Solenoids and <R74>

[cmwilson13]

u cant stop them mid stroke they will always extende if u put pressure to both sides ther is more surfuce area to extend then retract the rod blocks some of the retraction area
http://docs.engineeringtoolbox.com/d...c-cylinder.png
if u look at that picture u can see why there is less surfuce area to retract



yes u can plug the exhaust and it would stop somewhat in the middle

Originally Posted by jee7s

Just keep in mind that in either case you won't be "locked" in position. Air does compress, after all.

[implosionprez]

Yes, the compressability of air does make it a bit problematic. It does stop, as long as it's sitting stationary in our shop, with no forces or accelerations acting on it, but in competition, who knows if that will still happen!

[jee7s]

Duly noted.

So, I guess you really do need two solenoids then. I stand corrected.

[EricH]

Originally Posted by cmwilson13

u cant stop them mid stroke they will always extende if u put pressure to both sides ther is more surfuce area to extend then retract the rod blocks some of the retraction area
http://docs.engineeringtoolbox.com/d...c-cylinder.png
if u look at that picture u can see why there is less surfuce area to retract

You can stop them mid-stroke. It's been done. It's been done in FRC.

If you put the same pressure on both sides, the piston may move...

...Provided that the displaced air has somewhere to go. If that air has nowhere to go, then the piston's motion will stop as soon as the force on each side is equal. Motion will resume as soon as the air has somewhere to go again. By placing a single solenoid on the exhaust of a double solenoid, it is perfectly possible to gain control over where the piston stops.

[PAR_WIG1350]

http://forums.usfirst.org/showthread.php?t=16848

Sorry, but your question appears to have been answered...

[jee7s]

Originally Posted by PAR_WIG1350

http://forums.usfirst.org/showthread.php?t=16848

Sorry, but your question appears to have been answered...

Seems that one double acting valve may be the best you can do...

Using two secondary regulators may resolve the force balancing issue that's been pointed out, though that would take a lot of tweaking.

[cmwilson13]

What i said is still correct if u put the same presure to both sides IT WILL EXTENED. If u plug the exaust then the cylinder compress the air in the side wth less surfuce area untill the forces equilize

[Chris is me]

Originally Posted by cmwilson13

the air in the side wth less surfuce area untill the forces equilize

that equalization may be before it's fully extended. Potentially a particular, predictable amount before.

[implosionprez]

That brings us back to the original problem though, because you can't have more than one solenoid controlling the inputs of one piston, so you can't have a "stop solenoid", whether it's before the primary solenoid, in the feeder line, or after the primary solenoid, in the exhaust line. It's still illegal, according to <R74>

[wilsonmw04]

Originally Posted by implosionprez

That brings us back to the original problem though, because you can't have more than one solenoid controlling the inputs of one piston, so you can't have a "stop solenoid", whether it's before the primary solenoid, in the feeder line, or after the primary solenoid, in the exhaust line. It's still illegal, according to <R74>

so the way we have gotten around the lack of center locking solenoids in the past is now illegal. I wonder why they axed this after many years of it's use?

[implosionprez]

I have no idea. We have used it before, back in 2008 with Overdrive. I looked back at the 2008 manual, and there isn't a rule like this year's <R74>. It doesn't say anything about having to have pistons work through the movement of air through only one solenoid.