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With that load (750lb) centered at 5' in the middle of two supports at 10' long beam the tube deflected .635" and put 23.8 ksi of stress on the beam.
The mild steel is conservatively rated at 30k ksi so the beam did not bend and will return to shape .

You want to allow for dynamic loading, roads, bouncing etc. so use your calibrated eye.

These charts aren't intended to proof a material or beam in my eyes just to compare beam shapes/sizes against each other.
 
CarterKraft said:
3" channel 4.1 lb/ft 10' long supported at both ends and a 750 lb point load at 5'

1705096489289.png
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How does a 4"x5.x lb channel compare to the 3"?
 
Firstram said:
How does a 4"x5.x lb channel compare to the 3"?
Click to expand...
Gonna be a while before I can get run it, but generally increasing the section height has a much bigger increase in bending strength than increasing the thickness. I'd assume a 4" channel will be a good bit stronger than 3" in that direction.
 
CarterKraft said:
With that load (750lb) centered at 5' in the middle of two supports at 10' long beam the tube deflected .635" and put 23.8 ksi of stress on the beam.
The mild steel is conservatively rated at 30k ksi so the beam did not bend and will return to shape .

You want to allow for dynamic loading, roads, bouncing etc. so use your calibrated eye.

These charts aren't intended to proof a material or beam in my eyes just to compare beam shapes/sizes against each other.
Click to expand...
Ok so I see what I am Looking at now. So. The channel is a bit stiffer in bending, lower deflection as well as ksi.

So what does this mean in reality?

10' trailer, axle more or less centered under the deck.

This is what I need help with. Is 2x3. 120 wall too thin?
 
My math days trailer should be 1500-1800 lbs.

Using 4.5lb/ft ish plus axles tires decking etc.

That leaves me 3400 lbs capacity. Let's say 3k in reality. Plenty for me. Really 2k is plenty.

I got 3500lb springs as well... That gives me 2k assuming 1500lb trailer.

Tubeing size/thickness suggestions?
 
Java230 said:
My math days trailer should be 1500-1800 lbs.

Using 4.5lb/ft ish plus axles tires decking etc.

That leaves me 3400 lbs capacity. Let's say 3k in reality. Plenty for me. Really 2k is plenty.

I got 3500lb springs as well... That gives me 2k assuming 1500lb trailer.

Tubeing size/thickness suggestions?
Click to expand...
If you give me the spring hanger placement on the 10' length I'll run some numbers.

1705261676091.jpeg
 
Somethings to consider,
Will this be a "top rail" trailer? That effectively turns the side beams into a truss and IMO is the only reason a angle iron trailer works.
If it's not a top rail then the beam will really matter, if not then it's not near as critical.

Box section tubing is a rust problem for certain geographies.

An analysis of cost, weight and strength will need to be done no matter what you decide.
 
Java230 said:
Ok so I see what I am Looking at now. So. The channel is a bit stiffer in bending, lower deflection as well as ksi.

So what does this mean in reality?

10' trailer, axle more or less centered under the deck.

This is what I need help with. Is 2x3. 120 wall too thin?
Click to expand...

My car trailer is 4x2x.120 for the frame. 4x2x.188 for the tongue. Take it for whatever that's worth.... which is probably $50.00 with today's inflation. :flipoff2:
 
CarterKraft said:
If you give me the spring hanger placement on the 10' length I'll run some numbers.

1705261676091.jpeg
Click to expand...
Main frame will be 6x10. I was thinking 4' tongue?

I've only ever built one little trailer.... And it had super short tongue on purpose.

Just deck, no side rails at the moment. Stake pockets and drop in sides.

Im trying to keep it as light as reasonable and be able to put 3k if needed perhaps? I don't haul more than 1500 generally.
 
Here's a example of the load calc, sort of random axle placement, first hanger at 5' second at 7' which gets you a 72" axle placement, you might want more or less...
This is a 3x2x1/4 angle on the 3" leg, 2" leg horizontal

1705262698125.png

1705262829212.png
 
I purposely didn't include the tongue section, I don't really thing it matters generally because it can be different than the main frame and triangulated to the top rails.
 
CarterKraft said:
I purposely didn't include the tongue section, I don't really thing it matters generally because it can be different than the main frame and triangulated to the top rails.
Click to expand...
For the tongue, I was planning A frame back to the front spring hangers. With a solid piece of 2x2 front to back.

I use a piece of receiver tube so the hitch is removable.

4' tongue ? Maybe less? I'm thinking 4 is plenty long since it's a longer trailer, so ball to axle is a bigger difference.
 
A couple of things to consider. If you buy 3500 lb springs, they are each only rated at 1750 each. Just sayin. I went 4” tube tongue for a couple of reasons. First I wanted to make an extra long tongue so I could turn sharp with it behind my fifth wheel and not have the box hit the generator mounted on the rear bumper of the fifth wheel. It’s worked out great. I went with a pretty heavy wall 4”. Can’t remember thickness now. I haven’t seen any downsides to it so far. But my trailer has sides that stiffen it substantially. Not sure I’d go that route with a flat bed. As a single pivot point on front is gonna mean a floppy cornered front end.
 
If you come up with 2 potential designs I can run them back to back other wise you can just copy any commercial design and know it's gonna be fine.
 
CarterKraft said:
If you come up with 2 potential designs I can run them back to back other wise you can just copy any commercial design and know it's gonna be fine.
Click to expand...
I'll do a quick sketch on Tuesday. Thanks for the help!
 
rockdog57 said:
A couple of things to consider. If you buy 3500 lb springs, they are each only rated at 1750 each. Just sayin. I went 4” tube tongue for a couple of reasons. First I wanted to make an extra long tongue so I could turn sharp with it behind my fifth wheel and not have the box hit the generator mounted on the rear bumper of the fifth wheel. It’s worked out great. I went with a pretty heavy wall 4”. Can’t remember thickness now. I haven’t seen any downsides to it so far. But my trailer has sides that stiffen it substantially. Not sure I’d go that route with a flat bed. As a single pivot point on front is gonna mean a floppy cornered front end.
Click to expand...

After having a longer tongue on my car trailer, going back to “standard” length tongue on the utility trailer kind of sucks.
 
rockota said:
After having a longer tongue on my car trailer, going back to “standard” length tongue on the utility trailer kind of sucks.
Click to expand...
Yeah I get that. I had one that was like 5' ball to axle. It was entertaining.
 
CarterKraft said:
If you come up with 2 potential designs I can run them back to back other wise you can just copy any commercial design and know it's gonna be fine.
Click to expand...

Here is a quick sketch. Not sure on tongue length or axle placement.

Axle at 6' seems about right.

Tongue Id prefer 3' I think just to keep it smaller overall. But I can be convinced otherwise.

1000020657.jpg
 
Java230 said:
Here is a quick sketch. Not sure on tongue length or axle placement.

Axle at 6' seems about right.

Tongue Id prefer 3' I think just to keep it smaller overall. But I can be convinced otherwise.

1000020657.jpg
Click to expand...
2x2x3/16" is not a option but this is 2x2x1/4
You can see this is much, much weaker than the other profiles tested due to the short 2" section height.

1705328917813.png


1705328836782.png
 
CarterKraft said:
2x2x3/16" is not a option but this is 2x2x1/4
You can see this is much, much weaker than the other profiles tested due to the short 2" section height.

1705328917813.png


1705328836782.png
Click to expand...
The 2x2 is just to tie the coupler into the tongue and trailer.
 
Java230 said:
The 2x2 is just to tie the coupler into the tongue and trailer.
Click to expand...
Oh yeah my bad, tubing not angle.
IF you run that tube full length like that it might make the cross members challenging.
IMO for a trailer like this I wouldn't bother with that. If you want to run it from the hitch to the front of the trailer cargo area no problem but running it full length isn't gonna gain you much.

I basically have this trailer but longer and narrower, it was a boat trailer we converted to dirt bike hauler.

This was the biggest load and it might have tweaked the tongue some, it doesn't have any triangulation for the tongue just the two 2x3 tubes.
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I figured it might help spread the "tugging" load out along the trailer (the 2x2)

This is why I want it really. Makes it hard to steal.
1000018948.jpg
 
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