Question about hydraulic post hole digger

[Scott65]

I read an article or two a while back about a couple of DIYers building some front quick attach post hole diggers. I can't find the threads on them but I don't think it will matter because I seem to remember reading them several times and not finding or understanding the lingo well enough to answer my questions:

The hydraulic motor, I believe what is used is a wheel motor, like what drives one of these tractors when a drive axle can't be used. I think I can handle sizing one up to my tractor's specs on hydraulic flow and whatnot (unless a hydro expert just WANTS to pitch in some advice on a model number, haha). But my question is, can these motors handle the force of being tipped up on end and having the force pushed against it directly with an auger bit, or does some sort of hub/bearing assembly need to be made so that the motor is only applying the turning force and the hub assy. is holding the vertical load?

Second question, any suggestions on how to get from motor shaft to auger shaft? It appears that most of the wheel mount hydro motors on Surplus's site are tapered, keyed shafts. And I believe auger bits come in either round or hex configurations. I don't guess I care which one, unless someone can suggest if one is more common than the other. I don't really need one that is stronger over the other, I've only got a Kubota L3301 (30ish H.P.). I don't have any auger bits, so I'll be purchasing whatever I need to fit on any adapter I can come up with or fabricate.

Thanks for any suggestions!
Build thread coming soon

 

[J_J]

You might consider something like this.

21.05 cu in DYNAMIC BMER-1-350 HYD WHEEL MOTOR

Have a machine shop build you an adapter for the auger you want to use.

 

[Scott65]

Yes sir, one of the very motors I was looking at. The only doubt that I had was that one is made to run a higher GPM. My Kubota is rated around 10, this one is 18. But on the flip side, I only need about half of the RPM (I think). I'm basing this off of commercially sold model's advertised specs. So I'm assuming this will sort of even out in the wash.

So by suggesting an adapter to directly attach the auger to the motor, do you think the motor will handle the downward force being applied directly to it? It won't push the shaft through the back of the motor or something?

 

[oldnslo]

You would have to look at manufacturers specs on the motor to see what bearing loads it will withstand. Most wheel motors have some axial load capability but are designed more for radial loading from the weight of the machine and corresponding drive forces.

Yes reduced flow rate (GPM's) also reduces the RPMs of the motor. 10 GPM will spin the 21 CIR motor at around 110 RPM @ 100% efficient. Again look at manufacturers data: It should have a chart or graph showing RPM Vs flow & Torque Vs pressure.

 

[BukitCase]

Here ya go -

http://www.dynamicfc.com/documents/BMER-1.pdf

At a quick glance, looks like you're good to go both axially and radially... Steve

 

[Scott65]

Great info, thanks for the help guys! I've got a nearly complete parts list I think. Now I'm just trying to decide about my valves. I have a real bad habit of going overboard, but I can't afford to do that right now. I have future plans for all sorts of home made implements for front and rear. But I think I'm leaning towards putting a set of spool valves next to the seat, one with a detent. I'll have 2 sets of quick connect hoses. I'll be able to connect either front or rear implements, depending on the task at hand. I don't think I'll ever need to use all at once. If so, then I'll pony up and buy more valves...

The two valves should work for most of my future builds I think. Front mounted, hydraulically powered box shredder and tiller will probably be next. For those, the detent valve will control the motor for blades/tines. The other will control tilt if I decide to add that for added maneuverability beyond what the FEL hydros allow. But for the auger, what I want to achieve is a rigid mounted bit so that it doesn't sway. I want it to be a one man operation. The FEL will control pitch forward and back. Obviously tractor drive and steering will get me to the location of the hole. One valve will run the motor. The other will operate a single ram. I will have the motor attached to a pivot that will allow it to swing side to side, but controlled by the ram, not free floating. I'm thinking of having something sticking up above and directly related to the auger bit with some sort of level to indicate the bit's location when its buried in the ground. I should be able to dig some pretty sweet holes with it when its done. Sounds good in my head anyway. Any thoughts?

 

[vwnotrunning]

Be sure to take pics and post some details if you proceed with this project. I have been interested in building something similar.

 

[Scott65]

For sure! I enjoy building stuff that I can be proud of. And enjoy just as much sharing how I did it. I only hope I get to proceed with this fairly soon. It sucks that this will be the slowest of all the projects I'm sure. Since its the first, it will be one of the most costly. This one requires me to have all of the hoses and valves before any of it works so I will need to take my time and order components a little at a time. Once I have the hydros in place, the other projects should be a little easier to manage. But I will keep everyone posted. I will start a new thread though so that the title will reflect a show and tell rather than questions. That way people searching for answers will know to look there instead.

 

[BukitCase]

This should get you started, if you haven't already found it

2 SPOOL SV VALVE OPEN CENTER W/POWER BEYOND

Your tractor appears to be open center hydraulics at less than 12 gpm, which those are rated for - depending on how you plumb for the extra hydraulics, you might need the Power Beyond - if not, you can replace that plug with the standard plug. Choosing the stacked valves instead of a one piece body will let you expand by buying more sections and longer tie bolts.

Once you start down this path, you will likely want more things under hydraulic control - in my case, one future project (a serious back blade) will need side-to-side, blade angle in two directions, top and tilt, etc... Steve

 

[Scott65]

Thats kind of funny. I had just clicked the link myself for that valve. It was still loading when I switched over to read your post. Great minds think alike I've always heard... I am reading another thread right now too of someone who used a loader valve for top and tilt, which was part of what I wanted to implement into this design. I'm undecided if I want to dedicate circuits and leave that, or save money and use front hydros when needed, switch to rears when needed, tnt when needed, etc. I realize its a pain to be switching hoses and stuff all the time but I have A LOT of projects to be doing right now. I love working on the tractor, but my wife, not so much! So I have to spend carefully. I'll keep reading this other thread and price out the loader valve route. I may decide thats the way to go on TnT and do it separately. Then do the stacked valves that you linked to for my other accessories.