My Frame Plan

[TD4FREEW/CTD]

well, after reviewed several other threads, i've decided that since i do plan on using this trailer off road, i would rather go the brick poo house method of construction. mainly at the tongue.

im still thinking 14ga for the frame but i'm contemplating either using 2x2x1/8", or 2x3x14/13ga. i want to keep the compound frame design and use some triangle gusset stock on the center beam. i do also plan on having a propane tank and storage on the tongue, so i want macheesemo.

whats the deal on 2x2x1/8" vs 2x3x14ga? they cost about the same, so either one is an option feasably. is the thinner walled rectangle stronget (in the ways i need it) than the 2x2x1/8"?

[Esteban]

Andrew's Tongue Strength link up above in the Design Library has a chart with strengths and weights of metal shapes. Here's what it says for the two you asked about.

2"x2"x1/8" Square Tube has a vertical capacity of 15,600 lbs./inch. It has a horizontal capacity of 15,600 lbs./inch too. It weighs 3.05 lbs./foot.

2"x3"x14G Rectangular Tube has a vertical capacity of 20,600 lbs./inch. It's horizontal capacity is 16,500 lbs./inch. It weighs 2.67 lbs./foot.

The 2"x3"x14G Rectangular Tube looks to be stronger in both directions and lighter as well.

I wonder why Andrew didn't show an A-frame tongue made from 2"x3"x14G in his Even Simpler Look-Up Table? Andrew, is there a safety, engineering, fabrication, or some other good reason not to use 14 gage material for a tongue? :thinking:

If may calculations are right, a 48" long A-frame tongue built with 2"x3"x14G rectangular tube would be good for a maximum loaded trailer weight of about 1,717 pounds - per the Aussie rules. I used the higher vertical strength of the tube and ignored it's lower horizontal strength. Is this correct Andrew?

[angib]

Yes, thinner but bigger sections will always be stronger than thicker but smaller sections, until you reach the point where the tube walls become fragile or unstable - no problem with 14ga there, I think.

I didn't include 14ga simply because it seemed few people wanted to use it.

Welding thinner material needs to be done with care, particularly to get the right size of weld bead - contrary to what a lot of people think, a too-big weld bead is not good as it will encourage cracking, though it's not as bad as a too-small bead which won't be strong enough.

Andrew