Need help buying a hydraulic motor

[woodlandfarms]

I asked this in my brand specific forum but came up a bit short on advice

So here it is again

So here is the deal. I may have access to a tiller and a Post Hole digger, all powered by a conventional PTO. The price is good enough for me to consider rigging a hydraulic motor (making them swapable) and using my 3pt adapter... Still have a few things to iron out (how to get the 3pt to work with my system and make a motor swappable) but I don't get the basics.

So looking at Surplus, which of these would be the best motor... And why the one you recommend over the others. They all seem to take the same GPM and Rotate at the same speed, just the cubic inches are different.

Surplus Center

My tractor is rated at 3000PSI at 18GPM.

 

[J_J]

I believe the rpm's on those motors are to high for a post hole digger. On some of the hydraulic post hole diggers, they just put a hyd motor on the gear box. The largest of those hyd motors have about 2780 in lbs of torque, and if you reduce the rpm via a gear box to about 150 you should have some good torque.

The models below have a 3.18 : 1 So if the hyd motor turns at 600, then the auger would turn at 200 rpm.

Are you trying to turn the auger directly, or go through a gear box? One of the PT guys made himself an auger using a hyd motor, and coupling the two parts with a heavy duty chain. Will try and find a picture.

 

[woodlandfarms]

Hey JJ. No, a buddy is selling some of his gear. A nice 3PT Geared Post Hole Digger and a 5 ft Rotatiller. Both 3PT PTO Powered. I want to make them Hydraulic. Just make some sort of mounting plate and a coupler and slap a motor on. Looking to purchase the right one.

I have a PT to 3PT adapter but I know there will be some playing around. And what he is selling the gear to me for makes it quite worth my effort to make this work. So no, no direct drive of a Post Hole Bit, going into a normal gear box.

I am asking this because all the motors seem to read the same except for cubic inches and I am very confused.

 

[J_J]

There will be a rpm difference with a set GPM. As the cu in increase, the shaft speed will reduce. Since the input to a standard 3pt is 540, then you can use any of the motors, but the larger motors will have the greatest torque. The 2,18 ratio will get you into the rpm range of the auger. I believe the PT auger turns even slower. I have one of those, but have never measured the speed. Of course you can vary GPM;s to the motor for speed control. My PT has one of these valves for speed control.

https://www.surpluscenter.com/item.asp?item=9-064-50&catname=hydraulic

I believe your GPM's is solenoid controlled, so then you might need a motor spool control valve like this.

https://www.surpluscenter.com/item.asp?item=9-7458&catname=hydraulic

Especially for auger reverse.

 

[woodlandfarms]

thanks JJ. So I am going to order the largest motor, correct? I will work on flow controls once I get through the simple set of issues installing it. As I see it I need a coupler and a mounting plate and I should be good to go. Then I will put in hydraulic controls...

 

[radman1]

If you want to use the motor on different 3 pt driven attachments (mower, tiller ect), then I would use the 7.63 motor. This will give you near 540 pto speed with your 18 gpm output. If you want max torque for the PHD, then use the 9.59 cu inch motor. You won't get 540 pto with the 9.59, but you don't need or want 540 pto speed using a PHD. I use a pto driven PHD at much lower than 540 pto speed on my tractor.

Also remember, the hydraulic motor will loose significant efficiency compared to the direct drive of a tractor driven pto. The hydraulic motor will produce much less hp/torque.

 

[J_J]

He can simply reduce engine rpm to get the GPM's he needs for the speed on the hyd motors post hole digger or tiller.

Just use the largest motor you can find.

Consider a reverse valve.

Carl, do you have the post hole digger yet?

Turn the shafts and determine the gear ratio.

With the down force on the PT, and reverse, you should have a good setup.

 

[J_J]

When you are connected the tiller, determine the rotation of the drum by looking at the tines, the cutting edge of the tines. Turn the drum the correct way and notice which direction the input shaft turns. The gear box may have one ratio, and the pulleys have another ratio.

You will also have to consider the mounting plate for the tiller, as to which side to mount it on. Do you want the tiller to fwd till or reverse till.

With a reverse valve, you can select the correct direction.

Typically, fewer passes will be needed with a Reverse Tine Tiller. Forward Rotation Tillers tend to 'walk' on hard ground. Reverse action 'sucks' the tiller into the ground. This tiller buries large clods first, wtih smaller clods falling on top creating a perfect seedbed.

Reverse tilling is also when the tines are turning opposite of the wheel travel direction.