Self plumbing 3PH PTO driven PHD?

bam747 · Aug 26, 2005

Does anyone know of any manufacture that makes a two axis fully self plumbing 3PH PTO driven post hole digger?

I'm looking for the same self plumbing capabilities associated with skid steer mounted PHDs without having to purchase an expensive hydraulically driven PHD mounted on a 3PH boom or a FEL skid steer QA or FEL bolt on mount (assuming my tractor has enough hydraulic GPM flow to operate it!).

All the 3PH PTO driven PHDs I know about only have a single axis leveling mount for the auger, not a true self plumping mount. This may be a limitation of the U-joints used on the PTO shaft that powers the auger's gear box.

beenthere · Aug 26, 2005

I don't think the skid steer PHD's are 'self plumbing'. The PHD auger when digging deeper is plumbed in a skidsteer by backing up and/or moving sideways to keep it straight up and down (or curling the quicktach a bit).

Once the point of the auger starts digging, the top must be re-positioned to keep the auger going straight down.
The only advantage of the hyd over the PTO is the ability to reverse directions and 'unscrew' a stuck auger.

Maybe others can enlighten me further. /forums/images/graemlins/wink.gif

JerryG · Aug 26, 2005

To plumb the other axis, you adjust the crank for the lift arm. If your tractor has one, most do.

bam747 · Aug 26, 2005

All...

I understand that there are ways to work around the limitations of a typical 3PH PHD when it comes to digging holes on a slope. As suggested, you can adjust the lower link arms on the 3PH manually or, preferably, using the hydraulic tilt of a T&T kit. Or, you can make sure the long axis of your tractor is always aligned on the fall line of the slope, which might not always be possible.

My issue is that you just do not have this problem with most skid steer style augers and I don't see why 3PH augurs can not be designed with the same mechanism.

For "enlightenment", here is some quoted text from Bobcat's website describing their auger attachments (link)...

"Dig 6-inch to 42-inch holes with speed and plumb-line accuracy. The heavy-duty hydraulic auger bites in with high torque power. Because of a unique knuckle-joint design, the auger will hang plumb even on uneven terrain. Three models to choose from."

This is exactly what I mean by "self plumbing".

If you're using one of Bobcat's "straight line" lift skid steers, you probably don't have to reposition the skid steer much at all to get a plumb hole even on a slope as you burry the auger. I realize that on a utility tractor 3PH or FEL or radius lift SS you will have to reposition as you dig the hole, but at least the hole automatically starts plumb.

If you really want to see Bobcats self plumbing augers in action, have a broadband internet connection, and a browser that supports QuickTime, check out this link to a Bobcat QuickTime movie on their augers.

BTW, I've been doing my homework and know that there are many other manufactures of skid steer QA augers that also provide true self plumbing (Rhino, LandPride, Woods, etc.).

All this self plumbing action requires is a mechanism with two axis pivoting to go between a 3PH post hole digger boom and the gear box. Why no manufactures appear to make 3PH PHDs with this feature mystifies me. I assume there must be a technical issue with U-joint angles on a PTO driven PHD, but I can't for the live of me figure out why hydraulically driven 3PH PHDs appear to have the same limitations.

JerryG · Aug 26, 2005

I see what you are saying now. The reason that a PTO digger only pivots in one axis is because the power is being transmitted from the tractor. Since it comes for the tractor, if the auger was to hang in a way that it couldn't turn, the PTO would try to rotate the gear box around the PTO shaft. The typical bobcat auger has a hydraulic motor attached to the gear box. If the auger on the BC was to lodge, the hydraulic motor would only try to twist the gear box around the auger. It can't because of the way it is bolted. I don't know if I made it clear enough for anyone to understand or not.

gabby · Aug 26, 2005

</font><font color="blue" class="small">( Does anyone know of any manufacture that makes a two axis fully self plumbing 3PH PTO driven post hole digger?
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I think you're expecting too much. Even if you start out plumb it won't stay plumb as the auger head goes down.
gabby

bam747 · Aug 27, 2005

Ah ha! I'm starting to see the light! Thanks JerryG... /forums/images/graemlins/smile.gif

At least now I see why 3PH PTO driven PHDs only pivot front to back and not side to side. If the auger head could pivot from side to side, the torque applied by the PTO shaft to the input shaft of the 90 degree PHD gear box would be able to twist the gear box and auger sideways.

The motors on the hydraulically driven augers used on skid steers use planetary gearing and are inline with the auger shaft, so they do not need a 90 degree change in rotating direction. This means the mount for this type of hydraulically driven auger only has to resist torque around the axis of the auger shaft but the shaft can swing freely in any direction 90 degrees to the shaft.

Or something like that...

I'm not sure I'm articulating this properly, but at least I can see in my mind what's going with PTO and inline hydraulic motor driven PHDs.

And now I also think understand why the hydraulically driven 3PH PHDs have the same mounting system and issues as the PTO driven models!

If you look carefully at the hydraulically driven 3PH models, they use the same 90 degree gear box as PTO driven models but replace the PTO drive shaft with a hydraulic motor. None of the hydraulic 3PH PHDs I've seen use the same inline hydraulic motor that is used on the skid steer models.

However, fundamentally, I can see no reason you couldn't hang one of the inline hydraulic augers with its two axis swinging mechanism off a 3PH boom. But, judging by the prices of skid steer augers, that would be an expensive way to go!

bam747 · Aug 27, 2005

I was expecting too much from a 3PH PHD.

As has been pointed out, you do have to understand that the auger head on the end of the 3PH PHD describes an arc as it moves up and down. You'll have to compensate for this by moving the tractor back and forth as the auger head moves up and down.