Dump Trailer Problem

[Silver_Knight]

I have a 6x12 Texas Pride dump trailer with a single pump and a single hydraulic cylinder. It is a power up gravity down model. I bought it new about two years ago and almost immediately the trailer started having problems lowering. I would have to get up on top of the trailer to put extra weight to get it to lower from the highest position. Here lately I have to do this when it is not even in the highest dump position.

I live about 4.5 hours away from the factory and don't really use it very often so I really would hate to take it to them for repair. The other day while it was in the lifted position I decided to take loosen the hydraulic lines to see if it would start lowering, which it did not. I actually took both lines completely off the pump and it would not lower until I got up in the trailer for the extra weight. And now it drops a few inches and stops, drops a few inches stops and so on until half way down then smooth the rest of the way.

I think by doing this, it rules out any pump issues. Does this indicate a bad hydraulic cylinder?

 

[Heywood Jannockitov]

Are the hinge pins on the dump box seized, rusted, bent, preventing the box from overcoming the resistance from the hydraulic cylinder? Are the pins greaseable?

 

[Silver_Knight]

They are not greasable or rusted and do not think they are bent. I did squirt oil the best I could yesterday and went up and down about 10 times without any noticable change.

 

[Silver_Knight]

Forgot to mention that fluid only came through one hose..up and down. The other hose that is connected near the part of the cylinder that where the shaft come out did not have any fluid flowing in it.

 

[Wis Bang]

Maybe the internals of the hydraulic cylinder are loose, or incorrectly installed and are cocking and hanging up until you apply extra pressure? Unlike a tractor trailer which has alot of weight, it wouldn't take much resistance to slow/stop your dump body.

Unless there is some kind of check valve you should have gotten oil from at least one line.

 

[J_J]

Forgot to mention that fluid only came through one hose..up and down. The other hose that is connected near the part of the cylinder that where the shaft come out did not have any fluid flowing in it.

Since you are using a single action cylinder, the port with out a hose is the vent hole, and has no fluid in it. On your motor assmbly, there is a solenoid to release fluid back into tank. Make sure the trailer is down all the way. There is probably an adjustment so you can control the close/down speed. Take whatever is in the port out and clean it and blow air through it. It should be just a filter to keep out dirt/dust.

 

[J_J]

In a single action cylinder, you are putting fluid in the push side, and when you release the valve, the fluid come out that same port back to tank, and the trailer bed should drop, based on the fluid flow, which is usually metered by a valve. Clean out this valve.

Probably something like this.

https://www.surpluscenter.com/item.asp?UID=2009082014480959&item=9-1479&catname=hydraulic

 

[Skyco]

He said it had TWO hoses!
My power up gravity down dump trailer only has ONE hose. There is no need for two, sounds like they may have put the wrong cylinder config on it.
Where does the other end of the hose connected to the top port, where the rod comes out, go, what is it attached to?

 

[J_J]

How about some pictures of the cylinder, and the solenoid set up?

The shaft end hose is probably just hooked up, but gong nowhere , maybe has a filter on the end of the hose.


They make a kit for double acting pump. maybe something got mixed up some whee.

 

[Silver_Knight]

Here you go. I think the hose on the bottom of the picture is the pressure and the top hose is the vent. BTW, the oil in the picture on the frame and cylinder is from me oiling the cylinder and end bearings and pins. There are no leaks.

 

[Johnagain]

When you disconnected both hoses did you get any fluid out of the pressure hose? With both hoses disconnected the box should have dropped very fast. If this doesn't happen the next test should be disconnect the vent hose at the cylinder when the box is PART of the way up. BEFORE YOU DISCONNECT THE HOSE PUT A 2/4 OR STEEL PIPE SO THE BOX DOESN'T DROP ON YOU. After removing hose then raise box up and remove the pipe or 2/4 and see how fast it drops. if it drops fast then the vent hose might have a plug or trash in it. You might also want to check the fitting I know that sometimes the teflon tape they put on the fitting wads up and can plug the fitting or hose.

 

[ditzel]

I have a 7x12 bri-mar dump trailer with the same problem. my trailer is about 6 years old and the problem started happening last summer. I was thinking it was the pivots seizing up, i have greased the crap out of them, but its still real slow and noisey coming down.

 

[westcliffe01]

The bushing on the front end of the single acting cylinder can also be dry and seizing up. More than likely all of the above, cylinder rod bushing, and pivot pins seizing up.

 

[Leejohn]

Let me guess at this. I would say a bent shaft, and its cocking the piston and binding on the end cap. with that cyl all the way out it wouldn't take a lot to bend it. Get the cyl out and see if it goes in and out by hand, if not take it apart and have a look. what size is the shaft? Maybe they just put the wrong cyls under the trailers and that is why the other guy has the same trouble.

 

[Scotty370]

My totally un-educated guess is that they used a double-acting cylinder in a single action application! That ram sure looks like it's got pressure ports on both ends. What they've done would work fine, as long as the upper void stayed clean and somewhat lubed! I'll bet that there's 'junk/rust/plugged-vent/condensation' or all the above in the upper void that the rod retracts into. I'd be disconnecting the ram to the workbench, and cleaning up everything. I might even pressurize the upper port, and 'power-retract' that rod by "bumping" the pump switch. If it retracts, a few cycles, might get you back in business! As always, be careful of pressurized lines and ports! ~Scotty

 

[RRILEY]

I had this problem with mine and it was a bad battery. Does, or did your battery have enough amps to run it up and down a few times a day loaded with no problems? Mine was used but still only about one year old and a junk battery. I got one of those that look like a six pack and is also rated for marine use. Have not had a problem since. Cranking amps and duration. Maybe this can help. I think that is why the guy returned the trailer.

 

[Silver_Knight]

But what about me being able to disconnect both hoses while the trailer was in the raised position and still not lower on it's own? The trailer will lower if I put a couple of hundred pounds up in it (me). The battery has been charged well during testing and would raise it many times without any hint of being low.

I think it has two do with the cylinder being that both hoses were completely taken off of the pump, but this is my uneducated guess since I do not know the theory behind a single action cylinder.

 

[westcliffe01]

Worst case scenario, the bore of the cylinder is getting rusted and causing the piston to bind. But this is less likely since one would normally get a bit of seepage past the seals on the piston.

Support the raised box and remove a cylinder and strip the upper part to see what is going on. Just trying to mive it by hand with the hoses removed will give you an idea of the condition.

But what about me being able to disconnect both hoses while the trailer was in the raised position and still not lower on it's own? The trailer will lower if I put a couple of hundred pounds up in it (me). The battery has been charged well during testing and would raise it many times without any hint of being low.

I think it has two do with the cylinder being that both hoses were completely taken off of the pump, but this is my uneducated guess since I do not know the theory behind a single action cylinder.

 

[RAF]

I think you have some junk blocking it. If you took both lines off the bed should of dropped and oil should of squirted all over. I am thinking it might be a piece of the gland or packing in the cyl. I have replaced many cylinder gland and packing on my 580CK and have seen many pieces of packing in the cylinder. Your lines and conections are smaller in diameter. I think you need to take the connections off at the cylinder. I would take the cylinder out so that you don't have to jack up the bed. With lines off and with alittle effort the cylinder should move. If it dosen't you allready have it out to take to the hydraulic shop. unless you take it apart your self?

 

[Scotty370]

The theory behind a single-acting ram is simple. Your pump only has to pressurize the lower/base cavity, to apply pressure to the piston and seals, to raise the trailer bed. Unlike a double acting cylinder, that you would reverse the fluid flow to the rod end, for retraction, it simply relies on the weight of the trailer bed to force it back down. Now, 'enter the second hose'! Typically a SA ram will only have a vent at the top to allow the air to exit the top cavity during the pressurized extention cycle, and, allow the air back in the ram during the 'gravity' return. Since your is plumbed from both fittings, I suspect that the top line from the rod end is just plumbed back to the resevior, (There must be a vent on the pump/resevoir) Thus, when working properly, the gravity compression of the cylinder during lowering, would suck fluid out of the resevoir, slowing the desent, and lubing the upper chamber. (Probably a good thing!) Since you detached the hoses at the pump unit with no further luck, I suspect that there is a restriction in one or both of the hoses, or as prevoiusly mentioned a mechanical flaw/bent-rod etc. I'd remove the hoses at the cylinder, and see if you can move the ram. Note the above safety warnings about blocking! Don't crush yourself! We all want to know how this turns out!!
Edit: Oopp's RAF and I typing at the same time! ~S