Adding a spool valve

[Eugen]

@thebuildist your work on this is impressive. Not much room there at all, it's kinda scary to even think of starting something like this. Amazing progress, and fingers crossed that no leaks find their way in (or rather out). You're doing now what many of us have thought doing but most of us are not equipped with your knowledge and courage! Thank you!

[Jancoe]

Bob, it's looking like you got that pb sleeve figured out. That looks like a factory piece right there. Jealous of your machines and your skills. Keep up the good work.

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[thebuildist]

Well, so far, so good. I've just finished the initial pressure and driving test, and everything seems normal. It's not the final test, though, because the new extended pressure line is currently just operating as a return-to-tank line, so no real pressure there yet.

But at least I've confirmed that everything still operates normally, power steering, forward and reverse, including the new TCV linkage upgrade.

Here are a couple photos, showing the new pressure line and return line.

It looks a little crazy with the pipes sticking up in the air, but the tractor won't ever actually look like this. The pipes need to come up high like they are in order to reach the loader valve which will be positioned something like this mock-up photo:

When the loader is removed, the vertical standards/receivers will be left behind, and these new vertical pipes can be secured to the standards and will be somewhat concealed by them. So it won't look so crazy once it's all put together.

But before I put it together, I need to get the new loader valve piped in and put it under enough load to trip the pressure relief valve, which will be the actual pressure test. Once I can trip the relief valve without any leaks, then I'm clear to reassemble the loader subframe/crossmember, and put the loader on, and pipe up all the cylinders to the new valve.

To that end, I've just ordered a fitting I need to hook up the return line from the loader valve. So I'm stuck for a bit until that fitting comes in.

[Eugen]

Nice work Bob, looking forward to the big pressure test!

[thebuildist]

I have a sinking feeling.

I cobbled together a return line hose so I can do a test. Again, the return line is only 10 or 12 psi, so I built up a temporary adapter using JB Steel Stick. It's ugly but good enough for a temporary return to tank line.

Then I plugged in my new valve and dead-headed one of its spool's ports with plugs. So with the engine running just above idle, when I pull that lever, the pressure line is essentially plugged, and it should trip the pressure relief valve, either in the new valve or the TCV.

And when I do pull the lever, you can just barely perceive the engine change pitch for a second. About like the engine changes pitch when you've raised the deck all the way up and reached the top. A just-noticeable drop in rpm for a second.

Surely if that line were back-feeding 2000+ psi, it would meaningfully bog the engine, right? Especially just above an idle.

Tomorrow I'm going to rig up a gauge so I can see what PSI it's hitting. But my sinking feeling is one of the following:

1. My PB sleeve isn't sealing, so the slightest back-pressure is just venting around the sleeve straight to tank. I don't think that should be the case. I made it carefully and to spec, so I have no reason to think it wouldn't seal. But until it's proven, who can say?

2. The power beyond port is downstream of the lift circuit. I'm thinking this is more likely. Now that I stop to run scenarios through my mind, I think the way the TCV is designed that the PB sleeve is downstream of the lift circuit, not tied directly to the travel circuit. The travel spool feeds the lift circuit, the lift circuit feeds the PB port. If that's the case, then the lift circuit pressure relief is actually what's in effect for the PB port, not the main pressure relief. And that jives with what I think I remember about the 64X series: they use a PB configuration, and their lift cylinders are only around 700 or so PSI. And I now have my valve configured like a 644. So the reason the engine is barely straining is because I'm only developing 600 or so psi in my PB pressure line before the lift circuit pressure relief trips.

If that's the case, I think I'll have to go back to the drawing board, abandon the PB route and go and back to using the proportioning/splitter valve. Because I've chosen relatively small diameter cylinders, so to get the stength I want I can't even consider anything less than about 1500 PSI to the loader valve. And I can't crank the lift circuit's relief valve up that high without risking damage to the deck lift cylinder. Heck, I'm not even sure it CAN go that high.

So I'll sleep on it and try to get a gauge on it tomorrow. No real panic until then. But as of now I have a sinking feeling.

Bob

[Spike188]

Oh Bob, I feel for you. These are the kind of things I lay awake thinking about.

[DavidBarkey]

"Then I plugged in my new valve and dead-headed one of its spool's ports with plugs. So with the engine running just above idle, when I pull that lever, the pressure line is essentially plugged, and it should trip the pressure relief valve, either in the new valve or the TCV.
Quote"

@thebuildist Bob , I am assumiing you put an Oring on the PB fitting . That being said . Did you count the turns and replicate for the bypass valve in the valve body after machining ? If I remember correctly this tractor has power steering . At an idle , it may not create enough flow past the deverter valve to set off pressure releaf valves . Did you check your releaf valve setting with a guage at the port on the pressure in side of the TCV ? You may just need to up the RPM.

[Jancoe]

Bob, the loaders had the same lift cylinder as yours 4xxx does. The 6xx loaders lift relief was set to 1200? Psi. Changing the lift relief spring will increase your psi. Again why can't you increase lift relief? What size cylinders are you using for your loader?

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[thebuildist]

Yes, I did both those things. And I just tested it with the gauge, and I think my suspicion is confirmed.

I put a gauge right on the port coming out of the new spool valve, dead-headed to the gauge. And with the engine at full rpm and the lever pulled it's pushing right around 720 PSI. To me, that rules out any issue with the pb sleeve, I would think if it were bypassing the sleeve it wouldn't develop that much pressure.

And that figure is right around what the lift circuit relief valve would be set at. So unless someone more knowledgeable can convince me otherwise, I think that the PB port is on the same pressure galley as the lift circuit, and the lift circuit's relief valve will be in effect for the PB port.

So I'll never get more than... what? 1,000 psi max out of this line. And that means it isn't going to work for me.

I think it's time to look at what it will look like to pipe in the splitter valve.

Bob

[thebuildist]

Bob, the loaders had the same lift cylinder as yours 4xxx does. The 6xx loaders lift relief was set to 1200? Psi. Changing the lift relief spring will increase your psi. Again why can't you increase lift relief? What size cylinders are you using for your loader?

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I'm using 2" ID cylinders for both boom and bucket. For the boom I think 1200 is plenty. For the bucket, due to the fact that the cylinder is "pulling" to lift the bucket (which reduces its strength due to the lower area of the piston) and the fact that its position when it needs to be strong is one where is has little mechanical leverage means that I really need around 2000 psi to have the strength I'm planning on. (1000# lift at the lip of the bucket) I was assuming 2500 in the design.

I guess I could go up to 1200 with no problem. To go higher than that I think I'd need to rework the deck lift cylinder to increase its max pressure. I have an old tie-rod cylinder I could consider cutting down....

Can that spring be easily sourced? I guess I could pull it and measure it and just try to shop for a spring with the spec's I need.

Bob