Power Beyond vs Series for loader valve?

[BatesBunch]

California, I'm a little late on seeing this, but am glad that you are up and running again. As you stated, this thread has a lot of information for future reference.

I am in the process of rebuilding a loader (old Kubota Model 1200) for my YM1500D. I have fabricated a new triangular return plate that will replace a blank/cover plate on the upper right side of the transmission housing to serve as a tank return from my loader control valve. I had consulted with Mr. JJ quite a while back (before starting my tractor refurb project) (here) and settled on using the PB feature to power the 3PH and have a dedicated return to the reservoir. My research also showed that some folks had no issues with loader valves plumbed in series, while others did have problems.

I will try to get some pictures up for reference in the next day or so.

 

[BatesBunch]

California, here are my plans for the dedicated tank return from the loader control valve (I believe that I may have the same loader valve as you (without running out to the shed to verify) with a very similar mount).

As described in the previous post, I fabricated a new triangular plate to replace an existing cover plate on the right side of the transmission (above the axle/brake housing). This was cut from a piece of scrap 3/8" steel plate using a cutting wheel on a 4 1/2" angle grinder. The center of the plate was drilled and tapped to 3/8" NPT as I plan to install the 3/8" NPT 90-degree elbow as shown in the pictures. My intentions are for the tank return hose to run from the control valve, under the right step and banded to the original hydraulic tubing, to the return fitting in the transmission.

Pictures 1 & 2 - location on the transmission/cover plate to be replaced (there is also another one of these on the left side of the transmision if needed for an alternate return)
Picture 3 - new plate fitted
Picture 4 - new plate next to original cover plate
Pictures 5 through 8 - completed adapter plate

I had thought about drilling and tapping the original cover plate (off of the tractor), but decided not to as it was thin aluminum.

I hope that this may spark some other ideas as it was my intention to have a clean install while also keeping the operating area as clear and neat as possible.

 

[winston1]

Nice job with nice pictures. Just curious, what is behind that plate? Bound to be there for a reason.

 

[Car Doc]

Nice write up and great job and yes clean is the only way to do anything, definitely waiting on the followup! :thumbsup:

 

[California]

You do nice work! The whole tractor is going to be like new.

That is a great addition to the thread, showing the proper way to do a tank return. Somebody will find this description useful in the future.

What is behind the plate? Is that simply an opening for some optional component that was not used on this model?

 

[BatesBunch]

There is nothing behind the cover. I assume that it was for optional equipment or an alternate arrangement. There is a 'shoulder' or round opening that has a diameter about the size of the extended round part of the original cover plate (shown in picture 4 above) and the thickness of the transmission housing. After that, it is open to the upper part of the transmission housing. These two plates on opposite sides of the transmission remind me of those near the bottom that hold the hydraulic screen.

The update will be a while as I am sandblasting the loader with a small 20 lb pressure blaster from HFT. It works well, but takes a while with a small home set-up.

My wife and mother-in-law have jokingly asked if this was going to be a working tractor or a pretty tractor. They know that I am not looking forward to the first scratch!

 

[kenmac]

The little Yanmar looks GREAT ! :thumbsup:

 

[joshuabardwell]

Folks, I have enjoyed reading this thread a lot. I don't know much about hydraulics, but I enjoy listening to those who do. If I can go back to this comment on page 1:

Brian the stacking, doubling, of pressure makes sense. But I think it also means that the doubling can be avoided by never having the 3-point under pressure in its Lift position while using the loader valve.

It seems to me that if one had, for example, a ballast box, or a box blade that rode on the three-point even when it was not being used, then one would regularly be using the loader while the 3-point was under pressure in its lift position. But folks on the thread are talking as if that's an unusual situation. In the interest of my own education, am I missing something, and if so, what? Perhaps it's this: that "under pressure" refers only to actually moving the 3-point up, not just resting it in the up position?

 

[California]

... "under pressure" refers only to actually moving the 3-point up, not just resting it in the up position?

Yes, exactly. The lift handle routes fluid to the hydraulic lift cylinder in Lift position, but after that you move the lever forward slightly to Hold position This seals the passage so fluid can't escape back out of the hydraulic cylinder, and the lift stays up.

At the same time, when the handle is in Hold or Drop position, the full output of the pump goes right through that 3-point control (no back pressure) and drains back to the transmission sump.

 

[winston1]

Yes, exactly. The lift handle routes fluid to the hydraulic lift cylinder in Lift position, but after that you move the lever forward slightly to Hold position This seals the passage so fluid can't escape back out of the hydraulic cylinder, and the lift stays up.

At the same time, when the handle is in Hold or Drop position, the full output of the pump goes right through that 3-point control (no back pressure) and drains back to the transmission sump.

I must comment on this. I recently puts a new o-ring seal on my lift piston. It will now stay up indefinitely when sitting in the up position with a load on it. I have actually left the lift up for days watching it. However, when the tractor is in use with the load in the up position it will very slowly descend and after a small descent it will raise back up that small amount. Saying all that to say I would have back pressure at that time. I am assuming there is a little leak by in the lift valve. I really don't know why it does it when running, yet, won't do it when sitting. Just know it does.

 

[winston1]

No response to my email to Akon. OK, guru's, based on my pictures and description of my valve, is there any way for you to know if a plug in that top inner opening could convert me to power beyond. I think I am crafty enough to come up with a plug if that could be the answer. Or is there some testing or something I could do to give a better handle on how my valve works?

Possibly something like this. I could cut a slot in the hex part for a screwdriver? http://www.ebay.com/itm/2-M16-1-5-x...408&pid=100011&prg=1005&rk=1&sd=400169542285&

Also plugs available with alan heads but I really think I need a gasket surface.

 

[oldnslo]

Companies Like Parker Hannifan, Zero-Leak, Eaton-Aeroquip, etc all make metric plugs. Do you have a Parker store or another hydraulic shop that carries fittings in your area?

 

[winston1]

Companies Like Parker Hannifan, Zero-Leak, Eaton-Aeroquip, etc all make metric plugs. Do you have a Parker store or another hydraulic shop that carries fittings in your area?

Probably do, but do you think a plug or a sleeve of some kind is what will have to be in the opening?

 

[California]

Take a look back at posts # 39 and 40. I posted a picture of the plug that came with my new valve but I think it's more likely you need one like JJ's second picture where the plug has an upper and lower shoulder, each with an o-ring.

The theory of operation here is that the return, drain, from the descending cylinders is normally combined inside the valve with the PB fluid that went straight across the valve. Then this new plug separates the two flows so pump pressure goes out the PB and minor pressure from the cylinders dropping goes out the Tank exit.

If you can see some way to isolate the two flows you've solved the problem. (Plus plumbing from Tank outlet to transmission return hole.)

 

[California]

I recently puts a new o-ring seal on my lift piston. It will now stay up ... for days. However, when the tractor is in use with the load in the up position it will very slowly descend and after a small descent it will raise back ... don't know why it does it when running, yet, won't do it when sitting.

One possibility is the lever is too far back and the cylinder isn't totally isolated. If you can attain a perfect seal when parked, then maybe mark that position and use it while running?

Or - the implement is so heavy that fluid goes out the relief valve when you hit a bump driving around? My backhoe does this.

 

[oldnslo]

Probably do, but do you think a plug or a sleeve of some kind is what will have to be in the opening?

Since it threaded I would say yes. It would be kind of difficult to have a fitting with two different thread sizes line up perfectly so that they would screw together. Without having the valve in my hand I can not gaurantee this 100% though.

Can you tell where the tank port and PB port connect in the valve body compared to where this internal plug would go. It should isolate those two flow paths while allowing the pressure port to flow to the PB port. That is how the Prince LVT valves are made.

 

[winston1]

One possibility is the lever is too far back and the cylinder isn't totally isolated. If you can attain a perfect seal when parked, then maybe mark that position and use it while running?

Or - the implement is so heavy that fluid goes out the relief valve when you hit a bump driving around? My backhoe does this.

Doesn't matter what height the 3 point is at when running. Just setting still with a load it will very slowly ease down until the lift catches it and raises it a 1/4" or so. I don't mean a few seconds, more like minutes before it does it. If the tractor is off it will set at any height and hold it there for days. I know that probably doesn't sound right but I'm telling you that is what it does and I'm sticking to it.

 

[California]

If anybody's still reading my portion of this thread ...

I plumbed in a pressure gauge in front of the new loader valve to see what's going on.

Ghenges, JJ, and others who recommended against plumbing in series have it right - the pressure at the input side of the valve can go to the SUM of the loader valve and the 3-point's separate relief settings under certain conditions (which are best avoided!).

The new Prince loader valve properly bypasses at 2000 psi when the loader cylinders reach the end of their stroke. And separately, the 3-point lift bypasses at 2300 psi at full lift. (Should be 2000 per the manual). You can hear the engine load down a little.

Returning the lift lever to Hold (slightly forward) brings the gauge down to 50~500 psi and the engine doesn't sound loaded. If the lever is set for -0- psi the lift settles down, imperceptibly slowly. (Like Winston observes).

But - lift lever at Lift postion, full up, and one of the loader cylinders at its end where the Prince valve is bypassing through its relief, and I saw the gauge pinned hard, probably 4000 psi. And the engine is clearly working harder. Don't Do This is the obvious lesson. I think the loader valve is facing the full 2300 psi back pressure 'downstream' regulated by the lift valve's bypass. Prince's install instructions allow only 500 psi back pressure.

I have avoided doing that (Lift and loader valves used at the same time) since I bought the tractor because it didn't sound right. I'm going to leave the Prince valve in series like the old AICO valve was for the past 30 years, and I'm going to leave the gauge mounted so I have more precise information.

 

[Scotty Dive]

I am surprised we do not have more failures. I am still digging out from 30 inches of snow and can tell you that using a back blade and the front end loader at the same time is pretty common place.

 

[Normmm]

What about one of the trans drain plugs. It says it will handle 500 lb back pressure so it doe not have to return to the top os the tank.