technical question generic position control valve

Does anyone know if a valve is made to control a cylinder the same way a 3 point quadrant operates? Where the position of the lever equates to the position of the cylinder in the lift range.
stay with mechanical hydraulic devices for now, electronics don't exist for this topic
I am curious for educational and future reference reasons.

The closest readily available devices i've found so far are power steering valves of the non load reacting type. However, they are not directly tied to the cylinder in a way that guarantees the same cylinder position every time the control is placed in the same spot AND the input turns to output ratio is too high.

How does the touch control valving on a farmall c control rock shaft position? What's the correct technical name(s) for the type of valve? Same questions for Teledepth--how it works(i've heard it doesn't) and what's it called? Back to the touch control, is it reliable returning to the same spot? How about the 3 point on a big 4x4 with external cylinders. How does that system work? what are the controls like, do they even have draft control? i've never been in the cab.

Without knowing about the big 4x4s, seems like what i'm trying to visualize with the hydraulic control valve would end up being similar to teledepth. So what's out there in parts needed from common hydraulic suppliers and manufacturers? Is there a way such a system could be reliable on par with 06/56 series position control?

If you were to use the control, required plumbing and mechanical devices on a 3 point retrofit of a classic farmall, would they become overly bulky and complicated compared to using common open center double acting lever valves? Or could it be done about the same as typical?
Cost wise, would it be slightly higher than
common way or high enough that a newer tractor factory equiped would be more cost effective? I already have a hypothesis on the money--get a new tractor.
so for the sake of learning lets discuss what would be entailed to do this anyway. My mind needs some technical stimulation

time for some technical discussion
-karl f

ps next topic is draft control <evil laugh> >

Try this site
http://www.surpluscenter.com/item.asp?UID=2009110322101982&item=9-4500&catname=hydraulic

that item number comes up as a blank page with the message of "discontinued..."
i found it here (not sure how much longer that link will be active) https://www.surpluscenter.com/pages/018.pdf

that is a spring to center control valve. I want to find one that moves within a quadrant and whose relative position equals the position of the cylinder/rock shaft like a modern tractor's 3 point control. does it even exist?

thanks for the reply though. been lookin on that site for about a year for various valves for my (armchair) experiments.

karl f

You need a valve with input and output levers with a follow up linkage arrangement. Take a look at like a 4 or 560 with teledepth where all the external linkage is out in the open so you can see it. It would take some pretty sofisticated hydraulics to go along with that as you would need some way to unload the hydraulic circuit once you reached neutral unless you had a closed center system to start with. Look at all the mechanism that is used on say 06 series tractors to accomplish this position control.

The system is probably similar to the power steering system used on W-400-450-560-600-650 and 660.

A hydraulic cylinder with a long stroke is attached to the drag link. The cylinder has a hydraulic spool valve attached to its end near the connection to the drag link. When the steering wheel is moved, the valve ports open until until the cylinder catches up and restores equilibrium. At that point, the steering spindles cannot move until the operator rotates the steering wheel again.


650


660

Wardner, it looks like the drag link still has a mechanical connection, right?

karl f

The drag link has a ball on its end where it goes into cylinder. When the ball moves in responce to the steering wheel, it pushes the spool valve in either direction. When the cylinder housing moves, it tries to center the ball so that power is stopped. These cylinders are available as aftermarket items. Search on tractor power steering. Below is an example but there are others as well. I think they cost around $400-500.

If you went to a hydraulic house, they might have a similar servo system in different sizes and capacities.

pete- thanks for the comments. where could find a valve like a 560 teledepth valve other than a 560 era farmall with teledepth? usually oem valves are proprietary design so create some challenges if mounting on a completely different machine.
i've been inside the lift cover of a 656 and it seems more complicated than teledepth could be, yet it is much more reliable.

I'll have to stop at a salvage yard in the summer when i have free time and do some learnin if i see a 560.


karl f

The premise is really very simple:

When you move the quadrant lever to a position, it moves the "hole" part of the valve out from under a "cover," allowing oil to flow out the hole.

Some part of the hitch mechanism is connected to the cover part of the valve, so that when the hitch moves, the cover moves. Things are timed such that when the hitch gets to the desired position, the cover has moved back over the hole, stopping hydraulic flow.

We had a 560 with the tel-a-depth system for many years. Of course we never used the fast hitch for plowing or anything like that. It was an adjustable-height drawbar and it made a great bead breaker for tires. The tel-a-depth worked just fine.

Wardner, thanks for the pictures and commentary. Any research you put into it as well.
It would be nice to have the money to buy up all kinds of cylinders, valves, pumps, etc. and experiement, even if not practical, there's something to learn. i'm trying to picture a 3 point or implement lift based on the power steering cylinders--with levers, an axis, and cable/rods it could be done. could get complex, but who the heck eliminated electronics? (tongue in cheek).
Might work ok on a C farmall sized machine. I should look into the big 4x4s from the 70s-80s. maybe that's how they work?

karl f

mkirsch,
you must have serviced and maintained the tractor to keep it working properly

i agree the fast hitch is a handy drawbar. It can be more, but 3 point trumped it years ago.

too bad hydraulic parts are hard to make because of tolerances, although a crude demonstration device could be made to show the concept.

karl f