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Author Topic: Hydro Ax 411 hydraulic pump  (Read 1839 times)

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Offline dpgrand

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Hydro Ax 411 hydraulic pump
« on: January 19, 2019, 09:16:11 AM »
I have a 411 with a shear head that I bought a few years ago for cutting fire wood and, as others on this site have mentioned, it sure beats the chain saw.  Recently, it seems to me that it has struggled to cut larger trees  As a result, I would like to test the pump pressure to see if that is the issue.  So I have 3 questions:  1) what is the best way to test the pump pressure on this machine?  2)  Does any kind of repair manual exist for this machine?  3)  Where in Minnesota (or nearby) can I go for parts and/or advice on this machine?

Thanks, in advance, for any assistance!

Offline mike_belben

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Re: Hydro Ax 411 hydraulic pump
« Reply #1 on: January 19, 2019, 10:16:46 AM »
Start near the pump and find a pipe plug or SAE port to tap into.  Try to be upstream of the relief valve.  Adjust or shim the relief and recheck if you find a low pressure condition.  For the sake of troubleshooting, a second gauge downstream [like say temporarily tapped into the shear cylinder extension port with a tee swivel] will be very handy for determining if youve got a pressure drop in between.  With this info we can begin pinpointing the leakage.  Infared temp gun is very handy for this, a leak will be hotter than the rest of the system.  Fluid not doing work is dissipated as heat rise. 

Guages are cheaper than guessing at parts.  One little o-ring chunk or broken spring in a relief valve can cripple a machine and be repaired for free, quickly, with precise diagnosis.
Revelation 3:20

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #2 on: January 21, 2019, 03:25:01 PM »
Thanks for that advice.  One of the reasons I asked the question is that we checked pressures where hoses come off the pumps and got readings of 200-300, or about 10% of what we expected.  I am 99% sure we are getting more pressure than that given the machine seems to be quite cable of moving itself around and cutting down most trees.  We will look for another port closer to the cylnders and test that.

Offline kiko

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Re: Hydro Ax 411 hydraulic pump
« Reply #3 on: January 21, 2019, 05:06:36 PM »
I am familiar with the hydroax machines but mainly from the E series up and dealt with a few Bs.  Typically 2-300 pounds would not cut any tree.  Your drive system and hydraulics are separate except for a common tank.  I speculate you have a two pad gear box behind the engine.  The pump on top would be your hydrostatic drive pump. The pump on the bottom is a two section gear pump, one section runs the boom tilt and clamp arms and the other runs the shear cylinders. Sometimes both sections of the pump will be combined in shear function only, this will be done by combining two valve sections when  activating the shear function. That can be determined by following the shear cylinders hoses back to the control and seeing if they tee to two sections.  Are the controls for the shear functions pilot operated? If so and it is using two valves, the pilot hoses for the two valve sections will also be teed  together . Pressure needs to be measured at the end of cylinder travel while continuing to hold the function engaged.  Pressure measured while the cylinder is moving will not be accurate or useful.  It matters not where you check the pressure as related to at the pump or the lines near the cylinder.  The pressure will be the same any where in the circuit.  When you measured the 2-300 psi were you activating the shear function?.  When the hydraulics are in neutral the only pressure that should be anything other 0 would be the hydrostatic charge pressure which would be present in the entire loop in if the hydrostatic system, about 2-300 psi

Offline BargeMonkey

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Re: Hydro Ax 411 hydraulic pump
« Reply #4 on: January 21, 2019, 05:37:08 PM »
Dumb question. Have you checked the gap and bevel on your shear knives ? I'm assuming your shear function is on the floor ? Check linkage for proper throw ? 

Offline Grandpa

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Re: Hydro Ax 411 hydraulic pump
« Reply #5 on: January 21, 2019, 09:18:28 PM »
I seem to have a dim memory of a story about a pebble under the shear peddle creating a similar problem.

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #6 on: January 24, 2019, 10:03:20 AM »
Thanks for all the comments and suggestions.  We are making progress.  We measured the pressure at the valve body that is located between the loader arms in front of the cab.  When opening the shear the pressure maxed out at 3200#.  When closing the shear the pressure maxed out at 1400#.  According to the spec sheet I have I think both of those should read 2250#.  That suggests to me that one or two pressure relief valves need adjustment and/or repair, which leads to my next question.   We think we have identified 2 pressure relief valves on this valve body (see attached pic).  Assuming these are relief valves, the first question is which one does what?  The second question is ... is there another relief valve I should be looking for given the opening pressure and closing pressure are different?

Again, all your comments and suggestions are much appreciated!

The really good news for me ... the pump is producing adequate pressure so I don't need to spend $2500 on a new pump. 

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Offline mike_belben

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Re: Hydro Ax 411 hydraulic pump
« Reply #7 on: January 24, 2019, 11:08:09 AM »
Theres infinite ways to plumb a machine and only a good schematic and often being in the equipment's presence to correlate can really give you certainty of the design.  

The higher than anticipated pressure is interesting.  2250x2 = 4500.  

4500-1400 =3100.  Energy cannot be created or destroyed, only transferred right?   So you sorta seem to have one leaking over to the other.  I kinda wonder if the manufacturer used a hydraulic regeneration of some sort to open the shear faster.  I thought this was only on extend stroke but im not certain.  Regen is when you direct exhaust fluid from one end of the cylinder to the end you are filling in order to make it stroke faster.  This can be a physically complicated looking thing and ive never seen one in person.  A regen valve would look like any other relief or load check or cushion, id think. 

When you got the pressures, i assume the gauge read much lower until you maxed out the cylinder stroke? Is that correct?  For instance, a skidder blade may start to raise at 400psi, and only max pressure when the cylinder hits the stops.  Pressure is half the picture.  Its a measure of resistance to pump flow.  If something doesnt resist the pump, the pressure does not rise.  If you did not have flow against a load, you would not have a pressure rise [a density of fluid molecules acting against a gauge piston area and correlated to a number we humans can then use via the gauge sweep or LCD display] inside of the conduits and components to measure.  

So where im going is we definitely have a load and a pump flow to achieve 3200# so thats great.  Now when i think we are low on one side and high on the other, my brain says the fluid volume intended on the low side has made its way to the high side.  The next question is how.   A veteran troubleshooter can probably tell you pretty quick but im not he.  

In tandem to this issue that i attribute to unintentional leakage, is the overpressure.  Thats where youve got a relieve valve [think spill port really, they keep a circuit from getting pumped too full, by bleeding off excess at a preset pressure] that is either jammed up, shimmed up, somehow not being allowed to drain back to tank via crushed hose perhaps, or just plain ol cranked up too high by whoever wanted to run harder. 
Revelation 3:20

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #8 on: January 24, 2019, 11:59:33 AM »
Yes, the pressure started low but when the shear hit wide open the pressure reading maxed out at #3200.  Similarly, when closing the shear the pressure started low but when the shear was 100% closed the pressure reading maxed out at #1400.

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #9 on: January 24, 2019, 12:02:36 PM »
To address another question ... the gap and bevel on the shear knives are both good.  The knives are actually in excellent condition and we make sure they are sharp and beveled before we starting cutting.

Offline kiko

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Re: Hydro Ax 411 hydraulic pump
« Reply #10 on: January 24, 2019, 03:28:18 PM »
In the picture the adjustable valve on the left is the main relief, it is the working valve for open and close, likely there is nothing wrong with it and should need no adjustment.  The valve on the right in the picture is the port relief, that is where your problem lies, however there is another port relief on the opposite side of the valve section with the two hoses on it.  I can tell you which one is for the open and which one is for the closed. This can be determined by having someone close the the shear to determine which hose pressures up. Then the port relief on the same side of the hose will be the one you are dealing with.

Offline kiko

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Re: Hydro Ax 411 hydraulic pump
« Reply #11 on: January 24, 2019, 03:52:48 PM »
If you are not confident it is a bad port relief you can swap them front to back and see it the problem move to open.

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #12 on: January 24, 2019, 04:13:49 PM »
Thank you for those 2 VERY helpful comments.  We had thought of switching hoses, but didn't want to risk finding out where the weak link was when running pressure 50% greater than recommended.  However, we can certainly switch the hoses just to check and see if the pressures reverse themselves.  I think our next step will be to check the pressure relief valve on the right.  If simply screwing it in a bit doesn't increase the pressure, then we will have to dig a little deeper into it.

Given your comment on there being a couple other pressure relief valves, I took another picture and attached it as a pdf.  Are you suggesting there is an adjustable valve of sorts under the 2 big bolt heads in this pic?  If so, we might have to remove the entire valve body to get at the lower one which would screw out horizontally.

Lastly, given the pressure at the valve is 3200# and the specs suggest 2250#, would you suggest we try to decrease that pressure by screwing out the left pressure relief valve a bit?

Again, THANKS for your kind assistance.  I feel like I am getting close to understanding how this issue is going to get fixed.

PDF FORMAT NOT ALLOWED ON THE FORUM. IMAGES MUST BE IN JPG FORMAT AND BE UPLOADED TO YOUR GALLERY.

[attachment deleted by admin]

Offline kiko

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Re: Hydro Ax 411 hydraulic pump
« Reply #13 on: January 24, 2019, 06:34:23 PM »
That control valve in the picture should have three adjustable valves.  Two valves are visable in the first picture now gone.  The one on the left is called a main relief.   The main controls working pressure of the shear circuit, both open and closed. The relief that is on the right is called a port relief. It function as a saftey relief . So.. it will only leave seat if the main does not unseat at its  pressure , or the load builds back pressure exceeding the setting of the port relief.  There is one port relief for open and one for closed.  So your closed port relief is unseating below spec pressure.  The other port relief valve is on the back in the exact same spot as the port relief in picture on right.  Also since the port relief(s) psi setting is above the main relief setting,  just turning the port relief screw in will not show on a gauge . You have no idea what the unseat pressure is . So if the main was to fail and unseat it may take 5000 psi to unseat the port .  Something gonna blow. IMO Next step,  Swap the PORT RELIEFS  and see if the low pressure moved and let us know.  You might find a piece of debris or a blown orings in process. The relief valve will come out as a complete unit and are easily swapped. Disturbing hardened hoses is best not done esp those short hoses to bulkhead.  

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #14 on: January 26, 2019, 08:43:34 PM »
We pulled the valve out and rebuilt it.  We were able to set the port relief for opening the shear at 2200#, which is good news.  We weren't able to set the port relief for closing the shear any higher than 1400#, and that was with it virtually closed.  We then reversed the port reliefs and got 3000# on opening and 600# on closing.  Logic (not our experience) suggests we have a 1 way leak in a hydraulic cylinder, or there is another relief valve in the shear head.  Any suggestions on next steps?

Offline kiko

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Re: Hydro Ax 411 hydraulic pump
« Reply #15 on: January 26, 2019, 09:38:22 PM »
Please repost the pictures so we can tell exactly which valves you are turning. You can eliminate or confirm the cylinders by plugging the hoses to the the shear cylinders then checking the pressure.  Anything is possible I suppose  , but I have never seen cylinder piston packing fail and cause a one way bypass.  If the piston is loose from the the rod it may.  So you have not touched the main relief? Only the ports?

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #16 on: January 27, 2019, 10:15:57 AM »
I have attached a copy of the first pic I uploaded.  The relief on the right, which handles shear opening, and the relief opposite this on the back side (not in the the pic), which handles shear closing, were the two we adjusted and swapped.  We did not touch the left front relief.

Offline mike_belben

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Re: Hydro Ax 411 hydraulic pump
« Reply #17 on: January 27, 2019, 01:05:52 PM »
The only thing coming to mind is that poppet relief valves work on differential pressure across a barrier wall.  Normally you only read about the explosive effects of stacking them by accident where a pair of 2500 psi reliefs in series plumbed valve blocks without a power beyond kit ends up generating 5000 psi at the pump.  

This is a wierd one.  Is there any chance youve got some wacky hose routing error where one side of a relief is seeing suction from the pump?  Im not coming up with much else.  Cracked valve?
Revelation 3:20

Offline Skeans1

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Re: Hydro Ax 411 hydraulic pump
« Reply #18 on: January 27, 2019, 01:41:10 PM »
Ive had this issue before with a swing section in a buncher, switched reliefs, switched compensators, and secondarys ended up a small crack internally in the passages it wasnt much fun to find or figure out.

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #19 on: January 27, 2019, 02:55:24 PM »
I was thinking the same thing: an internal crack in the valve somewhere.  Thank you, both, for confirming my logic.  Given the age of this machine, it might take me some time to track down a replacement valve body.

Offline Skeans1

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Re: Hydro Ax 411 hydraulic pump
« Reply #20 on: January 27, 2019, 03:05:17 PM »
Find the valve tag it should have all the info you need to find a replacement section or complete valve.

Offline kiko

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Re: Hydro Ax 411 hydraulic pump
« Reply #21 on: January 27, 2019, 04:24:31 PM »
Cracked valve, that makes four of us.  Finding a salvage valve may not be to hard. Hydroax used that valve over many models, those with hot saw as well I believe.

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #22 on: January 29, 2019, 03:23:01 PM »
Not that I doubted any of you ... but we blocked off the hoses going to the shear cylinders and still only got 1400#.   I have found someone with a valve but, I suspect he will wait a few days for this cold snap to pass (minus 40-50 wind chills) before pulling it off the machine.

Offline mike_belben

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Re: Hydro Ax 411 hydraulic pump
« Reply #23 on: January 29, 2019, 03:40:42 PM »
Before you buy it, just verify that the pin in your valve spool isnt worn out and only travelling partial stroke.  An 1/8" groove will prevent a spool land from fully blocking the tank port and create a low pressure condition.

There is no question now that you have a pump capable of hitting your desired pressure and a valve that is providing a partial path back to tank.  The last thing is to find this path. If its not a crack its gonna be a worn spool, worn bore or stroke positioning issue
Revelation 3:20

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #24 on: January 31, 2019, 05:23:33 PM »
Thanks for that additional piece of advice.  We will double check that.

Also, I have a related question ... at the back of the shear head there is a block with lots of hydraulic hoses, AND what appears to be a valve of sorts.  What is that valve for?  Does that have something with the timing of the opening/closing of the grapple arms?  See attaced pdf pic.

Offline mike_belben

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Re: Hydro Ax 411 hydraulic pump
« Reply #25 on: January 31, 2019, 06:11:50 PM »
Realistically it could be anything but having a hand adjust handle suggests it may be a flow control.  If so cranking them in restricts flow, often in one direction only. A check ball unseats for full flow the other way.  It could be on the input or output side of a cylinder to control its travel rate. 

Kiko may know exactly what it is. Im only guessing.
Revelation 3:20

Offline kiko

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Re: Hydro Ax 411 hydraulic pump
« Reply #26 on: January 31, 2019, 06:53:16 PM »
I am not familiar with that particular valve, but I would suspect it is a flow control or a sequence valve.  When you headed of the cylinder hoses was it before or after that valve?  If the hoses were headed off after this valve, it might be wise to head it off between this valve and the one we were previously discussing.  

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #27 on: February 10, 2019, 09:45:01 AM »
Quick update:  I located a replacement valve and it is currently in route.

Offline dpgrand

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Re: Hydro Ax 411 hydraulic pump
« Reply #28 on: February 22, 2019, 10:42:43 PM »
FINAL REPORT.  We got it working, with 2250 psi on both shear opening and closing, but not without a second highly improbable twist to the tale.

So, we got the used valve unit I ordered.  We picked it apart, cleaned it, and replaced all 20 O rings, just like we had done to the original valve unit that wasn't working.  We installed it with no problems and tested the PSI.  We had 3000 PSI on one side and virtually zero on the other side.  These readings suggested we were going backwards and, as a result, we were VERY frustrated and decided to call it a day.  In fact, we called it a "2 whiskey" night.

The next day we called our local hydraulic shop to see if they knew anything about this valve unit, and they didn't.  Given everything else we had done, we decided the issue had to be in the relief valves, so we pulled them out of BOTH UNITS again to inspect them more carefully.  Note that each unit has 3 pressure relief valves, 2 high pressure reliefs that control PSI for opening and closing the shear and 1 low pressure relief that controls ______, and they look identical except for the big nut on the exterior side.  In that inspection process we noticed that in the "new" unit someone (before us) had replaced one of the high pressure reliefs with a low pressure relief.  So, we took one of the high pressure reliefs from the old unit and replaced the misplaced low pressure relief in the new unit and ... IT WORKED AS INTENDED.

Again, MANY MANY thanks to kiko and all the rest of you who chimed in to help us solve this problem.  Next week we plan to cut wood ... in 30" of snow ... and I am looking forward to working with 50% more power on the shear head.


Offline old-iron-habit

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Re: Hydro Ax 411 hydraulic pump
« Reply #29 on: March 13, 2019, 10:09:40 PM »
We pulled the valve out and rebuilt it.  We were able to set the port relief for opening the shear at 2200#, which is good news.  We weren't able to set the port relief for closing the shear any higher than 1400#, and that was with it virtually closed.  We then reversed the port reliefs and got 3000# on opening and 600# on closing.  Logic (not our experience) suggests we have a 1 way leak in a hydraulic cylinder, or there is another relief valve in the shear head.  Any suggestions on next steps?
They are a double seal on the internal ram in the cylinders. A one way leak is not unheard of. A easy check is to hold it at pressure the way the pressure is lower. Put it on a tree it can not cut to have the cylinder bypass in mid stroke. Within 45 seconds or so the leaking cylinder will get warm where the oil is bypassing the center ram seal. It will not only ID if that's the problem but also show you which one is leaking.


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