How do you control the length a piston will extention/retraction?

[Daniel_LaFleur]

Originally Posted by rc_cola1323

could you use this

http://www.alibaba.com/product-gs/20..._Five_Way.html

In previous years (including last year) valves not supplied in the KoP were not legal to use, so these would not be legal (although this could change in the future)

Originally Posted by rc_cola1323

and could anyone give more info on how to stop a ram using a three way solenoid

I'm assuming that when you say ram you mean actuator (cylinder).

You would need 2 3-way valves on the primary side of the cylinder and seal the secondary side.
The first valve is used to add pressure or seal the primary side.
The second valve is used to release pressure or seal the primary side.

When you actuate the first valve pressure will build on the primary side of the cylinder and start moving the rod. as the rod moves the gas on the secondary side will be compressed and pressure will build. When you seal the first valve the rod will continue to move until the pressure on both the primary side and secondary side of the cylinder are near equal (difference being friction).

To retract the cylinder you'll just need to activate the second valve.

*Note* the pressure on the sealed secondary side needs to be above atmosphere when the cylinder is fully retracted or the cylinder will only partially retract when the second valve is actuated unless you assist the cylinder with some external spring source like surgical tubing

*Note2* you could add 2 more valves on the secondary side and reverse the actuation from the first side to get quicker (while less efficient) response.