Plumbing, Wiring, and Controlling a 3 Position Cylinder

[Boe]

Originally Posted by Gregor

3. Finally, can you share some neat implementations of 3 position cylinders on FRC robots?

Ive never used one but im nearly certain they are used in power take offs to give your shifter a neutral allowing you to switch drive train power to another mechanism (ie climber)

here is a picture of 254s 2010 pto they used a three position cylinder i believe http://www.chiefdelphi.com/forums/sh...4+2010+gearbox

[Michael Hill]

I made a cut-away of 3-position cylinder (attached) so you can see the plumbing. This is a bimba 3-position cyl.

If you pressurize the front (left in picture) port, the cylinder retracts all the way. If you pressurize the rear one, it goes to the middle position (because the rear rod has a shorter range of motion). It pushes the forward rod out, but not as far as it could. If you pressurize the middle port, the rod comes out all the way.

If you want to keep track of the position, Bimba sells an option to have a magnetic piston.

http://www.bimba.com/Products-and-Ca...hree-Position/

[DELurker]

Originally Posted by Michael Hill

I made a cut-away of 3-position cylinder (attached) so you can see the plumbing. This is a bimba 3-position cyl.

http://www.bimba.com/Products-and-Ca...hree-Position/

Looked at Bimba's site today, and the random tech tip of the day was...

http://www.bimba.com/Global/Library/..._Cylinders.pdf

[CENTURION]

Originally Posted by Michael Hill

I made a cut-away of 3-position cylinder (attached) so you can see the plumbing. This is a bimba 3-position cyl.

If you pressurize the front (left in picture) port, the cylinder retracts all the way. If you pressurize the rear one, it goes to the middle position (because the rear rod has a shorter range of motion). It pushes the forward rod out, but not as far as it could. If you pressurize the middle port, the rod comes out all the way.

If you want to keep track of the position, Bimba sells an option to have a magnetic piston.

http://www.bimba.com/Products-and-Ca...hree-Position/

I don't think your cutaway did it's thing right. Because the way it looks, two of the ports would send air right into the rod, and not extend or retract anything.

[T^2]

Originally Posted by CENTURION

I don't think your cutaway did it's thing right. Because the way it looks, two of the ports would send air right into the rod, and not extend or retract anything.

I'm not sure how it is possible so send air "into" a cylinder rod. It looks like the the darkest gray in the picture (gradient) is the cavity in which the rods can slide back and forth, and the lightest gray is where air can enter, but not a rod. I think air can flow freely between the light gray and dark gray sections, and the boundary simply indicates where the rod stops.

[CENTURION]

Originally Posted by T^2

I'm not sure how it is possible so send air "into" a cylinder rod. It looks like the the darkest gray in the picture (gradient) is the cavity in which the rods can slide back and forth, and the lightest gray is where air can enter, but not a rod. I think air can flow freely between the light gray and dark gray sections, and the boundary simply indicates where the rod stops.

Yeah, I did a pretty poor job describing what I meant.

The solid light grey areas (where you can see the cutaways of the threaded ports), don't seem to allow the air from the ports to actually go anywhere (except for the port on the blind end of the cylinder).

If the cylinder is built like the diagram in Travis' post shows, then there is clearance around the rod to allow airflow, but as it is, I'm not seeing it.