Frame tube size feedback please

[StormRider]

I'm ready to start building, and I'm trying to decide what tube size to use.
This trailer should be well under 1500lbs, and I'm building it for offroad use.
I'll add 2 cross members where the springs attach to the frame, and some angle iron to support the floor.
The middle leg of the tongue design is to allow extending the tongue in tight situations. Normally the trailer will be towed with it retracted.

Is 2x3x.078 square tube a good choice for this build?

[dh]

My .02,

.125x2x2 for the frame, a little beefier for the tongue, maybe .125x2x3

I'm sure Andrew will chime in on this one, I'd go with what he says, I did, and he kept me from over building.

[dh]

Also, I would put the tongue under the frame and second X-member, it is a lot stronger then just butting it up to the first X-member

Edit:
Added a pic

[eamarquardt]

I agree that 2X2 (2X3 overkill but better) for the frame would be fine. I'd suggest using a 3X3 X 1/8 (or 3/16) for the tongue. I'd mill/cut a slot in the tongue piece so that the 2X2 cross members (I'd go to at least one or two cross members beyone the first as it would be a lot stronger and would weigh just a tad more) would fit in the tongue tube and weld the two together.

If you look at the pic below you will see that this is exactly what I've done. The first cross member is a 2X2.



The three by three for the tounge is maybe 3 or 4 times stronger for a tongue than 2X2 of equal wall thickness.

Also you might consider mounting the springs on angle iron and bolting the angle to your tubing. This will spread the load a bit better and allow easy servicing of the suspension should you ever want to modify it.



If you used 2X3 side rails it would be easy to notch them and have the 2X2 go right through them, then you'd be verrry close to your sketch. Just change the tongue and side rails keeping the 2X2 cross members.

Cheers,

Gus

[StormRider]

2x3x.078 is about .5lbs/foot lighter than 2x2x.120, so if it's sufficiently strong, the 2x3 would be a better choice weight wise.

As far as the tongue is concerned, since it's an A design, most of the force is transferred to the outside frame rail, so i'm not sure pushing the center bar back to a 2nd crossmember would be worth it on such a small trailer.

Of course, I could be wrong :)

[dh]

2x3x.078 is about .5lbs/foot lighter than 2x2x.120, so if it's sufficiently strong, the 2x3 would be a better choice weight wise.

As far as the tongue is concerned, since it's an A design, most of the force is transferred to the outside frame rail, so i'm not sure pushing the center bar back to a 2nd crossmember would be worth it on such a small trailer.

Of course, I could be wrong

I agree with putting the A-members on the first X-member, I put mine on the second because I wanted to push them back, so they end right under my propane tank, but I would still tie the center member into the second X-member.

Do you have experience welding .078? It can be a little tricky without a good welder and some experience.

What is your estimated trailer weight?

What are your frame dimensions?

Even if you used 40' of tube in your frame, your would only save 20lbs. Thats less then a case of beer.

[StormRider]

I've got a nice welder, a millermatic 180, and some experience on thin material, probably not enough.

There's about 50' of tube involved in the trailer- it's 5x8.

I tend to massively overbuild stuff, and I thought I'd start this project with something slightly more reasonable.

[dh]

In the end its up to you. If you didn't have doubts about your selection in materials you would not have asked for opinions. We gave you ours, and that is all they are, opinions, take it or leave it. If you have ever read Doug Hodder's posts, just remember his quote, "Build what you want, nobody else has to camp in it." But also remember Mikes, "Quality is remembered long after cost is forgotten."

Also remember what I said in my first reply, get with Andrew.

[StormRider]

I appreciate the feedback from everyone. I decided to go with 2x3x.120 for the main frame. I'll start a build thread soon, picked up 40' feet today :)

[boxcar]

Good call on the tubing size. 2x3 is much stiffer than 2x2. and the 120 thickness will alow a beter pen weld that won't be as prone to tearout. I agree on taking the tongue to the second crossmember as well.While overbuilding can be costly. As an offroad builder I have rairly seen an overbuilt trailer of a good design fail in the ruff. I have seen many under built or even what could be considered adiquitly built trailers fail miserably on the trail. Look forward to seeing the build.... Boxcar...Here is my salution to the offroad tear . The entire rear is on a slide out and can be removed when not needed for the atv. And it floats during water crosings.
The exo wile adding stifness to the overall design was more for bump protection and to suport the cargo basket.... Have fun....

[LanM]

I was just talking to a trailer builder this afternoon about the options for building a 5x10 with hard off road use and 35" tires in mind. I was asking about 2x2, or 2x3, and he said he'd prefer to build it with 3" channel. He said it would be cheaper, weigh a little less, and would be easier to maintain since I'm in salt territory. Does anyone else agree with that, would 3" channel be a good alternative?

[boxcar]

Absolutly not!!!!!!! Channel iron is no where near as light. Or as structuraly sound as square or rec tubing for a given weight or guage. It is a little easier to work with in some cases, but not all, and the quality of steel is not compareable. If you are woried about corrosion , make sure that the tubes are all sealed . I:E no holes or open seams that allow moisture to enter the tubes.
Channel iron tends to have no memory. It takes a bend very easily and retains it. Tubing is torsional. It has a lot of memory it tends to want to return to it's original shape [img]:thumbdown:%20....[/img]Boxcar...

[LanM]

Thanks for the tip. So you think 2x2 or 2x43 would be best for my application (not to thread jack but I'm sure it would benefit the original poster as well)?

Going for a 5x10 (5x8 plus 2 foot storage chest)-obviously weight conscious but capable of heavy rock crawling. I'm not even positive a 5x10 is a good idea, or if I should just go military trailer/roof top tent like most others----but I want it to be a 4 season setup capable of month long excursions if necessary.

[Larwyn]

I was just talking to a trailer builder this afternoon about the options for building a 5x10 with hard off road use and 35" tires in mind. I was asking about 2x2, or 2x3, and he said he'd prefer to build it with 3" channel. He said it would be cheaper, weigh a little less, and would be easier to maintain since I'm in salt territory. Does anyone else agree with that, would 3" channel be a good alternative?

Yes, especially in a salty environment. I cannot see what is happening inside that tubing.

[asianflava]

My .02,

.125x2x2 for the frame, a little beefier for the tongue, maybe .125x2x3

I agree, the only thing the frame does is keep the tongue, axle, and body connected. The body is a stiff box (unless you built it without shelves) that keeps the frame straight and rigid.

The axle is connected to the body via the frame. Welding the axle to the frame is better than bolting to the body (though some would argue that point) because the stress that the axle goes thru is distributed across the entire body.

The tongue bears the brunt of the load. A 2x2x1/8 single tube tongue won't do (unfortunately I know) I wanted to go to a 2x3x3/16 but it wasn't available they gave me 2X4X3/16 which is overkill. I would think that 2x3x1/8 for a hybrid a-frame tongue should be fine.