Dump Trailer Damping

[AlanB]

Hi all, I have a 6 X 10 Homesteader dump trailer.

Looks like this

Dump Trailers, Hydraulic Dump Trailers From Homesteader Trailer

Hmmm, the link takes me to different than I copied, I have the 6 X 10 MX

It is power up and gravity down.

It use an electric over hydraulic pump unit with integrated solenoids to control flow.

It has a 3.5 X 30 hydraulic cylinder, similar to this

Surplus Center Item Detail

This cylinder is now leaking at the end caps.

Last night, I tightened the bolts holding the cylinder together, but I am sure it probably needs to be rebuilt. (O-rings changed)

Why I believe it is now leaking is that when they are doing mulch, they load the wheelbarrows from the back of the trailer.

When they have pulled off all that is within reasonable reach, they close the doors and hoist the trailer, that drops all the mulch back to the rear of the trailer. At this point, they drop the trailer.

When you drop this trailer, what you are doing is opening a solenoid that allows the hydraulic fluid to flow back through the one line in the system into the resovoir.

The problem is that when loaded heavy, the trailer drops quite quickly. It drops quickly enough that it concerns SWMBO and then she releases the button, which closes the solenoid, which stops the fall, SUDDENLY which I think causes a huge spike in the cylinder pressure, which I think is why my end cap seals (o-rings probably) are leaking.

So, my idea is to put a restrictor in it that is controllable. I am thinking along the lines of a valve of some form, that she could switch between restricted, and non restricted flow.

You would not want restricted flow with an empty trailer, it would not drop.
You would not want restricted flow while lifting, it would overheat / overwork the pump unit, and slow down the lift.

Anyone have some thoughts or is there a simple snubber that I am not thinking about that could help with this?

Making it double acting has also crossed my mind, but I think I would need a different pump unit to do it pracitcally.

Thanks for your insights.

 

[mwb]

You can get one-way flow restrictor; basically a check ball with a hole in it. You will have unrestricted flow one way and restricted the other.

I can't think of any easy solution for switching bewteen empty and full load return though. The best i can think of is to install a pressure relief valve on the cylinder side of your vent solenoid. At least if it is shocked, the relief valve will help cushion it.

The problem with the relief valve is that it might open (say 1000psi) but it may not close until a lower pressure (say 900psi). This may cause the cylinder to continue to drop.

Another option may be to install an air ballast tank - sort of like what would be used to stop water hammer. The 'problem' with hydraulics is that it doesn't compress - therefore you blow seals. If you have an accumulator this might reduce the magnitude of the pressure surge.

 

[Skyco]

Wonder what is different from my dump trailer? It drops a reasonable rate whether loaded or not. Releasing the button mid drop doesn't result in any shock. I think, but I'd have to go look, the hydraulics is a package from Prince.
There is a solenoid valve on the electrically driven pump that is electrically activated to drop the body. There is only one line to the cylinder, pressurized it raises, then when the down button is pressed the solenoid releases pressure back into the reservoir. The solenoid is mounted on the pump as an integral unit.

 

[kennyd]

So, my idea is to put a restrictor in it that is controllable. I am thinking along the lines of a valve of some form, that she could switch between restricted, and non restricted flow

Surplus Center has them, Click HERE

 

[MichiganIron]

Sounds like a good application for a pressure sensing flow control valve. There are several types available, Surplus Center carries a good variety. You can have the line pressure from you dump cylinder control the flow rate for the gravity down. The flow through the valve is constant, compensated for pressure. They get a little pricey, but would be cheaper than re-packing cylinders.

 

[Wayne County Hose]

There's a load of solutions for this issue. Accumulators, pressure compensated flow control valves, etc. How about changing the habits of the operator. That would be the easiest and cheapest.

 

[AlanB]

There's a load of solutions for this issue. Accumulators, pressure compensated flow control valves, etc. How about changing the habits of the operator. That would be the easiest and cheapest.

The operators habits are now changed (but you have to be there to see what folks are doing, as they do not see it as a problem)

But it still drops pretty dang fast and "hits" mighty solidly at the bottom.

 

[AlanB]

Surplus Center has them, Click HERE

Kenny, that was exactly what I was looking for, obviously I did not look hard enough, and was browsing their site and overlooked it.

Thanks.

I think mount that in the control box, and just dial the knob when we find this situation.

 

[Farmerford]

Alan:

For a few dollars more consider Surplus Center Item# 9-4169-8, a Prince pressure compensated adjustable flow control valve. With the excess flow port blocked, it works just fine on my front ender loader to control the rate of descent and, since it is pressure compensated, the rate of flow does not vary (much) with the load. It does not have a check valve, so the flow is controlled in both directions (though it is not pressure compensated when flow is into the controlled flow port). I solved that problem by adding a check valve in parallel.