What to use for trailer frame?

[Stuckinthe80s]

So I've finally conceded to building a camping trailer for when the family is with me as it is SOOOO much easier than trying to cram everything inside the truck with us. Nevermind the setup/teardown will be so much nicer if I do it right.

I have a 4x6 utility trailer that I am going to use as the base for this. It isn't exactly how i would have built it but it seems to be pretty stout and it's what I've got. I want to keep it pretty simple and still be able to use it to haul stuff when I need to. That might change over time but for now it is the direction I'm going.

What I want to do is cut off the side rails that are currently on there and build taller sides that will be strong enough to hold a 4 person RTT that is fully loaded with me and the whole family. I'll use some square tubing to make really simple cross bars that can be installed/removed as needed:

My question is, what should I make the framing out of? I have a tendency to overbuild stuff and although I do want to make sure we don't break the framing while we're all inside the tent, I don't want to build it so stout that the trailer weighs a ton either.

I'm thinking 1x1 for the parts in blue and 2x2 for the cross bars. What say you? The drawing of course isn't to exact scale but I do want to have the sides be at least 18" tall, maybe taller.

Is 1x1 strong enough as drawn? If so, what thickness? Thanks in advance for all the advice!

 

[AimCOTaco]

Too many rectangles, needs more triangulation.

2x2 x .120 wall in the corners would add lots of stiffness, then 060 1x1 for the rest maybe?

You could pump it into fusion360 or similar and run some simple FEA with your mass up top and see how things look.

 

[Stuckinthe80s]

Too many rectangles, needs more triangulation.

2x2 x .120 wall in the corners would add lots of stiffness, then 060 1x1 for the rest maybe?

You could pump it into fusion360 or similar and run some simple FEA with your mass up top and see how things look.

fusion360....HA! I'm lucky to have a dry erase board in my garage that I can draw on.

 

[AimCOTaco]

Your MS paint skills are next level.. F360 would be a breeze for such a skilled mouse hand.

 

[rover67]

what are yagonna put on top of it? will it have drawers in it or just be a cavity?

 

[Stuckinthe80s]

@rover67 I'll be mounting a big-ass roof top tent on top of it. The tent is around 180 lbs and with all 4 of us in there and the two big-ass dogs, it will be pushing the 750 lb weight limit of the tent itself. So gross weight I'm building to support is probably close to 1k lbs total.

As far as drawers go, I'm still undecided. The builder in me wants to build something like this:

That might be a later project though as I would like to get some use out of it for what is left of this year.

No matter what I don't want the tent to be up high as a lot of "adventure" trailers have it. The drawers would be nice to have a camp kitchen built in but I keep going back and forth about it. It would be nice to still be able to use the trailer as a utility trailer when it isn't pulling camp duty.

 

[Stuckinthe80s]

Too many rectangles, needs more triangulation.

I thought that was going to be a concern. I'm assuming that skinning the sides in some sheet metal would help with triangulation?

 

[DaveInDenver]

If you weld the skin on it could work but riveted or screwed will loosen with time as the parallelogram frame tries to rack.

A few 45° angles, cross members, corner bracing, that sort of thing. Think about how roll cages, race car or buggy frames look.

If I might presume to speak for Andy design for strength so that you're not relying on every weld to hold solely in tension. Get compression on the tubes in the joint so it's mechanically strong, metal pushing metal, and the weld or bolt is just holding it together.

Or the Go Fast camper shell. Picture in your mind's eye the force vectors in the space frame - down from gravity and flopping in the RTT, up from suspension bouncing, forward and backward from acceleration and braking. You always have multiple "somethings" resisting the force in shear, tension and compression.

 

[DaveInDenver]

FWIW, another option is to use FreeCAD, which is an open source parametric CAD similar to SolidWorks. It has a FEM/FMEA/FEA (whatever you want to call it) module built in natively.

https://www.freecadweb.org

 

[DanielChase]

Phil Tillerman is buying a trailer. Has lots of thoughts on the matter, paging @3rdGen4R

 

[Shuksan]

I would rent my trailer out to club members/people I know if they want to try it out and get an idea of what they want. I have a 2-3 person RTT on top.

 

[rover67]

I honestly think I'd do .065 wall for most of it and focus on triangulation or big gussets. 120 wall is awfully thick for anything really unless there are big spans or whatever. I'd skip up on the material size to get the strength out of it before jumping up on wall thickness. Your dynamic loading is gonna be with no people on it, when loaded up with warm sweetness its gonna be still (or mostly still..relatively speaking).

 

[ccslider]

We build Ruger frames at work and they look like this.

 

[rover67]

Yeah the trailer base or main frame part should probably be decently beefy so the suspension and tongue can be attached to a strong base. You've already got that part built/sourced tho and I bet it's pretty beefy.

 

[Stuckinthe80s]

Yeah the trailer base or main frame part should probably be decently beefy so the suspension and tongue can be attached to a strong base. You've already got that part built/sourced tho and I bet it's pretty beefy.

Yeah, the frame is kind of overbuilt. It is a home made gig that I think was used for a 4 wheeler.

Here is what I was able to get done Friday night. I went to Alcam Metal as they are just down the road from work and I could go at lunch. They have a scrap pile I was able to dig through and get what I needed. It wasn't exactly what I was looking for but it will work, I think? I used 1.5x1.5 .083 on the 4 corners and then 1x1 .120 on the supports in between. Then I laid 1.5x3 .063 on top. If they would have had more 1.5x1.5 I would have just used that all the way around but they didn't so here it is. I still need to add the triangulation (shown in blue) but it's getting there.

Don't zoom in too far on the welds. I'm a grinder, not a welder.

Thanks for everybody's help with this!

 

[rover67]

Oh yeah!!!!

 

[Corbet]

That will be plenty strong

 

[nakman]

Yeah man that looks bomber... don't stress on the welds to much, let the material do most of the work, IOW keeping the structure itself load bearing vs. relying on weld joint to hold it up. Looks like you could have a party on that thing.