UPDATED Building a bi fold ramp gate is done.

[skip68]

My utility trailer is 14×6 and the barn doors are junked.  I had ramps but they didn't last.  So, I've decided to make a 8×6 bi fold ramp gate.  I've seen several ideas off the web and have a good start on it.  The basic frame is done, I bought 6 heavy duty weld on hinges with grease fittings and am stumped on how to know what size torsion springs I need.  
I want it to be easy to use with one hand.  

I'm guessing the total weight will be around 200-225 lbs.   But, the point where the ramp mounts to the trailer will have a tremendous amount of pressure on it as it's folding out.   So, my question is how do I figure out how much spring I need?    

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[draftingmonkey]

Skip, not sure what spring to use, but have you considered a winch to raise and lower the gate. The cable would attach at the midpoint/hinge point of the folding ramp.
Depending on how it is mounted a winch could be used to help load/drag cargo onto the trailer too.
Also, are you installing wheels or rollers on the lower end of the ramp so it can roll along the ground as it opens?

[skip68]

Yeah I already got a 2k winch.  I took an old receiver hitch, cut it down and welded it to my trailer.  Then made a mount for the winch so it goes into the receiver.  Works great.   I've considered using it for the ramp but that's a lot more fabrication.  Would be slick though.       
I like the wheel idea.     

[skip68]

Dammmmmmm, I love the roller idea.   I can put 2 or 3 rollers right at the edge that stick down just enough to allow it to slide.   Thanks drafting.    
I've thought about wheels but they'd dig into the ground if I wasn't on pavement.   I'll look some up.   Again, thanks.   That's perfect.   

[draftingmonkey]

Skip, the fabrication should be minimal.  If your loads are not higher than the walls of the trailer, use a piece of angle iron on the front wall and on the rear cross brace to add rigidity for a couple of pulleys. With the winch already mounted on the front of the trailer hitch the cable can run over the pulleys to a bracket you can weld in the middle of the ramp, upper half adjacent to the hinge.  If you use taller loads a 4x4 mounted to the front of the trailer with a pulley on top and a removal one that can fit in brackets at the rear would allow the cable to move over the top of the loads. A 4x4 should be able to handle the 225-250 lbs lateral load of the ramp.

For rollers something like a gate roller similar to this http://www.affordableopeners.com/ramset-800-83-35-guide-roller-6-black-ram-accessory.html

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Getting closer.   I made boxes to protect my new LED lights.  Getting closer.   

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Another few days and this trailer will be new again, kinda sorta.   

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Last one for tonight.       

[skip68]

Update.  Thanks for the advice draftingmonkey.  I did do the winch and pulley system like you'd suggested.  I mounted the winch upside down under the front A frame of the trailer.  Bought 50' of 4,000lb wire cable and 7 4,000lb pulleys.   The winch cable hooks to the first pulley in the middle under the trailer and the ramp gate cable runs through it.   Then the ramp cable goes to the back through 2 pulleys in the center rear sending a cable out each side.  They then get sent up via 2 more pulleys (one on each side) through the inside corners of the trailer.  Then through 2 more pulleys one on each side and out the back hooking to the ramp gate.  
I made the cable ends on the ramp removable by taking out a pin so when it's down they can pop off out of the way.   I also built a step on both sides in front of the tires and added a battery up front.  I have a controller in the front and one at the back of the trailer that's movable.  I still need to clean up the wiring and that's pretty much it.   It takes less than 30seconds to lower or raise the ramp gate.   I just love to push that button.    
I also wired the battery to the trailer wire harness so it's on the 12V pin for charging from the truck.  

                          I tore all the old wood siding off and built a steel frame for the siding and new wood.  The ramp has two spring latches on each side.  One latch keeps the 3 foot extension ramp latched to the main ramp.  The other latch locks the ramp gate to the trailer.    

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[draftingmonkey]

I like it  .  The hidden pulley/cable setup that you used, while more fabrication intensive than my suggestion, really turned out nice.  Thanks for the update as I really enjoyed seeing the process from start to finish and am glad to hear you are happy with your "push button" ramp.

[ws23rt]

I too give a A nice clean way to save wear and tear on the back.---Now if you could use some of that Nevada sun to make it go instead of gas powered.

[skip68]

Thanks guys.     
I could put a solar panel on it to maintain the battery.   
Nah, I think I'm about done.    I did however end up cutting out several bars to try and lighten the ramp and cut off 1 foot of the extension ramp from 4 down to 3 foot but it was still tooooo heavy by hand.   I'm still going to put some rollers on the end of the extension ramp so it'll slide like you said draftingmonkey.     
I think I went overboard on this project but I'm going to do this power ramp setup with a car trailer.   Just larger scale.   

[Daytona R/T SE]

So...

Where's the remote control ?

[Steve P.]

I don't have any pics of mine, but I cut and welded a piece of pipe and a steel dowel and made very heavy duty hinges. If you lower the tailgate an inch or so, you can slide it to the right for complete removal. Also used a boat winch bolted to the PASS side upper rail to crank up the tailgate.. It takes next to nothing for even a guy with a bad back to lift. (2) vertical pins lock the gate up...

The winch, cable and all the pulleys seems like a bunch of extra problems to me.. Not to mention the cost... But I you you props for doing it yourself, skippy!!!!!   

[skip68]

    thanks Steve.   I considered something similar to what you've done with a boat winch but that still requires more effort than pushing a button.       actually it only cost about $100 for pulleys, cable and miscellaneous.   I've had the winch for a couple years already.   But it was a bunch of extra work putting it all together.   

[ws23rt]

When I tackle a project like this for myself I tend to over complicate it from the beginning. The path to the end is a list of compromises but it still is generally over done or over built. That's the way I get satisfaction when I'm done.

Making that trailer to just meet the functional need is a different kind of project and only meets the one objective. --utility-- you have both utility and the extra.

[Steve P.]

I've been thinking about building a new utility trailer. The next one will be a tilt trailer for easy dumping. Was considering using a winch to do the lifting of the front end of the bed.. I've seen a few done this way that looked like crap, but I think I could make one that would do the job better and look much better. Hydraulics would be better and stronger, but that would mean buying an expensive set up.

A while back I saw a video of a trailer a guy built for transferring boats.  He painted boat bottoms. He said he would pick up the boats at the lake with his trailer and take them to his shop. There he would raise the boat on the trailer and set blocks under it. I 2 steps pulling the trailer foreword, he could pull the trailer out from under it and work on the hull. It looked like crap, but did the job.. I helped a buddy get his boat off his trailer for hull repairs by lifting the rear of the boat with a gentry crane on wheels. I'd say it was much easier and faster and I am sure it was safer than watching that guy..

[skip68]

The next and last major thing I want to do to this trailer is switch the axle to one with electric brakes.  I had it on the scales and empty it's 1,480 lbs.    It's ok behind the suburban but would be nice to have brakes.  Especially when I load it with firewood as I've done in the past and will again.   
Hydraulics would be the best way to go Steve if you've got more money than junk to haul.   Way too expensive IMO but sure would be nice.   I'd love to have a dump trailer but I think that's way above my skill level to build properly.   
I know what you mean ws.  I've over built this in several ways for what it's really going to be used for. 

[Steve P.]

So you've got a bit more than 2000# room for hauling... My 7 x 12 ' utility trailer was just over 1000# without the drive up gate.. I can lift it alone, but it's HEAVY!!!!!!!! 

I like overbuilt things, but adding brakes to a single axle trailer may not be a good idea.. With a second axle I'd say, no problem. If one brake grabs before the other your load could easily get away from you...

[skip68]

Ooooohhhhh, I didn't know that.   I hadn't thought about uneven braking with single axle.      That could be a bad thing.  I'd helped my neighbor clean out a rental house and had just over 4,000 lbs of crap in the trailer.  One wheel braking might tend to push the truck sideways.     
I'd better do some homework on a trailer site first.