My pneumatic counterbalance

[Uguessedit]

Davo, I know this post is old and you may no longer be around so taking my chances here. I’m working up a pneumatic setup myself with a 550 cylinder 35/60 and utilizing 35 roller chain and sprockets. I have an old propane tank for a reservoir and I am down to figuring out what needs to be done for air control. This is where I am confused and I have struggled finding information online hence the old post. I have no previous pneumatic experience. My mind tells me if I push 40lbs of air in the lower and upper cylinder I will lock it and defeat the purpose I am after. How do we achieve the motion necessary to counter the head and appropriately differentiate the air pressure from one port to another? Do you have a diagram and or suggestion of pneumatic valves I would need to make this happen? Obviously I need a regulator. Is there a solenoid to either side that is turning on and off by the motion control outputs as direction changes or is this less complicated than that? My logic isn’t clear here however my mechanical abilities are certainly fine given the proper information. Hopefully you or someone else see’s this post and can help. Thank you.

When I had the gearbox apart I installed brackets to the top about halfway between the motor and spindle for counterbalance cables to attach to. Made up brackets to mount the pulleys to. They are 2 1/2 in steel from grainger. The cables are vinyl coated 1/8 in. The cylinder is 3.25 in bore, 21 in stroke. New unit off ebay $50.00 to the house Hose runs from a 9 gal air tank to the rod end side of the cylinder. 40 psi in the tank seems to work great, gives about 240 lb of pull on the cables. Im going to add one more cross brace to the pulley mount and then i will pull it off and paint it. I will also mount the tank up under the stand.Dave

[neilw20]

It is pretty much all here.
You need to read the thread from the start.
Air goes into one side of the cylinder only, at some fixed pressure.
If the volume of the tank is large in comparison to the volume of the cylinder, then once charged to a fixed pressure to balance it, nothing else is needed.
The smaller the tank, the greater the pressure change from one end of travel to the other. Just have the tank volume a lot larger than the cylinder swept volume.
If the air temperature is much lower than when charged, the pressure will become lower. eg. hot summer, to freezing winter.
If you want it to operate over a wide range of temperatures, with no manual adjustments, then a regulator would solve this.
Alternatively, just use a counterweight, and no air complications are needed. Just a bucket of concrete.

[Jim Dawson]

It is pretty much all here.
You need to read the thread from the start.
Air goes into one side of the cylinder only, at some fixed pressure.
If the volume of the tank is large in comparison to the volume of the cylinder, then once charged to a fixed pressure to balance it, nothing else is needed.
The smaller the tank, the greater the pressure change from one end of travel to the other. Just have the tank volume a lot larger than the cylinder swept volume.
If the air temperature is much lower than when charged, the pressure will become lower. eg. hot summer, to freezing winter.
If you want it to operate over a wide range of temperatures, with no manual adjustments, then a regulator would solve this.
Alternatively, just use a counterweight, and no air complications are needed. Just a bucket of concrete.

Yup, what neilw20 said. That's the way mine works. The bucket of concrete works too.