modifiying trailer for dump action?

[KsM715]

Hi all. Ive lurked here off and on for a few years, Lots of great info.

Ive searched for a few hours now and cant find the answers Im looking for. Im getting a m105a2 military surplus trailer in a few weeks and need to modifiy it into a dump trailer. The questions I have are: 1. Ive seen to different ways of mounting the cylinder, one way with the cylinder from the frame to the box and one with the cylinder mounted to a sissor (spelling?) type frame inbetween the frame and box. Its not a big trailer and I dont intend on loading it heaping over with dirt or gravel, Is mounting the cylinder from the frame to the box strong enough? Is there a way to figure out how far forward or back the cylinder can be mounted?

The pics are of the trailer like I want to build and of the trailer Ill be using.

 

[RonMar]

I would say a lot depends on how the trailer is assembled. It is far better to design a dump trailer from the beginning as such. A dump trailer is a dump box on a strong trailer frame. Most trailers not designed to dump, incorporate the box as part of the frame to save weight and materials. Converting one of these to dump can require a LOT of work and re-design of the frame and box to accomplish this.

The scisors framework lift design allows you to use a shorter stroke cylinder, and less hydraulic fluid, so a smaller resovoir is required. The scisors framework also more precisely controls the travel of the box and the forces applied to the cylinder. Fully extended cylinders can be damaged by uncontrolled side forces. The trailers that use a single cylinder and no scisors framework require a very long cylinder. Any flex in the box from uneven loading can put large side loads on this cylinder, so a very stiff box and pivot point are needed to keep from damaging the cylinder.

When converting something to serve another purpose, I always find it best to either draw the original into my CAD program, or build an Exact scale model. The CAD program is of course much less work, and easier to modify. You have to know where you are, before you can decide where you need to go... Once I have the original mocked up, Then I can experiment with different ways to achieve my end result, and get my brain around all the variables involved with the project.

Good luck with your project.

 

[joes_427_vette]

Sometimes the converting is more expensive and agravating than starting from scratch. Good luck with your project. I have looked at enough of them to know how I want it constructed so it will provide years of trouble free service.
Some of these conversions end up being money savers which relate to goobered up attempts to look like an original. Make a plan and don't cut corners in strength and safety matters. Remember... we like progress pictures !

 

[wushaw]

This is what I built, it is a little different from what you will be getting. You already have the box, you will need to build a frame on the bottom of the box for the actuator and pivots and build another frame for that to sit on.
http://www.tractorbynet.com/forums/build-yourself/116440-building-dump-trailer.html

 

[GuglioLS]

Hi all. Ive lurked here off and on for a few years, Lots of great info.

Ive searched for a few hours now and cant find the answers Im looking for. Im getting a m105a2 military surplus trailer in a few weeks and need to modifiy it into a dump trailer. The questions I have are: 1. Ive seen to different ways of mounting the cylinder, one way with the cylinder from the frame to the box and one with the cylinder mounted to a sissor (spelling?) type frame inbetween the frame and box. Its not a big trailer and I dont intend on loading it heaping over with dirt or gravel, Is mounting the cylinder from the frame to the box strong enough? Is there a way to figure out how far forward or back the cylinder can be mounted?

The pics are of the trailer like I want to build and of the trailer Ill be using.

Here is my dump trailer project:
CLICK HERE

I agree it's much easier to design and build a dump trailer from scratch. Although modifying an existing trailer to function as a dump trailer can be equally rewarding.

Personally, I would go with a straight hydraulic cylinder lift mechanism vs a scissor lift due to simplicity. "Will mounting the cylinder from the frame to the box be strong enough?" I seriously doubt it. The cylinder mounting points will need to be beefed up where it will withstand the maximum force available from the cylinder for a safety / failure factor of at least 2-3X the force of the cylinder. Additionally, the cargo box will most likely need to be stiffened up so as to support the weight of the load between the rear pivot hinges and where it gets lifted by the hydraulic cylinder (so it doesn't fold in half when being lifted).

"Is there a way to figure out cylinder placement?" -It depends on the weight being lifted, total angle of lift, bore and stroke of the cylinder, vs the available hydraulic pressure, unless your a genius at trigonometry and calculating mechanical force, it's basically more or less trial and error. First determine what angle dump you want, (45* is a good rule of thumb for a dump trailer). Then find out how much space you have to work with to determine the retracted length, stroke and bore of the cylinder. Hint - over kill is the rule of thumb here. The lower and more forward the cylinder is away from the rear pivot hinges will give the best mechanical advantage. I used two 2.5" dia 16" stroke cylinders - one on each side, or it could have been done with one 4" cylinder in the center. I opted for two cylinders to spread the load and forces over a wider area.

If you need help determining exact cylinder placement, bore and stroke....Post some pics and dimensions when you get your surplus trailer taken completely apart, then we can all take a look at it for a better assessment.

Larry

 

[Renze]

The trailer in the picture has a very high ground clearance, which means that you can place the cylinder allmost vertical: Thats most beneficial, as it will give the most lifting force with the smallest cylinder.

Most i've seen in American dumptrucks are scissor lift, though in Europe, telescopic cylinders are much more popular: they are suspended on a pivot mounted on the rod side of the cylinder, and with 3 or 4 stages, they can be positioned upright, in the middle under the bed and still tip 70 degrees.
Over here, there are lots of telescopic cylinders available at stores, mostly made in India.

Whatever you decide, remember that horizontal placement of the cylinder requires a big cylinder and beefy hinges, and gives only a limited lift force where it is needed most: when the bed is horizontal. Then when it tips up, the cylinder gets more effective when the dirt is already starting to roll out, which means you loose a lot of speed to pump oil into that big cylinder.

The more vertical you place it, the more efficient the overall design, both mechanically and hydraulic.

 

[Renze]

"Is there a way to figure out cylinder placement?" -It depends on the weight being lifted, total angle of lift, bore and stroke of the cylinder, vs the available hydraulic pressure, unless your a genius at trigonometry and calculating mechanical force, it's basically more or less trial and error.

I'm not a genius, i did some dumptrailers in my previous occupation, but just a little fiddling with Autocad and 2nd year high school physics is enough to figure this out.. Autocad (or the chinese copy of it, www.zwcad.org) is a great substitute for everyone who didnt care about sinus and cosinus back at school

 

[GE222]

RonMar did a greeat job of hitting most of the highlights.

I also agree that a scissors type lift assembly is the way to go.

Almost all larger dump trucks use a straight compound cylinder which is incorporated into the design of the box as well as the frame.

Check out an older grain truck or an old farm wagon, they both used the scissors type lift assembly. I have seen a number of people try to use them as a light duty dump truck with poor results as they were never designed for gravel or dirt. They should work great with the size of a dump box as you have pictured.

If you hunt around, you might be able to find a scissors assembly for cheap at a farm auction if you aren't in too much of a hurry. I believe that the Surplus Center also sells them in case you want to purchase a new one of get an idea to build one from scratch.

Also keep in mind where the hinge point is located. I wouldn't put it all the way at the back of the box, but putting it too far forward can be even more of an issue as the load is being dumped with the box and load raised up. While there is not an exact science, I think around 5% of the box should overhang. A typical grain truck can have 30% or more; however, grain typically flow very easily and not get hung up.

 

[KsM715]

Wow thanks for all the responses and insight. Im not in any hurry and usually tend to take awhile to actually doing and of my projects. (lots of time for research and parts searching) I am going to brace the underside of the box somehow. There is tons of ground clearance under the trailer but I dont want to mount the cylinder vertical, I dont think I need that much power to worry about that and i want to keep the trailer looking almost stock. I will take pics when I get around to doing it.

 

[Renze]

Whatever you decide, remember that horizontal placement of the cylinder requires a big cylinder and beefy hinges....

The more vertical you place it, the more efficient the overall design, both mechanically and hydraulic.

I was contradicting myself quite a bit here: Off course i meant that a HORIZONTAL placement of the cylinder is quite inefficient.

....but I dont want to mount the cylinder vertical, I dont think I need that much power to worry about that...

Actually the forces that occur on the box and hinges, when trying to punch out the dump box from a near dead angle, is what worries me

I agree with, if a standard scissor lift for dump trailers is available from surplus center at a decent price, its not worth your time and effort to fiddle with it yourself.


One more thing to consider: We have an old dump trailer, which is basically a 3 sided dump body on an ages old Bedford chassis, with the frame rails bent together into a V shaped towbar. The problem with this dump is that i allways get stuck with it with a dumped bed: The axle is too much in the middle of the bed. When dumping, the center of gravity shifts behind the axle, which means that the trailer will try to lift the tractor from the drawbar.

few weeks ago a load of garden mulch mixed with brush and branches, plugged up behind the tailgate, which caused my 3011 to be lifted off the ground... that was quite a scary situation.
I had to pull it forward with the 5245 before the plug released and the weight was releasing off the rear end of the dump body.
Believe me you dont want that to happen, it gives such a funny feeling in your belly when you realise that the tractor rear wheels are spinning freely, being lifted a foot off the ground...