Multiple cylinders on a solenoid

[robogeek753]

This is probably going to sound like a stupid question but I wanted to make sure.
If I wanted to put two or more cylinders (or pistons or whatever you like to call them) onto a single celenoid (via 2 T-quick connect fittings) would it work and/or would the effect be any diffrent than having two celenoids each on one cylinder off of one regulator?

[Kevin Sevcik]

It will work. They will not extend at the same time, most likely. Water, air, and electricity all take the path of least resistance, so the piston with the least load/friction will extend faster and/or before the second piston. This would be a problem even with seperate solenoids, though not quite as big. The only sure fire solution is basically to seperate the two solenoids with check vales and things so they're operating from different pressure sources.

[gburlison]

Originally Posted by robogeek753

This is probably going to sound like a stupid question but I wanted to make sure.
If I wanted to put two or more cylinders (or pistons or whatever you like to call them) onto a single celenoid (via 2 T-quick connect fittings) would it work and/or would the effect be any diffrent than having two celenoids each on one cylinder off of one regulator?

We have run two cylinders off of one solenoid valve many times. It is better if both cylinders are identical, but it is not necessary. The only difference is that the solenoid valve has a maximum flow rate and if you want the cylinders to move fast, two will move slower than one. I would look at the specs of the valve and pick the one with the highest flow rate if the speed is a concern.

[Chris Fultz]

it is done regularly - especially with pneumatic shifters to be sure they are firing at the same time.

you will have a hard time noticing any difference in response.

[David]

Originally Posted by Chris Fultz

it is done regularly - especially with pneumatic shifters to be sure they are firing at the same time.

you will have a hard time noticing any difference in response.

although, at least with the andy mark shifters, you can notice that there is a diffence in the time it takes a gear to engage

if you're not careful you can turn when you shift

[kmcclary]

Originally Posted by Kevin Sevcik

It will work. They will not extend at the same time, most likely. Water, air, and electricity all take the path of least resistance, so the piston with the least load/friction will extend faster and/or before the second piston. This would be a problem even with seperate solenoids, though not quite as big.

The only sure fire solution is basically to seperate the two solenoids with check vales and things so they're operating from different pressure sources.

Actually, you'd STILL get the above problem with that method. Think about it. Nothing has changed WRT the loads themselves.

Off the top of the head, I can only think of two ways to insure they move together perfectly in sync:

A) Mechanically tie the pistons together via some mechanism. (But heck, if you did that, why bother with two cylinders in the first place???)

B) Use closed loop controls, position monitoring, and more complex valves than are supplied, to monitor and "throttle back" the faster cylinder based on its motion. (This is MUCH more complicated, and rarely if ever worth the effort!)

Honestly, if you REALLY need two things to go EXACTLY together, figure out a way to mechanically couple them, and drive them both with one cylinder simultaneously.

One example might be to use a differential bell crank. With servos, you simply use opposing ends of the "X" horn on the top of the servo, and run links out both ways.

With a cylinder, you "float" the "X" - two opposing ends go to your two devices, and a third end runs over to your cylinder. When the cylinder pushes or pulls on the crank, the two devices switch together.

(Warning - With ANY bell crank system, be sure to use a spring loaded "servo saver" ends to prevent over-run freeze-up. Otherwise, the load that switches first and hits ITS stop will freeze the crank. This could prevent the other load from fully switching!)

Does this make sense?

- Keith