Seeking advice for a secure hand crank

I’m designing an interactive art piece for public display that will include a simple LEGO hand crank driving a perpendicular shaft. Since it may be used by young kids I’d like to create a crank that cannot be pulled off. For both shafts I’m currently using a “technic axle with stop” with the stop on the inside, which successfully keeps the axle and gear from being pulled out. And for the crank I’m currently using a “Crank 1x3, Steering Knuckle Arm” with the friction axle hole slid onto the...