Hi All,

Sooo, I am ordering parts for my CNC machine that I am building. A very heavy ATC spindle, 2nd hand to me from a Biesse Rover, 95lb weight, I figure the Z axis up and down weight at 192 lbs, ouch! Using a big steel tube for the Z as the spindle uses a flange mount.

Counterbalancing this monster, originally I was going to use gas struts. But, they have dampening, and the pressure is not adjustable. The dampening is the big thing. I actually contacted a supplier on aliexpress and asked about getting springs without dampening. Of course, they don't have any.

Right now, I am looking at two 32mm bore 300mm stroke pneumatic cylinders. By my calculations (P1V1 = P2V2) and PSI x bore area in sq in = spring force, that gives me about 77 PSI required mid stroke for each cylinder. My compressor will do 90 PSI, so I can fill the reservoir. I'm looking at a reservoir of half a gallon to one gallon. Half a gallon or about 115 cubic inches would work for me. That would give me perfect balance mid stroke, and 11lbs at the top and 11 lbs the other way at the bottom of the stroke.

I'm thinking about attaching a bottle to the gantry, perhaps a fire extinguisher, or two 1LB propane tanks. Ideally, a square reservoir perhaps 3" x 1.5" three feet long more or less would be nice. I have thought about trying to make one from 1/8" wall square steel tube and half inch plate, but I'm not certain that this is a good idea. I sure as heck will not be trying to pressurize pvc or anything suicidal like that.

Any ideas out there on what to use for a reservoir?

For the cylinders I am thinking about these:

https://www.aliexpress.com/store/pro...706226382.html

I contacted the supplier and asked for some info. As far as I can tell, it’s 3/8” BSP Thread to connect to the pneumatic cylinder.

I was thinking of two of these to connect to the two cylinders using 3/8” ID standard compressor hose.

https://www.aliexpress.com/item/Pack...794683816.html

I don’t have any experience with these cylinders. I hope they don’t leak, as I don’t plan on having them continuously hooked up to an air source, I figure I can top it up once a week if I need to, if it’s more than that, then I need to rethink.

I'll have a QD fitting to top up the pressure (at the reservoir) and two additional fittings to connect to the two hoses at the reservoir.

Also, does anyone have any experience with the fittings that you simply push a hose into?

Also, the pneumatic cylinder has a 1/8" hole for air to go in and out. I'm wondering if that might be a bit restrictive for my purposes. All of the 32mm bore pneumatic cylinders I have seen have 1/8" air inlet holes.

Any advice on what to use for a reservoir, or fittings, or cylinders, appreciated.