making a fold-down trailer door

jesusgatos

Explorer
I'm turning an M103A3 trailer (10ft flatbed military trailer) into an enclosed trailer that I'm planning on towing behind Mah Deuce. Designing the enclosure right now, and I'm wondering how I should go about making the read door. I'm pretty sure I'd like to do a fold-down door that will also function like a ramp (you know, like all the toy-haulers). Seems like something like garage door springs might work well as an assist, and I was thinking about using cables at the that would extend from the top rear corners of the box, and would be connected to the top corners of the door. I'd like to be able to lock the door into a horizontal position, in order to use it as an extension of my trailer when I'm parked. Basically, just a clean, flat area where I can work on stuff, or use as a patio, or whatever...

If any of you have built anything like this, or have any ideas for me, I'd appreciate the input.

EDIT: I'd like to open this up to get more input about the overall design and construction of the enclosure itself. I was planning on building it out of steel tubing, but now I'm having second thoughts. I just don't have much experience working with composites and all that stuff. I started a thread over on pirate4x4 about this project, and someone directed me to another forum all about building custom travel-trailers, and now my head is spinning. Here's what I posted:

I've got a small flatbed trailer that I want to turn into an enclosed trailer. The trailer that I'm working with is called an M103A3 trailer (basically just a 10ft flatbed version of the popular M105 military trailer).

I've never built an enclosed trailer before, and I don't have any idea what type of materials I should be using, but I took some measurements and this is what I've come up with. I'm going to be towing this trailer behind an M109 that I'm converting into a motorhome, and plan to spend a great deal of time off-road. So needs to be able to survive the bumps and scrapes you'd expect to encounter when taking a trailer places it wasn't meant to go.

The plan is to mount the enclosure to the deck using the existing stake pockets, so I can remove the enclosure (using an A-frame hoist on the front of my truck). Then I'll have a flatbed trailer and a shed. This is something that I'll probably only do when I'm setting up camp somewhere for an extended period of time, or when I have a specific need for a flatbed trailer, but I like the idea of having the option.



The red tubing is 2 x 2" x .120-wall.
The yellow tubing is 1 x 2" x .120-wall.
The blue tubing is 1 x 2" x .090-wall.
The pink tubing is 1.25" round x .120-wall (fits into a slot at the front of the trailer deck)

SolidWorks tells me that this combination of tubing should weigh about 623lbs. Plus, it's going to have a small door on the front right side for easy access, as well as a fold-down rear door / ramp.

I haven't decided what type of assist-mechanism I'm going to use on the rear door, but I'm leaning towards something like a torsion-type garage door spring. I do know that I want to be able to lock the door into position when it's horizontal, so I can use it as an extension of the trailer deck.

What do you guys think?
 
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biere

Observer
In researching enclosed trailers to turn into a camper I ran across someone who had to repair their door due to a water leak letting water get into the door and it weakening the wood in the door.

He beefed the heck out of the door while it was apart from what I recall.

I have looked at a few toyhaulers and such and I really like the idea of having a flat patio to use as well but right now I am wondering what it would take for me to consider a door solid enough to do that.

I am halfway thinking about going with barn doors and using ramps, I don't really mind little ramps much and barn doors give you a couple walls to block wind and a tarp across the top will give you a roof as well. Can go open 180 degrees and have 2 solid walls for a shower setup perhaps.

I also considered making a door open upwards so it made a huge roof but I think that would be a pain to figure out but it would make a heck of a roof and it would be easy to get some tarps for a couple walls.

I plan to see what others have to offer because I just wonder what it takes for a door to support a 500lb quad and 300lbs of gear and me on that quad riding it into the trailer.

Some of the better patio setups used a few jackstands to help support the door instead of making the cables carry the entire load.
 

jesusgatos

Explorer
Like I said, I'm pretty set on building a fold-down door. I'm going to be hauling dirt bikes, and ramps work just fine, but I'd really like to be able to make use that space as an extension of my trailer when I'm using it as a workshop, or as a patio, or...

I don't think building a door strong strong enough to use as a ramp/patio will be too hard. Pivots are easy. As far as raising & lowering the door/ramp, right now I'm thinking about using some type of cable arrangement. If I anchored one end of the cable to one of the top/rear corners of the box (inside the opening), then ran the cable down to a small snatch-block at the top corner of the door/ramp, then across the top of the door/ramp to another snatch-block at the top corner of the door/ramp on the other side, and then back to another snatch-block at the other top/rear corner of the box, that would allow me to use one mechanism to raise/lower the door/ramp. Maybe a small electric winch? Maybe a hand-crank? I don't know. The trailer deck is about 3ft off the ground and the door is going to be about 6ft4in tall, so I'll need to be able to pay-out & take-up about 11ft of cable if I go from corner-to-corner. I haven't looked at any of the toy haulers (I know, I should). What are they all using?

I've already got one stabilizing jack at the back of the trailer and I'm hoping there will be enough weight up front to keep it from tipping. I'd just rather not have to lower jacks to support the door (when using it as a patio deck) if I can avoid it. Only because it's one more thing to do. But that's a good suggestion, and they'll be easy to add later if I end up needing them.

Not sure what people are using for seals around these type of doors. Not too concerned about it though. The entire enclosure is going to be removable, so I can set the enclosure on the ground and use it like a shed, and I'll be able to use the trailer as a flatbed. So it's not going to be water-tight anyway, (at least where the walls meet the deck).
 

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jesusgatos

Explorer
Started looking into garage door springs, and the torsion-type springs look like they might work pretty well in an application like this. But the only garage door shop in town is already closed for the weekend, so I'll have to wait until next week to check them out.
 

jesusgatos

Explorer
If I can put the torsion bar at the bottom of the door, concentric to the hinges, I won't need anything more than fixed-length cables like you'd find on a tailgate, and those would only be necessary when I wanted to use the door/ramp as a patio. Otherwise, I should be able to raise and lower the door/ramp without any type of cables or anything. But then, if I install the torsion spring like a normal garage door and use it to wind cable/s, that would might be kind of cool too.
 

bftank

Explorer
what about using something simple like cable, pulley, and weight system, like on old windows? have the wieghts rest in a bucket bolted to the floor when the door is up.
 

jesusgatos

Explorer
That's a good idea, but the cables will have to travel about 11ft from fully open (on the ground) to fully closed, and the trailer is only going to be about 6ft4in tall inside, and the deck is about 3ft off the ground. What I'm getting at is that it would be kinda hard to get that amount of travel out of a system with weights like you're suggesting (unless I rigged a bunch of pulleys and even more weight). Plus, I'm not wild about the idea of carrying a bunch of 'dead weight'.
 

jesusgatos

Explorer
1st post edited to solicit additional input regarding the design and construction of the enclosure that I need to build.
 

ntsqd

Heretic Car Camper
Some of the later toy-haulers use a series of torsional coil springs around the hinge pin. Cables are a PITA when the door is down and you're going in and out of the door/ramp. When used as a 'porch' do not solely support the door with cables, build into the door some support method or carry separate supports for this use. Tube size is more important to stiffness than is wall thickness. I think that you have way too many studs and joists in the design, and not enough diagonal/parallelogram strength around the large door opening. What will kill the box the fastest, and is what kills the cheap toy-haulers, is the lack of rigidity at the big door opening. If that end of the box can move in a parallelogram fashion, it will. And that will tear up the upper corners first, and then the whole box will become fatigued. May be able to build the door latches to use the door to reinforce the opening while in motion.
 

jesusgatos

Explorer
Thanks for the input. That's pretty much what I was thinking about trying to adapt from a garage door (the torsional springs). I still need to go look at some toy haulers and visit a garage door shop. The main reason why I want to use cables is to keep the whole thing self-contained. I would just rather not have to deal with support legs, even if they're mounted to the door on hinges and they're adjustable. But maybe I should re-think that. I put a vertical upright at every point where there's a stake pocket in the flatbed deck. Might be re-thinking this whole thing if I end up building something out of fiberglass though. The more I think about it, the more I like that idea. Great point about using the door and latches to reinforce the back end of the enclosure.
 

Manchild12

New member
Thanks for the input. That's pretty much what I was thinking about trying to adapt from a garage door (the torsional springs). I still need to go look at some toy haulers and visit a garage door shop. The main reason why I want to use cables is to keep the whole thing self-contained. I would just rather not have to deal with support legs, even if they're mounted to the door on hinges and they're adjustable. But maybe I should re-think that. I put a vertical upright at every point where there's a stake pocket in the flatbed deck. Might be re-thinking this whole thing if I end up building something out of fiberglass though. The more I think about it, the more I like that idea. Great point about using the door and latches to reinforce the back end of the enclosure.
So what ended up being your final result? I'm considering a similar concept of a ramp door on the back of a school bus, similar deck height, similar desire for a flat deck. Anything you can add? Words of caution?
 
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