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  1. #1
    Silver Member Tim Stuart's Avatar
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    Jun 2007
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    118
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    Coldspring, TX
    Tractor
    Mitsubishi bd2h dozer, Gradall G3WD, New Holland TC35a, Chevy Dump Truck

    Default Hydraulic post hole digger

    Guys looking for some input, I am looking to build a hydraulic post hole digger 3 point mounted to drill 4" holes. I am looking for a hydraulic motor that I can used to power it. I have a lot of clay soil so the motor will need to be reversible so if it hangs I can reverse it to back it out. I have a New Holland TC35a tractor that has a fronted loader that I want to take off and use the quick connects and the tractor hydraulics to power the post hole hydraulic motor on the back 3 point. I have been looking at the Surplus Center website but things get a little confusing to me when figuring RPM, Pressure, and GPM.

    My tractor Hydraulic specs are as follows:
    Type: open
    Pressure: 2275 psi
    Valve flow:9.8 gpm

    I think I need a low RPM, high Torque motor correct? Like everyone else I am looking for low cost options.


    Regards,

    Tim

  2. #2
    Veteran Member
    Join Date
    Apr 2009
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    1,023
    Location
    Port Angeles WA

    Default Re: Hydraulic post hole digger

    Quote Originally Posted by Tim Stuart View Post
    Guys looking for some input, I am looking to build a hydraulic post hole digger 3 point mounted to drill 4" holes. I am looking for a hydraulic motor that I can used to power it. I have a lot of clay soil so the motor will need to be reversible so if it hangs I can reverse it to back it out. I have a New Holland TC35a tractor that has a fronted loader that I want to take off and use the quick connects and the tractor hydraulics to power the post hole hydraulic motor on the back 3 point. I have been looking at the Surplus Center website but things get a little confusing to me when figuring RPM, Pressure, and GPM.

    My tractor Hydraulic specs are as follows:
    Type: open
    Pressure: 2275 psi
    Valve flow:9.8 gpm

    I think I need a low RPM, high Torque motor correct? Like everyone else I am looking for low cost options.


    Regards,

    Tim
    "Valve flow" is not the number to use, pump flow through valve, at a desired engine rpm, is what we need.


    The lower rpm (high motor displacement) the higher torque you will get...what is the desired output rpm on the motor....also, check efficiancy on gerotor motors, some are low efficient...

    LSHT motor (Low Speed High Torque) is what you need

  3. #3
    Silver Member Tim Stuart's Avatar
    Join Date
    Jun 2007
    Posts
    118
    Location
    Coldspring, TX
    Tractor
    Mitsubishi bd2h dozer, Gradall G3WD, New Holland TC35a, Chevy Dump Truck

    Default Re: Hydraulic post hole digger

    Not sure what you ar asking. Here are the specs for my tractor.

    GENERAL INFORMATION


    Manufacturer New Holland Agriculture

    Model Year 2007

    Model Boomer Compact - TC35A FWD



    MEASUREMENTS
    Length 3-Point Horizontal: 125.2 in. (3,180 mm)
    SuperSteer: 129.5 in. (3,289 mm)

    Height With ROPS: 95.5 in. (2,426 mm)

    Width Minimum: 66.6 in. (1,692 mm) with large ag tires

    Weight 3,231 lbs. (1,466 kg) with ag tires

    Wheelbase 73.5 in. (1,867 mm)

    Fuel Capacity 13 gal. (49.2 l)

    ENGINE
    Cylinders 3

    Gross Horsepower 35 hp (26.1 kW)

    Displacement 101.1 ci (1.65 l)

    DRIVETRAIN
    Transmission Make 12 x 12 SSS

    Drive Type FWD

    HYDRAULICS
    Standard Pump Flow 9.8 gpm (37.1 lpm)

    OPERATIONAL
    Power Take-Off Gear Transmission: 29.6 hp (22.1 kW)

    Lift Capacity @ 24 in. Behind the Balls: 2,025 lbs. (919 kg)

  4. #4
    Veteran Member
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    Port Angeles WA

    Default Re: Hydraulic post hole digger

    Quote Originally Posted by Tim Stuart View Post
    Not sure what you ar asking. Here are the specs for my tractor.


    HYDRAULICS
    Standard Pump Flow 9.8 gpm (37.1 lpm)
    "HYDRAULICS
    Standard Pump Flow 9.8 gpm (37.1 lpm)"

    Suppose this is the closest we can get...
    Sorry I am asking PIA q's, but there is a difference between pump flow capacity and desired max valve flow.....valve can let through higher flow, but at a high pressure drop (power loss)

    This is a big industry problem that pump displacement and max/min rpm range is provided.It happens all the time on tractors...

    If we assume 1800 rpm and a 1811 rpm (9.8gpm) and 2275 psi at PRV, that is about 13hp hydraulic power in put.
    With inefficiency in pump, valve and motor, you will have about 8.5hp available on the motor shaft.....depends on the efficiency numbers and pressure loss input.

    At 60 rpm as motor speed we will need a 27 cui/rev motor
    and expected torque will be about 750 tf-lb

    I hope someone can fill in if I stepped into any "traps"...
    This online Google spread sheet shows how i have been calculating....feel free to play with your own numbers in the spread sheet, The GREEN cells are for YOUR INPUT


    Hoover the mouse cursor over cells to read my comments

  5. #5
    Elite Member Chilly807's Avatar
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    Sep 2009
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    3,200
    Location
    Nova Scotia
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    Kubota L3400DT

    Default Re: Hydraulic post hole digger

    Slower rpm shouldn't be a problem, but usually they turn about 150 rpm at PTO speed. I thought about doing this myself but opted for a PTO driven digger in the end.

    Sean

  6. #6
    Super Star Member J_J's Avatar
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    JACKSONVILLE, FL
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    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: Hydraulic post hole digger

    This is the data from a Rhino auger. If this is about the normal rpm for augers, then find a hyd motor that will give you this rpm, with the hyd GPM, and pressure. Crunch the figures and see if the torque is enough to dig a hole.

    POST HOLE DIGGER:

    *
    Auger RPM is 170.
    *
    Hitch Type - Category 1 & 2.
    *
    Gear Ratio - 3.18:1.
    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

  7. #7
    Silver Member
    Join Date
    Nov 2009
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    127
    Location
    Austin, Texas
    Tractor
    Kubota M5040

    Default Re: Hydraulic post hole digger

    I have a Beltec 3 pt pto with hydraulic down pressure post hole digger $$$$. Goes thru solid rock, concrete, and granite. It is fantastic in how fast it can dig a hole. Look at them and how they are built. They also mfg and sell the bits with carbide teeth, $$$ but worth it.

  8. #8
    New Member
    Join Date
    Dec 2010
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    15
    Location
    Missouri
    Tractor
    Kubota MX5100

    Default Re: Hydraulic post hole digger

    Tim any news on this project. I am comtemplating the same thing myself. I have had to use a pipe wrench to back a auger out of a hole one too many times. I was looking at these
    Worksaver Hydraulic Post Hole Diggers
    They look pretty simple to add a hydraulic motor
    Looking for a low cost suggestion. My tractor is in the 9 to 11 GPM range
    Attached Thumbnails Attached Thumbnails -614h-gif  

  9. #9
    Super Star Member J_J's Avatar
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    JACKSONVILLE, FL
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    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: Hydraulic post hole digger

    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

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