To adjust or not to adjust.

[JC-jetro]

I think we are getting closer and narrowing it to a couple equally unlikely possibilities...If the diagrams aren't incorrect.. then when you unscrew the gauge reading -0- witht he lift up.. and under a test load.. nothing too big.., then a few oz of oil should shoot out the gauge port and the lift should drop.. if it dont drop... the books wrong... if it does drop.. gauge is bad...

soundguy

I guarantee ya when the lift is up and the gage screwed on , the 3 point will drop if I unscrew the gage or loosen it. I'll get to the bottom of it and will report. I have taken the cylinder head totally apart and there is no hidden check valve there. The hole with an oring that you see on the pic below on the right side is oil inlet to the lift. middle hole is rate if drop with the needle valve, and the one on the left side of it the check valves inlet to the piston. you can see day light thu the gage inlet on the right side to the safety relief plug on the left side. there ain't nothing more in between.

The hole on the lift cover matches the piston oil inlet in the pic below.

this is the only way to feed the piston and this is a two way passage way , flow toward the piston to raise, and bleeding oil back thru the same passage way to drop.

I'm officially bamboozled as of now


JC,

 

[Jerry/MT]

Soundguy,

It is indeed a puzzler as I have my gauge between piston and the spool valve. If I have a an implement up in the air without any doubt I have oil trapped between the piston and the spool valve, that's exactly what it hold the implement up. Please look at the diagram below with directional arrows, the only highly unlikely scenario is that I have my rate of drop knob completely in closed position, if then I lowered the implement, the pressure is relived to diffy without the lift dropping but I have not done that though. What I have not shared with you all is that is the second gage I got, the first one could not read anything at all and the second one was sent to me after I called Northern. can hardly see that I got two lemons in row, although have to admit "Murphy" and I go way back

This is at all not a concern but it is only my curiosity, I'll get to it when I get a chance and will report.

There is something missing in this diagram. As I pointed out previously, the only way for fluid to get out of the cylinder to drop the lift is if the flow control valve is open.
If the flow control valve is closed, the fluid is trapped by the #2 check valve per your diagram.
If that flow valve is always open, then the the pump must always supply holding pressure to the piston to maintain position and you would measure a constant pressure for a given load and position at your measuring point. This is not your stated case.

Most of the systems I am familar with have a feed back control on the control valve that dumps pressure when the desired position is reached and pressure is only applied if the cylinder leaks down and allows the position to change. Then the pressure is reapplied until the set position is again attained and then the pressure is released by the control valve. My Ford 4610, when holding a round bale on a three point spinner, will "hicup" ( The sytem will pressurize the cyinder as a result of the leakdown and regain position. It does this about once a minute.)as a result of some cylinder leakdown as the control tries to maintain position of the bale.

I'm not trying to be critical but this is an interesting puzzle and I'd like to understand it. Is there any spiking that you notice on gauge that might damage it? A 3000 psi gauge does not have much dynamic margin for pressure spikes when you are trying to meassure a pressure around 2300 psig. A 5000 psig gauge would be better for this use.

 

[Soundguy]

Most of the systems I am familar with have a feed back control on the control valve that dumps pressure when the desired position is reached and pressure is only applied if the cylinder leaks down and allows the position to change. Then the pressure is reapplied until the set position is again attained and then the pressure is released by the control valve. My Ford 4610, when holding a round bale on a three point spinner, will "hicup" ( The sytem will pressurize the cyinder as a result of the leakdown and regain position. It does this about once a minute.)as a result of some cylinder leakdown as the control tries to maintain position of the bale.

I'm not trying to be critical but this is an interesting puzzle and I'd like to understand it. Is there any spiking that you notice on gauge that might damage it? A 3000 psi gauge does not have much dynamic margin for pressure spikes when you are trying to meassure a pressure around 2300 psig. A 5000 psig gauge would be better for this use.

I agree.. the standard ford unloading valve works that way.. as the cyl leaks down to a pint that the valve is opened again by internal linkages.. then it re-pressurizes.. bobbing on a leaky lift on an old ford is classic leakdonw and circuit regenration.

At this point.. if JC says the lift drops and oil comes out the hole when the gauge comes out.. then the gauge has got to be bad.. I don't see many other possibilities if he has the parts in his hand and there are no check and he can see right thru from the gauge port to the flow control manual valve..?????

soundguy

 

[JC-jetro]

There is something missing in this diagram. As I pointed out previously, the only way for fluid to get out of the cylinder to drop the lift is if the flow control valve is open.
If the flow control valve is closed, the fluid is trapped by the #2 check valve per your diagram.
If that flow valve is always open, then the the pump must always supply holding pressure to the piston to maintain position and you would measure a constant pressure for a given load and position at your measuring point. This is not your stated case.

Most of the systems I am familar with have a feed back control on the control valve that dumps pressure when the desired position is reached and pressure is only applied if the cylinder leaks down and allows the position to change. Then the pressure is reapplied until the set position is again attained and then the pressure is released by the control valve. My Ford 4610, when holding a round bale on a three point spinner, will "hicup" ( The sytem will pressurize the cyinder as a result of the leakdown and regain position. It does this about once a minute.)as a result of some cylinder leakdown as the control tries to maintain position of the bale.

I'm not trying to be critical but this is an interesting puzzle and I'd like to understand it. Is there any spiking that you notice on gauge that might damage it? A 3000 psi gauge does not have much dynamic margin for pressure spikes when you are trying to meassure a pressure around 2300 psig. A 5000 psig gauge would be better for this use.

I sure opened up a can of worms jerry..

the only way for fluid to get out of the cylinder to drop the lift is if the flow control valve is open.
If the flow control valve is closed, the fluid is trapped by the #2 check valve per your diagram.

perfectly agree with the above statement.

If that flow valve is always open, then the the pump must always supply holding pressure to the piston to maintain position and you would measure a constant pressure for a given load and position at your measuring point. This is not your stated case.

perfectly agree with that too , only as you said it not my stated case. when I turn the tractor off and hyd flow the 3 point hitch will not drop.

Most of the systems I am familar with have a feed back control on the control valve that dumps pressure when the desired position is reached and pressure is only applied if the cylinder leaks down and allows the position to change. Then the pressure is reapplied until the set position is again attained and then the pressure is released by the control valve.


I think the answer might lie somewhere in the statement above. I'll refer to my manual later I faintly remember recommendation to remove the feed back arm before pop off pressure test. I'll check and report. I was like what the heck , if the relief valve is chattering and reliving that ought to be where the relief pressure setting is.

I'll report back. Thanks for all the quality responses. Again, this is all to quench our curiosity and have a little brain work out, it'll do us all good to give the old noggin some work out.

JC,

 

[JC-jetro]

Well I got to hit the sack guys , got a pretty busy day at work tomorrow. I'll be doing some deer hunting this weekend, If I get a chance I'll swing by and give it another dose of investigation.

Good night guys.

JC

 

[JC-jetro]

Howdy guys.. a bit of a update.

I tried to check/calibrate my pressure gauges few minutes ago against calibrated air pressure with the following result. I can make about 120 psi with my air compressor and maintain the same in a portable air bottle. I rigged up the right fittings and quick connect it to the compressor. I tried my original bad gauge, at 120 psi and I read zero.. no surprise there. I rigged up my second so called good one and dang thing still read zero. well I tapped it very gently to the wood table and voila it read around 120 psi give or take some. I picked the original lemon gauge and it read exactly the same as the second gauge. I can't explain why the Bordon tube in the gauges were sticking. Last year, I came across a defective acetylene torch to be trashed and picked up the oxygen gauge to fiddle with. I knew it was not designed for liq but used it anyway to check the lift, I know it showed 1500-1700 at the pop off but can not remember if I checked the pressure with implement hanging in the air and tractor off. Mind is a terrible thing to lose.

If I get a chance will give go/no go test per Soundguy and will report.

I should have beat the darn gauge with a stick to wake it up I suppose when I was testing it on the tractor.


JC,

Oxygen gauge:

 

[jinman]

JC, what a mess! If you find out it was only the gage reading wrong, you are gonna feel like using that gage for target practice. You've suffered way too much grief over this for it to be a faulty gage.

 

[JC-jetro]

JC, what a mess! If you find out it was only the gage reading wrong, you are gonna feel like using that gage for target practice. You've suffered way too much grief over this for it to be a faulty gage.

I could not agree more Jim, I'll get to the bottom of it hopefully later today. Suffering... is the story of my life. lol


JC,

 

[SPYDERLK]

Howdy guys.. a bit of a update.

I tried to check/calibrate my pressure gauges few minutes ago against calibrated air pressure with the following result. I can make about 120 psi with my air compressor and maintain the same in a portable air bottle. I rigged up the right fittings and quick connect it to the compressor. I tried my original bad gauge, at 120 psi and I read zero.. no surprise there. I rigged up my second so called good one and dang thing still read zero. well I tapped it very gently to the wood table and voila it read around 120 psi give or take some. I picked the original lemon gauge and it read exactly the same as the second gauge. I can't explain why the Bordon tube in the gauges were sticking.
If I get a chance will give go/no go test per Soundguy and will report.

I should have beat the darn gauge with a stick to wake it up I suppose when I was testing it on the tractor.

JC,

Thanks for for the good supporting info and continued inquiry on the puzzling hydraulic circuit that continues to supply force without indicating pressure. I am very interested in the hidden issue.
On the 3and5 kpsi gauges not indicating 120 w/o a coax... Im not too surprised. Down that low in the range its a pretty low signal force acting against static friction. A little tap randomizes the friction force. Sometimes [not in this case] gauges rest the indicator needle against a stop above zero - - usually apparent in the graduations.
larry

 

[JC-jetro]

howdy all, back from my fact finding mission and few good tid bits to share.

JC, what a mess! If you find out it was only the gage reading wrong, you are gonna feel like using that gage for target practice. You've suffered way too much grief over this for it to be a faulty gage

Well, Jim was right but as things in life are not always black and white. These are my finding before we put this dead horse to his final resting place.

1) performed go-no go test and as I suspected and Soundguy corroborated it the lift arms promptly dropped. The diagrams I posted and in the manual are perfectly good and represent the design. There was no additional check valve of any sort between the spool and the the piston inlet other than what shown. With lift arm position control attached the hyd popped off at around 1800-1900 psi. The manual says about 2000-2100 psi, engine hot and high rpm. My engine was not very warm and I tested it around 1500 rpm.

2)Position control feed back is absolute essential piece of information here. With it removed I achieved a bit higher than 1900 before it popped off.

3) with position control put back in , 300 lbs scoop up in the air and The gage read about 200-300 psi as was expected with engine running or off.

The gage measured the pressure caused by hanging implement against closed spool port. I increased weight on the scoop by standing on it and the static pressure went up which is perfectly logical.

What was interesting and also previously known was the key "neutral position" of the spool valve factor. Raising the implement few inches up and down made almost no fluctuation in the pressure reading , in other words the pressure was the function of the weigh being raised. Feed back arm very very quickly moved the spool to by pass. conversely, with the feed back arm removed as I lowered and raise the lift system the gage always showed around 1600-1700 psi without any by pass, unless I raised it so much where it started to pop off.

Problem solved OR "THERE NEVER WAS A PROBLEM". I did not fiddle with adjustment as I did not think it'll buy me anything at all specially WHEN it was not even needed.

Finally, my 3 point design is exactly the same with many of the NH TC model tractors. The casting may be a bit different but lift cover, cylinder, piston, piston head and it's associated rate of drop , check valve and etc are the same and well designed, much better than JD, or Kubota with the exception of Kubnota grand L's with external tandem lift cylinder. This thread should have some universal use for NH owners.


JC,

don't go away now!​

With all of that said after I put every thing back and the scoop in the air I
read zero pressure again. Why?? This one is a puzzler, can anyone tell me why... The reason is a valid one and noteworthy.


Any one wanting to take a crack at it.?


Hey Larry, You're welcome. I do enjoy trouble shooting and your points were well taken.