Bobcat T300 HACK. Sauer Danfoss S90 Pump as drive motors. Help! Failure, Loop Flush

[LoadTest]

I want to replace the LSHT drive motors on my 2006 t300 with 75cc EDC S90 pumps coupled to some torque hubs. The t300s are hard on drive motors, have about half the drawbar pull of the competition to begin with, and are slow. Sauer Danfoss said the pumps could be used as motors if I pulled out the charge pumps. But its up to me to ensure I take into consideration the following:

1) As far as the charge pump size, that involves a bunch of factors. First, did the motors you are replacing have loop flushing? How do you plan to flush the loops to control heat in your circuit? The amount of loop flush will affect the size of charge pump required.

2) Consider the system protection type that is in the pump used as a motor. If you have pressure limiters they could cause the pump to stroke or destroke depending on the operating condition and pressures. You need to make sure you understand how that will work in all machine modes.

3) You need to make sure you understand the potential failure modes.


The OEM drive pumps are 55cc s90's that will stay for now until upgrade them to same 75cc s90's i'm wanting to use as drive motors, probably with a hybrid powerplant.

#2&#3 doesn't seem like a big deal. If my figuring is correct I'll have about 3 times the original tractive force before the limiters kick in to protect the pump.... If that would even happen on the 75cc drive side and not 55cc pump side first. And the use as drive motors is going to be much more intermittent then the OEM 55cc pumps driving them, so if the 55cc's are keeping themselves cool from the factory, the 75cc's probably aren't generating much more heat then the oem drive motors they are replacing. The only issue I can think of is if I have the drive motors just barely stroked(small displacement) and I head down a steep hill with a heavy load. I am often driving off of cliffs that I am unable to drive back up.

I have no clue about #1

What do you guys think, should this be plug and play once i pull the charge pumps? Is there anything else to consider? I can make them fit and cut my own sprockets or modify oem ones.


Parking Brake: The hold back(w/out the parking brake) of the oem system is almost sufficient. If anything it just creeps, i'm guessing this has to do with the loop flushing??? Should I try to utilize the 75cc s90 on the drive side as a quasi parking brake? If not I have another plan.

 

[oldnslo]

Is there a reason you cannot install larger variable displacement motors Vs pumps. Motors would be designed as motors and would eliminate a lot of your concerns.

I believe the 51 series Sauer motors have electric displacement and or hydraulic displacement that would automatically increase the displacement/torque once the pressure reached a preset point.

Will the drive train handle this increased torque?

Roy

 

[LoadTest]

The OEM motors are junk(even when they are working) and cost about $2500 a piece rebuilt. I already have a dozen of the s90 pumps sitting on the shelf so would like to see what they can do as motors. Any kind of motors, especially variable, are hard to come buy for cheap.

 

[oldnslo]

I want to replace the LSHT drive motors on my 2006 t300 with 75cc EDC S90 pumps coupled to some torque hubs. The t300s are hard on drive motors, have about half the drawbar pull of the competition to begin with, and are slow. Sauer Danfoss said the pumps could be used as motors if I pulled out the charge pumps. But its up to me to ensure I take into consideration the following:

1) As far as the charge pump size, that involves a bunch of factors. First, did the motors you are replacing have loop flushing? How do you plan to flush the loops to control heat in your circuit? The amount of loop flush will affect the size of charge pump required.

Some wheel motors have built in flushing valves. If you know the exact model of these motors you should/may be able to find some literature that will tell what the flushing/cooling flow was on these motors.

2) Consider the system protection type that is in the pump used as a motor. If you have pressure limiters they could cause the pump to stroke or destroke depending on the operating condition and pressures. You need to make sure you understand how that will work in all machine modes.

You will also have to figure out how to keep the pump "on-stroke" since its default position is zero stroke.

3) You need to make sure you understand the potential failure modes.


The OEM drive pumps are 55cc s90's that will stay for now until upgrade them to same 75cc s90's i'm wanting to use as drive motors, probably with a hybrid powerplant.

#2 doesn't seem like a big deal. If my figuring is correct I'll have about 3 times the original tractive force before the limiters kick in to protect the pump.... If that would even happen on the 75cc drive side and not 55cc pump side first. And the use as drive motors is going to be much more intermittent then the OEM 55cc pumps driving them, so if the 55cc's are keeping themselves cool from the factory, the 75cc's probably aren't generating much more heat then the oem drive motors they are replacing. The only issue I can think of is if I have the drive motors just barely stroked(small displacement) and I head down a steep hill with a heavy load. I am often driving off of cliffs that I am unable to drive back up.

I have no clue about #1

What do you guys think, should this be plug and play once i pull the charge pumps? Is there anything else to consider? I can make them fit and cut my own sprockets or modify oem ones.


Parking Brake: The hold back(w/out the parking brake) of the oem system is almost sufficient. If anything it just creeps, i'm guessing this has to do with the loop flushing??? Should I try to utilize the 75cc s90 on the drive side as a quasi parking brake? If not I have another plan.

 

[CJONE]

As far as the "flushing" or loop cooling that is easy, you could do it with a Eaton relief block with a charge relief set at 20 psi or so below your charge pump relief. As far as the pumps converting to a motor, I can see a couple of problems. The swashplate would have to be set at 3-4deg min and if the motor was on the lowside and you put full flow to it I don't know if the reliefs would react fast enough to keep from a overpressure. Controlling the swashplates will be fun also. Why don't you trade 2 of your pumps for motors. If the pumps have certain options they are worth a trade for motors and would be close in $$$. I would have to inspect the pumps first but if they are new you would not have much in the trade and have a system set up without any conjuring. CJ

 

[LoadTest]

I would have to inspect the pumps first but if they are new you would not have much in the trade and have a system set up without any conjuring. CJ

Its hard to find a good deal on decent size motors that will handle even close to the 5000psi. Are you saying you have motors and would be interested in a trade?

 

[CJONE]

Its hard to find a good deal on decent size motors that will handle even close to the 5000psi. Are you saying you have motors and would be interested in a trade?

Yes depending if the pumps are new. You can buy new motors for under 3K each. Now before we get too far into this you know piston stuff is designed for high speed and does not develop the torque a low speed motor has. What are you replacing? is it already piston stuff? What is the displacement of the existing motors? CJ

 

[LoadTest]

The swashplate would have to be set at 3-4deg min and if the motor was on the lowside and you put full flow to it I don't know if the reliefs would react fast enough to keep from a overpressure. Controlling the swashplates will be fun also.CJ

What is significant about the 3-4deg?

Can you explain this more: "if the motor was on the lowside and you put full flow to it I don't know if the reliefs would react fast enough to keep from a overpressure. " The oem s90 pumps shouldn't be able to push more pressure to the motors(s90 pumps) then they can handle or the oem system would kill itself.

CJONE is helping me locate some motors, but i'd still like to try to convert one of these pumps over. Its good for the DIY community because even though the list price on these pumps is more then a motor, motors are hard to find on the surplus market and always much more expensive. Plus Bobcat might even take notice and spend a lil more money on power and a little less money on fluff.

So heres some more thoughts:

The OEM Bobcat motor is a Rexroth: MCR10F1120F250z32B5M1L/48SF4P0S0395H
1120 cc
10L/min flushing
And unknown special order features.(SO395)
Nom Output @250bar(3625.9psi)= 4010Nm (2957.6 ft-lbs)
Max Output@400bar(5801psi)=6420Nm(4885.2 ft-lbs)
Max Seed 150rpm


The Planetary Hub I want to replace the oem motor with is:
34.6:1 Ratio
Nom Output=5270.7Nm (3887.5 ft-lbs)
Max Output=10541.5Nm (7775 ft-lbs)
Max Input = 4500rpm
Max Output= 150rpm (per mfg spec)

Here is the 75cc pump specs that I would like to try to run as a motor behind the planetary hub:
Flow @ Rated speed=270L-m (71gpm)
Torque @ Max Displacement= 1.19 Nm/bar
Min Input Speed=500
Rated Speed=3600
Max Speed=3950
Max Working Pressure=450bar (6525psi)
Max Pressure=480bar (6960psi)
Max Low Loop=45bar (650psi)
Min Low Loop=10bar (145psi)

Loop Flushing the OEM pumps that were flushing out the oem motors:
I was told by a rebuilder of the OEM drive motors that there is no loop flushing valve, but that is obvious not true per the data tag on it. So I would use a auxillary loop flushing valves. Sun Hydraulics makes them, or i could use the Eaton relief block.

Control Pressure:
I could tap charge pumps on the oem pumps to derive my charge/control flow for operating the new motor(s90 pump). But I not sure it would be enough flow, and I risk the oem pumps. So I would probably opt for either a separate aux pump(since the pressure/flow is small, or tapping into the work function gear pumps on the machine and using a regulator.

Loop Flushing the new motors(s90 pumps)
Do you think I need additional loop flushing to keep these cool, even if the oem pumps are loop flushing? There would be some flow out the case drain. If so, then I would use the sun loop flushing valve. If you need a separate valve for each pump.

Pump vs Motor Control Conflicts:
I would keep the motor(s90pump) stroked fully, until I want to speed it up and would destroke it with an input from the operator. So the only conflict I can see there is if I have it destroked for more speed and I increase the load on it and spike the pressure to the point of it trying to destroke itself thru the multifunction valve, meanwhile I am trying to stroke it and I'm not sure what the net effect would be. But I could just back of the drive controls to reduce the pressure I'm putting to it so the multifunction valve will close and I can then stroke it for more power- not a big deal with this machine, and probably avoidable all together with just a few minutes of learning to operate it.

Are there any other features that a motor would have that the pump won't?
Any guesses on what the output torque of the pump would be when used as a motor?

I'm still studying this. Any input is appreciated. Pics always help. 1)oem motor tag 2)OEM motor 3)Actual machine 4)Sauer Danfoss's suggested s90 use diagram 5)My modified version using the pump as a motor and pulling from the oem pump charge circuit to control the motor(but I don't think I want to do that)

 

[LoadTest]

5th pic:

 

[CJONE]

What is significant about the 3-4deg?

Can you explain this more: "if the motor was on the lowside and you put full flow to it I don't know if the reliefs would react fast enough to keep from a overpressure. " The oem s90 pumps shouldn't be able to push more pressure to the motors(s90 pumps) then they can handle or the oem system would kill itself.

CJONE is helping me locate some motors, but i'd still like to try to convert one of these pumps over. Its good for the DIY community because even though the list price on these pumps is more then a motor, motors are hard to find on the surplus market and always much more expensive. Plus Bobcat might even take notice and spend a lil more money on power and a little less money on fluff.

So heres some more thoughts:

The OEM Bobcat motor is a Rexroth: MCR10F1120F250z32B5M1L/48SF4P0S0395H
1120 cc
10L/min flushing
And unknown special order features.(SO395)
Nom Output @250bar(3625.9psi)= 4010Nm (2957.6 ft-lbs)
Max Output@400bar(5801psi)=6420Nm(4885.2 ft-lbs)
Max Seed 150rpm


The Planetary Hub I want to replace the oem motor with is:
34.6:1 Ratio
Nom Output=5270.7Nm (3887.5 ft-lbs)
Max Output=10541.5Nm (7775 ft-lbs)
Max Input = 4500rpm
Max Output= 150rpm (per mfg spec)

Here is the 75cc pump specs that I would like to try to run as a motor behind the planetary hub:
Flow @ Rated speed=270L-m (71gpm)
Torque @ Max Displacement= 1.19 Nm/bar
Min Input Speed=500
Rated Speed=3600
Max Speed=3950
Max Working Pressure=450bar (6525psi)
Max Pressure=480bar (6960psi)
Max Low Loop=45bar (650psi)
Min Low Loop=10bar (145psi)

Loop Flushing the OEM pumps that were flushing out the oem motors:
I was told by a rebuilder of the OEM drive motors that there is no loop flushing valve, but that is obvious not true per the data tag on it. So I would use a auxillary loop flushing valves. Sun Hydraulics makes them, or i could use the Eaton relief block.

Control Pressure:
I could tap charge pumps on the oem pumps to derive my charge/control flow for operating the new motor(s90 pump). But I not sure it would be enough flow, and I risk the oem pumps. So I would probably opt for either a separate aux pump(since the pressure/flow is small, or tapping into the work function gear pumps on the machine and using a regulator.

Loop Flushing the new motors(s90 pumps)
Do you think I need additional loop flushing to keep these cool, even if the oem pumps are loop flushing? There would be some flow out the case drain. If so, then I would use the sun loop flushing valve. If you need a separate valve for each pump.

Pump vs Motor Control Conflicts:
I would keep the motor(s90pump) stroked fully, until I want to speed it up and would destroke it with an input from the operator. So the only conflict I can see there is if I have it destroked for more speed and I increase the load on it and spike the pressure to the point of it trying to destroke itself thru the multifunction valve, meanwhile I am trying to stroke it and I'm not sure what the net effect would be. But I could just back of the drive controls to reduce the pressure I'm putting to it so the multifunction valve will close and I can then stroke it for more power- not a big deal with this machine, and probably avoidable all together with just a few minutes of learning to operate it.

Are there any other features that a motor would have that the pump won't?
Any guesses on what the output torque of the pump would be when used as a motor?

I'm still studying this. Any input is appreciated. Pics always help. 1)oem motor tag 2)OEM motor 3)Actual machine 4)Sauer Danfoss's suggested s90 use diagram 5)My modified version using the pump as a motor and pulling from the oem pump charge circuit to control the motor(but I don't think I want to do that)

Without getting too wordy, a fixed disp motor will still react either in track stretch or whatever then open a stat relief. You want a variable motor well what if you have the swashplate angle at 1 deg, or o. Where would the pressure go? Hopefully the reliefs would open in the stat but what if they do not react quick enough? The OEM's spend millions of dollars figuring out this stuff and usually there is a reason they don't do what you are wanting to do. I have spent alot of years learning and there are some things I don't want to learn the hard [read expensive] way. CJ