Sickle bar hedge trimmer - hydraulic flow seems problematic

[PaulL]

I have a new MX5200. In theory it has 30lpm flow, or a bit more.

I purchased a sickle bar hedge trimmer. It's a Chinese / cheap one, but from a local agent. So there's a level of support, but not brilliant.

It hasn't worked well from when I first assembled it. I initially thought it was just taking time to blow through air locks in the rams etc, but it's still not going well. I've been running pretty much at idle, and the agent suggested that I should run higher revs and push the flow through, blow out any airlocks. But I think that's a wrong diagnosis, and I'm suspicious that there's debris or some misconfiguration/something broken in the valve block that is leading to a blockage under higher flows.

With that summary, let me work through what's going on.

Firstly, how is it set up? I have a single rear remote on the tractor (a second one with detent on order, but not here yet). There's a feed and return that plug into those, and goes into a hydraulic block on the hedge trimmer. That has 4 valves - 3 that operate the rams, and one with a detent that is used to run the hydraulic motor on the head. The motor is a pretty simple rotary motor with an arm to convert that into reciprocating motion - so it doesn't seem to care which way the flow runs.

What I am experiencing is that I can get things working / limping along if I gradually crack the valves, and ease into things. But as soon as I ramp up the flow at all, or ramp up the revs at all, it seems to dead head. I can hear the pump labouring a bit, and the pipes all jump like they've suddenly got pressure on them.

It then won't go until I reverse the remote to relieve the pressure, and work all the valves on the block to relieve pressure on each of them. I can then creep the remote back open, and work the valves carefully.

It's a bit hard to work out exactly what's going on, but it looks to me like the return is blocking when I have higher flow. I'm imagining some sort of debris or a flap valve inside the hydraulic block that I can get a bit of flow past, but when I ramp up the flow it blocks the return. That then holds pressure until I reverse the flow (or turn the tractor off then work the valves). I'm assuming that my solution therefore is to take it all apart and disassemble the hydraulic block, look inside and clean it all out. That'll make a mess everywhere with oil and leakage etc.

Having said that, I'm no hydraulic expert, and so I'm interested in whether anyone has seen anything like this before and/or has anything to contribute. I figure I can ask the agent to give me a replacement hydraulic block, but I'd have to take all the hoses off to replace it anyway - once I have the hydraulic block off I may as well take it apart and look inside.

Attached a couple of videos of the behaviour, it's a bit hard to see - it mostly just looks like I'm incompetent, but if you listen carefully you can hear that actually it's briefly running a function, then the pump is under load even though nothing is moving.

Videos:

Trying to get the rams and the head to work

This one is mostly working, but still a few stalls, and it's only at idle

This is a close up of the controls and the hoses - you can see which ones are getting pressure. It's shorter than I thought it was, but since it's raining I'm not going out to get another video
https://youtube.com/shorts/rcOGmIbzjzo?feature=share This one it's basically working

 

[Russell King]

If you can show us the way the hydraulics are routed to the rear that might get better help.

@TheOldHokie may have some suggestions.

 

[McMXi]

@PaulL, can you connect the sickle bar hoses directly to the rear remotes and see if it'll run that way without stalling out? This would eliminate any problems with the hydraulic motor that drives the sickle bar head. Also, I assume that all the rams work fine.

The valve block is very much like the Summit Hydraulics multipliers I have on both tractors except you're operating the valves via levers and I have buttons on joysticks that control solenoids to open/close the valves. I imagine you have to hold the lever that operates the rear remote in the open position as you operate any of the levers on the sickle bar valve block.

I'm not sure what's up with the thing that looks like a valve on the inlet to the valve block. Is that a way to adjust pressure?

You're probably close on the 30 LPM since my MX6000 has 9 GPM oil flow.

 

[PaulL]

I spent time today disassembling the whole hydraulic block, and looking inside. Nothing much to learn inside there, it looked pretty much like I might expect (not that I know that much). No loose pieces.
When I reassembled it it all worked briefly, which was very exciting. Then it stopped again, basically the same behaviour.

No, the rams don't go reliably either - basically everything has the same problem, any significant flow and the whole thing stalls/locks up. That's why I figure it's something in the valve body itself and not any of the individual rams or motor - basically all the functions have the same behaviour.

I don't think I have the parts to connect the hoses directly to the hydraulic outlets. Although maybe the hydraulic connections on the input line would screw off and screw on those. Hmm. Let me try that.

I did notice that each of the "slices" in the block have a small valve thing with a spring on it, and those were a bit stickier than I might have expected. Is it possible one of them is sticking? Otherwise, I think I'm asking the place I got it from to send me another hydraulic block.

One thing I couldn't work out is how to get some of the hoses off, they don't seem to have swivels so they wind up. The hydraulic block has some sort of double fitting that looks like a swivel. I can loosen the outer nut right off till it's loose on the metal shaft, but the hose still doesn't seem to swivel. Replacing the hydraulic block without swivels on those hoses will be very hard.

Anyway, some photos and more video. The first picture has the removable bit inside the o-ring towards the top. I'm guessing this is a pretty standard layout - it's not some unique thing? The spring isn't shown in this photo, but each did have a spring and I did replace them.






And the longer video, that probably doesn't tell us much. But you can hear it stalling and the pump labouring - I basically creep the remote open, and at a certain point (flow related?) it stalls and doesn't release the pressure until I run the valve backwards. It's not shown in this video, but I can get the same behaviour on the rams, it's just harder because the rams don't have detents, so I need two hands to do that (and can't hold my phone at the same time).

Sickle Bar Hedge Trimmer - After Reassembly

Same behaviour as before really, perhaps a video that shows a bit more what's going on.

youtube.com

AI tells me that based on my description it's almost certainly sticking check valves, and that I just need to try harder on the hose swivels because they are there and they should work. It's suggesting that on cheap valves there are often manufacturing burrs or debris, and giving them a good clean and checking the seats could resolve it.

It pointed out that it's a new machine so I should just send it back - but that's about 3 days of shipping. Also, it's as much work to remove all the hoses and the block either way (whether I replace the block or repair the block) - once the block is off and the oil is all over everything, it's not that big a deal to then disassemble the block and see if I can resolve it. I'm leaving this location on Tuesday and not back for a month or more. Potentially this is a fix that has to happen next time I'm here.

There was some suggestion it might wear in if I just use it. Is that plausible? I have to use it low revs and slowly, but if it will slowly get better, that's something I could do.

 

[North Idaho Wolfman]

I'm suspecting that you need to run this unit off of a Power beyond circuit and not a remote circuit.

 

[PaulL]

I'm suspecting that you need to run this unit off of a Power beyond circuit and not a remote circuit.

The supplier thought it would run of a remote circuit, and it has bayonets on it, which to me implies it would run from an outlet, not plumbed in. A power beyond circuit would not normally have bayonets?

 

[PaulL]

OK, a bit further research. It works partially, so I wondered whether just using it would free it up over time.

Interestingly (having thought some more about it) it's pretty clear it's not the individual valves. With no valves on the block open, it should just be an open circuit. If I open the remote slowly then the fluid flows. But if I open the remote too quickly, or with too many revs, I can hear it dead head. Running the remote the other way, then back again, frees it up. So it seems to me that something is getting pressure behind it then locking instead of opening. But working it back and forth for a few minutes it seemed to get freer - less inclined to stick. But it still sticks with much more than 1200 revs, so a long way away from where it should be.

Am I right in thinking this is pointing pretty clearly at those check valves sticking?

Sickle bar hedge trimmer again. No valves open - just supply circuit

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

youtube.com

 

[North Idaho Wolfman]

The supplier thought it would run of a remote circuit, and it has bayonets on it, which to me implies it would run from an outlet, not plumbed in. A power beyond circuit would not normally have bayonets?

The other reason to see flow issues like this is from mismatched or faulty quick disconnects.

 

[Old Machinist]

I don't know how or if it compares to the ones they sell for the mini excavators but I adapted one of those to run off my third function and mounted it to my loader. I didn't incorporate any cylinders for positioning other than the loader's normal functions. My little machine is only rated at 5 GPM so it is below the recommended range on the cutter.

The hydraulic motor will bind easily. Mine had serious flaws in the actuator arm design. The flat bar that actually operated the cutters broke within a few minutes on mine. I had to weld it back and reinforce that. I also figured out which way to run the motor to put the least amount of stress on the actuator arm which was clockwise as you look at the front of the motor. The other thing I found was the bearings in the ends of the actuator arm would bind and destroy themselves if you tightened the nuts. It didn't have a spacer or crush sleeve in between those so if you tightened the nut it put pressure against the races. I packed new bearings and double nutted the fasteners to prevent adding preload on the bearings.

When I hit something too thick for it to cut it just jams. I have to reverse the flow and pull back on it to get it unstuck from the limb when it does that.

 

[PaulL]

The other reason to see flow issues like this is from mismatched or faulty quick disconnects.

Mismatched in what way? They seemed to plug in fine, and I think my MX has standard pioneer. Although the female fittings on the tractor don't have collars on them, you just pull to disconnect, which I haven't seen before. Are they perhaps some special valve type, and need a special male fitting?

The flail mower with hydraulic side shift came from the same place, looks to have the same fittings, and works fine. That makes me very suspicious it's the hydraulics on the hedge trimmer, not the tractor end or the connectors.

I do still have the option of connecting the motor hoses directly to the outlet (bypassing the hydraulic block). I just need to see if the screw fittings on those hoses have the same threads as the male pioneer fittings I have.

 

[TheOldHokie]

Mismatched in what way? They seemed to plug in fine, and I think my MX has standard pioneer. Although the female fittings on the tractor don't have collars on them, you just pull to disconnect, which I haven't seen before. Are they perhaps some special valve type, and need a special male fitting?

The flail mower with hydraulic side shift came from the same place, looks to have the same fittings, and works fine. That makes me very suspicious it's the hydraulics on the hedge trimmer, not the tractor end or the connectors.

I do still have the option of connecting the motor hoses directly to the outlet (bypassing the hydraulic block). I just need to see if the screw fittings on those hoses have the same threads as the male pioneer fittings I have.

1. Stop taking things you do not understand apart!! All that does is add more potential for breaking things that are working fine.
2. The remotes are probably not the best choice but should work fine as a supply. Your trimmer has its own open center control valve and can be plumbed just like a Kubota backhoe. You really do not need any valve in the tractor side.
3. Start doing some basic diagnostics on the supply plumbing. Sounds like you have an incomplete/deadheaded circuit. That is easy to test. If you want guidance on how to test just ask.

DAn

 

[McMXi]

The hydraulic motor will bind easily.

This is why I suggested running the hydraulic motor and cutting bar directly off the rear remote. If it won't run like that it's not going to run as it's currently configured. Would it be shocking if this Chinese implement and valve body is a poorly designed, poorly executed pile of junk ... nope.

You could even disconnect the linkage between the motor and cutting head to make sure you can run the motor without issue at max oil flow. Then if that works reconnect the linkage and retest. If you get through those tests without issue then you know it's related to the valve block. If not, there's either an issue with your rear remote or the hydraulic motor or the cutting head.

My experience with hydraulic pumps/motors on implements is limited to the Land Pride HD25 PHD that I run off the third function on both tractors, the chute rotation motor on the Land Pride snow blower, and two pumps on a pair of JD turnover plows. They all work perfectly running off rear remotes or third functions.

 

[McMXi]

Mismatched in what way? They seemed to plug in fine, and I think my MX has standard pioneer. Although the female fittings on the tractor don't have collars on them, you just pull to disconnect, which I haven't seen before. Are they perhaps some special valve type, and need a special male fitting?

I have the same fittings on my MX and there's nothing special about the male Ag fittings that interface with those. You can use poppet or ball type although the ball type are more restrictive when it comes to oil flow.

I like the couplers/fittings that came on the MX but despised the leak fest Faster versions that came on the M6060. I replaced the M6060 fittings with Ag couplers from Summit Hydraulics that don't make a complete mess of the back end of the tractor. I simply don't need the features that the Faster provided such as break-away since I no longer have a need to disconnect any of the three pairs. One pair feeds the Summit Hydraulics multiplier, one pair is for the hydraulic top link and the third pair is for the hydraulic side link.

 

[PoTreeBoy]

Mismatched in what way? They seemed to plug in fine, and I think my MX has standard pioneer. Although the female fittings on the tractor don't have collars on them, you just pull to disconnect, which I haven't seen before. Are they perhaps some special valve type, and need a special male fitting?

The flail mower with hydraulic side shift came from the same place, looks to have the same fittings, and works fine. That makes me very suspicious it's the hydraulics on the hedge trimmer, not the tractor end or the connectors.

I do still have the option of connecting the motor hoses directly to the outlet (bypassing the hydraulic block). I just need to see if the screw fittings on those hoses have the same threads as the male pioneer fittings I have.

We seem to have encountered several bad quick connects lately. Can you temporarily eliminate them? The odds of all load check valves being faulty is pretty slim.

 

[TheOldHokie]

We seem to have encountered several bad quick connects lately. Can you temporarily eliminate them? The odds of all load check valves being faulty is pretty slim.

Unfortunately I think there are way to many possibilities at this point. I would suggest something really basic, simple, and informative.

1. Disconnect the implement return line quick coupler
2. Remove the tip and stick the hose in the oil filler.
3. Start the tractor, fully open the remote, and observe flow coming out of the return hose.

There should be a strong steady flow of oil coming from the hose. Report the result of that test.

Dan

 

[Old Machinist]

Unfortunately I think there are way to many possibilities at this point. I would suggest something really basic, simple, and infirmative.

1. Disconnect the implement return line quick coupler
2. Remove the tip and stick the hose in the oil filler.
3. Start the tractor, fully open the remote, and observe flow coming out of the return hose.

There should be a strong steady flow of oil coming from the hose. Report the result of that test.

Dan

This should have been done from the beginning but with the return hose in a container. First thing I did with my china mower was to connect the supply and put the return in a bucket to flush it out. THAT oil went into the waste can.

 

[McMXi]

We seem to have encountered several bad quick connects lately.

Yes, as @North Idaho Wolfman alluded to above. I've never encountered a bad coupler (other than leaky Faster couplers) and I have a LOT of implements with hydraulics, not to mention the remotes and multipliers on both tractors. Then again, I don't buy shit, bottom of the barrel couplers from Amazon which no doubt are what these Chinese manufactures shove on the end of their implements.

Quality couplers are expensive, but if you want a a trouble-free owner/operator experience it's one way to improve the odds of that happening. The Land Pride STB1574 that I picked up for my friend with the L47 had flat faced couplers installed by the local dealer. They charged him their cost on the couplers with a minimal labor fee, but even still, the bill was well over $100. Is he going to have problems with his snow blade and tractor? I very much doubt it.

The false equivalence theory is alive and well it seems.

 

[PaulL]

OK, so I have two things to check:

1. See if I can connect just the motor hoses to the supply, and see if that goes. That checks the motor and the couplers (although I may have another set of couplers, which would remove that from the equation too). Since I get the stalling with no motor running / no rams running, and I get it on all the rams too, I don't think this is likely to be the issue

2. Remove the return coupler, and put the hose into the tank fill. See if I get steady flow. I would expect that when it stalls I'd get no flow, if I don't then that coupler was the issue. I can presumably also do this the other way round, since it also stalls when I run the remote backwards - so I can swap which I'm treating as supply and which as return, and put that other one in the tank as well.

I have a full day today, and have to pack. Start driving at 7am tomorrow morning and won't be back here for at least a month, probably a bit more. So thanks a lot for all the input and for explaining things in a way I can understand - I can see what people are getting at. I agree, the fittings do seem the most likely answer, and my dealer gave me spare fittings for exactly this reason, I expect them to be high quality. Swapping them in may be the first and easiest change.

 

[TheOldHokie]

OK, so I have two things to check:

1. See if I can connect just the motor hoses to the supply, and see if that goes. That checks the motor and the couplers (although I may have another set of couplers, which would remove that from the equation too). Since I get the stalling with no motor running / no rams running, and I get it on all the rams too, I don't think this is likely to be the issue

2. Remove the return coupler, and put the hose into the tank fill. See if I get steady flow. I would expect that when it stalls I'd get no flow, if I don't then that coupler was the issue. I can presumably also do this the other way round, since it also stalls when I run the remote backwards - so I can swap which I'm treating as supply and which as return, and put that other one in the tank as well.

I have a full day today, and have to pack. Start driving at 7am tomorrow morning and won't be back here for at least a month, probably a bit more. So thanks a lot for all the input and for explaining things in a way I can understand - I can see what people are getting at. I agree, the fittings do seem the most likely answer, and my dealer gave me spare fittings for exactly this reason, I expect them to be high quality. Swapping them in may be the first and easiest change.

Just do the return hose test as I described and tell us the result.. Its quick and will answer a lot of questions. Your assumptions about what the results mean are suspect.

Dan