My First Attempt at a Dump Trailer

[irsmun]

I have gotten so much good information off of this forum for free that I thought I'd attempt to give back by documenting (if I can remember to take pictures while working) my latest "project"- a 7x14 hydraulic dump trailer.

This is my second trailer to build and my first dump trailer. A little history:

I'd never welded before and I wanted to learn. I also needed a trailer. I had access to welding equipment and I found someone with experience to teach me. I built a 6x10 utility trailer and it works and looks great. Its been 4 years and my appetite for something larger combined with my dislike of unloading the trailer (you can also throw in the price tag of a new one) started me on this quest.

So here I am. I have very little welding experience except what I gained on the first trailer, so expect to see some sloppy (but strong) welds. Its nothing that a grinder and paint can't fix. This will not be a professional how-to. This will be my experience and what I learn on this build so that it will maybe help others...plus I get a dump trailer out of this thing.

My first trailer started with an old boat trailer frame. Remember the part about never welding before. I thought being able to start with a square frame was a great idea. Now, with my second, I have another donated boat trailer so my frame is already there, my lights, axles, etc. It is a tandem 3500# rig giving me 7000# of gross weight to play with. I haul a lot of junk around and I need more space than tonage. So even though 7000# will limit this trailer (for its size anyway) I am aiming to get a weight capacity of 5000# by keeping my build under 2K. I think this will be a challenge.

So here are my goals.

1. Build Cheap- because if I had the cash I'd buy a new one.
2. Light but Strong - engineering is going to be important since it will have 4' sides (3' with fold down 1'), gates, ramps, and a 10K winch mounted. So I'm going for less material efficiently placed with strength as its purpose. (interestingly using less material will also help goal 1) Over building is not an option.
3. I want to keep the tongue weight down. I will be initially be pulling it with a 1/2 pickup.
4. Low to the ground. In order to keep my ramp size down and make it easier to load, I want it as close to the ground as possible.
5. 50-60 degree dump angle. 45 won't cut it. I don't want to shovel stuff out. 55 degrees will be what I shoot for.

I'm going with a single hydraulic cylinder. Its a 3.5x36. It will be set to start at a 15 degree angle which should give me 6225# of force at start at 2500 psi. I did the math with installing it pushing toward the rear hinge and that put the connection point only 4' back. That left 9' of trailer that it had to lift. I am very uncomfortable with that. So I spun it around and now have it pushing toward the front. Now its connection point is a little over 7' back from the hinge, a much more advantageous placement.

Which brings up a question I'd like to present. What are the advantages/disadvantages of front verses rear mounted placement of the cylinder? Most dump trailers opt for the front placement pushing toward the rear.

 

[mikehaugen]

I would have to guess that front to rear requires less force, therefore a smaller cylinder. I don't think the pin position on the dumping part of the trailer is the only thing that determines force required. Then again, it could be as simple as needing less plumbing if the power unit is in the front of the trailer. When producing many trailers, I guess that a few dollars for hoses may add up.

I saw a thread (though I did not read it) in I believe that trailers and transportation section that discusses scissor vs. direct cylinder lift. Maybe read that over if you haven't already to get some ideas.

 

[irsmun]

Hi Mike, I guess I don't understand what you mean by "less force". The cylinder will lift with the same amount of force no matter which direction right? This cylinder will produce somewhere around 24,000# total. I can see the extra 17,000 going more into the frame box with a rear mounted vs a front. Is that what you mean?

Something advantageous I do see is that the axles will support a lot of the downward push of the lift.

 

[mikehaugen]

I apologize, but after re-reading your post I understand you a little more. I thought that you meant rear facing vs. front facing, but lifting from the same point. In that case, which I could be wrong, I think it would take less force with the cylinder in front of the lifting point. If the trig works out to have the lifting point farther forward, then yes it will be more advantageous.

Another consideration is if you have too steep of a dump angle is that it may give you significant negative tongue weight. Not a huge deal unless you have a real light truck, and you would have to remember not to ever dump it unless hooked up to the truck. This is an interesting project and I will be watching it with great interest. I have in the past considered a dump trailer, but I would not use it enough to justify the cost, even if I built it myself.

Also there are great stresses on a dump trailer, I hope that you're welding is better than you make it sound- and make sure that you design it in a way that it is not putting too much stress on the welds. I am not sure that building something as light as possible is a great idea unless you are an engineer or have a lot of design experience, and are a decent welder. Not to put you down just not sure that your goals are realistic. I have built/ designed a lot of things, and still don't try to save weight. I overbuild everything.

 

[mikehaugen]

Just to add something, when you look at existing trailers they are usually built a certain way for some reason (lifting angle etc...). I would use their designs and material selection as a minimum. That should give you good guidelines, and remember they are designed by engineers (hopefully anyway) and welded by professional welders (hopefully anyway). Although "engineer" and "professional welder" don't always mean that much.

 

[irsmun]

Thank you Mike. Safety is also a goal. I thought it went without saying. I do tend to overbuild as well. I will have to make a conscious effort not to. I am mechanically inclined and work well with wood but metal was a new frontier. I look forward to getting more skills in this area. Also, I will have a professional welder at my disposal to examine my welds (the depth anyway) and help if I need it. My first trailer is quite stout and I guarantee you I put it to the stress test. Anytime you try to pull a tractor stuck in the mud out sideways with a 10K winch mounted on the front, that will stress every connection point there is. It held well.

I will use this trailer often so I am spec'ing it for my needs. I wish I had bigger axles and then I would not have to worry about the weight but I have what I have. Hopefully building it in front of this forum will allow enough eyes to catch a potential mistake or hazard.

 

[Rara Avis]

http://www.tractorbynet.com/forums/build-yourself/116440-building-dump-trailer.html

 

[irsmun]

Great job and well documented. I have looked at your build before. Nice job.

Here is how I'd like to do the dump box frame. I want to distributed the pushing and pulling throughout the box with as little weight as possible.

 

[mikehaugen]

If the ground clearance wasn't an issue, you could move the "hinge" a little forward of the tailgate. This would mean less force required to tilt, but would leave the tailgate pretty close to the ground.

 

[meburdick]

Don't "try to keep the tongue weight down". Build it and distribute the weight of the trailer so that empty or full you will get between 10 and 15% of weight on the tongue. If you build it so that the tongue weight doesn't exceed 500 lbs, for example, you're going to have too little weight on the tongue and it won't tow safely.

If your tow vehicle maxes at 500 lbs of tongue weight, you can't tow *any* trailer over 5k gross without a WDH safely. Build it "right", not to suit your tow vehicle.