Car trailer reinforcement

[Mopar14]

Hi folks. I have a 2006 Big Tex 12pi-20 car trailer I bought a year ago and recently took the deck boards off. Having done that I noticed how inadequate the frame structure is for the weight class (12,000 lbs.) For those of you that are familiar with this trailer, you know what I mean.
I am planning on beefing up the frame by adding 5x2x3/16 inch rectangular tubing under the axles all the way to the back of the trailer.
My concern is I am not sure how to attach the tubing to the existing 5x2 channel frame. Because the channel is running outside of the angle iron subframe , I cannot z cut and continue with channel nor is channel wide enough for the spring hangers.
Because the top angle iron is offset from the channel, my tubing will have a 7/16" gap from the channel. Not to mention I will have to cut an inch wide section lengthwise down the edge of the inside of the channel to accommodate the tubing.
Does anyone understand my explanation and does anyone have any helpful hints?
Thanks

 

[vintagespeed1956]

after seeing the pics, i would be inclined to use 2x4 or 3x5 .120 tube to build a rectangular perimeter frame with a central backbone & a couple x-members, sleeve holes in it for your leaf spring & shackle hangers, then use all the cutoff channel for bracing within the new frame.

.188 is heavy especially 3x5 and will add a ton of weight that isn't really necessary. imho.

 

[f150skidoo]

The easiest would be to add more material to the top of the frame rails. By either getting 2 more angle irons and turn it upside down to turn the current angle iron frame rails into a tube by using the existing angle and the new material. Or another option is to continue the ladder side rails right to the end of the trailer which would really stiffen things up. But the amount of work involved in cutting and fitting to add a rectangular tube to the bottom of the existing rails I would just paint it as is and put a new deck on and just sell it and buy a heavier duty trailer.

 

[kerrynzl]

Forget bracing underneath [all the bending loads are under compression]

Modify the top rail [photo 2] so it goes the the full length but triangulate it down at the rear and diagonal brace the front creating a truss shape

For the wooden deck glue the planks together so the whole deck is tied as one

 

[Nor'Easter]

If you think the structure is inadequate, you should call and ask for an engineer. Those trailers aren't sent out the door with a hope and a prayer.

 

[j p smith]

Forget bracing underneath [all the bending loads are under compression]

Modify the top rail [photo 2] so it goes the the full length but triangulate it down at the rear and diagonal brace the front creating a truss shape

For the wooden deck glue the planks together so the whole deck is tied as one

What kerrynzl Said!

Part of the strength of that trailer design is the top rail, when that was cut out it changed the structural integrity of the trailer. imho.

 

[APEowner]

What kerrynzl Said!

Part of the strength of that trailer design is the top rail, when that was cut out it changed the structural integrity of the trailer. imho.

Yup. This is the real problem. Someone cut the top rail off and that's an integral part of the frame. No doubt they did that because the top rail is in the way when you use an equipment trailer like that for cars. Personally, I'd either cut the whole thing about and build a proper car trailer using the axles or replace the upper rail, sell it and buy something that better fits my needs.

 

[Showkey]

Agree the perimeter of the trailer was built like a floor truss....take the top off you got problems.

 

[A_Pmech]

Keep in mind that large section changes in beams, especially when combined with welding, will promote fatigue cracking.

Kerry has a great idea. Failing that, be sure you "fishmouth" or gradually end your stabbed on structural members and avoid welding across the beam tensile members.

 

[Mopar14]

Thanks for all the replies people. Lots of good ideas for sure. The top pipe was heavily damaged and I planned on replacing it with schedule 40 pipe. Not much difference in weight. My biggest concern with this trailer is the sideways bending. Right now the axles are offset sideways by one inch. I will try to pull the trailer with a few come a longs to try to straighten it out. Then maybe add a few x members to reduce side travel.

 

[kerrynzl]

Thanks for all the replies people. Lots of good ideas for sure. The top pipe was heavily damaged and I planned on replacing it with schedule 40 pipe. Not much difference in weight. My biggest concern with this trailer is the sideways bending. Right now the axles are offset sideways by one inch. I will try to pull the trailer with a few come a longs to try to straighten it out. Then maybe add a few x members to reduce side travel.

X members are not needed if it has a full floor.

Shiplap cut the wood and glue it together and it will increase bending strength both vertically and laterally.

Car haulers are easy because the 4 footprints are out by the main rails.[cart a bridgeport mill strapped in the centre is a different story]