Is this solenoid Legal?

Technical Pneumatics
1

Thinking about using this to release our climbing mechanism.

2

Given the restrictions on R34, no.

Electrical solenoid actuators, no greater than 1 in. (nominal) stroke and rated electrical input power no greater than 10 watts (W) continuous duty at 12 volts (VDC)

https://firstfrc.blob.core.windows.net/frc2019/Manual/HTML/2019FRCGameSeasonManual.htm#R34

3

If you’re looking for 4# / 18N of force, you’re unlikely to find a legal solenoid. Perhaps a linear servo? The “light duty” ones here are under $75* and may fill the bill. A bit slower (fastest of these is 32mm/s) but easy to control with a PWM.
https://www.servocity.com/servos/linear-servos

  • Under $75 is required for servos per R34.