Re: spindle counterweights

I just joined this group after following it for a couple of weeks.
I'm in the process of assembling a CNC router. The Z
axis will be fairly heavy as I plan on using a 3 1/4 hp router head.
My plan is to use a pneumatic cylinder to balance the weight on the Z
axis. The cylinder will be connected to a small surge tank. The
pressures will be controlled by a regulator with pressure guage.
Hopefully the system will be tight enough so that an external air
supply will not normally be required. Has anyone tried this system
and/or do you have any alternate suggestions? Bob Lemon