Adding a spool valve

[Eugen]

@thebuildist I didn't want to say anything so you can make your decision undisturbed. But I would have chosen the same direction.

One thing I don't understand is why have two returns to the tank. Why?

[thebuildist]

Because I'm using this new multipurpose device as a tee. Both ports are part of the "return to tank system", but only one of them will actually run to the tank. The other one will actually RECEIVE tank oil from my power steering valve. That way I don't have to cut in another tee in the "return to tank" manifold.

Bob

[thebuildist]

I know it's crazy to try to make my own hydraulic component. But it's by far the least effort required to get from here to a working setup. I've taken the time to work up the schematic of what I'm talking about doing. It's easier to see it on paper than to follow my long description.

Here's the schematic of my system now:

And here it is after the new dual port pressure relief valve.

Bob

[Spike188]

Bob, the hydraulic path drawings are awesome. I am sure you have answered this question before. What cad system are you using. The detail of the pump and tank would be time consuming to draw. AutoCad was my goto 25 years ago followed by 3d versions. I had a detailed awing of a 40,000 sqft plant with machinery and office furniture down to an inch, taking months of spare time. Lately and I have messed around with lunix based free cad.

Drawings like yours take a lot of upfront time but once developed make modifications quick and simple. The thought process that one goes through while drawing brings ah ha moments that make system design issues well thought out.

Keep up the great work.

[Eugen]

@thebuildist I wanted to ask for a diagram, but I realized it would be very difficult to do it. Seems like you have it already, very nice drawing and that is much easier to understand.

[thebuildist]

@Spike188

First of all, thanks for the compliment. But I have disappointing news: I'm not able to produce these using CAD. I do use CAD mostly a shareware program that I started using in the '90s and I've just never graduated from. It's strictly 2D and not terribly easy to use. But it's what I'm used to so unless I want to spend a lot of time to learn something else, it's good enough for my 2D needs.

But for these, I started with a black and white image pulled from the hydraulics manuals from this site. Then I use an open source image editing program called GIMP. First I painstakingly removed the watermark. Just for clarity purposes to show that this is an individual person's creation not something put out by case / Ingersoll.

Then I realized that color coding the various lines makes it a lot clearer so I did that.

Then as my design has evolved I have evolved the picture with it. And it does produce a clear, easy to follow image. But it's very labor intensive to work on. If it could be done with CAD it would be so much faster!

But if anybody's interested I would be glad to share the GIMP-native file that I used to produce them. Since Gimp is open source, anyone can freely download and use it.

Bob

[Eugen]

Having used gimp, freecad, and almost any other free program out there, I appreciate how labour intensive it is and also that you're sharing it with us. I wish I could help.

[thebuildist]

Ok, I'm ready to machine my Dual Isolated Port Hydraulic Relief Valve with Integrated Outflow Tee.

My actual block of steel I'm starting from is 3.93X3x1 inches.
I took the time to wind a couple of 1/2" OD springs using .038 music wire. These are what will drive the check ball. Being hand-wound, they're ugly, but they're strong enough to overcome the viscosity of oil, while being weak enough to easily allow fluid inflow at around 30psi or so. So they should work fine.
I took apart the pressure relief section of an old TCV from a 442. I measured the hole diameter(s) and depth(s) carefully.

So I've updated my drawing to reflect those real-life dimension, and I'm ready to begin work on the valve body.

I'll post some pics once I have it machined.

Bob

[thebuildist]

So I've got the body machined for the new relief valve. I started with the actual relief valve chamber/hole, and within about 30 seconds I hit a major roadblock when I snapped off my 3/16" drillbit deep in the hole. An hour of tedious frustration, and I was able to continue.

I measured the relief valve chamber of a spare TCV and drilled this as closely to those measurements as I could. About the only tricky part is the beveled lip down deep where the steel ball will have to seal against. I used a drillbit to create the hole, then ran the drillbit backwards in an attemp to kind of burnish it to a clean finish.

Next I drilled one of the outlet holes, and tapped and beveled it for SAE #6 Female. Then I drilled its deep passage that reaches all the way into the relief valve chamber. I wanted to pressure test the relief valve, and I needed this hole to be in place, so that my pressure test air had a place to escape.

Then I drilled out the first of the two inlet check valve chambers, so that I could fit the rubber tip of my blowgun in there for a tight seal, and assembled the pressure relief ball, spring and screw stud.

Then I went ahead and shot 120 PSI air in there. I was hoping to hear and feel no air esacaping at the lower right outlet hole.

That didn't happen. It was putting up meaningful resistance, but there was clearly a good amount of air hissing out of the lower right outlet hole. Which meant that my relief ball wasn't making a good seal against its seat.

I thought of a couple possible solutions: 1. Try to grind the seat with a beveled stone in a dremel. 2. Tap/pound the ball bearing down into the hole to deform the steel into a shape that makes close contact. I decided the first option is more predictable and less risky. And the second option could damage the ball bearing and I don't have a spare of that size. So I decided on option 1. However, I don't have a beveled dremel grinding stone of that shape and size. So I chucked up a similar one in my dremel and used a grinding wheel dresser to dial in its diameter and give it a 45 degree bevel. Worked like a charm. But when I stuck it in the hole I found another problem, that the shaft is too short. It wasn't even reaching the top of the hole, let alone leave enough sticking out to grip in the dremel chuck.

So I chucked up some 3/16" rod in the lathe and drilled a 1/8 ID hole in the end of it. I put some green loctite in the hole and rammed in the shaft of the dremel stone. So now I had extendED the shaft of the dremel stone by an inch, but it wouldn't fit in the dremel anymore. No big deal. The slower speed of a cordless drill is probably safer/better anyway. So that's what I used.

After I ground that inner seat for 20 or 30 seconds I cleaned/blew everything out again and reassembled the relief valve components.

This time it held 120psi of air without any perceivable leakage. If it can seal air this well, it'll be fine for 15w-40 oil.

Finally I went through and drilled/tapped/reamed the final holes and passages, as per the drawing.

I have 4 ea. SAE 6M X JIC 6M adapters on the way. I'll ream a seat for the check ball seat into the SAE 6Male end of the two inlet fittings. The check ball seal will be a lot easier to seal, because the harder the fluid pushes, the harder it seals. The relief valve is just the opposite, you have only the spring pressure to keep the fluid contained, so the ball to seat mating surface has to be super clean/smooth.

So now I wait for my fittings to come in the mail. But it's basically finished. Hooray!

[Eugen]

Very cool!