Pneumatic Air Hammer Design Help

[skdaddle]

I am new to this forum and want to say hello to everyone, also to ask for someone to help me with an air circuit problem. I want to use two air cylinders on either side of a 500 lb. weight that will be used to raise and drop the weight as a pneumatic drop post driver. I have two 2 1/2" bore double acting cylinders with 12" strokes that I would like to use. I have very little knowledge of air circuitry but can read and figure out schematics to put something together. I know it will need a pilot valve, but not sure if a 4 way or 5 way is best, also flow controls, limit switches and exhaust valves. I have a 30 gallon shop air compressor that puts out 9 cfm but I think more may be needed to achieve an optimum 30 hits per minute on a continuous cycle of the cylinders.
Can anyone steer me in the right direction to get this project started? I have welding equipment to construct the hammer body, just need a layout on the air components so I can attach everything to the steel pipe and weight.
Please let me know where I need to begin, I'm trying to decipher online pneumatic circuitry symbols but having trouble matching them up with actual parts they represent.
Thanks in advance for any assistance you can provide.

 

[Les Jones]

I think you will need to raise the weight using the cylinders but release it with a mechanical latch so that the restriction of the air escaping from the cylinders does not slow down the decent of the weight.

Les

 

[skdaddle]

I was hoping by using a 12" stroke with double acting cylinders that the back pressure would not be that affected by the exhaust port size, but if my cylinder port sizes are not large enough, I might have to find (or have built) cylinders with 1" ports to accomplish what I need. Thanks for pointing this out to me, Les.

 

[skdaddle]

Les, I failed to mention that I have a capstan winch that will raise and drop the hammer thru a rope and pulley system, which is what you were alluding to on the release phase, but to do this with the capstan I need a rail system that the hammer can roll up and down on to keep it aligned with the work below it. My hope was to just suspend the pneumatic hammer from above with an excavator so it would just sit on top of the post and we would lower the excavator with the hammer as it drove the post in the ground without having all the ropes and man handling involved. I am sure this is a do-able project, just have to work the wrinkles out. Thanks again for your help.

 

[KeepItSimpleStupid]

I don't think your going to get anywhere without talking directly to a manufacturer of air cylinders. You usually want to control the exit port to control the exit air.

You, effectively want one port controlled and the other wide open, but way more than usual which I think translates to a custom port probably the size of the piston.

This https://www.peninsularcylinders.com/CFG/HH_Air_NFPA_Cylinders/HH_Air_NFPA_Port Types.htm references oversized ports, but still not a range of sizes.

 

[shortbus=]

I don't think your going to get anywhere without talking directly to a manufacturer of air cylinders. You usually want to control the exit port to control the exit air.

There is another way of doing this, something called a "quick dump valve". It is used on single sided cylinders for this type of thing, controlled pressure in one direction and no restriction in the other. Though he want's to use air for this, most of this type of driver uses hydraulics.
https://skidril.com/hp1000.html?gclid=EAIaIQobChMI6IDO1ZjT2gIVBrXACh3yNgevEAQYASABEgJ9zfD_BwE

 

[large_ghostman]

If your using a digger or tractor to place this, then hydraulics would be a better way to go. You only need to make sure you have a hydraulic take off valve free (or add one) on the digger.

That would then open you up to using a large tipping trailer ram, these can be had for little money second hand. They can raise pretty fast and should drop like a stone with the valves opened.