Hi guys, I'm wondering if anyone could advise me on a servo that would be able to pull the trigger on a spray paint gun. It needs to quite strong, as the handle is rather stiff, but it also needs to release quickly.
Any suggestions would be appreciated!
Whatever you do, don't go cheap - go for a metal-geared, dual ball-bearings on the output shaft. Fortunately, most servos with those specs are fairly powerful (and none too cheap). What you might want to do is use a fishing scale to measure the amount of force needed to move the handle (attach the scale to where you plan to attach the connecting rod for the servo). Once you know that force, then you can calculate what the torque-rating of the servo will need to be.
First of all, do you really need a servo ? I guess all you need is an on/off function, right ?
I see two options
Use a solenoid valve to control flow of air to the paintgun. Use a string or clamp (or any other method) to keep the valve on paintgun in open position.
Actuate the valve. Just as you wanted to do it in the first place but use a car lock actuator
They are really powerful. Simply apply current and it extents. Change polarity (or use other wire) and it retracts
I'll post a video of it later (if I manage to find it)
EDIT
Found it 
Here a guy uses it to open a valve on a spudgun.
Big servos.