M936 hydraulic filter question

[KN6KXR]

OK well had some more time today to play. Got stuff done found stuff out. Here's what I found:
1) After settling overnight I pulled about 3 gallons of oil out of the tank into a bucket. It's a caramel color so there's stuff in it. No water though. I let that settle in the bucket for a few hours before pouring it back in. Leftover in the bucket was fine sediment like charcoal just a tiny bit. I'll need to figure out a rehab for the tank or PM schedule to keep the oil super clean. I'm thinking a pump to a filter and back in the fill. For now it's OK.
2) I then adapted my hydraulic pressure gauge to the valve block as instructed in the TM. The plug is 1/8" so I used a 1/8" to 1/4" adapter. At a later time I think I'm going to install an elbow, shutoff and quick disconnect with plug. Just like my tractor so I can make sure it's correct without taking the whole thing apart. Some oil came out but if you are ready for it a blue towel got it up so not a lot. Truck likes to be oily anyways. So @gstirling nothing too crazy here.
3) Found the TM for this is more or less completely wrong. One I'm referring to is the one I posted above. Fact is there is no pressure to set a relief unless a valve is actuated and the system is two-blocked to lift the relief and adjust. The TM says 1250 rpm and this is OK because the pressure is OK there but the speed isn't. Especially with no load. I tried different rpm and settled at 1700 because that's design. I then found the current setting about 2100-2200 psi. To do this I used the boom all the way up (try to keep going it lifts the relief) and the boom retracted (keep retracting it lifts the relief) and both. I played with the range and there's no way 1350 psi is going to work. Not even close. So I recall Wes saying something about 2200psi unless you replace hoses. I noted my hoses are labeled 2400 psi. So I set it at 2200. The relief tops out about there you can go higher but it takes more turns you know your at the limits. Maybe Wes @simp5782 will chime in about this.
4) I then left my gauge on there and tried my test object. My test object is my MQ DCA25 generator and it weighs about 2800 pounds. During this test I tried low (1300) and high (1900) rpm ranges. When throttling up I noted the transmission shift (I assume from the kick down) and it was about 1700rpm so @Jaydog996 you're onto something there. It was the same story as before: lift, extend, boom all good rotate NFG. The rotation left direction, when it does, runs the gauge up to 1500 then breaks free and jerks. Going right if you're gentle you'll just flat out go to 2200 psi and ride the relief with no motion. If you jerk it then it'll break free (at 1900 rpm but not at 1500) but once again it jerky and not controllable.
5) I then checked it all out at 1900 rpm unladen again and it works great. Pressure gets up to maybe 500psi rotating but turns smooth and controllable.

So with that I'm looking to the rotator table hydraulic motor, gear alignment, some type of binding under load? Seems like a big job. I think the pump, filter, fluid, relief, valve block, hoist (only 500 psi to lift 3k pounds) all check out. You have any thoughts or pointers please post them up. I'm kinda bummer I have a crane that can lift but not rotate a load......

 

[simp5782]

2200 psi unless you replace your hoses to 3200 etc.

Yours may be rated at 2400 but that was 10+ yrs since they were replaced. Unless you want a hydraulic bath and rustproofing the whole wrecker

 

[KN6KXR]

2200 psi unless you replace your hoses to 3200 etc.

Yours may be rated at 2400 but that was 10+ yrs since they were replaced. Unless you want a hydraulic bath and rustproofing the whole wrecker

Haha thanks Wes. Actually I've been tempted to just get a hudson sprayer with WD-40 and just slather the thing......

So the charcoal color to the hydraulic fluid and the viscosity seemed a bit thick. You think it's possible those kids at RSMS stuck 10-40 in there years ago? Previous owner never used it (for real). I came along and added 20+ gallons of ISO 32 (10wt) but it's still too thick and shows up on the rotator? I'm considering sending a sample in to a lab before I buy 2 drums would be a lot cheaper to know first. Ever hear of that happening? Trying to come up with ideas easier than pulling the thing apart.

 

[simp5782]

Haha thanks Wes. Actually I've been tempted to just get a hudson sprayer with WD-40 and just slather the thing......

So the charcoal color to the hydraulic fluid and the viscosity seemed a bit thick. You think it's possible those kids at RSMS stuck 10-40 in there years ago? Previous owner never used it (for real). I came along and added 20+ gallons of ISO 32 (10wt) but it's still too thick and shows up on the rotator? I'm considering sending a sample in to a lab before I buy 2 drums would be a lot cheaper to know first. Ever hear of that happening? Trying to come up with ideas easier than pulling the thing apart.

I use 10w from Rural king in everything I have. Simply cause it was $200 for 55gal drum. I bought like 6 barrels before before sleepy took office.

 

[KN6KXR]

I use 10w from Rural king in everything I have. Simply cause it was $200 for 55gal drum. I bought like 6 barrels before before sleepy took office.

Yeah well those days are gone. I called around locally, got on the web, looked around quite a bit. I think I'm loking at just under $500 a drum. So that's a grand to change it. Kinda hoping that's what it is and not at the same time.... project is taking big bites. Blackstone is sending me some sample bottles. An oil analysis is $30 seems like money well spent. I'll circle back and post up when I have results.

 

[simp5782]

Yeah well those days are gone. I called around locally, got on the web, looked around quite a bit. I think I'm loking at just under $500 a drum. So that's a grand to change it. Kinda hoping that's what it is and not at the same time.... project is taking big bites. Blackstone is sending me some sample bottles. An oil analysis is $30 seems like money well spent. I'll circle back and post up when I have results.

The hydraulic oil should be fine. The more you run it the more the moisture works it's way out.

Sinopec hydraulic oil is $435 a drum delivered to your door.

I have a place about 2hrs from
me in Sikeston, Missouri that has it for $308 a barrel still.

There is a machine that you can rent to separate water from oil etc but they are far between.

Just run it for a few hours.

You can pump it out using a Milwaukee transfer pump or drill pump thru a smaller micron filter setup. My winches are 5 micron filtered.

You shouldn't need ro replace it though. I've got some that is 10yrs old in some equipment

 

[KN6KXR]

Well my UOA came back and the fluid is just fine. Actually the viscocity is a bit lighter than ISO 32 recommeneded after I put in a 5 gallon pail of AW 46 I had so I'm a bit suprised by that. Certainly the elimination of the fluid being a problem was worth the $30 for the analysis. No water in it at all.

So I'm still having the rotation with a load issue. All else works great but if you pick up a 3k pound load and go to swing it just runs up on the relief. If it does move it's jerky as hell. I lubed the heck out of the turntable with the one zerk provided. Rotated it in maybe 30 degree increments, gave it shots, repeat all the way around. I need to test it again. Probably lube it again as well. I either have a rotator motor issue or a rotator bearing issue. Also totally possible the bearing is full of ten year old congealed grease and stuck. I had some winch rollers on the vehicle that took a bunch of grease along with a big pipe wrench to get rolling again.

Has anybody had the rotator bearing apart? The TM's don't show how it's built. If I were to guess I would say it's a simple beveled thrust type bearing without pads or rollers. Super simple design. Also can't find anything indicating there's a clearance adjustment, gear backlash or other setup. Anybody know this please post it up I'm curious and want to get it working properly!

 

[Mullaney]

Well my UOA came back and the fluid is just fine. Actually the viscocity is a bit lighter than ISO 32 recommeneded after I put in a 5 gallon pail of AW 46 I had so I'm a bit suprised by that. Certainly the elimination of the fluid being a problem was worth the $30 for the analysis. No water in it at all.

So I'm still having the rotation with a load issue. All else works great but if you pick up a 3k pound load and go to swing it just runs up on the relief. If it does move it's jerky as hell. I lubed the heck out of the turntable with the one zerk provided. Rotated it in maybe 30 degree increments, gave it shots, repeat all the way around. I need to test it again. Probably lube it again as well. I either have a rotator motor issue or a rotator bearing issue. Also totally possible the bearing is full of ten year old congealed grease and stuck. I had some winch rollers on the vehicle that took a bunch of grease along with a big pipe wrench to get rolling again.

Has anybody had the rotator bearing apart? The TM's don't show how it's built. If I were to guess I would say it's a simple beveled thrust type bearing without pads or rollers. Super simple design. Also can't find anything indicating there's a clearance adjustment, gear backlash or other setup. Anybody know this please post it up I'm curious and want to get it working properly!View attachment 860153

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Most of us know nothing about it and how the rotation motor works on the M936. Might even be all of us for all I really know. The TM's show nothing but the shape of the motor and all the tech info is that you refer the problem to the next level of maintenance. Apparently those folks and their books if they have any are not something they share

I am just GUESSING but I can't help but wonder if there is a problem with the brake on (inside) the rotator motor. Let me explain: When you pick up something heavy, it needs to STOP right now when you release the hand operated valve that moves the crane. If the crane is lifting something from "off to the side" the brake holds the boom still - rather than simply rotating the boom to "over the top" of whatever you are trying to lift. Trying to lift against any side load on the boom is BAD mojo and should be avoided by the way.

But, you lift something heavy and start rotating it... You stop moving where you want to set it down... The brake - where ever it is - needs to apply itself and hold that load in place. An incorrectly adjusted check valve might be a possibility. It might also be that there are three lines on that motor. Two of them might be a inch or so in diameter and possibly a third that engages or releases the built-in brake.

AGAIN, just a guess but that does happen on certain other non-military cranes. If we are spit balling, that could explain the jerky motion. Brake on, Brake off and both happening quickly. Possibility is that one of the rotation motor hoses has collapsed inside its wire braid (and the outside might look just fine). Another possibility is fluid pressure. How much do you have and where are you measuring and what engine RPM?

All are a guess. Hoping to hear more...

 

[KN6KXR]

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Most of us know nothing about it and how the rotation motor works on the M936. Might even be all of us for all I really know. The TM's show nothing but the shape of the motor and all the tech info is that you refer the problem to the next level of maintenance. Apparently those folks and their books if they have any are not something they share

I am just GUESSING but I can't help but wonder if there is a problem with the brake on (inside) the rotator motor. Let me explain: When you pick up something heavy, it needs to STOP right now when you release the hand operated valve that moves the crane. If the crane is lifting something from "off to the side" the brake holds the boom still - rather than simply rotating the boom to "over the top" of whatever you are trying to lift. Trying to lift against any side load on the boom is BAD mojo and should be avoided by the way.

But, you lift something heavy and start rotating it... You stop moving where you want to set it down... The brake - where ever it is - needs to apply itself and hold that load in place. An incorrectly adjusted check valve might be a possibility. It might also be that there are three lines on that motor. Two of them might be a inch or so in diameter and possibly a third that engages or releases the built-in brake.

AGAIN, just a guess but that does happen on certain other non-military cranes. If we are spit balling, that could explain the jerky motion. Brake on, Brake off and both happening quickly. Possibility is that one of the rotation motor hoses has collapsed inside its wire braid (and the outside might look just fine). Another possibility is fluid pressure. How much do you have and where are you measuring and what engine RPM?

All are a guess. Hoping to hear more...

I see what you're saying. I've worked on ship steerage systems and deck crane systems that have such brakes. Also electrical and hydraulic elevator motors where brakes are essential. This system has a mechanical brake with adjustment for the hoist (I haven't looked inside but it has no pilot actuator and must be released/engaged by a torque mechanism within) but it has no such obvious device for the rotation. I know from tuning the valve block pressure relief to 2200psi that the valve system is a "dead end" when valves are in nuetral. I assume that this is the lock for the boom/extend/rotate and on the hoist they saw fit to add a mechanical brake as well to prevent creep of the load. Why not for the other functions I'm not sure.

The behavior is that unloaded it's quite smooth. Only when you load the boom does the rotation run up on the relief and get jerky. You have to run the rpm's up around 1700 on this model because about 1600 you can actually hear the drive shift in to top gear. Not so with the manual transmission you can just stick it in 5th. With the Allison you have to get it to kick up all the way so 1700rpm is the deal. Anyways I think if it were a brake issue it would drag loaded and unloaded to at least some extent. On my list of things to do I'll add popping the inspection cover on the worm reduction drive and see what's going on in there. If there is a brake it'll be there. No other place it could be.....

I did look up the bearing for the rotator table and although I can't find a PDF or DWG of the bearing the; manufacturer specializes in roller bearings of this type. This one specs something like 56 ball bearings. So it isn't a simple thrust or plate. With the loaded/unloaded behavior it makes sense that if the balls were congealed in 10 year old (or older) grease or had somehow been exposed to corrosion it would hit hard points and stop. I'm going to do a few things here I think and the first is to run the piss out of it. The second is to see if I can get an access point to those bearings and take a look. Or lube them better for that matter. The last check I can think of would be to jack the boom up and check the play. Though there isn't a spec to be had it's possible the bearing manufacturer can provide one. That would tell me if the job is just a matter of "play with lube" or a total nightmare.

More to follow.....

 

[Mullaney]

I see what you're saying. I've worked on ship steerage systems and deck crane systems that have such brakes. Also electrical and hydraulic elevator motors where brakes are essential. This system has a mechanical brake with adjustment for the hoist (I haven't looked inside but it has no pilot actuator and must be released/engaged by a torque mechanism within) but it has no such obvious device for the rotation. I know from tuning the valve block pressure relief to 2200psi that the valve system is a "dead end" when valves are in nuetral. I assume that this is the lock for the boom/extend/rotate and on the hoist they saw fit to add a mechanical brake as well to prevent creep of the load. Why not for the other functions I'm not sure.

The behavior is that unloaded it's quite smooth. Only when you load the boom does the rotation run up on the relief and get jerky. You have to run the rpm's up around 1700 on this model because about 1600 you can actually hear the drive shift in to top gear. Not so with the manual transmission you can just stick it in 5th. With the Allison you have to get it to kick up all the way so 1700rpm is the deal. Anyways I think if it were a brake issue it would drag loaded and unloaded to at least some extent. On my list of things to do I'll add popping the inspection cover on the worm reduction drive and see what's going on in there. If there is a brake it'll be there. No other place it could be.....

I did look up the bearing for the rotator table and although I can't find a PDF or DWG of the bearing the; manufacturer specializes in roller bearings of this type. This one specs something like 56 ball bearings. So it isn't a simple thrust or plate. With the loaded/unloaded behavior it makes sense that if the balls were congealed in 10 year old (or older) grease or had somehow been exposed to corrosion it would hit hard points and stop. I'm going to do a few things here I think and the first is to run the piss out of it. The second is to see if I can get an access point to those bearings and take a look. Or lube them better for that matter. The last check I can think of would be to jack the boom up and check the play. Though there isn't a spec to be had it's possible the bearing manufacturer can provide one. That would tell me if the job is just a matter of "play with lube" or a total nightmare.

More to follow.....

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So I hate not to be able to contribute more, but I will definitely be interested to see what happens.

@Csm Davis may have more information about the rotation motor.
Past experience and lots of wreckers at his place

 

[charlesmann]

@KN6KXR i think you may be on to something with the bearings being bad/corroded or congealed grease, but i would think even congealed grease, would be able to pushed through. when you are picking up a load and trying to rotate it, where are you picking the load from, directly off the back, 90* off the sides and/or in-between 90 and directly off the back? i could see directly off the back, +/- 10* from stowed, that those bearings could be corroded to the point that with the rotator acting as the fulcrum and the load applied, it putting a lot of weight on those bearings and if stuck/corroded in place, they would cause a crabbing issue similar to what you describe.

When we inspect out flight control rod end bearings, if there is any ratcheting, we try and lube first, purging old grease and debris out, and if its still ratcheting, we replace the rod ends. I have opened some up and found flattened bearings, crushed/ground up bearings and just worn out form sand and junk getting inside the lip seal bc after lubing, folks don't floss the purged grease, and grease attacks dirt and dirt works its way past the seal and into the bearings.

 

[KN6KXR]

@KN6KXR i think you may be on to something with the bearings being bad/corroded or congealed grease, but i would think even congealed grease, would be able to pushed through. when you are picking up a load and trying to rotate it, where are you picking the load from, directly off the back, 90* off the sides and/or in-between 90 and directly off the back? i could see directly off the back, +/- 10* from stowed, that those bearings could be corroded to the point that with the rotator acting as the fulcrum and the load applied, it putting a lot of weight on those bearings and if stuck/corroded in place, they would cause a crabbing issue similar to what you describe.

When we inspect out flight control rod end bearings, if there is any ratcheting, we try and lube first, purging old grease and debris out, and if its still ratcheting, we replace the rod ends. I have opened some up and found flattened bearings, crushed/ground up bearings and just worn out form sand and junk getting inside the lip seal bc after lubing, folks don't floss the purged grease, and grease attacks dirt and dirt works its way past the seal and into the bearings.

I'm testing the load from about straight aft to 90 right (as viewed from the gondola). Haven't tried other directions. The load is just under 3k#. According to a mechanic I ran into they tested full extension 5k# 360 so that's my goal. I'm going to reach out to this fellow that told me that: he spent 40 years in the Army (18 enlisted) and ran a motor pool (managed 25 mechanics in the sandbox) with these in it. Super knowledgeable met him when I took the wrecker to a car show.

I hear what you're saying. The bearing could be brinelled. That would suck. Yeah most likely in the stowed position. My property has a bit of a slope and when you spin you can feel it load on the uphill a little, swing over and settle downhill but it's pretty damn smooth until you pick up a load. I had some issues unloaded before I started exercising it (right when I picked it up) but I was still figuring out that I needed 1700rpm and was 20 gallons low on fluid. So My hope is that those issues weren't linked and just the exercise will work it out. I think I'm going to try smaller loads (I have some logs and such I can strap and swing) and turn with those then work my way up. The rest of the system works great as I went to hoist on a stump the other day almost straight aft and got the front tires a foot off the ground. So seems the pump and all is pretty healthy!

I'm going to chase down the manufacturer of the slew bearing (either Kaydon or Rotek) and see if I can get some advice on how to look in there. If it's possible. My experience with brinelled bearings is you can really see the pattern of the dimples. Also maybe I can get a max play tolerance because that would be pretty easy to measure and calculate. Will post up what I find.

 

[Mullaney]

I'm testing the load from about straight aft to 90 right (as viewed from the gondola). Haven't tried other directions. The load is just under 3k#. According to a mechanic I ran into they tested full extension 5k# 360 so that's my goal. I'm going to reach out to this fellow that told me that: he spent 40 years in the Army (18 enlisted) and ran a motor pool (managed 25 mechanics in the sandbox) with these in it. Super knowledgeable met him when I took the wrecker to a car show.

I hear what you're saying. The bearing could be brinelled. That would suck. Yeah most likely in the stowed position. My property has a bit of a slope and when you spin you can feel it load on the uphill a little, swing over and settle downhill but it's pretty damn smooth until you pick up a load. I had some issues unloaded before I started exercising it (right when I picked it up) but I was still figuring out that I needed 1700rpm and was 20 gallons low on fluid. So My hope is that those issues weren't linked and just the exercise will work it out. I think I'm going to try smaller loads (I have some logs and such I can strap and swing) and turn with those then work my way up. The rest of the system works great as I went to hoist on a stump the other day almost straight aft and got the front tires a foot off the ground. So seems the pump and all is pretty healthy!

I'm going to chase down the manufacturer of the slew bearing (either Kaydon or Rotek) and see if I can get some advice on how to look in there. If it's possible. My experience with brinelled bearings is you can really see the pattern of the dimples. Also maybe I can get a max play tolerance because that would be pretty easy to measure and calculate. Will post up what I find.

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I think somewhere you stated that the 1500 /1800 RPM engine speed was something you were told? If not, that is a requirement. Running at idle speed for example will end up "smoking" your Allison transmission. Might be that it is written down in the TM, but I have seen that number in writing many times.

The only difference in the hydraulics themselves would be how quickly fluid will move - and because of that speed is increased. Same amount of "power" but slower... Figure you already know that part but it was worth saying for future readers of this post.

 

[KN6KXR]

Yes. The Allison needs to be in 5th. You can hear it shift when you get past about 1600rpm. That's where the 1700 number comes from. It's easy to miss and it'll actually work at 1500 pretty well but be sluggish as you said. It's been pointed out here a number of times. When you are new to the machine you can miss it there is quite abit going on. As you work it you get more tuned in.

 

[KN6KXR]

Found the problem with the rotation.

 

[charlesmann]

Found the problem with the rotation.

Is that the swing motor or gearbox?
I would venture to say that has some to with the swing issue, but its odd that without a load, it operates fairly normal but under a load, it doesnt. May be more stuff chewed up.

 

[KN6KXR]

Is that the swing motor or gearbox?
I would venture to say that has some to with the swing issue, but its odd that without a load, it operates fairly normal but under a load, it doesnt. May be more stuff chewed up.

It's the swing gearbox. Swing motor also has issues I disconnected it with the lines attached and ran it: rattles one way smooth the other. So it's off to a local shop for a rebuild. I'm pretty sure this is the issue of the loaded/unloaded. For all I know it sounded and behaved like crap unloaded as well because I've never had experience on one of these in good shape. It just showed up as a non movement issue when you got it over a couple thousand pounds. For sure I'm the first one to try and use it as designed. Previous owner got it from DRMO and parked it in a hangar for 5+ years. I'm sure he exercised it for demonstration but that's it. Had 2090 miles at purchase from him; he got it after reset from RSMS.

I have a friend I met at a local car show who spent 40 years in the Army as a mechanic in the motor pools. 18 years enlisted. Managed 25 mechanics in the sandbox. I ran this by him he thinks the RSMS contractor is at fault. He noted that by 2012, when this unit was reset, that they were fully aware the vehicles were going to DRMO. So they just checked the boxes and shoved it out the door. I'm finding a LOT of other items that fit this scenario. Just wasn't proof tested. Not much care given.

Amazing drama getting it out of there. Have to remove the suction line from the tank. Had to drain the system. Very tight spot with large fittings under the crane. Everything painted shut, stuck, big chunks of rust painted over. I like working on stuff so in the grand scheme of things it's OK. Getting past my disappointment of the unexpected money it's going to cost me in parts at the end I'm going to be glad knowing it'll be done the right way when I'm through. Fully mission capable.

 

[KN6KXR]

Side note from department of "that's kinda weird": the gear description from the NSN is it's made from "copper alloy overall". Huh. Screams sacrificial gear to me. The helical gear is steel 8620H. That's a case hardened 80 ksi material. My worm gear may be OK (I'll have to inspect). So whomever made this made the spur gear the failure mode. KInda interesting.....

Side note the bearings are qty 3 SKF 309 and qty one SKF 5212. Ebay looks pretty promising might only be a couple hundred in bearings.