Hydraulic Motor

YotaOnRocks

YotaOnRocks

Well-Known Member
Joined
Jul 17, 2007
Location
Madison
Anybody here have experience with hydraulic motors or know someone? My brush cutter from Carolina Attachments has been problematic ever since I picked it up. It is now out of warranty and up to me to fix it and they have no desire to help me in the least bit. I took the motor off and tore it apart and found what I thought was significant damage but would like for someone with some knowledge to confirm before I spend the coin and time to source a replacement. Motor in question is a Dynamic BMK6-200-CC-FE-SF5, it is a roller gerotor design.
 
YotaOnRocks said:
Anybody here have experience with hydraulic motors or know someone? My brush cutter from Carolina Attachments has been problematic ever since I picked it up. It is now out of warranty and up to me to fix it and they have no desire to help me in the least bit. I took the motor off and tore it apart and found what I thought was significant damage but would like for someone with some knowledge to confirm before I spend the coin and time to source a replacement. Motor in question is a Dynamic BMK6-200-CC-FE-SF5, it is a roller gerotor design.
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They are pretty simple if you can diagnose where the problem is. But usually when there is a problem, it sends pieces of the problem all around the rest of the motor and hydraulic system, so its an even bigger problem. Post up some pics and I/we may be able to help.
 
jeepinmatt said:
They are pretty simple if you can diagnose where the problem is. But usually when there is a problem, it sends pieces of the problem all around the rest of the motor and hydraulic system, so its an even bigger problem. Post up some pics and I/we may be able to help.
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I'll get it torn back down in the next few days and post some pics. Thanks
 
Heavy Equipment Repair in King is where I'd take it if you want someone to look at it, they specialize in hydraulics. My uncle works at Jack's 2 days a week, and the way he talks of the mechanics I wouldn't trust them to work on anything (as in he delivered a lawnmower that they didn't tighten the blades on and the blades fell off on the trailer).
 
Tried to use the tip of the screwdriver to point to areas of concern. Every place the rollers ride have some spots but the first pic is the worst.
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I also can't turn the output shaft by hand, but it may have so much bearing preload that it is normal idk
 
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Looks like they are not sharing part numbers so you may have to contact a local distributor for part numbers. At a minimum, you'll need parts 13-19, and also maybe housing #12. You might can get away without replacing shaft #14 also if the splines still look nearly perfect.
 
I think I might bite the bullet and just buy a char lynn motor instead of another crappy chinese one with no parts support. I can't get anybody to call me back about trying to buy an entire replacement motor much less some parts for it. Anybody recommend an Eaton hydraulics dealer? I really hate spending another 2k on this cutter but it's kind of a paperweight the way it sits.
 
YotaOnRocks said:
buy a char lynn motor instead of another crappy chinese one
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excellent idea, but do flush and replace filters...yes the filter circuit should catch most of it but anything remotely simple would get some clean fluid at minimum pumped and dumped...........





doors wide open fellas!
 
WARRIORWELDING said:
excellent idea, but do flush and replace filters...yes the filter circuit should catch most of it but anything remotely simple would get some clean fluid at minimum pumped and dumped...........





doors wide open fellas!
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Do you think filters and fluid are really necessary? It's about $600 dollars to but them and they have less than 100 hrs on them
 
YotaOnRocks said:
I think I might bite the bullet and just buy a char lynn motor instead of another crappy chinese one with no parts support. I can't get anybody to call me back about trying to buy an entire replacement motor much less some parts for it. Anybody recommend an Eaton hydraulics dealer? I really hate spending another 2k on this cutter but it's kind of a paperweight the way it sits.
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I'd figure out an adapter and get one of these, haha (no idea if rpm is right)
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jeepinmatt said:
I'd figure out an adapter and get one of these, haha (no idea if rpm is right)
View attachment 382963
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Well to be honest I'm hesitant to put more money in it not knowing what caused the failure. According to the motor specs I am pushing about 2gpm more than it can take, but I told the people at Carolina Attachments my machine specs and they said I would be fine, so are they idiots or am I for trusting them. I feel like even after putting a new motor in it I'm going to be constantly worried about when it will fail next.
 
That original motor had no more than 10hrs on it and I would guess that number is really closer to 4 hrs of actual run time.
 
YotaOnRocks said:
Well to be honest I'm hesitant to put more money in it not knowing what caused the failure. According to the motor specs I am pushing about 2gpm more than it can take, but I told the people at Carolina Attachments my machine specs and they said I would be fine, so are they idiots or am I for trusting them. I feel like even after putting a new motor in it I'm going to be constantly worried about when it will fail next.
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What's the flow on your machine? That motor is rated for 40gpm continuous which is pretty darn high.
Screenshot_20221017_201340.jpg
 
Sorry my machine is rated at 40gpm on high flow, I thought it was 41.
 
YotaOnRocks said:
Do you think filters and fluid are really necessary? It's about $600 dollars to but them and they have less than 100 hrs on them
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Itty bitty pieces caused the failure, heat, or just crappy parts. Or all of the above. Now your back to itty bitty pieces.
To many of those has made valves and systems cause chaos in my maintenance history.

Some piece of something in a basic spool valve is enough to chase problems for days on equipment I used to maintain.

But then again it was company money vs, downtime.

Given the low hours I'd change it and make darn sure the fluid is correct. Something went wrong. Did it ever sound or feel starved? Cavitation from just fluid pulverization can damage pumps. It is in the pump (fluid) but either not leaving or supplied fast enough. Or a return circuit doesn't flow enough to reduce heat in a static operation depending on the flow pattern.
Lots of variables.
 
WARRIORWELDING said:
Itty bitty pieces caused the failure, heat, or just crappy parts. Or all of the above. Now your back to itty bitty pieces.
To many of those has made valves and systems cause chaos in my maintenance history.

Some piece of something in a basic spool valve is enough to chase problems for days on equipment I used to maintain.

But then again it was company money vs, downtime.

Given the low hours I'd change it and make darn sure the fluid is correct. Something went wrong. Did it ever sound or feel starved? Cavitation from just fluid pulverization can damage pumps. It is in the pump (fluid) but either not leaving or supplied fast enough. Or a return circuit doesn't flow enough to reduce heat in a static operation depending on the flow pattern.
Lots of variables.
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I ran it for probably 2 hours mowing grass before I realized it was making noise. I had the front door shut and the radio cranked up, when I stopped to take a break I heard it as the cutter was winding down and started to investigate.

The cutter spit an oring out of a drain plug on the side of the motor and it logged in the check valve, there is a check valve in the hoses between the pressure and return line at the cutter motor, I believe I ran it for that 2hrs with the check valve stuck partially open. I'm guessing that allowed for turbulence in the hydraulic fluid?
 
YotaOnRocks said:
I ran it for probably 2 hours mowing grass before I realized it was making noise. I had the front door shut and the radio cranked up, when I stopped to take a break I heard it as the cutter was winding down and started to investigate.

The cutter spit an oring out of a drain plug on the side of the motor and it logged in the check valve, there is a check valve in the hoses between the pressure and return line at the cutter motor, I believe I ran it for that 2hrs with the check valve stuck partially open. I'm guessing that allowed for turbulence in the hydraulic fluid?
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In a low load, high flow situation the bypassing fluid may have caused starvation.....think about it. The check valve being plumbed to dump into the return line is only when the motor sees extreme load spikes. Cutting grass it was basically in an open no load condition of sorts. dumping any fluid for a amount of time short circuited the pump. This in turn caused less fluid for heat control, and or its on lubrication.
Lots of pumps are built and operated with a minimum flow just to keep the fluid in its state of (ERR MADE UP TERM maybe "FLUIDITY") . To little in a high speed high density design pulverizes what is available into tiny spherical BB's of (hard) fluid. Think erosion by the fluid BB's. This type of wear is usually different and at locations different from your damage. Yours looks like the start of heat related galling just before it got real real ugly.

Whine in full hydro front steer is often attributed to aeration. In a fully bled system that never introduces air after bleeding or never sucks the system dry cavitation of the nature I described is often the culprit. Too small a suction line, to long of one vs. diameter, or just poor routing will cause it. Fluid dynamics can get funked out when the balance isn't met.
 
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YotaOnRocks said:
Well to be honest I'm hesitant to put more money in it not knowing what caused the failure. According to the motor specs I am pushing about 2gpm more than it can take, but I told the people at Carolina Attachments my machine specs and they said I would be fine, so are they idiots or am I for trusting them. I feel like even after putting a new motor in it I'm going to be constantly worried about when it will fail next.
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Have you put a flow meter on your pump to verify that? Your pump is probably a little less and loosing it through the case due to wear. However, if your concerned about to much flow you can put an inline flow divider and dump excess to tank. Also, stay away from White motors, they are junk.
 
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