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

[Mike1955]

Air makes things bounce when trapped but since he is lowering air would be less likely to cause bounce since load induced pressure should not be changing significantly. Yes it would bounce like a pogo stick if you stopped lowering.

 

[Mike1955]

Another thing to is maybe it isn’t a hydraulic problem. Maybe the metal is springy. At this point all options are open

 

[Sodo]

Thanks BCP that was a great compilation on cylinder chatter!

Searching the DB-1277-A returns only a "new model" that has the same partnumber. The new model is clearly a different pump.

I have never changed the hydr oil, I bet it's the original 1998 oil.
I don't think it had a hard life, I think it was used by a wood-floor company to dump tearout wood floors. It doesn't have any dents. But I will definitely change the hydr oil!

The cylinder is permantly tipped up with the seal head high. Do you think it's worthwhile to disconnect it and tip it fitting-end up and cycle it?

It does a lot of it's chatter at the bottom of its stroke so I doubt the cylinder is binding.
At the bottom of its stroke the forces are increasing and the chatter becomes more violent. Springy metal could be a contributor.

 

[oldnslo]

Fenner Fluid Power was purchased by SPX several years ago but might be worth trying to call there facility in Rockford, Illinois 815 874-5556 they might have some one still working there in product support from the Fenner division.

 

[Sodo]

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.

oldnslo this explanation makes sense.

I should probably call EZ-Dumper first before calling the pump mfr.
How likely would positioning the cylinder such that cycling it would eject an air..... be the easiest solution? I can go under the trailer and do that if the pins coooperate.

What about adding a bypass circuit that has a restrictor, with a valve.
In normal conditions the valve is open and it runs fast / normal.
So I'd never close the valve except if I know it's gonna chatter.
But on those few conditions while heavy I close the valve and it restricts and of course lowers slowly.

This would be placed in the pressure side of the power-down, right?

As simple as this is, "there's ALWAYS something" and it ends up taking half a day.
I really hope it's something simple, like getting air out or adjusting a pilot valve etc.

 

[JCoastie]

It worked well for a couple decades right?
I'd take it to a hydraulic shop, and pay an hours labor and get a pro's opinion on what's wrong before I went randomly putting a band-aid on something that needs stitches or a cast.

 

[Sodo]

It worked well for a couple decades right?
I'd take it to a hydraulic shop, and pay an hours labor and get a pro's opinion on what's wrong before I went randomly putting a band-aid on something that needs stitches or a cast.

Trade it in on a new one! I see comments on the F-150 forum like ".....you didn't even ask your Ford dealer?"

....not my style. I like to sniff out the problem, understand it, learn something, chat with other problem solvers. Lotta old fellers here with a lot of knowledge.
And possibly make it better than new for $50.
That's why I'm here.

Calling pros..... not my style either. They have a right to make their living from those who are too busy or unable to DIY. Plus anytime I've talked with pros I they say "we're currently booking about 8 weeks out....".

 

[Leejohn]

I have used Fenner Fluid Power on 3 trailers, all were double acting never had that happen. One was used on a trailer I made for 32' pontoon house boat for Woodward Governor. I Know a guy that worked there before they sold to SPX. If it comes down to it I can try and get his number, if he still with us. He had his hands in getting it off the ground for them. I well go alone with others that you have a air lead, check your hoses out real good.

 

[Sodo]

OK thanks. I've been watching the behavior. It pushes hard from down low. As the bed gets real high, the trailer unloads the ball on the hitch and pulls up on the truck a little. Shortly after, the cylinder starts to unload and now the bed is trying to tip - and the cylinder is actually holding it back from tipping, while still extending.

During this transition between pushing up, going over the top, and then holding back, the cylinder behaves like there's air at the top of the cylinder. I will try to think of a way to get that air out. The ports are on the sides of the cylinder, so I can see how air can get trapped. So do I have to take both pins out and tip the ports up vertical to get the air out?

Attachments

• 
  trailer hydraulics.jpg

  672.9 KB · Views: 1,059

It's a loaded trailer, ~5,000# of dirt in it so it will take some thought to be safe. It has a safety-prop. I'm inclinded to set it on the safety then use chain & binders and bind it down onto the safety prop. If I dump the trailer then I can't test if it's fixed. But if I get squashed I can't test it either.

 

[oldnslo]

Cycle the cylinder full stroke a couple of times when empty should help remove any air.