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Originally Posted by Why_A_Username?
The gist of what i got from your post is that basically flow rate is equal too, if not greater than PSI in importance, because it is hard to maintain a constant PSI. We want a fast-fireing solinoid with a wide flow in between the resovior and the barrel tube to minimize the pressure drop between the two. Our current design has multiple barrels so thst presents a challange for multiple resovior connections. Thanks for the great reaponse!
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A bit of experience from 2014. We had a pneumatic catapult to launch the giant ball that year. We initially used our in-house SMC Solenoids. About halfway through the season, we started having issues (some Teflon tape had gotten into the solenoids) and we started looking for alternatives. We also started to log the air pressure on both sides of the solenoid for debugging purposes and were very shocked by the pressure differential. We had up to a 30 PSI delta across the solenoids.
The key item with flow rate is that at some point increasing your PSI has zero effect on the performance of the system. There is only a finite amount of air a given solenoid can pass (as I understand it from the aerospace engineers, the air can travel no faster than the speed of sound through the solenoid, speed of sound at what pressure is TBD). For solenoids, we had very good experience with the ones from Automation Direct (low cost, HIGH flow). Related note, I also recommend using Single Solenoids (as opposed to Double Solenoids). If you do use Double Solenoids, ensure both solenoids are 'off' prior to firing. We found there was a noticeable performance difference with the SMCs when we went directly from Forward to Reverse on the solenoids vs. Forward-Off-Reverse (we also had a significant time we were at Off).
One final item is to watch your pneumatics connections orifice size. You're not limited to the FRC legal 1/8" NPT or the 0.16" tubing. The larger you go the higher flow rate you can have. The tubing diameter, length, orifice sizes and quantity will have an impact on your system. You can also parallel Solenoids for greater airflow. Again, you aren't limited by FRC rules here. Just ensure you maintain safety so you don't hurt yourself during development.