

Re: Welded Frame Horror Stories
 

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)

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

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

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

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 McMaster for more info)

Kind or works like this

/off topicness

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

#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.

Re: Welded Frame Horror Stories
 

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? :D ), 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: )

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

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?

Re: Welded Frame Horror Stories
 

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.

Re: Welded Frame Horror Stories
 

This is the one thing I'd like to try to avoid. We have the capability to build a second frame, and our design makes it extremely easy (comparably to most other drive setups) to swap an entire drive train, but I am still somewhat worried about a frame taking the kind of beating our team would give it. 393 might remember, and 177 definitely will- we aren't especially kind to our robot with defense. Basically, if we get a chance to shove, we will, regardless of the orientation of our robot, or the damage that might be inflicted upon it by pushing. (Basically, an 8-foot fall could be significantly kinder to the robot than a regional). As a result, stuff gets bent, out of whack, but it's nearly impossible to shear a properly bolted component- holes or bolts. If it gets too bad, you just drill a few new holes, grunt the pieces into place, and you're good to go- basically with a connection as strong as when you started.

If a weld breaks during one of our thrash/spin/flip maneuvers, it may be a far more dire situation than if we had used a bolted connection.

Questions:

1. I plan to use a large bolt in bushing that doesn't require mounting holes- the casing has threads to be clamped into a hole. the hole will be ~ .75" in diameter- can I cut that hole before welding?

2. I plan on using a plug (round tube) that welds into this hole in the frame so that I may clamp down on the sides of the channel without bending it in- can I weld two flush surfaces, sand off the weld, and still have a strong connection between the surfaces?

3. We will need a guard around the wheels to protect them, and I was considering a welded, 1/16" tube skirt, bolted onto the interior frame for ease of replacement. 1/16" frame people, will these skirts get beat up unbelievably badly? They can bend up some, but will they just end up as mangled robot appendages in need of amputation?

Thanks, I'm trying to compile all of your knowledge before we attempt to depart from our standard. I want to make sure this is really going to work, and is work the effort.

Re: Welded Frame Horror Stories
 

Just remember the spare part weight limit.... 20 pounds of custom-fabricated items may not be sufficient for a frame.

Re: Welded Frame Horror Stories
 

...but there is always sticking the spare in the crate, at which point you're only limited by how much you can fit in the crate. (Then again, knowing what they charge for crate overages, I'd almost rather deal with the broken weld. :rolleyes: )

Re: Welded Frame Horror Stories
 

Just remember.... welds difficult to repair and even when repaired not near as strong as the original....

I know welds work most the time and have their place but i guess i'm an old fashioned fastener type. :rolleyes:

-Q

Re: Welded Frame Horror Stories
 

That certainly works too, if you can disassemble the frame, or wedge it in somewhere. Or you can ship a second crate for spares*.

(Also, I'm now recalling that the rule was 25 pounds, not 20....)

*The 2006 rules say that you may enter one robot per team. But if the spare (meaning identical, for all intents and purposes) robot is a spare fabricated assembly, and is packed in "the crate" (presumably meaning "one of the crates", since teams are allowed to ship 2), are you really entering twice? I think not, since the robots cannot compete simultaneously. So you could do even better than just a spare frame, if you really wanted to annoy everyone.

Re: Welded Frame Horror Stories
 

Hmmm I think I hear phones ringing. Panic calls to the Rules committee to figure out how to close THAT loophole, which you could drive a truck through. Have you considered a career in Law Mr Lall?

Re: Welded Frame Horror Stories
 

So, you can't compete at the SAME event, but could you compete at a DIFFERENT event with the 2nd robot? I guess that would effectively be two seperate teams, with two separate robots, with two separate budgets, under just one school...

(Sorry, I'm not trying to hijack this thread... should we split it off into something different?)

BEN

Re: Welded Frame Horror Stories
 

this is an excellent example of a frame that could have been designed with 3 or 4 welded sub-frames, that are bolted together

then if one side got smashed in you only need to replace that subframe section, instead of needing to bend metal back into shape, or to weld on an alum frame (which conducts heat very well) at a regional.

Re: Welded Frame Horror Stories
 

is welding any better than bolting? we use extruded aluminum and we had a small problem with bending but if was easily fixable.

could someone tell me what is so much better or worse about the two

Re: Welded Frame Horror Stories
 

weight. You lose all the weight of the bolts by welding.

You also don't have to worry about bolts loosening themselves, and going around retightening everything

Re: Welded Frame Horror Stories
 

Two teams at one school is allowed (two entry fees are paid, two numbers are assigned, etc.). Your school could compete at two simultaneous events, but since there's only one robot per team, your team could not. According to the rules, any custom-fabricated robot part can have fabricated spares that aren't part of the robot until installed, as long as they're identical to what's on the "real" robot. And if you ship spares in the crate, there's no weight limit.

Re: Welded Frame Horror Stories
 

as far as the square tube frames go has anybody used 1x1x1/16" tube since with bumpers dent resistance wouldn't be an issue. i just know it would be interesting to weld but it would be alot lighter. i'm planning on using a tube frame for a prototype drivetrain and would like some opinions on 1/8" or 1/16"
i think wildstang used 1/16" this year not positive though.

i was also thinking hybrid such as 1/8 for the outer rail and 1/16 for all smaller assemblies and small braces just to keep it light and strong

Re: Welded Frame Horror Stories
 

The practice chassis we built last Fall was made from 1x1x.0625 and welded and we have had no trouble with it at all. The competition chassis was bolted together rather than welded since we outsource our welding, so I can't say with any authority how it would've withstood the rigors of an event.

Though most of the work I do uses bolts, I always use 1/16" wall tubing when I can.

Re: Welded Frame Horror Stories
 

yes, definately!

If metal is welded correctly the metal will fail somewhere else before the weld will break

if you use a bolt you must drill holes in the metal, which makes it weaker at that location. A bolted frame will almost always fail at the bolt holes, or the bolts themselves will break, when the metal is stressed beyond its limit.

It will take more force to break a welded frame apart than a bolted frame.

BTW, this is how you test your welding skills. you weld two pieces of metal together, then you bend the metal or pull it apart till it breaks or shears. If the weld breaks it was not a good weld.

Re: Welded Frame Horror Stories
 

So you just yank the metal appart with your he-man-ness?

But a weld is alot stronger then the plain metal itself. If I remember correctly(which there is a 50% chance I don't) it has to do with when you weld you are melting the 2 peices together the same way metal is formed, then the extreme heat changes also heat treat it a little to help make it stronger.

Re: Welded Frame Horror Stories
 

I was under the impression that, with the exception of the fact that you're adding extra metal around that joint, a weld is actually far weaker in a heat treated alloy. For example, with 6061 T6, the weld is reduced to T0, and therefore, the weld was at a disadvatage to the rest of the material. The only way to restore the strength is to reduce everything to T0, and re-heat treat.

On a side note, what's a good way to heat sink a frame so that it warps far less when welding? I remember 67 talking about doing that when they were welding their 2005 bot. I also thought they re-heat treated it.

Re: Welded Frame Horror Stories
 

I think(again not sure) that this is only true for heat treated metals and not standard metals
The best solution would be to take your time and do it right. just use spot welds all the way around allowing it to cool some before starting the next weld. Running a bead all the way around and going too quick will likely warp thin metal.

Re: Welded Frame Horror Stories
 

Andrew is mostly correct. the -T6 represents a heat treatment called "solution heat treatment and artificial aging". When you weld it, you're removing the heat treatment, but not to -T0 (that doesn't really exist); it's actually the -F "as fabricated" temper, which means that no control of the heat treatment was employed during fabrication. There's more here, and even more in MIL-HDBK-5. It's possible for a weld to be stronger or weaker than the surrounding metal—there's no universal rule. The suggestion to take everything to the -O temper (that's "annealing"), and re-harden to -T6 is good in principle, but probably bad in practice because of the difficulty finding a suitable hardening oven (to fit an entire frame), and the difficulty of dealing with deformation and uneven heating. In industry, it's (very) occasionally necessary to do this, but stiffening jigs and distributed heat sources will be employed if there's any worry about deformation and uneven application of the heat treatment. More often, though, wrought aluminum alloys and similar metals come hardened from the factory to their highest strength level.

Re: Welded Frame Horror Stories
 

We do this in low stress areas of our robot.

Re: Welded Frame Horror Stories
 

To prevent your frame from warping during welding (and to make it stronger), I recommend a design with pieces that fit inside each other, like the first pic on my earlier post. That 1x1 tube in the lower front and rear goes clear through the 1.5x2" side rails. That frame came out flatter than flat.

Re: Welded Frame Horror Stories
 

Heheheh...

Since team 269 began using welded steel frames in 2004, we have not had many problems at all (save rusting - but we learned quickly from that one!). That is, of course, until this year. Within days of shipping our robot in 2006, our frame was a gigantic box - taking up as much of the allowed dimensions as possible. After a pre-ship scrimmage, we realized that we wanted to make some rather drastic modifications that involved cutting off two of the corners of the box to form a sloped front to the 'bot. Of course, after doing so, you simply cannot leave stray ends of square steel tubing because that is, frankly, not structurally sound. Nor is it safe. So alternate pieces of steel were masterfully gas-welded on by one of our mentors to finish the slanted portion (we already had our electronics firmly in place and did not have time to completely un/re-wire our robot).

Everything was honky-dory until the Championships rolled around. I was messing with the netting and noticed a fissure in one of the gas welds. After pointing it out to some of the other kids on the pit crew, we checked all of the gas welds and found another one that was snapped clean through. Luckily, we were just barely enough under weight to allow for repairs involving a very long, threaded rod and some pieces of sheet metal that were used to stabilize the junctions of steel in necessary areas.

The moral of the story is probably to do things 'right' the first time. The counterpoint is that change happens. Rather than being a horrible loss, this was a great learning experience.

Re: Welded Frame Horror Stories
 

This year 1103 used a welded drive. The only problems we had were because of some afterthought parts that were add using rivets. I'm not really a builder, but I think we used 20-22 gauge aluminum.

NOTE: I'm not considering the turret/tower assembly part of the frame. Because we believed the turret didn't need to be welded if it was attached to the corners corners of the drive.

Re: Welded Frame Horror Stories
 

This is an important point: don't use an electric arc welder on a robot with its electronics attached. That can easily become an expensive mistake. If you must weld, use a torch like they did. (And welding with a torch doesn't really work on aluminum. It oxidizes too fast without shield gas.)

Re: Welded Frame Horror Stories
 

thanks for the input on my 1/16 questions i'm now planning on creating a hybrid frame with an outer 1x1x1/8 rail and 1x1x1/16 innards to keep it light from some of the scant frames i've seen on here i think it should be pretty robust :D

Re: Welded Frame Horror Stories
 

we did this on our base in 2005....worked incredibly well....i would recommend to any team with a professional welder, otherwise 1/16th is very difficult to weld....

Re: Welded Frame Horror Stories
 

We've gone with welded frames since I can remember. Havent ever had a problem with them.