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Protecting Hydraulic Motors

20711 Views 42 Replies 11 Participants Last post by  Rockdog, 
ING6018
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There has been some discussion lately about hydraulically motor driven attachments. Over time, repairing/replacing these motors is becoming more difficult. For example, I have an HRM48H 3 point finish mower. It is an early unit (J.S. Barnes motor - no case drain). The motor recently had an oil leak and I found out my motor is obsolete and NLA. Parts are NLA. Later motors are available (I would need to add case drain), however, they are also obsolete, expensive, and parts are NLA. A local hydraulics shop replaced o-ring seals and used a liquid gasket material in place of the OEM carrier seal (everything works OK as of today). But, all this has me thinking about motor longevity and future options for repairs/upgrades.
So, here is the question. Is it possible to increase longevity by adding a check valve in parallel with the motor to reduce some of the stresses (especially a sudden shutdown)?

The following diagrams illustrate the concept.

Diagram 1 shows the combinations for hydraulic oil flow through the PTO.


Diagram 2 shows flow through a unidirectional motor (3pt Finish Mower, Hydravac, Hydracutter, Chipper/Shredder).


In this application, reverse should never be used (the PTO Handle Stop Bracket is installed to prevent reverse flow). To the best of my knowledge, an OEM unidirectional motor has a check valve to prevent reverse flow (please provide reference info if this is incorrect).

To minimize stresses on the motor, it is recommended that operators reduce engine RPM when starting, or stopping the motor. Because of the inertia of the high rotating mass, suddenly shutting off the mower under high RPM (Forward to Neutral) puts a lot of stress on the motor. The mower blades continue to spin, which, in effect, turns the motor into a pump. However, the A/B ports are hydraulically locked. This means the motor must have some internal mechanism or case drain to allow fluid to move and dissipate pressure without blowing seals.

Which brings me back to the original question. Would a one-way check valve installed across the motor ports help protect the motor?

Figure 3 shows the check valve.


Forward
This valve has no "soft start" affect on the motor (I'm still working on that) so, for now, the best options is to reduce engine RPM before engaging the deck.

Neutral
However, look at the second example. When the operator moves from Forward to Neutral, ports A/B are hydraulically locked. With the check valve, the motor could continue to rotate and pump oil in a closed loop (blue arrows). This would allow the motor to wind down slowly and minimize pressure issues.

Reverse
Also, if the lever were inadvertently put in Reverse, The valve would allow the hydraulic oil to circulate back to the tank.

I realize that if I have overlooked some fundemental law of physics, the outcome might not be pretty.

Thoughts?
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ing3018
I have the hydraulic motor disassembled from my recently acquired chipper because the shaft seal is leaking. Whether the P.O. of this unit shut it down suddenly or if it was used without the case drain line hooked up, I'm not sure. While examining the motor, I was thinking that if the supply and return lines were tied together in front of the motor through a valve, that that could provide a way to safely shut the motor down at speed. It might also give a soft start ability, too. This wouldn't help in an emergency situation, of course.

I think your check valve concept has merit, but I've no real experience to base that on.

I am wondering if the case drain is up to the task of accepting the full flow of oil at full operating speed without excessive pressure on the seal? My tractor is an early 3018PS. According to the hydraulic diagrams, the case drain appears to be plumbed into the return line of the power steering. Later models appear to have the case drain line plumbed into the return line after the oil filter, just in front of the oil tank. I've not actually checked my tractor to see how my drain is hooked up, having just looked at the diagram just this morning. I've seen older posts alluding to the case drain return line connection point as being critical, but I never gave the matter much thought until now.

Paul
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ing3018
I visited a local hydraulics shop yesterday to ask about sourcing a shaft seal for my chipper's motor. He had had other Case and Ingersoll owners stop by in the past and knew at a glance what my motor was when he saw it. His advice was to purchase a different motor (non-Ingersoll), due to the high cost of the shaft seal replacements and to add a check valve.

He showed me a hydraulically powered fan assembly they had fabricated for a customer. There was a check valve installed in parallel with the hydraulic motor's in and out ports, just as your diagram shows. He explained that the motor was operated by automatic controls and that due to the inertia of the spinning fan blade, the check valve gave the fluid a harmless flow path when the control closed.

I'm going to pursue this with my chipper.
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H
What that shop is suggesting you do EXTERNALLY is what Ingersoll's motor supplier did INTERNALLY to make things simple. But this motor design used by Ingersoll is not common, which equates to low production, which equates to high cost for replacement motors.

If your hydraulics shop has a "different motor" in mind, then we would like to know. The displacement must be correct as must the shaft diameter and length. I'd also want to know if the front bearing is a roller type or just the motor housing. I am not disagreeing with that counterman's advice in any way but advice must be usable if it is going to be practical. If the gentleman cannot provide you with a suitable brand and model number of replacement motor, then his advice cannot be acted upon.
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ing3018
On the chipper, the motor is connected to the cutter assembly with a lovejoy coupler. The shredder hammer mill head and chipper head shaft are supported by their own bearings. My OEM motor only has a sleeve bearing on the output shaft, both inner and outer.

I agree that I've got some more homework to do to gather information to help me decide which way to go with this. The chipper does not need to be an attachement that gets used while in motion, thus an extra hose and check valve on the exterior of the motor will not hamper the usefullness of the unit.
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ing3018 said:
On the chipper, the motor is connected to the cutter assembly with a lovejoy coupler. The shredder hammer mill head and chipper head shaft are supported by their own bearings. My OEM motor only has a sleeve bearing on the output shaft, both inner and outer.

I agree that I've got some more homework to do to gather information to help me decide which way to go with this. The chipper does not need to be an attachement that gets used while in motion, thus an extra hose and check valve on the exterior of the motor will not hamper the usefullness of the unit.
Click to expand...
I don't think that extra plumbing and a check valve will hamper the operation of the Vac either. IMO... they should have designed the Vac the same way the chipper was. Take the radial load off of the motor shaft and it will last longer.
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ING6018
One of purposes for starting this thread was was to begin consolidating information related to the OEM hydraulic motors and possible alternatives.

I had purchased an o-ring kit for my HRM48H 3 point finish mower due to a minor oil leak. Over the past couple years, the leak worsened and I contacted Brian to see what other parts might be available. Brian told me the motor is obsolete and no longer supported. Seal kits are no longer available. He located a motor kit ($758), but it is also considered obsolete. Finding seals and parts in the future will be iffy.

A local hydraulics shop got my unit running. But, finding seals and replacements in the future means searching around for NOS, buying used, or finding alternatives.

I started researching on MTF and the yahoo case group looking for solutions/alternatives. I also expanded the search to include other hydraulic decks, Chipper Shredder, Hydracutters, and hydraulic snowblowers. I am trying to create a cross reference between motors to see which would cross or substitute to other motors. So far, progress is slow and the information seems fragmented.

I'd be interested to know if anyone else had been down this road and found non OEM motors.
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Boss448
I'd like to give this a bump to keep it in front of C / I owners. I agree that because the hydraulic pumps and motors are the hearts of our tractors and implements that any useful information about repairs and substitutions will be helpful to many of us at some point.

JN
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ING6018
A few months after I started this topic, a related thread came up over on the yahoo case GT forum:
http://groups.yahoo.com/group/casegarde ... age/103813

A member had acquired a All Hydraulic (AH) mower deck and the motor had an unusual fitting. After a lot of discussion it turns out the motor was equipped with a check valve. Dealers Brian Hildreth and Bob Myers are aware of the devices, and mentioned some motor replacement kits included the valves. So, this looks like a viable option to help extend the life of these motors.

The only potential negative to this option I can think of is safety related. Without the check valve, the attachment motor stops quickly (especially important in an emergency). With the check valve, the motor would free-wheel and wind down more slowly.

No details were identified in the yahoo thread as to specifics (like opening pressure, etc.). Any additional info Brian or Bob have would be appreciated.
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R
What you are looking at doing will work. It is nothing new really but I dont think a regular check valve is what is normally used. Take a look at HydraForce's web site. I'm sure you'll find what you need there - or give them a call. I think if you go with something that shuts off when a certain amount of pressure is reached it will give you soft start.
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1031d
Something else not to overlook is filtration. Dirt+hydraulics=boat anchor!
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InTroubleAlltheTime
:goodpost: I am reading this thread with interest and slowly getting an understanding of the issue at hand. I took a look at the parts manual and you can see where the check valve is built in:

http://www.manuals.casecoltingersoll.co ... marked.pdf

I would be interested in the specifications of the hydraulic motor for one or both of the finish mowers as part of the discussion. Displacement, shaft, RPM and mounting, etc. Could anyone be so kind as to post this information?

:222: :446: Best Regards, Rich
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ing3018
InTroubleAlltheTime said:
:.........

I would be interested in the specifications of the hydraulic motor for one or both of the finish mowers as part of the discussion. Displacement, shaft, RPM and mounting, etc. Could anyone be so kind as to post this information?

:222: :446: Best Regards, Rich
Click to expand...
You can make some inferences from reviewing the part numbers for the various motors. Here's what I learned about the chipper motor. You may decide for yourself by reviewing the part manuals if this answers your question.

Paul
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ING6018
InTroubleAlltheTime said:
:goodpost: I am reading this thread with interest and slowly getting an understanding of the issue at hand. I took a look at the parts manual and you can see where the check valve is built in:

http://www.manuals.casecoltingersoll.co ... marked.pdf
Click to expand...
A key distinction here is that the unidirectional motors already include protection from incorrect flow:
1) A PTO Handle Stop Bracket that is added to the PTO to keep the lever from being moved to "reverse"
2) A check valve on the motor to block oil flow in the reverse direction.

This part of the system works well. Incorrect hookup or putting the PTO in "reverse" results in that familiar "squeal" as the check valve on the motor blocks flow to protect the motor and the PTO relief valve kicks in. Although the text describes the valve, I did not include the built-in check valve in the diagram (I will add it for clarity).

The purpose for this thread is to introduce the possibility of adding additional protection to these expensive motors, especially those with high rotating mass (mowers, vacs, chippers, brush cutter). When the PTO is shut off, the ports are blocked and the motor is dead-headed. However, the rotating mass keeps spinning down, and the motor continues to rotate, essentially turning the motor into a pump. The additional check valve is designed to allow the oil to circulate in a low pressure loop as the motor winds down.
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ING6018
ing3018 said:
InTroubleAlltheTime said:
:.........

I would be interested in the specifications of the hydraulic motor for one or both of the finish mowers as part of the discussion. Displacement, shaft, RPM and mounting, etc. Could anyone be so kind as to post this information?

:222: :446: Best Regards, Rich
Click to expand...
You can make some inferences from reviewing the part numbers for the various motors. Here's what I learned about the chipper motor. You may decide for yourself by reviewing the part manuals if this answers your question.

Paul
Click to expand...
Over time I have been reading through posts and archives at the various sites trying to get as much information as possible about attachments with hydraulic motors. Unfortunately, when it comes to finding detailed information, the sources are scattered and information fragmented.

As Paul mentioned, if you compare the various parts diagrams, it is possible to draw inferences. For example, when looking at the various parts lists, you find that the same motor was used on multiple attachments. In some cases, a specific motor was used on both regular and All Hydraulic (AH) attachments. At first this seems odd, since we know GPM is higher in AH tractors. Turns out, in the case of 3-point finish mowers, different sized drive pulleys were used to adjust for the difference in flow rate and motor RPM. The HRM48H uses a 7" drive pulley, the AHRM4H (All Hydraulic version) uses a 6.4" drive pulley.

These motors are not sold separately, and the parts list shows part numbers for replacement "Kits" (C46213 for HRM48H and C46214 for AHRM4H). Haven't confirmed this but I suspect the kits include the same motor and appropriate sized pulley for the application (and possibly the additional check valve-although no has come forward to provide additional information about the factory setup).

When I get enough additional information about the hydraulic motors I will start a thread to roll up all the relevant data into one spot.
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T
there is a special kind of valve used to keep lift-gates and similar apps from going down too fast. it is a spring-loaded ball check with an adjustable bypass feature. in one direction the valve does just about nothing, the incomming pressure pushes the ball off the seat against the spring and flow is unimpeaded. in the other direction incomming flow and the spring both act to push the ball up against the seat and prevent flow. the bypass in the last one i had consists of a set screw, which ever so slightly prevents the ball from becomming seated, thus allowing a small flow of bypass.

with a hammer-mill type chipper shreader there is a tendancy for accidental sudden stops caused by something too big to chew getting into the grind-chamber. this is where your real extream overpreassure condition happens. normal turning on an off of the hydraulics doesn't come close the the pressure caused by the sudden hitting of something hard, not to mention mechanical stresses and loading caused by same. while the blue loop in the diagram will certainly deal with trapped oil from inertial run-on while the control valve is being activated, it may be a somewhat different story when it comes to the sudden overpressure condition i describe. for that, you need a device called an accumulator. this is essentially a pipe with one end sealed and what is essentially an air filled balloon inside. it can be installed on the branch of a tee fitting on the supply line. as a pressure surge occurs, the air in the chamber compresses, preventing the pressure from rising too high for a very brief period of time.

the combination of the bypassed check valve in the same possition as in your diagram and a small accumulator, should get you what you are after both in terms of protection as well as a soft start/stop feature! all of these pipes valves and fittings together should fit in your hand.
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ING6018
Rockdog said:
What you are looking at doing will work. It is nothing new really but I dont think a regular check valve is what is normally used. Take a look at HydraForce's web site. I'm sure you'll find what you need there - or give them a call.
Click to expand...
I am hoping an inexpensive ($10.00) in-line check valve plumbed in parallel with the motor ports will work for the soft stop function. So far, I haven't run across any information that indicates it wouldn't work, but I am still looking for specifics from guys with more experience in hydraulics.

Rockdog said:
I think if you go with something that shuts off when a certain amount of pressure is reached it will give you soft start.
Click to expand...

Soft start seems to be a more challenging issue. It looks like solutions require cartridges, which means subplates and manifolds. Again, hoping for a low cost option. If it is necessary to adapt each hydraulic motor driven attachment, the price can run up fast.

At this point, I am looking for a solution that would be plumbed directly into the PTO circuit (so it would protect any attachments with hydraulic motors).
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R
I believe you can purchase exactly what you are looking for through hydraforce. Take a good look through their website and then look for what you need on ebay. But be careful cause a lot of pricing for hyd valves and whatnot on ebay is no less than what you can get direct (except with direct you pay less due to shipping).

If I get a chance I'll take a look myself. I cant recall the name of the valve you need.

A simple in-line check valve will not provide soft start. You need a piloted one as previously mentioned so that it stays open until a certain pressure is reached and then it closes. What you want costs less than you'd expect.
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R
I think you want a dual counterbalance valve or cross-relief (dual possibly) valve. I believe these are under 50 bucks or so.

I believe the 'holding valves' these use is a counterbalance valve (or possibly a piloted check valve). The going rater for the valves and tubes is 200 bucks.
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ING6018
Rockdog said:
A simple in-line check valve will not provide soft start. You need a piloted one as previously mentioned so that it stays open until a certain pressure is reached and then it closes. What you want costs less than you'd expect.
Click to expand...
Due to my lack of experience in this field, I am treating the soft-start, soft-stop as two separate issues. The in-line check valve appears to be a low cost option for soft-stop, and I have been looking at separate options for soft-start. I did find a patent application for a soft-start (which includes a split flow and pilot operated valve). I was concerned this device (multiple cartridges, on a custom subplate) would be too expensive for our application.
Ideally, a simple and inexpensive solution exists that handles both, but I haven't stumbled across it yet.
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