Dump trailer bounces on the way down (if coming down heavy)

[Sodo]

How do I prevent the dump bed from bouncing (on the hydraulics) when I have to lower a heavy bed?
It seems kind of violent, it can't be good.
I suppose there is an accumulator, but how do I size it?
The trailer is about 3 yds (6'x10'x1.5')

Thanks for the knowledge!

 

[oldnslo]

Does this gravity down or have power down option?

If power down suspect there could be Pilot operated check in the load holding circuit. There is some load induced pressure so you need xx amount of pilot pressure to open the check. Then gravity takes over and load starts to run away so pilot pressure is lost and check slams closed. Then cycle repeats.

Putting a flow restrictor will help when loaded but could potentially slow down dropping an empty bed.

If gravity down not sure could cause that problem

 

[Sodo]

Thx very much for the help oldnslo!
Power-down. Upon bottoming the pump motor strains.

Usually the bed is empty and I'd like it to come down as fast as possible most of the time, but a little slower wouldn't hurt. I could try a restrictor, it sounds cheap & easy. It would be nice if it could sense high pressure and come down slowly if the bed is real heavy.

What do you think of this one?

And where's the best location for it?
I'm thinking on the bottom of the cylinder.

 

[oldnslo]

A question is where is the check valve presuming that it has one? Is there a block on the cylinder where both the rod end and cap end cylinder hoses connect? I can’t tell in the picture you posted.

I believe it would work best to have the flow control between the cylinder and check valve.

2 nd option is to find the check valve and replace it with a counterbalance or over center valve. This would provide a pressure regulation to lower and typically eliminates the chatter when lowering. Then you would have same lower speed empty or loaded but would not allow gravity down.

 

[Mike1955]

That bounce sounds a lot like air is somewhere in there. That fluid would have to be compressing and that don’t happen. Just my two cents worth

 

[jmc]

That looks a lot like the underbelly of my EZ-Dumper. I bought it new from a serious hydraulic shop, not a "Trailers-R-Us" sales lot. Try calling the manufacturer or their competent distributor.

 

[Sodo]

Can't be any air. Wouldn't pumping both ways eject any air?
Yes jmc it's an EZ-Dump. I like it a lot. It's the same width as my truck, easy to reverse it straight in the mirrors. I bet it's 30 years old. I got it on craigslist. It's been great, I've worn out/replaced 2 good tires since. I cannot believe how much work this trailer has done.

I thought $4500 was a lot for a used trailer 20+ years old when new ones were costing $6000 & nice tractors could be had for $10k. But it's been a great $4500 purchase. I never could have got the work done renting. It's arguably worth more than $4500 today - which is no help cuz I can't do without it.

oldnslo here's pics of the pump.
There's a little box with a wire on the left side.
On the right jammed up against the battery is a hex-shaped item.
I don't see any other components or what might look like a check-valve.
The two hoses leave the pump and go directly to the cylinder ends.

My knowledge of hydraulics is simple and basic.....
I can't imagine what a check valve would do in a system that pumps both ways.
Doesn't the pump motor simply turn the direction you want the fluid to go?

Anyway if you can help me stop it from bouncing I will be happy.
It seems like it might pop a hose or wear out the pump or something bad will happen from the violent motion.

 

[oldnslo]

Is there a lever or switch you operate to lower? I suspect there is some type of valve in that pump housing to lower the load and it might have some type of flow control that is acting up.

Very, very unlikely pump runs in reverse to lower.

 

[Sodo]

It's the standard rectangular yellow switchbox with U and D buttons.

 

[oldnslo]

Then down is operating a valve to lower the bed. I believe you need to find a schematic for that power unit to determine what you have.