PTO pumps and using the transmission as the reservoir???

[design]

Has any on considered attempting the following?

During a transmission fluid change, drill and tap the transmission drain plug for a 1/2" npt tread. Add a 1/2" nipple (coming straight down), an elbow and a short piece of 1/2" pipe (heading straight back to the rear of the tractor) to a quick disconnect secured to the rear differential housing.
Modify the fill cap to allow for a return flow path.

Then one could add a PTO pump with an integral filter on the intake line to the new rear hydraulic feed line. Add the appropriate pressure relief valve and quick disconnect to the high pressure side of the pump.

Combine the flow that bleeds off from the pressure relief valve to the return lines from the implements and dump into the modified fill port, (AKA the plastic fill cap)

If one does this, you end up with the transmission being the fluid reservoir for the PTO pump. This would allow you to have access to 10 gallons of hydraulic fluid on board at all times.

1. Will the flow rate for a PTO pump by so high that there are air bubbles entrapped in the fluid in the transmission?
2. Will this hurt the other hydraulic pumps on the tractor?
3. Other issues?

-Design

 

[RonMar]

Well if the feed pipe is large enough to meet the demands of the pump, there shouldn't be any air drawn in and or no cavitation in the pump should occur. Pumps don't like filters on the inlet(restricted flow causes cavitation, air entrainment and heat in the pump. It would perhaps be better to extend the nipple up inside the sump as far as practical so you are not drawing fluid off the bottom of the sump. Then add a fine return filter and filter the fluid returning from whatever you are feeding the pump with.

Another thought: Large volume PTO Pump + high pressure = high heat. How are you going to deal with the added heat another pump and load will create? The tractor sump can dissipate a certain ammount, but the designers already took this into concideration with the existing pump/heat load.

 

[bindian]

Well if the feed pipe is large enough to meet the demands of the pump, there shouldn't be any air drawn in and or no cavitation in the pump should occur. Pumps don't like filters on the inlet(restricted flow causes cavitation, air entrainment and heat in the pump. It would perhaps be better to extend the nipple up inside the sump as far as practical so you are not drawing fluid off the bottom of the sump. Then add a fine return filter and filter the fluid returning from whatever you are feeding the pump with.

Another thought: Large volume PTO Pump + high pressure = high heat. How are you going to deal with the added heat another pump and load will create? The tractor sump can dissipate a certain ammount, but the designers already took this into concideration with the existing pump/heat load.

Ron is right about the heat. A reservoir is also a heat sink, meaning it helps dissapate heat. Add the heat from another pump and no more air flow or metal to increase the area of the heat sink and you will boil your fluid.
hugs, Brandi

 

[design]

Good thought on the heat. The tractor that I am thinking about is a 4000# 50 HP Kubota. I suspect the themal mass of the castings combined with the seasonal temperatures we see in NH would allow the chassis to be an effective heat sink. Remember, we have 10 months of winter and two weeks of rough sledding....

Thank you for the feed back on the return line for the filters. I can do that very easily.

The pump for this project will be either a Prince 11GPM or a Prince 23 GPM pump.

-Design

 

[john_bud]

I'll be negative on this one. I picture that pipe plug getting ripped off and all the fluid glurgaling onto the ground.

By the time you add a large hydraulic cooler & fan, a dual head hydraulic filter, all the plumbing and stuff, I'd bet you would have been better off to just use a 10-15 gal tank in conjunction with the PTO pump.

If this is to run the Bradco Hoe, I would caution you that you need to take into consideration the change in volume from the 2 stabilizer cylinders going from full retract to extended, the 3 large cylinder for boom, stick and bucket going from full retract to full extend. That's probably on the order of 2-4 gal of fluid.

jb

 

[RonMar]

If this is to run the Bradco Hoe, I would caution you that you need to take into consideration the change in volume from the 2 stabilizer cylinders going from full retract to extended, the 3 large cylinder for boom, stick and bucket going from full retract to full extend. That's probably on the order of 2-4 gal of fluid.

jb

As an idea of how much fluid difference there might be, With 2" rod diameters and 24" stroke cylinders, the difference in fluid used between fully extended and fully retracted for 6 cylinders of that size would be 1.95 gallons.

 

[Tim_in_IA]

Well the old IH tractors used the transmission as a resivoir for the hydraulics so I don't see why not. Only drawback is you have to keep the pto pump on and lose use of your pto, unless you are putting quick connects on. I would size the PTO pump to the capacity of the storage of the transmission so you didn't encounter the heat issues described above.

If this was an issue they make radiators for hydraulic fluid. (heat exchangers). You could plumb one in to further dissapate the heat.

You also need to make sure that the fluid used by the hydraulics matches the fluid recommended for the tranny.

By the time you factor all that other stuff in you might just want to buy a reservoir and mount it on whatever you are using the PTO pump for.

 

[BTI]

This would be a bad idea.
If you look at how big the supply line is running to your tractor pump you'll see why I say this.
On all of the tractors I've seen it's been at least 1" line even on the little tractors.
I also see this getting ripped of easily, even the 1/2" size.
1/2" isn't big enough to supply a 10 gal per min pump let alone a 23gal pump.
It does sound good in theory though.....

BTI

 

[crashz]

This would probably work just fine, but I'd also consider the fluid quality. Now the fluid supports the tractor transmission, power steering, FEL (assumed to have one) and the backhoe system. It will shear the fluid quicker, and suck the additives right out of it. Plus adds another system prone to contamination.

 

[Farmerford]

Design:

I have a Prince 11gpm pump on the PTO of a 43hp Kubota L4330 driving a Bush Hog on the FEL for clearing brush and small trees, with a 15 gal reservoir. The Bush Hog works pretty hard most of the time and often opens the relief valve in the pump circuit (adding to the heat), and on warm South Georgia days the fluid temperature gets to 160deg F. The tractor is hydrostatic, so its fluid stays around 130deg F. accord to the temperature gauge at the FEL valve. I suspect that if the heat from the PTO pump were dumped into the transmission the fluid could get close to the 180-200deg upper limit. A 22gpm pump would create more heat.

The intake line for the 11gpm pump is 1 1/4" diameter hose, about 30" long, and there is a 100 micron screen inside the reservoir. When the fluid is cold the vacuum guage shows 2psi of vacuum at the pump inlet, and it drops to 1psi when hot. The generally accepted upper limit for vacuum at the pump inlet is 5psi (though I have seen recommendations as low as 3psi and as high as 10), so you might need a 1 1/4" fitting at the transmission drain plug to keep the restriction low. That would stick out 4-6" and be exposed to damage.