Hydraulic Post Pounder

   / Hydraulic Post Pounder #21  
Just a thought. You already have the set up built and it might be worth considering an air cylinder in place of hydraulic. You'd have to carry a compressor but when you opened the valve, it'd drop in a hurry. It might be worth studying out.
I Never had much to do with air cylinders but do know they use them on some blacktop plants to open and close the drop gates quickly. WHOOSH and it's open or closed.
A neighbor used to have a snowplow on his tractor that he ran the lift with an air cylinder, except he used vacuum off the intake manifold to suck it up instead of pressure, but that probably wouldn't provide enough cfm for your use.
 
   / Hydraulic Post Pounder #22  
Did you get your problem fixed? If so, how?

This thread has been around since last July and your move to Idaho. Still, one more thought and a question or two.

Thought, most of the types that I can find pictures of look like they use about a 1" to 3/4" auxiliary return line in addition to the regular return line that would plug into the auxiliary hydraulic circuit. I did find a Vector Owner's Manual here: Vector Mini Excavator Model - Vector

I have also considered some type of regenerative circuit to move oil to the unused piston end of the cylinder from the rod end but this could require a shuttle valve. I've also thought about an accumulator tied to the piston end of the cylinder to accelerate the business but this would require more force on the rod end of the cylinder to execute the stroke against the force advantage of the larger piston end of the cylinder against an accumulator. Then the problem comes of how to charge the accumulator to the near requisite 1000 to 1500 psi. A nitrogen cylinder for charging is OK but you can only go so far.

I have been gathering steel and parts to build a drive for the last year. The debate rages with myself over whether to use the long stroke cylinder design such as the Vector or the short stroke cylinder and lever such as the Shelburne or Protech. The reversed block and tackle design such as the Black Cat just seems to be asking for trouble. Too many lines and pulleys. The spring and hydraulic cylinder such as the Worksaver and Shafer just don't appeal to me, don't like their rocking action.

On a completely different note I have contemplated trying to find an old plate compactor and build a vibratory unit. I'm pretty sure a hydraulic jack hammer would not produce enough energy to drive 4.5" pipe corner posts and so a small demolition hammer would be most likely required.

On yet another theme a trip hammer raised by a high speed chain and hydraulic motor may provide adequate cycle time and produce a smooth action.

This is a great project. I have sworn that I will never drill and concrete another post. The long planned re-fencing project will require construction of 50 brace, corner and gate panels.
 
   / Hydraulic Post Pounder #23  
We used to get John Deere cylinders that had a kit so they just dropped oil just swapped sides disk hit the ground instantly.
 
   / Hydraulic Post Pounder #25  
To go in a different direction, I would suggest that you have a vertical latch hook with a pivot running on a set of guides that catches a matching loop on the top of the weight when the cylinder is retracted. When the latch is extended all the way up it it's tripped and retracts out of contact with the weight and allows it to free fall. This doesn't involve handling the volume of oil vacating the cylinder! Use a wood splitter type valve/pump system for a fast retraction. In fact, you could almost use a vertical wood splitter for the base unit if you added an extra several feet and fabbed the link and trip mechanism!!
 
   / Hydraulic Post Pounder #26  
My uncle built them for years. Just used a cable to pull weight up, free wheel down. Simple and worked flawlessly. Made wood splitters out of the same rig. Worked like a pulpwood truck cable loader. I don't see how you can fast drop with hydraulics. Why cross ties? I work thousands of cattle, no cross tie fences, just corners and an H brace along.
 
 
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