Is there a way to share air from one reservoir to three cylinders equally? I mainly want it for expansion purposes
I also only have double acting cylinders
Sure thing! just use a couple T-fittings. For your application, they would probably be installed between your solenoid valve and the air cylinders, so the single solenoid valve actuates all three air cylinders simultaneously.
Be sure to use the SMC part number (KQ2T04-00A) if you’re buying the fittings from SMC: https://www.smcpneumatics.com/KQ2T04-00A.html
or another aftermarket supplier: KQ2T04-00A by SMC - Buy or Repair at Radwell - Radwell.com
You can use t fittings (picture below) to split air. It is beneficial to split the air after the solenoid so you only need one as opposed to three unless you want to have individually control of each piston.
If you use T connectors the air will split evenly
try using the t-connectors that are on the Vex website
you could use two connected together at one junction to equally split the pressure between three cylinders