Hydraulic post hole digger

   / Hydraulic post hole digger #1  

Tim Stuart

Silver Member
Joined
Jun 5, 2007
Messages
127
Location
Coldspring, TX
Tractor
Mitsubishi bd2h dozer, Gradall G3WD, New Holland TC35a, Chevy Dump Truck
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
 
   / Hydraulic post hole digger #2  
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
 
   / Hydraulic post hole digger
  • Thread Starter
#3  
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)
 
   / Hydraulic post hole digger #4  
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"...:laughing:
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
LSHT_drive.jpg


Hoover the mouse cursor over cells to read my comments
 
   / Hydraulic post hole digger #5  
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
 
   / Hydraulic post hole digger #6  
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.
 
   / Hydraulic post hole digger #7  
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.
 
   / Hydraulic post hole digger #8  
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
 

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