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  #1  
Old 03-06-2022, 02:54 PM
SuzukiSamurai SuzukiSamurai is offline
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Default Trailer build. Box steel thickness?

Building a "utility trailer"
Ok, more like a very custom boat/utility/camping gear trailer...

Steel frame with an aluminum box sitting on top. Boat rides around upside down on top of the box.
Approximate dimensions are 8' long x 5'6" wide.
The track width (distance between the tires) will be identical to a full size 3/4 ton single rear wheel pickup. (approximately 4' between the frame rails)

While the aluminum box may provide a little structural rigidity, I'm thinking the steel frame will be what carries the total weight of the trailer.

Planning on a basic (classic?) H frame design with the tires located in the center of the H (at the horizontal bar) The idea is to balance the load (with a slight front bias) so when I need to move the trailer by hand I can.

I have chosen to go with the Timbren 3500HD axle less suspension system.
3500 pound capacity.
There are three mounting holes that would drill through the frame 1.5" on center from the bottom of the frame.
This also means that the bottom half of the H will be completely "unsupported" (Leaf springs would spread 9-10" either side of the horizontal bar in the H, Timbren would be mounted completely above the horizontal bar in the H.


Now for the question:
Looking at 2x3" box steel for the frame. What steel thickness would/should I provision to handle the maximum suspension load? (3500 pounds including trailer weight)

1/8 wall rectangular tube? 3/16 wall tube? Something in between?

A different suggestion?
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  #2  
Old 03-06-2022, 03:42 PM
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Shade Tree Welder Shade Tree Welder is offline
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Quote:
Originally Posted by SuzukiSamurai View Post
Now for the question:
Looking at 2x3" box steel for the frame. What steel thickness would/should I provision to handle the maximum suspension load? (3500 pounds including trailer weight)

1/8 wall rectangular tube? 3/16 wall tube? Something in between?

A different suggestion?
1/8" is a good choice, that I what I would use on a small trailer. Commerical trailers like that often go with 16 ga.

I would recommend you look at torsion axles you can either bolt or weld on the outside of the frame.
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Old 03-06-2022, 03:45 PM
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milomilo milomilo is offline

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What would you estimate the total weight of the trailer fully loaded?
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Old 03-06-2022, 03:55 PM
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What would you estimate the total weight of the trailer fully loaded?
I was assuming 3500 lbs.
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Old 03-06-2022, 04:36 PM
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I was assuming 3500 lbs.
Thought he was only referring to the axle capacity. He might want to set the axle back a bit so the trailer has the right tongue weight.
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Old 03-06-2022, 04:58 PM
JBFab JBFab is offline
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1/8 would be adequate. You could use 14ga and stiffen up the axle mount area with some 11ga sheet.
Personally I avoid steel tube frames on trailers and opt for open shapes. The hss tends to trap moisture and rust out rather quickly.

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Old 03-06-2022, 06:06 PM
SuzukiSamurai SuzukiSamurai is offline
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Thanks for the replies.

Weight would be somewhere south of 3500 pounds.

I would say a "normal" weight would be in the area of 2200-2700 pounds (trailer, lawn chairs, boat, boat motor, gas, water, tires, spare, etc...

I did build a trailer out of 2x2 1/8 wall steel about 20 years ago. That was a little different design where the sides of the trailer "trussed" the frame. (still have the trailer)

That will not be the case here.

Essentially, I will be tossing up to 3500 pounds on a flat deck made out of 2x3 box steel. The aluminum is there to keep it from spilling off....

Is the carrying capacity that much greater for a section of 2x3 over a section of 2x2?
I ask because a similar trailer like I am planning on building had bent it's frame like a banana over the axle.... (made of 2x2 box)


I have already purchased the Timbren setup, so no changing that now...

Rust? Yes, a concern. Cap the ends of the box tube so no water can enter.
Weld tabs for screws and don't punch holes in the frame.
Which leaves me with the six 1/2" holes I need to poke through for the Timbren suspension....
Thinking of 1/2" ID tube welded through the frame. This will aid in keeping the water/air out and prevent the box tube from collapsing when bolting up the suspension hardware.
Comments?
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  #8  
Old 03-06-2022, 06:50 PM
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Quote:
Originally Posted by SuzukiSamurai View Post
Thanks for the replies.

Weight would be somewhere south of 3500 pounds.

I would say a "normal" weight would be in the area of 2200-2700 pounds (trailer, lawn chairs, boat, boat motor, gas, water, tires, spare, etc...

I did build a trailer out of 2x2 1/8 wall steel about 20 years ago. That was a little different design where the sides of the trailer "trussed" the frame. (still have the trailer)

That will not be the case here.

Essentially, I will be tossing up to 3500 pounds on a flat deck made out of 2x3 box steel. The aluminum is there to keep it from spilling off....

Is the carrying capacity that much greater for a section of 2x3 over a section of 2x2?
I ask because a similar trailer like I am planning on building had bent it's frame like a banana over the axle.... (made of 2x2 box)


I have already purchased the Timbren setup, so no changing that now...

Rust? Yes, a concern. Cap the ends of the box tube so no water can enter.
Weld tabs for screws and don't punch holes in the frame.
Which leaves me with the six 1/2" holes I need to poke through for the Timbren suspension....
Thinking of 1/2" ID tube welded through the frame. This will aid in keeping the water/air out and prevent the box tube from collapsing when bolting up the suspension hardware.
Comments?
Did you read my post about tongue weight?
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  #9  
Old 03-06-2022, 07:05 PM
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Cap the tube if you want, there will still be moisture/rusting inside. It’ll just take longer.

If you look around at most commercial built trailers, they all use c channel, I-beam and other open section materials.

My brother built a trailer from tubing, but it gets oiled every year or two, and parked most of the winter most years on dry gravel.


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  #10  
Old 03-06-2022, 07:31 PM
threepiece threepiece is offline
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Quote:
Originally Posted by JBFab View Post
Personally I avoid steel tube frames on trailers and opt for open shapes. The hss tends to trap moisture and rust out rather quickly.
Indeed, I have seen too many rusted tube frame trailers to consider using it.
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