Adding a cylinder and valve?

[davesisk]

I need some opinions. I'd like to plumb-in another valve to operate an additional cylinder (to curl a backhoe bucket, assuming I fabricate a backhoe arm, and eventually to fabricate a hydraulically controlled grapple, etc.) My machine is old and doesn't have the quick connect cylinder connections. I have the right knee lever, but it turns the hydrualic PTO on/off on my old machine. And unfortunately, whether you turn the lever up or down, the hydraulic fluid always flows forward (no reverse).

I was thinking of plumbing a valve in parallel with the hydraulic pto lever valve, but since they'd both be open center, this would allow hydraulic fluid to divert through the added valve rather than through the attachment I'm trying to power off the hpto, right?

So, a second possibility is to add the valve (probably to the left of the steering wheel) with hydraulic quick connects on all ports. That way I could run two quick connect hoses from the hpto to feed the valve (would have to turn the hpto on, of course), then quick connect the cylinder to the other ports on the valve.

OR

Would it be better to simply replace the single-direction hpto valve with a reversible hpto valve, since that's apparently what power-trac puts on the machines now? Would the valve that is currently used for the quick attach cylinder handle the 8gpm flow of the hpto?

Any idears, here?

Dave

 

[MossRoad]

On my PT425 there are several pumps. The one on the front is the variable volume pump that provides the drive power. On the back there is a pump that provides power to the steering, lift arms and auxilliary PTO(the one that operates the quick attach or power angle cylinders) There is a second half of this pump that provides the main PTO fluid. It is electrically operated(yours is apparently operated by the knee valve).<A target="_blank" HREF=http://users.beanstalk.net/godollei/pt425/PT425Pictures/PT425PTOPump.jpg>Click here to see the rear pumps that I'm talking about</A> The fat hose towards the engine is the main PTO and the smaller hose towards the rear is for the steering, hydraulic lift arms and aux PTO.

How many pumps are on your unit?

 

[davesisk]

MR:

Very similar to mine. On mine, there's the variable volume swash-plate/piston type hydrostatic drive pump mounted to the front of the engine, and the gear pump that powers the cylinders and HPTO mounted to the back of the engine.

Dave

 

[MossRoad]

Does your rear pump have the two, seperate sections like mine?

 

[davesisk]

MR:

To my understanding, yup!

Dave

 

[MossRoad]

Then I would guess that you would want to plumb an auxiliary circuit for operating cylinders off of the circuit for the pump with the smaller hoses, which should be the same pump that operates your current lift cylinders.

How you hook it up is still a mystery to me. Would you put it in series with the joystick valve?

 

[davesisk]

MR:

Good question. Since this stuff is all open-center, I'm pretty sure you can't plumb it in parallel, that would allow fluid to be diverted to the path of least resistance. I'm not sure you could plumb it in series either, because then you'd have to operate both valves to get whatever's behind the second valve to work...of course, I think that's what I was saying in my post above, ie. if I ran the output from the HPTO to a valve and cylinder, that would essentially be hooking them in series. I'd have to turn on the HPTO, then the added valve would operate the cylinder...sound right anybody?

Thx!
D.

 

[MossRoad]

Draw out a simple line drawing schematic of what you currently have and post it as an attachment. Someone here will pickup on it and we'll get some results /w3tcompact/icons/smile.gif

<font color=blue>I'm not sure you could plumb it in series either, because then you'd have to operate both valves to get whatever's behind the second valve to work</font color=blue>

I don't think so. I think the open center will take care of this. It will allow fluid to bypass the valve and go on to the next valve, and the next valve and so on. By activating the valve, you divert some of the flow to the cylinders. The farther you open it, the more flow. The rest of the flow just passes through, unused. Take your joystick, for instance. It is just two open center valves in series(I think). You don't have to operate one direction to get the other to work, right? Maybe series isn't the proper term. Maybe it is a series/parallel thing. Hopefully someone will pop in here and give us some guidance. Pleeease??? /w3tcompact/icons/laugh.gif

 

[davesisk]

Hmmm...you know, I think you're right about the open center thing and the valve in series...now that I think about it...

 

[Charlie_Iliff]

Dave: Although it may not be the cheapest way to go, I recommend the diverter valve that I installed. It uses the flow to and from your tilt cylinder, merely diverting it to the new circuit when the button is pushed. Mine is electric solenoid, but I assume you can find one with a mechanical control. I posted fairly thorough descriptions and a link to a paper on the web about diverter valves. I'd bet that with some careful shopping you're only talking a few bucks more than any other additional valve, and having it work with a button or trigger on the joystick is habit forming.
<A target="_blank" HREF=http://www.tractorbynet.com/cgi-bin/compact/showflat.pl?Cat=&Board=powertrac&Number=200406&page=2&view=collapsed&sb=5&o=0&fpart=>LINK</A>