John Coloccia
05-03-2009, 4:41 PM
So I'm sure many of you have a the small Shop Fox pin router. It's not heavy duty, but for light work it works GREAT...
...except the first 2 inches, or so, of the stroke going down. No matter how you adjust it, it does the first 2 inches at light speed, practically cutting the useful range in half.
After pondering for a couple of days, I realized what the problem was. As soon as you pressurize the top of the cylinder, the cylinder will go to an equilibrium position, even if no air is released from the bottom part of the cylinder. Once equilibrium is reached, it will proceed down slowly, controlled by the bottom valve (i.e. controlled by the flow of air OUT of the bottom valve).
The solution is simple. I put a piece of angle iron under the lock nut (the one that locks the depth adjustment threaded rod), and let it hang a bit off each side of the slide. Then I strung a bungee through one side of the angle, up over the frame, and through the other angle. The bungee is tight enough to make it so the slide doesn't move with the pedal depressed, and the bottom hose completely pinched off.
End result is the bottom valve now completely determines the feed rate from the top of the travel to the bottom.
I was so frustrated trying to get this to work right that I almost returned the stupid thing. Now I love it.
...except the first 2 inches, or so, of the stroke going down. No matter how you adjust it, it does the first 2 inches at light speed, practically cutting the useful range in half.
After pondering for a couple of days, I realized what the problem was. As soon as you pressurize the top of the cylinder, the cylinder will go to an equilibrium position, even if no air is released from the bottom part of the cylinder. Once equilibrium is reached, it will proceed down slowly, controlled by the bottom valve (i.e. controlled by the flow of air OUT of the bottom valve).
The solution is simple. I put a piece of angle iron under the lock nut (the one that locks the depth adjustment threaded rod), and let it hang a bit off each side of the slide. Then I strung a bungee through one side of the angle, up over the frame, and through the other angle. The bungee is tight enough to make it so the slide doesn't move with the pedal depressed, and the bottom hose completely pinched off.
End result is the bottom valve now completely determines the feed rate from the top of the travel to the bottom.
I was so frustrated trying to get this to work right that I almost returned the stupid thing. Now I love it.