Hydraulic Motor question

[Regal]

I did a search trying to find out what the gpm is on my tractor and found -- JD 4310 and the pump puts out 8.6 gpm @ 2500 psi.
Assuming that this is correct, and I want a motor to run continuously up to aprox 800 rpm at full throttle, and develop around 10 hp, what cu in displacement should I look for? How do you calculate gpm - psi - rpm- cu in - to know what you want?
I built a cab and have yet to complete the A/C. I have all the components but don't want to do all the modifications needed under the hood to make room for the compressor.My intention is to power an AC compressor mounted up in the cab roof with everything else.
I intend to cut into the pressure line that feeds the loader valve, run thru the hydraulic motor and back into the loader valve. The motor will run continuously and that's ok. I know it will vary with engine rpm and I'm ok with that too. Am I nuts??

 

[glastron23]

try this ... Hydraulic Calculator

 

[kennyd]

Am I nuts??

I think so...Sorry to offend.

 

[KennyV]

I intend to cut into the pressure line that feeds the loader valve, run thru the hydraulic motor and back into the loader valve.

Are you thinking of running this in series with the hydraulic system ? ... ??? this can not be a good idea. What size lines are you thinking of using? and why not use a belt driven compressor on the engine with refrigerant lines running to the roof mounted evaporator?, where are you planning to mount the condenser? Even if the hydraulic system is used as an either/or, AC drive or loader and 3pt isn't the roof unit getting rather busy??

 

[AKKAMAAN]

agree with the "kenny's".....running a cooling system with a "heating" system is not the right solution....:thumbdown:

better plumbing the AC lines to the roof than hydraulic lines.......:thumbsup:

 

[Regal]

glastron23
Thanks for the calculator. That's what I needed.
Kenny, Kenny, Akkamaan
It appears to be about a 5/8" line feeding the loader valve so I would use at least that large up to the hyd motor and back. I would plan on 3/4" fittings at the motor so as to not restrict flow. With full flow running thru the motor,unrestricted, the loader valve shouldn't know the difference. I was told once that an A/C unit pulls around 10 hp, so if I have like 14hp motor, it should run with ease.
The condenser/ evaporator/ heater core and fans are already mounted. Duct work is done and still have lots of room for compressor with drive motor. This will also keep all the lines short and not require much 134A. In order to mount a compressor on the engine I will have to cut away about 1/2" of the muffler and relocate the alternator. Too much change over.
If you think this is nuts, you should see what I tried first. A 120 volt pop cooler compressor powered by inverter. IT almost works. I think it doesn't like the rough ride. Works fine sitting still but not on the go.
Am I still nuts??

 

[oldnslo]

glastron23

Am I still nuts??

If you gotta ask....... Iowa stands for Idiot Out Walking Around

A concern I would have is that will this motor be up stream of the loader control valve. When you operate the loader both sides of the motor will see system pressure. This could potentially blow the shaft seals on your motor.


Roy

 

[Regal]

I had planned to put it in line before the loader valve. Isn't there a constant flow that travels thru this line and thru the loader valve, bypassing to return? I followed the line from pump back. It appears to feed the 3 pt and passes on thru wrapping around the back and into loader valve. I am only assuming that there is a constant flow thru this line. If not, I'm back to the drawing board.

 

[KennyV]

Isn't there a constant flow that travels thru this line and thru the loader valve...

BUT if you do infact put this in series, any pressure build up that is felt through the down stream systems, like loader or 3pt will be seen across the in and out of the hydraulic motor.
It is going to be quite a motor that will stand the pressure...

 

[mmurphy]

If you gotta ask....... Iowa stands for Idiot Out Walking Around

A concern I would have is that will this motor be up stream of the loader control valve. When you operate the loader both sides of the motor will see system pressure. This could potentially blow the shaft seals on your motor.


Roy

Well Roy, I tell everyone I am, the biggest idiot I know. Now I have an excuse!!!!!:thumbsup:

 

[oldnslo]

Well Roy, I tell everyone I am, the biggest idiot I know. Now I have an excuse!!!!!:thumbsup:

Glad i could help

 

[Regal]

Maybe I need to find another solution. Somewhere Iv'e seen a unit that was an alternator/hydraulic pump combination. Can't remember if it was for like a Lincoln Continental or for some piece of equipment or old tractor with power steering. The alternator shaft extended through and the pump was mounted behind it, driven off same shaft. I think I could make something like that fit under the hood.

 

[dfkrug]

Wow, REGAL, that's a tough crowd!

I am going to encourage you to try it.

First, you want to get a motor that is sized for your speed requirements,
and it should handle the 2500psi your tractor's pump supplies. The motors
will be reversible, so they can handle the max pressure they will run into
at either port. The power demand of your compressor will be less than
your tractor pump can put out, so that is not a problem. You do not want
a motor that can't handle the full 2500psi of the tractor, or you will have
to reduce the FEL RV pressure to whatever the motor limit is, and that will
reduce your FEL and 3-pt capability. So you can rule out the cheap
and common Charlynn S motors or White 200 series that have 2000psi
limits....you might have to go with something like a White 300 series.

If you run your motor after another valve, as you might from the Power
Beyond of the FEL valve, using the FEL will stop your motor when you
actuate any lever. That may be OK since your FEL use is intermittant. If
you have a valve that is downstream of your motor, then when
you actuate IT, your motor will also stop AND that valve may not
see full pressure from the pump as there will be some pressure
drop across the motor. Another approach would be to run the motor
off a detented spool of an AUX valve.

Since you propose to run the motor all the time, you will want at least
1/2" hose to reduce fluid heating. I assume you will use a compressor
with an electric clutch, like an automotive AC comp.

 

[kennyd]

If you run your motor after another valve, as you might from the Power
Beyond of the FEL valve, using the FEL will stop your motor when you
actuate any lever. That may be OK since your FEL use is intermittant. If
you have a valve that is downstream of your motor, then when
you actuate IT, your motor will also stop AND that valve may not
see full pressure from the pump as there will be some pressure
drop across the motor. Another approach would be to run the motor
off a detented spool of an AUX valve.

I think you touched on the main problem with his idea...The motor will always be robbing power from the hydraulic system. The limited flow of the pump will be fully realized I think trying to raise the loader, curling the bucket AND running the motor.

The Power Beyond line that is at the rear of the tractor (runs over top the PTO-under the seat) is after the FEL valve and before the 3PH.

 

[dfkrug]

I think you touched on the main problem with his idea...The motor will always be robbing power from the hydraulic system.

Yes, that is correct. Even if the A/C system is only drawing 10hp, that
is a lot, if you are asking your 33hp CUT to mow a field at more than
a crawl. With the A/C off, that power draw may be only 3-4 hp,
depending on engine speed and size of hose used.

Any valve upstream of the motor will get full use of all pressure and
flow of the implement pump. The 3PH will not, assuming it is last in line.

 

[kennyd]

The ONLY way I can even believe this would work is with a Priority Valve plumbed in just after the pump that would "dedicate" a portion of the flow to the motor with the rest going to the stock system. Plumbing that in would require cutting into the steel lines under the tractor.

Just not as good option IMHO.

 

[Regal]

Thanks for the debate guys. I really do want to hear all the pros and cons to this.
The 10hp to run the A/C is an estimate only. In reality I think it will be slightly less. A JD dealer told me that you don't find A/C available on less than 30hp tractors because they allow 20 plus horse for mowing etc. My hope is that by over sizing the hyd motor, it will never be overworked and wont cause undue restriction. I know there will be a power loss involved to some extent. As to loss at the loader valve, I only use it to raise the mmm deck and a front snow blade. I don't have a loader. Tractor's main use is mowing. The only pressure issue I am concerned with is when you hit the end of a cylinder and create a pressure spike in the feed line. But that would be very momentary.
It looks like the 3pt gets it's oil first. If this is the case then I could see some effect on the A/C motor when lifting it.
DFKRUG
Thanks for encouragement.
However when you say
"If you have a valve that is downstream of your motor, then when
you actuate IT, your motor will also stop AND that valve may not
see full pressure from the pump as there will be some pressure
drop across the motor."
Why would the motor stop? All oil has to pass through it as long the engine is running, right?
My son in law thinks he has a motor I can experiment with. Don't know the specs yet, may be way too big.
I want to look at this as - all I've got to lose is cutting into that steel line --welding up some fittings and putting it back normal if this whole thing tanks. OR worse yet -- buying a new one.
I don't want to give the impression here that I don't believe what some of your guy's concerns are. It's just that I'm not convinced yet that there isn't a way.
Want to hear more!!

 

[mmurphy]

Regal, I am not as concerned about hydraulic system as others but, more so of compressor. If you do not have a prioriy valve put in like Kennyd said, each time you take flow away from motor and then it gets it back, I would think that compressor may take a beating internally while in cycle. If you do go ahead with project make sure you get sized to what compressor pump that will be used, do not oversize it.

 

[Regal]

mmurphy
Are you referring to sizing the A/C compressor to it's system? Or getting a hyd motor that will not be too much hp to drive the compressor??

 

[dfkrug]

Thanks for encouragement.
However when you say
"If you have a valve that is downstream of your motor, then when
you actuate IT, your motor will also stop AND that valve may not
see full pressure from the pump as there will be some pressure
drop across the motor."
Why would the motor stop? All oil has to pass through it as long the engine is running, right?

Yes. When you actuate a valve downstream of the motor, oil will flow
(and the motor will spin) until the backpressure developed in your AUX
valve work port equalizes with what your pump can deliver. That would
place limits on how much work the downstream valve can do, but that
does not mean it could do NO work. Like the FEL, the demand would
likely be infrequent and last only a very short time. And if the compressor
stops for a second or two, so what?

If you do this on your 4310, you can access the hyd circuit by plumbing
into the hardline between the hyd pump and triple SCV, or at the
hardline that comes out of the SCV. I have used the latter route by
replacing that hardline with hoses and fittings. This means the 3-pt
valve will be the last in the series. You can see how I did it here:
see post #378
http://www.tractorbynet.com/forums/parts-repairs/146974-john-deere-4300-complete-rebuild-10.html

here is an example of sizing a hyd motor:
http://www.tractorbynet.com/forums/hydraulics/152388-converting-3-pt-concrete-mixer.html

Note that the motor itself won't determine the power required to turn it;
the load you put on the motor will determine that.