I'm fairly new to robotics, but I have this idea for a machine. I've done a bit of research but can't find exactly what I'm looking for. I need something that can either move back and forth at at least a 90 degree angle (like swinging a bat), changing direction on-the-fly, or something that can push an object into a wall really fast, moving back and forth with little-to-no lag time between switching directions (like a fast piston). The object being moved will be 3 to 5 pounds and it needs to be slammed against a solid surface with roughly the force of a punch.

I spent all day yesterday researching it and haven't found much. I was thinking a piston would be good, but I can't find one that moves in and out quickly enough to generate the force I need. I then thought servos sounded good, but I could only find tiny ones for little robots. A motor now seems like the best bet, but I haven't been able to find a way to make one change direction on-the-fly. I have one from an old bandsaw, but it seems like I need to rewire it any time I want to make it change direction. I know motor controllers exist for tiny robots that accomplish this but am not sure if there's something like that for a bigger motor.

  • $\begingroup$ you can "slam" in only one direction at a time, unless the object is somehow expanding $\endgroup$
    – jsotola
    Jul 6, 2021 at 21:13
  • $\begingroup$ My mistake - I meant the slamming needs to alternate, like hit one wall then immediately reverse and hit an opposite wall. $\endgroup$
    – bgavin
    Jul 7, 2021 at 23:27
  • $\begingroup$ a spring assisted pendulum may work ... think about a playground swing .... pull back, give slight push after release, give another slight push after the first hit $\endgroup$
    – jsotola
    Jul 7, 2021 at 23:51
  • $\begingroup$ Thanks for the idea. I think I have a plan. I'm going to see how a paint mixer works. The way a reciprocating saw works might be good, too. But I'll definitely add yours to the list. $\endgroup$
    – bgavin
    Jul 9, 2021 at 17:16

1 Answer 1


A scotch yolk will do what I'm trying to accomplish.

  • $\begingroup$ Beautiful mechanism $\endgroup$
    – guero64
    Feb 13, 2022 at 21:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.