curing bucket flop

ericm979 · Dec 8, 2017

I got a grapple and it's extra weight (and CG farther out) makes the bucket flop on dump problem much more noticeable.

I see that LS owners have had good results adding an adjustable restriction in the curl line to slow the dump down a little so the inflow from the dump line can keep up.

I want to add it between the hard line on the loader arm and the hose. The connections there look like 3/8 JIC but in searching here I see some Bransons use 30 degree metric fittings. Anyone know for sure? I have an email out to my dealer too.

Thanks.

ericm979 · Dec 8, 2017

Daves' got back to me and they're JIC 6. Yay!

Aquamoose · Dec 8, 2017

What tractor? I have a 3520 and it flops too.

ericm979 · Dec 8, 2017

3725. Rob from Daves' said that other customers have done the same thing. I ordered a 3/8 NPT 8 GPM PRINCE WFC-600 in-line flow control valve from surplus center and some NPT to JIC fittings. And a 1/4" flow control valve for the top cylinder on the 3pt. Sometimes I move the control lever a little too far and my chipper slams into the ground.

Aquamoose · Dec 8, 2017

Thanks for the info! My tractor’s from Dave’s. Good people. I put in an hydraulic top tilt on my 3ph. I font get why you’d need one for the rear. I adjust the 3ph knob to manage the drop speed and I do have a chipper as well.

oldnslo · Dec 8, 2017

On my 2400H everything on the tractor is 30 degree metric or BSPP ports while the FEL is standard JIC & SAE ORB ports. Not sure if the other Branson models are this way or not.

I installed a counterbalance valve on my dump circuit so that I get the same dump speed under all conditions. I.e. forks or empty bucket

ericm979 · Dec 8, 2017

What's a counterbalance valve?

BKBoiss · Dec 8, 2017

ericm979 said:
What's a counterbalance valve?

This sounds interesting. I also would like to know more.

oldnslo · Dec 8, 2017

A counterbalance valve is designed to prevent over center loads from running away. When installed correctly they will control the load or dumping bucket no matter what the load is or the speed desired to dump. You cannot dump the bucket without hydraulic power.

On a true load holding application like a man lift, these are usually set approx 30% higher than max rated load pressure. On my FEL I only wanted to prevent the floppy bucket so I set mine at the system relief pressure of 2500 PSI. I suspect that unless you have a large load on the forks or grapple a lower setting would probably suffice also.

Sun Hydraulics is the most common manufacturer of counter balance valves in the USA while Rexroth - Oil Controls is the largest manufacturer in Europe.

The attached Sun data sheet is just one of several different versions that Sun offers.

Connections are:
Port 1 or Cyl: connects to the end of the cylinder you want to control On FELS this is usually the rod end
Port 2 or valve: connects to the directional control valve
Port 3 or pilot: this connects to the opposite end of the cylinder or on FEL's the blind end of the cylinder.

I hope this limited explanation helps.

Slowpoke Slim · Dec 9, 2017

Very interesting. I'd like to hear more about it too. I hadn't really noticed a "flop", but my bucket dump control is extremely touchy, hard to do a finesse dump. Is this what you mean by "bucket flop"?

I'd also like to see a write up and pics when you're done Eric, when you can get around to it.

Thanks.

ericm979 · Dec 9, 2017

I needed more to understand the counterbalance valve and I found this chapter from a textbook: BOOK 2, CHAPTER 5: Counterbalance Valve Circuits | Hydraulics & Pneumatics

Sounds like the simple one way restrictor I'll be using is sub optimal, in that it's tuning will depend not only on the bucket load (which I knew about) but also the pump output (engine speed). Well it's cheap and easy to install anyhow. I wonder if it'll eliminate or slow the fast dump feature when set for normal dump?

oldnslo · Dec 9, 2017

ericm979 said:
Sounds like the simple one way restrictor I'll be using is sub optimal, in that it's tuning will depend not only on the bucket load (which I knew about) but also the pump output (engine speed). Well it's cheap and easy to install anyhow. I wonder if it'll eliminate or slow the fast dump feature when set for normal dump?

Presuming that your Fast dump is a regenerative dump then yes the flow control could slow the dump down depending on how it is set.

A counterbalance valve would also prevent the regenerative system from working.

Nice find on c'balance circuits explanation.

ericm979 · Dec 28, 2017

I got the flow control valve installed. It does slow the fast dump. I'll be running the engine at a consistent RPM (2000) to keep changes in pump output from being a factor. Also with the added weight of the grapple vs the bucket, and the cylinders to operate it, I want a faster pump speed. At times I have run the RPMs lower when using the bucket, especially when I have a ground helper and want to be polite.

I found a setting (about halfway in) that gets rid of most of the bucket flop but doesn't make the dump much slower. I have only tried it with the grapple so far. The valve's close enough to the operator's station that I can reach it if I stand and lean over, so it's pretty easy to adjust. It's the upper most line on the loader so it's right there on the loader arm.

The biggest problem with this has been getting one of the NPT to JIC adaptors in the valve to seal.

patrick_g · Dec 28, 2017

Just what is bucket flop?

I have been using my Kubota FEL for 15 years and never experienced what I think is being discussed. I do have a knob on a valve under the front edge of my seat which control the hydraulic flow so you can slow it down a bit to not be so fast/herky jerky if you want.

Patrick

Peter 315 · Dec 28, 2017

That knob at the edge of seat is for the 3 point hitch

ericm979 · Dec 28, 2017

Raise the loader and dump the bucket. When it gets near the bottom it flops back and forth a little like it's loose. The faster you dump it the more noticeable it is (possibly because of momentum). It's more noticeable with a heavier implement like a grapple than it is with a bucket. My Kubota B7100 didn't do it (though I only ever used the bucket on that, and it was a light bucket). LS tractor owners have also complained about the problem.

I think the cause is cavitation in piston end of the cylinders as you dump. The weight of the bucket/grapple pulls the pistons out faster than the fluid can replace it, creating low pressure. Adding a restriction in the output direction on the rod end is a band-aid (see oldnslow's posts above). I don't completely understand why some loaders do it and others don't but I suspect that Kubota just specs better loader valves.

oldnslo · Dec 28, 2017

ericm979,
The reason Kubota BX & possibly's B's don't have the problem with bucket flop is that Kubota uses a valve with regenerative dump. Regernerative dump connects both ends of the cylinder to pressure which help prevent the over running condition that causes cavitation.

Yes better valves that are designed to meter out from the rod end will also help reduce this problem.