making a post hole digger

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case310350

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I am making a post hole digger, have some hydraulic motors from a street cleaner. My question is on commercial units is the hydraulic motor isolated from the auger? so no down pressure is put on the motor?
 

skidsteer.ca

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Some hyd motots have extra hd outout shaft bearings to carry some out of the ordinary loading, but I would think in this case you will need a gear box anyway to reduce thr rpm and increase the torqe.
To my knowledge all the dirrect drive ones use a planetary sytem now instead of a chain reduction and the auger output shaft is not really direct to the output of the motor.
Ken
 

NHDealer

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Some hyd motots have extra hd outout shaft bearings to carry some out of the ordinary loading, but I would think in this case you will need a gear box anyway to reduce thr rpm and increase the torqe.
To my knowledge all the dirrect drive ones use a planetary sytem now instead of a chain reduction and the auger output shaft is not really direct to the output of the motor.
Ken
Probably the easiest would be to build a gear or chain reduction auger. Most "commercial" augers are planetary.
 

Tazza

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Probably the easiest would be to build a gear or chain reduction auger. Most "commercial" augers are planetary.
You will need to reduce the speed with chains and gears, you don't need much speed but you need the torque. As ken and NHDealer have said, the newer style units are compact and use planetary gearing. I have seen one that was very simple, the motor was linked to the drive with 2 gears and one chain. The biggest trick will the building the auger.
Let us know how it goes.
 

case310350

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Probably the easiest would be to build a gear or chain reduction auger. Most "commercial" augers are planetary.
whats the typical rpm of a post hole digger? I made one years ago out of the street cleaner brush motor direct drive, rpm's maybe 120. ths was a small motor but had plenty of torque, used a 9 inch auger. will hook up the bigger motor and check the rpm. since this was the drive wheel (tire mounted directly to the motor) of a three wheel street cleaner it may allready have bearings.
 

skidsteer.ca

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whats the typical rpm of a post hole digger? I made one years ago out of the street cleaner brush motor direct drive, rpm's maybe 120. ths was a small motor but had plenty of torque, used a 9 inch auger. will hook up the bigger motor and check the rpm. since this was the drive wheel (tire mounted directly to the motor) of a three wheel street cleaner it may allready have bearings.
If it carries the weight of the machine it will have bearings of some sort.
I try to get t checking the rpm on my bobcat 15 c auger, I have machines with 15 to 18 gpm
But I would guess 50 to 60 rpm at 17 gpm flow. I remember it was supposed to generate @ 1500 ft lbs torque at 2500 psi.
The wheel motor you have may be made to work at such low rpm with high torgue, however most motors need to run much faster then that.
If you know the machines max speed, you can figure the motor rpm from the wheel diameter, then you should be able to calculate the flow (gpm) your motor needs to run that rpm. Then system max pressure at your given flow will allow you to figure torque.
A 9” bit wold not need 1500 ft to work, maybey 400 to 500, but the bigger the bit the more you need.
Ken
 

Tazza

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If it carries the weight of the machine it will have bearings of some sort.
I try to get t checking the rpm on my bobcat 15 c auger, I have machines with 15 to 18 gpm
But I would guess 50 to 60 rpm at 17 gpm flow. I remember it was supposed to generate @ 1500 ft lbs torque at 2500 psi.
The wheel motor you have may be made to work at such low rpm with high torgue, however most motors need to run much faster then that.
If you know the machines max speed, you can figure the motor rpm from the wheel diameter, then you should be able to calculate the flow (gpm) your motor needs to run that rpm. Then system max pressure at your given flow will allow you to figure torque.
A 9” bit wold not need 1500 ft to work, maybey 400 to 500, but the bigger the bit the more you need.
Ken
It sounds like the motors you have may already have some sort of gearing inside.....
 

Skid Steer Solutions

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We use a direct drive motor, but it has a big support bearing to carry the side loading. Without it, you will toast your shaft seal and then your shaft. Typical speed is 7 RPM per gallon of flow.
 

Tazza

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We use a direct drive motor, but it has a big support bearing to carry the side loading. Without it, you will toast your shaft seal and then your shaft. Typical speed is 7 RPM per gallon of flow.
I was going to say you will need thrust bearings too, the “standard” bearings motors have are for side to side load, they don't enjoy being pushed end on and will fail. Being an auger you will have a few hundred KG pushing on the bearings that i can see being a major problem unless you have a coupling that has thrust bearings.
Keep us informed how it works out.
 
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