Dump Trailer

[Iplayfarmer]

Progress Update: Phase 2) Assembly

I got in about an hour and a half tonight working on the dump trailer. No pictures, sorry. I spent the time fabricating not documenting.

I started on the actual dump bed. I got the outer rim of the bed frame cut out and welded up. It's 3' wide by 4.5' long. I made 45 degree cuts on each end of each piece and welded along the seam. I've got my welder turned all the way down and I'm using 3/32" rod, but I still have to be carefull to not burn holes when the seam isn't butted together real tight. Talk about practice, though...I'm really learning a lot about welding throughout this project.

All of my cuts have been made with a $14 angle grinder that I bought 6 years ago at a "Truckload Tool Sale" at CAL Ranch. I'm burning through skinny wheels, but I'm sure I'd use up the equivalent in gas or other consumables with any other cutting tool. I used one skinny wheel all up to make the 8 cuts that I made tonight.

 

[bbabineau]

Perfect!

That's exactly what I was looking for. I just wish I could have seen those pictures about two weeks ago.

Does that much of an angle dump pretty good? Do you ever have stuff hang up in the bed?

From brush to top soil and decomposed granite I have never had anything hang up in the bed when it is fully up.

 

[Iplayfarmer]

Well, Add $30 to the cost of the trailer. That's my co-pay to the eye doctor today for extracting a metal sliver out of my eye.

I was wearing safety glasses and everything!

I felt something in my eye all day. When I finally looked in the mirror to see what it was I saw a little flec of metal embedded in my eyeball right next to the iris. As soon as I saw that I called my eye doctor and was in and he had it out within the hour.

I drove straight to Home Depot and bought the best pair of safety glasses I could find there. Apparently what I had wasn't good enough.

While I was in town anyway, I also bought a small remnant of cold rolled 1" rod to use as a pin for the eyes on the ram.

Hopefully I'll be able to get out to the garage tomorrow and do some more fabrication work.

 

[Iplayfarmer]

I decided to kill two birds with one stone. I've been planning to add some angles to the frame to make it a little more rigid. I added some triangles cut from diamond plate to the rear corners where the bearings will sit. This should give some rigidity to the frame and spread out the load from the bearings a little to help strengthen that point too. The first picture shows these angle pieces.

I got the frame of the dump bed started. The second pic below shows the outer frame with the two longitudinal supports welded in place down the middle. I cut the pieces out with 45 degree angles in each end for this outer frame and compared each side to it's companion to make sure they were exactly the same. I layed the pieces flat on the shop floor and tacked it together with a single tack in each corner. Then I measured each diagonal to make sure it was square. I did end up putting a tie-down strap across the one diagonal to rachet it in before welding the whole thing up solid. When it was all done I was within 1/16th of an inch on the two diagonals. That's square enough for me.

I'm planning to put two additional beams in accross the width of the bed. I'll bolt the wooden deck to these beams.

I'm going to wait to put these cross beams in until I figure out the placement of the hydraulic ram. I think I can come pretty close with some good old fashioned trigonometry, but I plan to tack things in place at first to try them out. I think it will still take me a few trys to get the dump angle how I want it.

 

[Iplayfarmer]

I need some advice on the placement of the hydraulic ram.

From all of my calculations, I can get more initial torque and a greater final angle of dump from a ram that is angled up and forward. the Dump bed attachment is further from the hinge point and therefore more torque, and the frame attachment is closer to the hinge point meaning that it can push the bed higher.

So why are all of the dump trailers that I see built with the ram going up and back? What am I missing?

 

[Reg]

I need some advice on the placement of the hydraulic ram.

From all of my calculations, I can get more initial torque and a greater final angle of dump from a ram that is angled up and forward. the Dump bed attachment is further from the hinge point and therefore more torque, and the frame attachment is closer to the hinge point meaning that it can push the bed higher.

So why are all of the dump trailers that I see built with the ram going up and back? What am I missing?

Your description of "up and forwards" didn't make sense to me - could be me.
I agree, just about all dump trailers seem to have their rams mounted at the "front" (opposite end of the bed to the hinge point) and as they raise the ram angles backwards.
By "torque" do you mean initial lifting force, or "leverage" against the center of mass ? (which I assume would be at about the mid point).

 

[Iplayfarmer]

Your description of "up and forwards" didn't make sense to me - could be me.
I agree, just about all dump trailers seem to have their rams mounted at the "front" (opposite end of the bed to the hinge point) and as they raise the ram angles backwards.
By "torque" do you mean initial lifting force, or "leverage" against the center of mass ? (which I assume would be at about the mid point).

Here are some of the principles I'm basing my decisions on. These may be where I'm missing something.

1) Dumping a trailer is a rotational motion. The principles of rotational force and torque are the acting principles.
2) The only portion of the force of the ram that is really used is that which acts at a right angle to the dump bed at the point where it connects to the bed.
3) At the beginning of the dump the upward force of the ram is proportional to the angle of the ram as measured from the bed. The "steeper" the ram angle is, the more of the ram's force is pushing at a right angle to the bed. (The upward force is the sine of the angle times the total force that the ram can exert.)
4) The force of the ram is the same as long as the angle of the ram is the same. However the torque that the ram exerts on the load is greater the further from the hinge point that the ram is pushing. The ram uses the bed like a lever. The further out on the lever the force is, the greater the torque. (think of a cheeter bar on a wrench.)
5) The force of gravity is what I'm trying to overcome. The force of gravity is always pulling down. There's some kind of calculation for the load and the torque it exerts against the bed, but since every part of the load is a different distance from the hinge it requires some calculus that I have forgotten. I do know that if the upward force is less than halfway out from the hinge, the upward force required to lift a balanced load is actaully greater than the load itself. That is because the hinge is actually pulling down on the load at this point rather than pushing up. As the bed tilts up the gravitational force is still directly down but the bed is not. The portion of gravity that is acting at right angles to the rotational motion of the bed decreases as the angle between the bed and straight down decreases. At the same time the portion of the force pulling out the back of the trailer is increasing as the angle of the bed increases from horizontal. At some point the portion of the gravitational force that is pulling out the back of the trailer is great enough to overcome the friction of the load against the bed of the trailer and voila...pile of stuff on the ground.

First scenario: Up and Back...

If I mount the ram so that the base is at the front of the frame and the rod is further back on bed, the initial force needs to be greater because the rod is further back on the bed. It exerts the same force but less torque. As the bed dumps the angle between the bed and the ram increases so the force acting at right angles to the bed increases while at the same time the force acting a right angles to the bed from gravity decreases.

Second Scenario: Up and Forward...

If I mount the ram so the base is closer to the axles (in this case probably between the two axles) and the rod is further forward on the bed, it exerts the same force as the first scenario, but more torque because it's further away from the hinge. As the bed dumps, the angle between the ram and the bed actually decreases, so the portion of the force at right angles to the bed decreases, but the force of gravity acting at right angles to the bed decreases as the angle between the bed and vertical decreases.

The second scenario seems to make more sense because I'd have more torque when I need more torque and less torque when I need less torque.

So why are most of the dump beds built with the first scenario?

 

[gemini5362]

If I understand what you said and I am not sure that I do. Is the distance the ram moves less or more in the first scenario. They might mount them that way because it allows them to use a shorter ( cheaper) ram.

 

[Iplayfarmer]

If I understand what you said and I am not sure that I do. Is the distance the ram moves less or more in the first scenario. They might mount them that way because it allows them to use a shorter ( cheaper) ram.

I was figuring the ram moves the same distance, the bed angle is what would change. In my particular situation, The bed actually dumps higher with the ram in the second scenario, but this is because the ram itself is half the length of the distance between the hinge and the front of the dump bed. A ram that is shorter in relation to the length of the bed would probably not travel enough to really do much in the "Up and forward" scenario.

I think there is more potential for the ram to dump the bed higher in the first scenario (up and back) if you're willing to mount the ram far enough back.

You may just have it.

 

[Iplayfarmer]

I got up early this morning and made some more progress. I've got some pics of what I've done, but first of all I'm posting a picture of what I woke up to this morning.

It's May 5th here just like everywhere else.