Trailer frame help

[oldcj5guy]

I have an Apache popup that has a broken frame. I have decided that this is the time to build it up to go behind the grand wagoneer. I will basically be setting it up to tow cross country and very light trail duty. Mostly down washboard and old dirt roads. I have the design all worked out for the new frame. The body of the trailer is 135" long. My plan is to extend the frame
24" past the front of the trailer before I start the taper for the tongue and add in a small deck like some of the newer popups so that I can mount the dirtbike and my norcold freezer for longer trips. I will be running 31's to match the hitch height to the wag and for some clearance.

Now that I have finalized the trailer frame design and given you some background on it my question is:

What steel should I use for the frame? I was thinking 2x4 .188 wall for the side rails and 2x3 .120 for the crossbars. Was thinking main side rails and a crossbar at the front and back as well as one at the front and rear suspension mount points.
Think this will be heavy enough? Would I be better off with C channel?


The other thought has been to make it a tandem trailer with about 6 to 8ft of open bed space to haul sleds or multiple bikes. Any thought on this?

Not worried about a serious ofroad trailer, just something better than a run of the mill popup. I will be doing a buildup this spring on my offroad trailer for more serious trips.

 

[Martyn]

What seems like light duty offroad, i.e. driving on washboard is actually what destroys trailers not the extreme stuff. It's all the vibration and bouncing that will kill your trailer.

That said regular c channel flexes under strain so I think rectangular tubing would suit your needs better.

I see the front deck as a potential design problem. We all would like the extra cargo space to fit all sorts of things including ATV's but it produces a huge amount of tongue weight. This makes the trailer virtually unmovable when unhitched and puts a lot of burden on the tow vehicle's rear suspension when hooked up. Shooting for 15% of your weight on the tongue when full loaded is ideal for the tow vehicle and the trailer.

I realize that many of the "big" names make ruggedized trailers with a front deck, but from a design standpoint you've got to scratch your head on that one.

 

[oldcj5guy]

My plan to offset the front weight was to move the batteries (2) to the rear and/or move the axle placement a bit. I'm not married to the front deck, that's why I came here to ask people that have had more experience building their own.

What thickness would you suggest on the c channel?

 

[jeepboyd]

I think it sounds good so far, maybe if you made a small mount on the front just for the bike ( 12") then add a receiver to the rear of the trailer to put a basket in when needed. just a thought, good luck in whatever you decide, keep us informed. also maybe look into some rear corner protection ( ie sliders) , small ditches will make the tail of your trailer drag the ground quick.

 

[Rezarf <><]

Martyn was suggesting to steer clear of the C channel. Tubing in the same thickness as C channel will nearly double the strength of the material. Do you have any idea of estimated gross weight?

I think you are in the right neighborhood, depeding on your weight.

FWIW, most of the companies are mounting those cargo racks up front to keep the weight forward, if you go off the back, then you get the dreaded trailer fish-tail... back and forth wagging movement.

If your willing to move your axle around, you can make this happen pretty easily.

Rezarf <><

 

[Funrover]

I would use 2x3 .188 box. I plan on slightly extending my pop up also bit I only plan to carry coolers and a extra propane tank!! The rear is gonna be modded to hole 2 full spares( I am in the process of potentiall converting to matching wheels axles etc as my tow rig) My camper has 2 x 3 box outer frame with c channel crossmember.. The camper is very sturdy and I take it off roading often and over washboards often!!! My biggest problem has been the roof.... I need to build one, the current repair has died due to washboard!

 

[Joanne]

Martyn is the trailer expert and I have to agree with him. The idea of a front rack is not bad, but it's what you want to load on it that isn't a good idea. If you were going to haul a couple of mountain bikes or some fire wood, it would work great. But adding a dirt bike to the tongue weight isn't something that I would want to do. It's all about weight balance and adding that much weight to either end of the trailer just isn't a good idea.

A lot of folks over in the teardrop trailer forum have asked the same question and there has never been a good solution presented. Good luck with the rest of your rebuild.

Joanne

What seems like light duty offroad, i.e. driving on washboard is actually what destroys trailers not the extreme stuff. It's all the vibration and bouncing that will kill your trailer.

That said regular c channel flexes under strain so I think rectangular tubing would suit your needs better.

I see the front deck as a potential design problem. We all would like the extra cargo space to fit all sorts of things including ATV's but it produces a huge amount of tongue weight. This makes the trailer virtually unmovable when unhitched and puts a lot of burden on the tow vehicle's rear suspension when hooked up. Shooting for 15% of your weight on the tongue when full loaded is ideal for the tow vehicle and the trailer.

I realize that many of the "big" names make ruggedized trailers with a front deck, but from a design standpoint you've got to scratch your head on that one.

 

[oldcj5guy]

I guess my mind was elsewhere when I typed my reply. I already have 6 sticks of 2x4 .188 just laying around for my offroad trailer project. What can I say, craigslist for $15 for a 20ft stick so I bought them all + 10 sticks of
1 7/8" .120 DOM for $20 a stick. Gotta love craigslist.


I'm not concerned with it being a little tongue heavy as the wag has 3/4 ton axles and overloads. I normally carry the dirtbike in a receiver mount rack.

 

[ntsqd]

The length of the tongue will also have an influence on what the final tongue weight is with any particular loading.
It's not a great book, but I'd suggest buying the "Trailers, How to Design & Build" vol. II from northern tool. It shows how to do what is, in essence, a shear/moment diagram that you can use to set what you want the tongue weight to be.

 

[oldcj5guy]

thanks for the suggestion on the book. I just looked it up and will order it tonight when I get to the house.