To channel or not to channel??

[Ol Yeller]

I've got a M416 trailer I'm rebuilding. I plan to have an extendable tounge (4') receiver tube and a receiver tube out in the back. I'm planning to use a piece of 2-1/2" I.D. DOM square tubing to run from front to back to install the receiver tubes in. The trailer was missing the lunette and mounting assembly when I bought the trailer. So given my receiver tube plan, should I channel the frame cross members so the 2-1/2" tube joins in with the rest of the trailer frame, or should I just run the DOM underneith the trailer frame and tack weld it/tie it into the cross members? Initially, I will run 33" tires, but plan to run 35's at a later point. I'm thinking to run 35's I will have to do a SOA. however, given the small amount of wheel well clearance I have now, I'm not so sure I wouldn't be better off to go ahead and do the SOA now. The biggest benefits I can see to just welding the DOM tubing under the frame is that it will keep a lower tounge height and less malesting of the original frame. So the question is to channel the frame, or to weld the DOM under it?

Thanks!

 

[R_Lefebvre]

I'd say it largely depends on how good of a welder you are. Channeling the cross members will really weaken them. If you do a real good job welding in the tongue, it'll be as good or better as original. If you do a bad job, it'll be weak and fracture.

 

['05TJLWBRUBY]

Hey Dennis, I forget the lift size you're running on your LJ Rubi, but I'd try to keep it similar if you're towing the trailer off-road. I vote to run your new receiver tube through the crossmembers and channel it, or make it part of your frame for strength reasons. There is some definite validity to the post above that if your welding is poor, you will weaken it, but this is your main tow point and your main beam that you will be pulling from. Essentially your entire trailer will be centered off this beam. I'd center it in the crossmembers and burn it in good and make it part of the frame itself, then be happy knowing it won't come apart later down the road. Towing off-road puts HUGE strain and stress on trailers in comparison to regular over-the-road use and I don't think that just running it under the center of the trailer and running 2.5" beads across the top would be enough with a loaded trailer and you'd eventually find stress fractures over time and find it separate down the road leading to failure. I could be wrong, but I would think that making it part of your frame and welding on at least 3 sides of the crossmembers as it goes down the center would make it much stronger and much less likely to fail in an off-road environment. Of course, I'm a bit biased too, here's how I did mine-I'm not sure how to link direct to the post, but mid way down the page on post #22 you can see the general idea of my build:

http://www.expeditionportal.com/forum/showthread.php?t=30224&page=3

Regarding the SOA-as you'll have it apart for the upgrade, might as well do it now. You'll avoid tearing it down again later and a little more room in the fenders won't hurt anything with 33's, you'll just be able to swap to 35's later when you wear out this rubber.

Also, just a word of advice regarding the receiver tube-when you buy the steel, be sure to test-fit before you buy it and find it won't fit at home. My main beam receiver tube is actual true "receiver tube" which measures 2 1/2" outside, true 2" inside diameter, 1/4" wall SEAMLESS. None of my regular receiver hitch stingers fit-my 2" ball for my regular 5x10 trailer that I tow behind my Jeep all the time, etc. It fits very sloppy in my Jeeperman rear swingout to the point that I've been meaning to weld on a few beads then grind them down as there's roughly 1/16" slop on all sides of the Jeeperman receiver and makes a heck of a racket and a pain while towing. Anyway, it won't fit in my true receiver tube. The ONLY stinger that fits is my new Lock-N-Roll hitch setup. It slips right in and is a TIGHT fit the way it should be. It measures 2" OD, while the inside of the receiver measures 2" ID. I'd literally have to shave the paint off the others to fit. Point being, I'd hate for you to buy 4.5' or whatever of your 2 1/2" tube, get it home then find it doesn't fit after you weld it in, then try to slip it through and find it won't go. Make sure it slips at the steel yard before you haul it home.

Best of Luck,

Mike

 

[ntsqd]

I wouldn't notch the cross members. I would put the tongue tube under them and add gusset plates. The shear strength of a weld bead is directly related to it's length - regardless of the weld bead section's orientation relative to the direction of the load. Adding gusset plates can radically increase the weld bead length and that is what you are after.

 

[Ol Yeller]

'05TJLWBRUBY - I'm running a OME/JKS hybrid with ZJ front coils, LJ rears, 1.25" BL, 1" MML. When the nitto's were new I netted 6" lift over stock. So the trailer tounge is fairly level with the Jeep now. If I do the SOA, the tounge will be taller and I'll have to use probably a 4" rise on Jeep side of the hitch.. I have thought about just staying with 33's on the trailer even after I go 35's on the Jeep. Once I change axles so I can run just one spare, I could still use the 35 in a pinch. Another thought I had the other day was to fab some longer spring hangers that would give me a couple inches. I'm still not sure what I think about that. The height differences I figure I'll run into is the reason I was thinking of just welding the DOM tubing under the frame cross memebers. By doing so, it would kinda offset the change by going SOA.

I do feel channeling the cross members on the trailer frame would look the best, but I wanted to see what others thought as far as strength goes. In essence, I wanted to do the same as what you did in your build. The biggest differences will be I'm modifying an existing frame instead of starting from scratch. I'm not so sure starting from scratch wouldn't be simpler. Anyway, as for the receiver tubes, I have a 4' and a 6" (store bought) and everything seems to fit as it should. I will take the tubes with me to make sure they'll fit in the 2-1/2" I.D. DOM before I buy it. At this point I'm thinking I want to be able to extend the 4' tube from about a foot all the way in, to maybe around 36-40" out. I've already bought a Lock-N-Roll coupler that I'll use with the trailer. The rear receiver will mostly serve as a point to mount accessories and as a potential extraction point.

As for luck... I'll need some of that. I still consider myself a newbie on metal fabrication. I've done some smaller projects but this will be my first major project. I suppose everyone always has to have their first. :Wow1:

ntsqd - Either way I end up going, I'll add some gussets. If I do end up channeling, I wouldn't cut completely through the cross members so I would add gussets to add in the strength for the tubing and cross members. That might be a bit overkill, but I figured it'd be better in the long run. Any particular reason you say to just weld the tubing under the frame?

 

[ntsqd]

snip.....
ntsqd - Either way I end up going, I'll add some gussets. If I do end up channeling, I wouldn't cut completely through the cross members so I would add gussets to add in the strength for the tubing and cross members. That might be a bit overkill, but I figured it'd be better in the long run. Any particular reason you say to just weld the tubing under the frame?

Mostly because an uninterrupted tube is preferable to one that has been interrupted (cross sectional change = stress riser), but also because w/o any idea of what the trailer frame actually looks like I'm picturing cross members that are not as tall as the tongue tube nor nearly as robust, which implies that they can use all the help that they can get. Could easily be totally erroneous, but it is the broader application advice.

There is also the aspect of how tongues are frequently built in this application type. The highest stress in the whole frame is at the transition from tongue to main frame. All too frequently the tongue is essentially just butt-welded on there. Better is for the tongue to underlap the main frame and extend back a reasonable distance. That gives the section modulus needed to keep the strain low.

I've been intending to write out how to design the tongue & frame based the weight of the trailer's components and their locations for a couple of months. I've even enlisted a fellow Engineer to check my work. I just haven't had the time to do the job.

 

[Ol Yeller]

Mostly because an uninterrupted tube is preferable to one that has been interrupted (cross sectional change = stress riser), but also because w/o any idea of what the trailer frame actually looks like I'm picturing cross members that are not as tall as the tongue tube nor nearly as robust, which implies that they can use all the help that they can get. Could easily be totally erroneous, but it is the broader application advice.

There is also the aspect of how tongues are frequently built in this application type. The highest stress in the whole frame is at the transition from tongue to main frame. All too frequently the tongue is essentially just butt-welded on there. Better is for the tongue to underlap the main frame and extend back a reasonable distance. That gives the section modulus needed to keep the strain low.

I've been intending to write out how to design the tongue & frame based the weight of the trailer's components and their locations for a couple of months. I've even enlisted a fellow Engineer to check my work. I just haven't had the time to do the job.

You are correct in your first paragraph. The frame metal is made of thinner and shorter C-channel.

The existing tounge as you can see in the picture below does extend towards the wheels of the frame. (You'll have to overlook the cutoff tube and with the jack. That's all going away. The guy I'd bought it off of had a bullnose coupler on it and during our move, I had to cut it off.) The original tounge is re-moveable. So I wonder if it would be better, to just remove the tounge, weld in my DOM tubing from front to back, and bring some tubing from my new tounge towards the wheels and tie it into the frame? I would be eliminating unneccessary weight and it would accomodate doing a SOA.

Here is what the trailer looked like when I first brought it home back in 01.