okay so I’m curious please about how I could use two solenoids to effectively move back and forward when I give them power with on/off switch please?

I’m creating a tennis ball launcher with my teacher, and I got some cool ideas here and I thought of putting them onto paper to show Sir.

Using the image please (Thanks to Solar Mike for this one), I would like to understand how a current could actually move them back and forward at same time? I know a solenoid is a metal piece with wire around it? enter image description here

  • 2
    $\begingroup$ Typically solenoid actuators use a spring to return them to their 'home' position, when the power is switched off $\endgroup$ Nov 25, 2021 at 13:46
  • $\begingroup$ If both pins are spring loaded and protruding in to the tube, then a motor could drive an eccentric cam and operate the pins sequentially with Pin 1 first. $\endgroup$
    – Solar Mike
    Nov 25, 2021 at 14:25
  • $\begingroup$ Magnetism can be induced by electricity and magnets can interact mechanically with stuff while they are pushed and pulled by electromagnets. Iron in a magnetic field turns into a magnet... $\endgroup$
    – Abel
    Sep 30, 2023 at 20:37

1 Answer 1


The linear actuators can be many things.

  • A solenoid coil (like you said)
  • a worm gear with a rack
  • a slider and crank mechanism etc.

Regarding the solution, think of the two pins connected on the same structure, and its the structure that moves back and forth. As the structure moves both pins move simultaneously.

When I say structure, you could imagine a mesh wire cage around (or a platform next) to the pipe that can be used to attach the pins, and the motor translates it.

  • $\begingroup$ Hi, Nmech and Solar, I’m struggling to visualise this please- so by simply having 2 solenoid with spring, attached to the cam would work. So when I press on, the cam moves once and pin moves back so ball falls forwards? $\endgroup$
    – Edwin
    Nov 25, 2021 at 14:38

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