# PTO Pump sizing



## jraylong (Jul 11, 2016)

I have a 1966 John Deere 1020., (about 40+ hp), I want to buy a PTO hydraulic pump to drive a 3 point hitch mounted backhoe with 12"bucket. I also want to use it to drive a woodsplitter that had a 10 hp gas motor drive. Gas motor is shot, so I am conveting it to JD power. What GPM should I be looking for in a PTO pump, and is Prince the only way to go?..Prince seems really pricey for what I want to use it for..I only will use it very occasionally. ...JOHN


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## Groo (Jan 17, 2020)

You need to check out the flow ratings of the valves you have. You might be able to estimate the spliters flow by using math if you know how fast it cylcles. I'm going to assume a backhoe is going to want more flow than a log splitter, but maybe not.

I'm not sure how PTO pumps work. I know normal gear pumps don't like to spin that slow, so maybe they are gerotor pumps? Thinking back on the shape, that probably is it.


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## marc_hanna (Apr 10, 2017)

12-15 gpm seems like the appropriate sized pump for the tractor, so if you haven’t bought the backhoe yet, you should size one accordingly. That might be a little oversized for the logsplitter though, so you might have to upgrade the valve and/or the cylinder or add a relief valve.


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## Groo (Jan 17, 2020)

marc_hanna said:


> 12-15 gpm seems like the appropriate sized pump for the tractor, so if you haven’t bought the backhoe yet, you should size one accordingly. That might be a little oversized for the logsplitter though, so you might have to upgrade the valve and/or the cylinder or add a relief valve.


I wouldn't size the pump based on tractor hp, other than to check that at rated flow and desired pressure that you are not exceeding pto hp.
https://www.womackmachine.com/engin...and-calculations/hydraulic-pump-calculations/
You definitely do not want to deal with excess flow with a relief valve. That is just instant heat, and I'm guessing a pto hydraulic system is going to have a small tank to begin with, so that excess heat becomes fatal fairly quick.
Now what you could do is remember to never run the engine over 1500 rpm or whatever when the pump is driving the splitter. Put another line on the tach if you go that route.


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## marc_hanna (Apr 10, 2017)

Groo said:


> I wouldn't size the pump based on tractor hp, other than to check that at rated flow and desired pressure that you are not exceeding pto hp.
> https://www.womackmachine.com/engin...and-calculations/hydraulic-pump-calculations/
> You definitely do not want to deal with excess flow with a relief valve. That is just instant heat, and I'm guessing a pto hydraulic system is going to have a small tank to begin with, so that excess heat becomes fatal fairly quick.
> Now what you could do is remember to never run the engine over 1500 rpm or whatever when the pump is driving the splitter. Put another line on the tach if you go that route.


Agreed, but you do want to maximize the PTO horsepower for the sake of the backhoe, otherwise you’re going to have a slow and weak backhoe.


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## Groo (Jan 17, 2020)

marc_hanna said:


> Agreed, but you do want to maximize the PTO horsepower for the sake of the backhoe, otherwise you’re going to have a slow and weak backhoe.


Dad wanted to stick the 3 point backhoe he got for his l2550dt on his yanmar yt359. I contacted the manufacturer of the hoe to get its flow rating. The yanmar has too much flow for it.
I had considered hooking it up to a rear outlet, but he didn't want to mess with new hoses, and I wasn't sure how to lock it open.

Now were I in the OP's shoes, I would find the specs for the desired hoe an go from there. If peak flow and pressure are more than 38hp, I would sacrifice speed to maintain full power.


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## marc_hanna (Apr 10, 2017)

Yes, again I agree with you. Some of these 3ph backhoes are absolutely useless. You definitely want to do your research and get a properly matched unit.


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## Groo (Jan 17, 2020)

Another option for the OP might be OEM hydraulics. Tractodata lists 10.5 gpm for that model. I do t know if he'd have to pick up an optional pump to get that, or if its already there, and he just has to tie in.


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## marc_hanna (Apr 10, 2017)

That would certainly be the preferred route in terms of price and performance.


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## Groo (Jan 17, 2020)

Here is another idea; 
If you are looking at a new backhoe, get one that has the tank and pto pump build in, then slap a couple of quick connects on the curl cylinder (or whatever), and hook them up to to the spliter when you and to split, just use the hoe's valves as well as the pump and tank.


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## ufdaland (Feb 25, 2018)

I have a PTO pump for $ 100 if you want to experiment.


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