Quad frame cracking fiasco… need input.

[BaitMaster]

I am In need of some input.

I did a repair on my quad last year. This is a semi regular occurrence for me to repair the rear rack from some failure, which considering what the quad goes through, is fair. We definately severely overload the quad so I am not mad at all for having to do repairs.

So last year, the tab that connects the rack to the frame broke off. The repair of that is documented in the baitmasters bench thread….

Basically I took a piece of 1/2” mild plate, shaped, drilled, tapped, put in the radius, and welded.

I used a TIG welder with ER70S6 rods.

Now, there is a crack there at the front of the tab extending down to about the mid part of the frame tube (bad).

The other side tab broke off last year as well, so I was planning on conducting the same repair this year. I’ll post pics of the not yet tacked setup for the second tab.

My question is, did improper welding cause this? Or just over stressing with a solid, immovable connection, and the other side breaking off in the meanwhile…..

Thinking of it, that frame is likely some sort of chrome moly. Is it not recommended to weld mild steel to chromoly? Did I use the wrong rod? Is my weld just the wrong profile?

I guess for reference so it’s known how bad we treat these racks, the rack is supposedly rated for 120lb of load. We typically carry 200lb + and do that over extremely rough, uneven terrain. For about 500km give or take a year.

Any knowledgeable input is appreciated.

 

[BaitMaster]

This is the setup for the other side. I’m ready to tack, then remove the rack and weld out the tab.

 

[Aliva]

I'm no metallurgist but I would guess that your over stressing the main tube beyond its capabilities.
A couple possible solutions would to replace the tube with a thicker walled version. Increase the length of the block to spread the stress over a larger area. Wrap the tube with a larger tube over a longer distance to spread the stress then weld the block to the new tube.

 

[Dan Dubeau]

It looks like it's right up against another mount on the bottom, so try and find a way to bridge those two loads so that section of frame tube isn't in a shearing load there. If that were mine to repair I would drill and vee out the crack, then weld it up. Then fit a saddle to the main tube, longer than the crack about 4" long and covering the bottom mount. Make the tab about 3" long to distribute the forces over a wider area. saddle is red, tab is green, welds are blue.


Atv tubes are pretty thin, I have no idea what kind of steel they are, but I have a feeling it's just going to keep cracking in the same spot unless you spread that load out a bit more no matter how you weld it. I twisted one up pretty good a few years ago. I had it hanging vertical chained between the barn posts, and pulling on various points with a porta pack and com a longs to straighten it back out again. I had to cut some tubes in a couple spots to be able to pull how I needed to, then rewelded them (mig) with saddles, and fish plates as needed. In the end I got it pretty damn straight again, and you'd never tell it was twisted like that, except for the bodywork that tells the tale. I was pretty underwhelmed by the construction when I started digging under the hood. This was a 2009 king quad. Certainly not built like my old 90's king quad (wish I never sold it )

 

[Susquatch]

I think Dan's advice is pretty solid. Cracks usually happen because of excessive stress or fatigue cycling. A poor weld, no matter what the reason, usually breaks at the weld.

You have to spread that load out, strengthen the part, or reduce the load. I like what Dan suggests. If the crack just moves, then you will need to strengthen the part. If that fails, it's prolly time to buy a beefier quad... LOL!

 

[Bandit]

As @Dan Dubeau is saying, you have to spread the load out over a larger area. It also appears there is another brace running up to the tube that is cracking, about 3,4, inches away. Depending on how the rack is put on to the frame, there maybe a pivot point with a long lever movement causing the problem that the "extra" load is making.
Anytime a mount is put out of line from another mount, loads often need extra material, which results in weight and/or breakage moving elsewhere as materials used are stressed beyond limits.
Metal will often break beside a weld, sometimes caused by metal changes from the welding.
Typed while @Susquatch was typing.

 

[Jswain]

Typical when you overbuild one spot it breaks in the next place. I like the thought of sleeving over the tube and then spreading the tab out over a few inches.

 

[BaitMaster]

Thanks fellas for the input, especially @Dan Dubeau for the clear effort with the drawing.

The thing is, this is an old 2002 Honda four trax…. They don’t make them like this any more…..

I doubt there’s a quad out there that could legitimately handle what we do with the quads year in year out….

We have clients bring their quads up and almost ALL of them break. And they haul no loads…. They just hunt.

This old girl handles the abuse with comparative grace when 202x quads are chewed up and spit out every year…

Repairing this bike or modifying it is honestly my best option.

I think I will come up with a plan to provide some extra support for that part of the subframe…..

 

[Susquatch]

I think I will come up with a plan to provide some extra support for that part of the subframe…..

Sometimes when you beef stuff up you just move the breakage to the next weakest link. It's better to spread the loads across a range of components each element absorbing its share of the load. Really beefy parts are famous for just kicking the blame up the system and doing this. Without good stress analysis tools, it's hard to do this properly. The best advice I can give is to make everything a little bit stronger but don't go overboard. It's an easy trap to get caught in.

 

[Tecnico]

Sometimes when you beef stuff up you just move the breakage to the next weakest link. It's better to spread the loads across a range of components each element absorbing its share of the load. Really beefy parts are famous for just kicking the blame up the system and doing this. Without good stress analysis tools, it's hard to do this properly. The best advice I can give is to make everything a little bit stronger but don't go overboard. It's an easy trap to get caught in.

This^^

D

 

[Dan Dubeau]

I agree on the older quads and build quality. My old 93 king quad was a brute. With 4 wheel diff lock and super low gear it would pull anything. No comparison to the newer ones at all. They don't make them like that anymore. I wish I never would have sold it.

I also agree that when you beef something up, you either fix the problem, or send it somewhere else. I wonder about beefing it up, but also engineering a rubber shock mount system. It'll handle the weight, I don't think 200lbs is a problem there, it's undoubtedly the shock loads on the rigid mount that's causing the issues. Might be more of a project than you want to bite off, but would no doubt solve the problem.

I can't speak about your method of repair, and choice of filler rod for tubing contributing to the issue as that's beyond my knowledge level. Shooting from the hip, I'd say it's more of a design issue, than a materials one though.

 

[DPittman]

The thing is, this is an old 2002 Honda four trax…. They don’t make them like this any more…..

I doubt there’s a quad out there that could legitimately handle what we do with the quads year in year out….

Yup they were good old quads, I had 3 of them between 2002 and 2006. I reluctantly went to Yamaha quads and only have fairly basic ones and nothing newer than 2012 but I would say they are equally as good, dependable and durable as the Hondas.
Yup if you overload it it will break. And the weight ratings are for fairly evenly distributed weight over the rack which is almost never the case when yer haulin' stuff. Add in rough pounding trails and you're going to bust stuff.
Personally, I'd repair the best I could then try to distibute my load the best I could and take it easy when you can on the rough stuff.
Just plywood across the racks helps to distribute the weight and can add strength. However the loss of easy tie down spots needs to be then addressed.

 

[BaitMaster]

This is basically how it’s set up. Those tubs are filled with about 100-120lb of rotting meat each. Then driven many miles through the woods….

 

[DPittman]

This is basically how it’s set up. Those tubs are filled with about 100-120lb of rotting meat each. Then driven many miles through the woods….

Looks well distrubuted and supported. Just too dang much. I'd hate to be the guy riding behind you

 

[Dan Dubeau]

This is basically how it’s set up. Those tubs are filled with about 100-120lb of rotting meat each. Then driven many miles through the woods….

You sound like a handy guy to know and have on speed dial......

 

[BaitMaster]

@DPittman the smell of the normal meat you get used to. The rotting muskrats/beavers are on a whole different level. Those will gag a maggot.

@Dan Dubeau i have a certain set of skills. Lol. If you are a black bear, running into me would be the equivalent of a person running into a dragon.

If you are a person, running into me is the equivalent of running into an undersized goofy looking goldfish