Best way to sister C channel to to Square Tubing

[kraythe]

I need to reinforce a frame of a travel trailer and I was considering sistering some square tubing to the flat side of C Channel. What I was wondering is what the best edge prep and method of welding this would be. I considered simply closing the C channel but I dont know how much more support that would grant me over the original C channel. I need to ramp up the carying capacity of the trailer frame by about 175%.

Incidentally, if I were to have the critical welds inspected, would ultrasound inspection suffice or would i have to get it xrayed?

Thanks in advance.

[Sonora Iron]

The square tube has a radius to it, can’t you just fill the radius top and bottom? How about plug welding?

X-ray a trailer???????????????????

[kraythe]

The square tube has a radius to it, can’t you just fill the radius top and bottom? How about plug welding?

I dont think plug welding will work because it will be under dynamic load. What I worry about with filling the radius over and under is will the long weld on top crack or have other bad effects like heat bending the frame? Would I be better off with an intermittent weld ?

X-ray a trailer???????????????????

Hey I dont know. I just want a way to verify the critical welds. Is it not possible to xray that? I have never had anything xrayed before. I suppose I could apply the "beat on it really hard approach" to testing but that seems a bit violent.

[Sonora Iron]

Would I be better off with an intermittent weld?

That is what I’d do!
Square tube is very expensive, what about using another C-Channel, back to back?

[kraythe]

That chart has concentrated loads at center but how does the math change if the load is relatively evenly distributed over the beam? If I use another C channel then I will have the same weld issue but I might have to cut out the other c channel at places where original members weld into the back of the c channel.

[Sonora Iron]

That chart has concentrated loads at center but how does the math change if the load is relatively evenly distributed over the beam?

Double it.

[JSFAB]

Why, do you need to double the carrying capacity of a travel trailer frame?

[kraythe]

Why, do you need to double the carrying capacity of a travel trailer frame?

So it carries more load of course. I want to put a bunch of things on it and I dont want to be restricted to the old capacity.

[Sonora Iron]

Why, do you need to double the carrying capacity of a travel trailer frame?

[Daniel]

Do not do a full weld, stitche weld is what you want to do.
2" weld 3 to 4 inches of space then 2" weld and so on.

[Jim-TX]

What size channel is the frame now? Is it mild steel channel iron or high strength frame material like cars use? If it's just mild steel, boxing it in will add considerable strength to it. Keep in mind that just strengthening the frame will not add any capacity to the trailer. On just about any trailer that I've ever seen the capacity is determined by the axles, springs and tires. Plan to put bigger axles, springs, and tires under the trailer when done. Don't forget the hitch also. It might have to be changed.

[Bodybagger]

The C channel floor of your trailer is not the weak link that dictates your trailer's capacity.

The weak links are the axle (particularly if it has no brakes) and the tongue. You won't increase your trailer's capacity without addressing these. And when you get into changing axles, you'll find out that it gets cheaper to obtain a trailer with a higher capacity.

BTW, any time you want to reinforce a beam, you will MINIMIZE the effect of the added reinforcement by sistering the second beam on the neutral axis in the web area.

It's called the neutral axis because it carries ZERO bending forces there.

You maximize the effect of added reinforcement by adding it to flanges. The flanges carry almost all of the bending forces.

[Sonora Iron]

You maximize the effect of added reinforcement by adding it to flanges. The flanges carry almost all of the bending forces.

Just asking here!

Wouldn’t installing another C-Channel back to back achieve this? Especially if he stitch welded the flanges top and bottom?

[Cornerstone]

Jolly good reply!

[Jim-TX]

Just asking here!

Wouldn’t installing another C-Channel back to back achieve this? Especially if he stitch welded the flanges top and bottom?

I think that it would. But the problem, if I understand it correctly, is that there are pieces attached to the outside of the existing frame. Cutting out for these might negate any benefits of the added channel.