VRV Toyhauler Cracked Axle Mounts

[keeena]

I did a frame inspection while I had the frame up on stands for a new set of tires. I was disappointed to find some pretty serious cracks in 3 of the 4 axle mounts. All 3 are cracked in a similar manner and 50% compromised. A bit concerning but glad I found it now instead of losing an axle while rolling on the interstate.

The axle mounts look to be bent up from flat stock instead of starting out from angle aluminum. It looks like the cracks originated at the bend which may have been initially fatigued due to the bend. I'd imagine its the lateral load (turning dual axles) which stressed these mounts?

My plan is to cut all of the axle mounts off and fabricate new ones out of thicker, structural angle aluminum.

I'm going to consult with some weldors, but anyone see an issue with this plan? Would you design them differently?

[DavidM]

That gob of weldment looks horrible. Yes, replace the angle and weld it right. You should be ok after that. Great pics BTW.

David

[Pinstriper]

Too hot and too cold all in the same weld. Impressive.

[keeena]

Too hot and too cold all in the same weld. Impressive.

  Yeah, some of the welds are pretty atrocious. I'm a hobby weldor myself and these would be embarrassing at my skill level let alone on a consumer product.

I'm going with 3-1/2" leg aluminum structural extrusion at 3/8" thick. Trickiest part will just be getting axles in the exact right position again. I plan on bolting the brackets to the axle so spacing is correct, tacking, and then remove the axle to weld the brackets out. I won't be doing the full weld out - I'll leave that to a pro.

I tried to find pictures of how ATC designed their axle mounting. I could only find pictures one of their cargo trailers but it looks identical to what LL does:

[keeena]

Easy part done - machined the new brackets out of 3/8" aluminum structural extrusion.


Compared to the stock brackets; quite a bit beefier and the corner is over double OEM thickness
 


With an axle removed the problem seems to be a not only how these are manufactured (bent), but also weld-induced weakness. These pictures are from the inside of the portion of the brackets which are still intact. You can see stress/hairline cracks already starting along the bend in a straight line. This line is right at the edge of the weld bead / start of the HAZ.



 

Even with the new thicker bracket I think it would be smart to avoid welding the "L" sections on that edge. I'm probably only going to weld the section where the tube clearance is. There will still be lap joint welds on the other 3 edges like the OEM one was.

[DavidM]

I wish I had your knowledge, skills and the tools to make it work. Looks like a great solution. But alas even in LL's glory days, I bet you couldn't get a job as an aluminum frame welder. They were too cheap (witness the quality of their welds).

And therein is the flaw in an aluminum frame. You either design it and weld it right or stick with steel- much more forgiving.

David

[keeena]

Kind of you to say David. I have some absurd condition where I need to know and be able to make/fix anything.     Woodworking, metalworking, electronics, any sort of house remodeling, etc... It's not my profession; just a hobby. Its a ton of research and self-driven learning. HUGE time & money sink but I enjoy it (usually).

I've also wondered if a steel main frame with the floor/wall/ceiling framing in aluminum may be the best of both worlds. I'd trade off some weight savings and aesthetics for improved strength and maintainability.

I finally got a quote - much higher than I was hoping for.    I haven't found a mobile welder who is available, let alone getting a quote for this option, so I'll be bringing to a shop. This shop said that a mobile welder would be about as much as if I bought the trailer in and had them do all the work (remove/install axle, cut brackets off, prep, locate) at their site. I'll be removing the water tank for access and bringing by next week. Will post final #'s and whatnot.

[DavidM]

I think LL was one of the few or the only builder to use an aluminum frame. It was a risky decision and as you and many others have discovered it requires skill to weld it right. One thing LL did do right in this regard is to build the frame for their fifth wheel in steel. Fifth wheels probably stress the frame much more than TTs as the heavy loads fall on joints, not straight aluminum members.

David

[keeena]

I never knew the 5th wheels had steel frames; I thought those were AL too.

Anyone have a 5th wheel TH for sale?

[keeena]

All done; hopefully won't have to worry about it again.


 


I made a minor change to the design; final one below in case it helps anyone else out. Diagram is for the driver's side; passenger side is just the mirror image.




 

[DavidM]

Nice looking aluminum welds.

David

[Merlin]

Nice fix. Too bad you had that hassle, but you did better than OEM work. I also double checked those joints on my camper prior to the last trip because of this thread.

[RV Squirrel]

I'm not qualified to comment, but will do so anyway.  This look better than new!  I had a crack in a weld in the tongue of my LL 14DBS.  It haunted me for quite some time until I took it to a shop.  I watched them do the weld, and got the impression that they were learning on the job.

The milled aluminum looks great.  Do you actually have a milling machine?

#Pinstriper, you had mentioned that the original weld was "Too hot and too cold all in the same weld."  Can you say why?  I'd spent a lot of time under my trailer yesterday, working on a project.  All the while I was wondering what is good and bad.

[keeena]

@RV Squirrel - yep, that is my knee mill. It's an Alliant (Bridgeport clone).

A weld which is too cold doesn't have enough penetration. The bead will sit on top of the metal and the bead edges don't blend into the base metal. Too hot is the opposite; the bead won't have good shape definition (washed out), base material will likely be undercut, and the heat-affected zone wider than it should be.

The welds on the new brackets are OK; not perfect looking but definitely good enough. If you're curious: do some photo searches for "GMAW Aluminum".

My fun unfortunately isn't over: I found a couple cracks in the frame itself when re-installing the water tank and brake electrics.    The cracks are in the full width crossmembers immediately fore and aft of the wheel well. I believe this is the most common location for cracks on both the TH and Camplites. I'll weld these up myself at some point; likely should've had gussets or doubled-up from the beginning? Have any of you guys had the crack in this location fixed? I'm curious how others solved this one.

[RV Squirrel]

My crack was not in the same location... it was near the tip of the trailer tongue.  I'd provide a picture, but it is dark and raining outside!  In my case, they simply welded over the broken weld, since the crack only seemed to be in the weld and not the rail.  It wasn't too pretty, but it seemed to be holding the last time I looked.

Thanks for the insight on cold and hot welds.  I'll be sure to look into "GMAW Aluminum".

It must be fun to have a milling machine.  I needed to cut an 1/8" slot in 1/8" stock in a recent project, and used a drill press with an X/Y translation vise to do it.  Even though I was using a cutting bit instead of a drill, it tended to wander as soon as I started the cut.  At one point, the chuck fell out of the drill press.  It was an amateur job, but still fun.

Sorry about the cracks in your frame.  I do wonder about the welds in the brackets that hold the water tanks up.  I seldom travel with the white tank more than half full, because I'm concerned that the weight will break the welds.  I also dump my grey/black as soon as I can.  Now I'll be sure to look at the other welds!