PTO pump for Post Driver

[Hosskix]

Hey guys, I recently bought a Shaver HD-8 post driver and have a JD 790 without power beyond.
I started pricing PBY because I didn't want to lose the function of my FEL by jumping off one of the curl circuits, then having to bungee the lever seemed like a pain.
Anyhow, JD quit offering the PBY kit for a 790 and just pricing the parts separately they'd cost over $400 (if you can find them separately!). Not something I'm looking for, plus having to tear the tractor apart to put it on and then losing 3pt function...So, I did some more digging and I came up with a PTO powered hydraulic pump and a 5 gal tank.

The pump output is:
8.0 GPM at 1000 RPM'S.
2550 PSI Pressure.

The driver requirements are:
3 - 4 GPM at 1500 PSI

First of all, I didn't notice the 1000 RPM's before I bought the pump.
(1) Is turning this thing at 540 gonna get me my 1500 PSI?
Does it matter if I'm a little short?
The GPM's shouldn't be an issue, from all I've read it'll just be slower if I'm short there, but I'm thinking 4 or so anyway which puts me in the middle of the requirements.

(2) Do I need to worry about a pressure relief valve?
I'm thinking that with an open center valve (which I assume is what's on the driver) it'll just circulate back into my tank, but is a tractor supply hydraulic tank going to hold 1000+ PSI return without a problem? If not and I need to put in a pressure relief valve, what the heck do I do with the excess PSI? I can't just dump it in my tranny; I'll eventually lose all my fluid!

(3) What about the heat of the fluid?
To my way of thinking, I'll be driving a post (5 min of circ, if that), moving the tractor, getting ready for the next post, engaging the PTO and driving that post, again 5 min of circ max.
Do I need to worry about cooling the fluid or can I just keep "a finger on it" and shut down for a while if it gets pretty warm?

I eagerly await your replies; one of these days I'll learn not to buy stuff until I'm sure they'll work for what I'm intending!
(I probably won't REALLY but it never hurts to have goals.)

 

[kennyd]

The PB kit should still be available, what part number where you looking for?

1. Lower RPM's will cause lower flow, not pressure.

2. The valve on the HPD should valve a PRV built into it...what valve is it?

3. Heat should not be an issue with a 5 gallon tank.

 

[Hosskix]

Thanks for the reply kennyd.

The PBY kit is part # BM18005, online parts gives me this message:
The part BM18005 is no longer available. Contact your local John Deere dealer for other options.

So I just selected all the parts individually and came up with a cost of $473, like I said, not something I'm willing to do, for all the various reasons.

I don't actually have the driver yet, it's being shipped to me, so I'm really not sure what type of valve is on it.
I'm just trying to think ahead and get everything I need on the way so that when I do actually have it I won't be waiting.

Anyhow, from what you say it sounds like what I've got on the way so far aughta work for me (with a relief valve added if there's not one on the supplied valve), good news!
Thanks for the help!

 

[kennyd]

The PBY kit is part # BM18005, online parts gives me this message:
The part BM18005 is no longer available. Contact your local John Deere dealer for other options.

The PB kit is considered a "whole good" and is not sold over the parts counter but rather through sales-you have to call and talk to a salesperson to get it...JD's crazy way of doing things.

Sounds like everything will work though the way you want it, don't forget to add a filter

 

[thomas91163]

The JD uses a variable displacement pump. You will need to change to a closed center otherwise it will bog down the tractor. I use the HD 8 myself and find it to be a good hobby pounder.

 

[kennyd]

The JD uses a variable displacement pump. You will need to change to a closed center otherwise it will bog down the tractor. I use the HD 8 myself and find it to be a good hobby pounder.

Welcome to TBN

But you are 100% wrong on this. The 790 as well as all of the JD lines of current (last fifteen years or more) CUT's are Open Center hydraulic systems. You must have a 70's or early 80's tractor?