hydraulics rules post hole digger

Posted by bc on October 17, 2008 at 09:49:44 from (70.130.55.114):

Hi guys. I've posted previously about my homemade hydraulic post hole digger project. I just wanted to run a few things by you before I fork over some bucks.

I've got the 2606 with a hoe and no pto. Have a 3 point mount on the front bucket for bale spear, etc. I have an old 2 point pto post hole digger homemade with a car rear end. I will either use that or I may buy a new 3 point one with pto so I don't have to mess with the mount. Anyway, the homemade one doesn't have a top link attachment point on it.

A new 3 point pto auger at TSC made for a cat 1 & 2 has a 3.18 to 1 gear ratio. Assuming a 540 pto speed, that spins the auger at 170 rpm. I assume these are made for 540 and not a 1000 rpm pto?

Given a choice between using a direct drive hyd motor at about 170 rpm or using the gear box and get a 540 rpm motor, I am leaning towards the 540 rpm motor which I could use on another homemade project(tree saw blade). I would weld up a bracket, etc to hold the motor and weld up a hub to mount it to the drive.

My 2606 has dual pumps with a 17 gpm and a 7 gpm which are probably pretty well worn but work the hoe and loader, but I still have steering problems. I assume the 2606 probably has a 1600 psi relief valve in it.

To pick a hyd motor, I come up with the following basic rules of thumb for hydraulics and I would appreciate it if you correct me where I'm wrong. I am looking at a charlyn H motor, 101-1003, 1840 psi, 590 rpm, 5.9 cu. in, & 1425 inlbs torque. Probably add a flow control valve and psi reducing valve/popoff. It calculates out to be a 15 gpm motor. I would probably run it at 12 gpm at 1600 psi. I would also add a control valve and some quick connects for the hoses like the bobcats have.

Basic hydraulic rules:
1. Never exceed the psi rating.
2. Never exceed the rpm rating.
3. With the cubic inch motor size remaining constant, the rpm's are directly proportional to the gpm applied, the more gpm you add(up to the max rating), the more rpm you get.
4. With the cubic inch motor size remaining constant, the torque of the motor is directly proportional to the psi, the more psi you add(up to the max rating), the more torque you get.
5. Any others?

I've looked at some hyd diggers being sold and they range from 8 to 10 gpm with a 6 to 8 HP Honda engine running them with the motor turning the auger anywhere from 75 to 200 rpm and some use a gear box and some don't.

Thanks for the help.

Replies:

• Re: hydraulics rules post hole digger RayP(MI) 16:18:34 10/17/08 (0)

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