Twindraulic loader hydraulic issue

[Bmor]

I've been working on attaching an old Twindraulic FEL to my '71 cub. I used the TM tractor bypass block and installed new hoses all around. The valves are Gresen Minneapolis (300 & 400). I put a Lenz filter from Tractor Supply between the valve out and the bypass block bottom port to catch any contaminants that might be remaining in the loader. Upon starting the cub, the touch control lever moved forward of its own accord and the Lenz filter split at the top seam, spewing out discolored Hydraulic fluid. I guess I deadheaded the system in spite of my best efforts not to; or perhaps something else is going on... Does anyone have any ideas? Thanks!

[Crimson Tim]

Has the loader been sitting not mounted? Could mud daubers or something have introduced a blockage into the hoses prior to assembly?

[Bmor]

It was sitting when purchased. I bought all new hoses and just installed them, but who knows what wat left in the pistons, valves and auxiliary tank. That was why I added the filter to the return line- but it ruptured when the tractor started.

[Crimson Tim]

What pressure is the filter rated for?

Is this the filter?
https://www.tractorsupply.com/tsc/produ ... _vc=-10005

That’s rated for 200 psi. Somebody who will know better will surely be along shortly to confirm/deny this, but I think the entire loader circuit is high pressure, including the return. So potentially up to 1200-1300 psi, minus whatever the loader itself is demanding at the moment. Anybody? Am I right on this?

I need to figure all this out, too. I have a Wagner loader that’s been sitting that i am slowly refurbing.

I’m not sure why the touch control lever moved, unless it was simply from the sudden loss of pressure in the touch control block.

[Rick Prentice]

I put a Lenz filter from Tractor Supply between the valve out and the bypass block bottom port

You have to remember that the touch control acts as a control valve also and a filter between the two control valves cant handle that pressure when the T/C is activated. Tim is correct.

Rick

[Bmor]

Got it. Perhaps you can help me understand why the touch control lever moved forward on it's own? And thanks to both of you for the helpful replies!

[Bmor]

The lever was moving forward and then the filter burst...

[Eugene]

The valves are Gresen Minneapolis (300 & 400).

Which hydraulic control valves do you have?

My reading, the Gresen 300 operates differently than the 400.

Suggest drawing out the current hydraulics schematics on paper. Then double checking the hydraulic fluid flow in each hydraulic control position.

[Jim Becker]

I believe a Gresen 300 is a valve for a one-way cylinder and the 400 is for a two-way. So there is nothing unusual about one of each being paired up on a loader. As Rick pointed out, the line out from the loader valves to the bottom of the bypass block carries pressure to the Touch-Control block. So when the Touch-Control is in motion, the line could carry up to the maximum regulated pressure of the system. When at idle, the line will have about 75 psi (with proper hydraulic oil. Improper oil could cause variations.)

What were the positions of the Touch-Control lever and the Touch-Control rockshaft before the engine was started. When the engine started, did the Touch-Control rockshaft also start to move? Did it rotate fully to it's limit of motion (forward I assume) before the filter exploded?

Normally, the rockshaft moves in response to movement of the control lever. Moving the lever moves the control valve and the rockshaft makes a corresponding move to return the valve to neutral. If the friction pad of the control lever doesn't have enough grip to hold the lever in place, the lever will move and the valve stays where it was. The lever and rockshaft both move until the lever hits the adjustable stop. If the rockshaft is still able to move at that point, the valve will then be moved to the neutral position and everything stops moving with the input pressure dropping back to the at-rest 75 psi. If on the other hand, the rockshaft does not have range of motion to move the valve, everything stops moving (deadheaded) and the relief valve opens (or in this case, the filter explodes).

All this suggests you need to:
1) eliminate the filter from that position,
2) increase the friction on the control lever, and
3) adjust the stops on the control lever to keep it from deadheading.

[BigBill]

I put filters on the suction hose on hydraulics on the wood splitters I build. Have you changed the hydraulic oil in the tranny?

[Bmor]

The Gresen 300 is to the lift one-way cylinders and the 400 is to the 2-way bucket cylinders. I got rid of the filter and put an inline pressure gauge in its place. I fired it up and everything mostly works. Sure as shootin', the pressure jumps to 1100 psi when the rockshaft is engaged by the touch control! The rockshaft is fine now and the loader cylinders work, but the one-way lift cylinders won't retract with out extra urging. There's still air in the system, so I'm moving the cylinders back and forth and topping off the tanks periodically as the air is purged. The pump is still howling quite a a bit from the air. I'm going to continue the process tomorrow outside in the light and fresh air.
I hope the non-retracting lift cylinder issue is just air trapped somewhere and not a valve or cylinder malfunction.. Has anyone had a similar problem?

[Bmor]

I tested it one last time tonight and discovered that the cylinders retract when the tractor is off, but stay put (unless urged) when the tractor is running. My guess is that the valve is the likely culprit- any thoughts?

[Jim Becker]

I assume the 300 valve only has 3 lines connected to it, correct? There is one hose between it and:
- the Touch-Control or bypass block,
- the model 400 valve,
- the one-way cylinder.
If this is correct, when the one-way valve is positioned for lowering, all three lines are connected together allowing the oil in the cylinder line to join the inflow and drain through the outflow. If the outflow dumps to the reservoir, the cylinder will retract from the weight of the loader.

However, in this configuration the outflow from the one-way valve either either becomes inflow to the two-way valve or the main Touch-Control system (depending on how the two valves are positioned). In this case retracting of the one-way cylinder has to overcome whatever back pressure the downstream valves put on the one-way valve output line.

As previously stated and seen on your pressure gauge, that line has 75 psi at rest (engine running) and can go considerably higher at times. If the one-way cylinder doesn't have enough weight on it, it won't retract when expected. In fact, if the Touch-Control valve is actuated at the same time, the loder can actually go up while you are trying to lower it.

Dumping the outflow from the loader valves directly into the reservoir effectively avoided the problem but disabled the Touch-Control rockshaft. The proper fix is to use something called a "power beyond" valve rather than the simple one-way valve. Most people didn't worry about this and everyone just lived with the poor manners of the loader.

[Matt Kirsch]

Hmm, in the short time I had a twindraulic loader on my Cub I never had a problem with it lowering.

Do you have the IN and OUT connected backwards perhaps? Strange things will happen when you try to run the pressure backwards through the valves. They work but exhibit odd behavior that makes you wonder if they are possessed.

[Bmor]

You are correct, the bypass block connects to the Gresen 300 one-way valve & the one-way is then connected to the 400 two-way way valve, then back to the bypass block. But shouldn't both valves be open center so as not to create more backpressure when at rest?

To answer Maat Kirsch, luckily I was able to read the faint "out" on the valve casting of the 2-way valve.