post hole pounder hyd return

[6sunset6]

I think this conversation wants to be in hydraulic but I will post one more time here.
It looks like a big weight is the best way to apply a lot of down force fast.
12" diam 18" high solid iron is 470 #
2" diam cylinder has an Area of 3.14 2250 psi will lift 7000 #
Now it gets interesting
A post is 8-10 feet so the bottom of the weight is up there , then the weight has to lift so it can drop, then the weight has to travel at least 3 feet.
Best to use the difference between the 470# and the 7000# to shorten up the stroke of the cylinder . multi part cable lay on the cylinder stroke. I worked this out once count the lines coming of the moving pulley and that is the mechanical advantage . anyway that's all mechanical.
This is the good part.
a 2" diameter cylinder with a 20 inch stroke is a vol of 63 ci . Say one second to drop the weight is equiv of 3768ci per min divide by 231 ci per gal and it comes out to 16 gal a min exhaust flow for one sec.
I think it wants to dump into the fill port through a big a hose as possible.
Not sure if a 20 gpm valve is really big enough either.
Food for thought. Unless I made a mistake someplace. always possible

 

[RickB]

You can downsize your cylinder diameter. Shaver uses a direct connection between the cylinder and the 'hammer' and their cylinder is no larger than 1-1/2" bore,maybe smaller. I have quite a bit of experience with a Shaver HD-10 driver running the return back to sump using a standard 1/2" ISO couplerto an open discharge. But that was years ago and Shaver supplied a 'real' return line. Depending on your actual flow, a 3/8 open return may be too small, but it may also work. Your existing valve stack cover should be drilled and tapped. If my math is correct, a one inch bore cylinder at 1500psi will create 1178 lbs of force to lift your weight in a straight push.

 

[6sunset6]

yes , a direct lift would work , it is just a very long stroke on the cylinder 3feet at least . My valve cover does have a plug in it. I have two remotes so the cover is about 3 inches from the tire. figuire an elbow would take 1/2 of that . Kind of close to the tire. R4.
Lots of ways to skin this cat. First I have to figuire out if I want a vegtable garden big enough to require a post driver.

 

[RickB]

You could always make the garden big enough to share with the critters & forget the fence!!

 

[jinman]

You could always make the garden big enough to share with the critters & forget the fence!!

How big would that be, Rick? I have this nightmare that I'm standing in front of my corn patch and every raccoon in the county has shown up for the banquet.

 

[SPYDERLK]

You can downsize your cylinder diameter. Shaver uses a direct connection between the cylinder and the 'hammer' and their cylinder is no larger than 1-1/2" bore,maybe smaller. I have quite a bit of experience with a Shaver HD-10 driver running the return back to sump using a standard 1/2" ISO couplerto an open discharge. But that was years ago and Shaver supplied a 'real' return line. Depending on your actual flow, a 3/8 open return may be too small, but it may also work. Your existing valve stack cover should be drilled and tapped. If my math is correct, a one inch bore cylinder at 1500psi will create 1178 lbs of force to lift your weight in a straight push.

The shaver cyl doesnt have a sealed piston inside. The "piston" actually only guides the end of the rod. It has big holes to let the oil get to both sides. The area of the rod is therefore the acting piston.
larry

 

[6sunset6]

It is really starting to sound like dumping the return oil fast is an engineered solution. The trick would be to get it right the first time. Not that the pro's manage to do that either.

It would be a really big garden to feed the SE NY deer herd. I am not sure it could be big enough ever. Maybe for a single crop like corn but for mixed vegtables they just go from one to another feasting.

 

[MikePA]

I have been having some delusional thoughts about building a post pounder. It would be interesting. One of the things I realize is that the hydraulic return from the lifter cylinder , on the way down , wants an unobstructed path to the sump. The best way is through the Transmission fill plug.

Attached are 2 pictures. One is what came with my post pounder and the other what a fellow TBNer developed for me. The factory solution (left pic) was to somehow position this in the transmission fill hole and secure it. It created a big mess. I replaced the black fitting on the left with a female quick connect. Works like a charm.

 

[6sunset6]

The second picture is probably the best way to go. Get a spare fill plug, Rick provided the PN, and drill and tap it for a pipe fitting.


I found a cross section of a shaver cylinder . looks like it runs on a 3 way valve with only one port in the cylinder . So no hydraulic applied pressure on the down stroke, just the weight. Pretty special cylinder, probably not available except as a spare.