Dump bed hydraulics

[Kiotikarl]

This is what i did for baby dump trailer, 3.5 bore X 24 stroke, same size s my load trail 5 X 10 dump trailer. Cost of brand new cylindre 340$ + 20$ for 2 brackets and pins.

 

[LD1]

When I did a dump bed on my old truck, I used a pair of 2-1/2" x 30" cylinders IIRC. 2500PSI tie-rod cylinders from baileynet.com. They were only $128 each.

For what the OP wants, he said his friends trailer had a 3.5" cylinder that was 25" long.

A pair of 2.5" cylinders is roughly the same lift force. A pair of 2.5 x 24" cylinders are $106 each

A single 3.5 x 24 is $145.

So its only about $60 more to go with two outboard cylinders as opposed to 1 in the middle.

But since there is already going to be a strong frame outboard, you dont have to worry about beefing the crap out of the lower cylinder mount, and the middle of the hoisted bed. Plus less clearance issues. Well worth the little extra IMO.

Probably the biggest reason I did it on my dump-truck conversion though was I had no good way to attach in the middle. Gas tank and driveshaft kinda made it hard to put a cross-member in there to attach the base of a single cylinder. So I just hung them on the outside of the frame. Less modifying things that way.

 

[hslogger]

The old farmer way was to build them with two cylinders on each side of the bed, attaching to an underslung gusseted brace on the frame. The only problem with it really was sooner or later one would fail and the bed and or truck would twist into a bad mess. Most modern farm trucks have a scissors type hoist and one big cylinder. It really is the way to go IMHO.

 

[LD1]

The old farmer way was to build them with two cylinders on each side of the bed, attaching to an underslung gusseted brace on the frame. The only problem with it really was sooner or later one would fail and the bed and or truck would twist into a bad mess. Most modern farm trucks have a scissors type hoist and one big cylinder. It really is the way to go IMHO.

If done properly, there is nothing wrong with a single or double cylinder lift.

The real advantage of scissor lifts is ground clearance and greater dump angle with a shorter stroke cylinder.

I've seen some pretty messed up scissor lifts also. Again, do it right, no matter what design you choose, and all will be well. Personally, as a DIY'er, I like the simplicity of a single or double cylinder lift. Scissors are more complicated, more time consuming to design/fabricate, and more moving parts to wear out.

 

[jwmorris]

Well I had to use my 300 cc Honda pin remover to pull the 2" solid bar stock pin to remove the bed from trailer, once I drove it far enough through with a hammer and drift to bolt to it with a chain.

Lifted it off the running gear and you can see more of what I have to work with. The bed is built from formed 3/16" steel with 3/16" thick "z" runners on 12" centers. Figure I will tie a few of them together with 2" box tube around the ram mount on the bed.

The frame will be extended to the rear with 2x6x3/16 to around 9', leaving 1' of overhang past the pivot. I think the 2" stock will work even with the extra load at the start of lifting.

With the around 17" of weld, I don't think any problems will come from just splicing it without reenforcement.

For the cylinder mount I can either go from front to back like Big Tex does or back to front like the first pic I posted and have plenty reinforce to.

 

[LD1]

IF you use a single cylinder in the middle, that bed needs some serious reinforcements.

 

[jwmorris]

I was planning on adding either 2x3 box tube or 2x2. The "z" cross braces are 3.5" tall so I have room for either.

These are some photos of a 2.5 Ton capacity BigTex, where the entire bed is only 2x2 box tube. I don't think it would be hard to make a stronger setup than they have.

I liked the double ram idea but found a 4x24 ram for $140 delivered and figured I only have to make one (although more difficult) mount. It will also reduce the hydraulic hose/fittings cost by at least 50%.

 

[jwmorris]

I also came across a few other methods in my searching.

 

[CDN Farm Boy]

The first pic you post has the cyl mounts in the wrong direction. Lots of range of motion of the bed with a short cyl but dump force will be really low, especially to start the dump. The most force from the cyl is applied when it is working at 90 deg to the bed. Without being able to measure and do calculations, I'd guess it never gets past 20 deg or so at full dump and probably only starts at 5 deg. The green farm trailer in your later post is the same idea but with the cyl mounted in the right direction. Base of the cyl away from the hinge with the top closer to it.

The grey scissor lift in the second pic seems backwards to all the ones I see but perhaps they are reversible?

I agree with LD1, if everything is done proper either single or double ram can work well. And either can fail just as easily. I recently saw a local landscaper destroy his telescopic ram trailer when one of the hinge pins fell out at full dump. Ram, ram mounts and other hinge are all toast.

 

[jwmorris]

I went to one last dealership to look at trailers and found one to copy the geometry.

It was only 5,200lb and used a 3" bore cylinder but with my 4" bore cylinder I think it should work for what I want.

It too was a 5x10, using the point where they meet and the front of the box as a reference, the front mounting point is 8.5" below the top of the frame and 31" back from the front of the bed.

The bed mount is 2" above the top of the frame and 64" back from the front of the bed.

The stroke is 24".

The rear pivot is 14" centerline from the back of the bed.