First of all, not an engineer. Clueless to proper lingo or terminology.

Project. Looking to create a compact, pen like device by using a 12v dc motor to create a reciprocating motion. Kind of similar to a sewing machine or even a tattoo pen. The reciprocating shaft needs to travel a 1 to 2 inches. The entire mechanism needs to be in a straight line, light weight with minimal vibration and easy to minor maintenance.

This is the best example I found to demonstrate the desired motion and shape. https://youtu.be/8MdA1leM6Y0

As far as rpm and torque. No idea but portable sewing machine-ish might better describe these types of stats.

Another criteria is the utilize off shelve parts. Like with the YouTube example, no idea how I could design the cam barrel.

Thank you in advance for your valuable expertise.

  • $\begingroup$ Why are you defining the means (12VDC motor) when you don't have any idea how it will work? Requiring off the shelf parts for something that specific means there's almost no point in trying to figure out a way because you can't execute that way anyways. What you've really asked for is to find something that already does what you want, so start thinking less custom. You need something to move back and forth so find a motor (solenoid) that directly moves directly back and forth, not spins. It sounds like you've hamstrung yourself though with the off-the-shelf combined with implicit power supply $\endgroup$
    – DKNguyen
    Nov 25, 2021 at 5:41
  • $\begingroup$ RPM and torque also matter a lot (well, actually strokes per minute and force since those are your actual requirements, not the use of a spinning DC motor). So you need to figure that out first. $\endgroup$
    – DKNguyen
    Nov 25, 2021 at 5:45
  • $\begingroup$ I do have an idea how it will operate. Trying to find the words to describe it by providing examples. Like the portable sewing machine has a range of 200 to 500 spm. Modern tattoo maching has pen like shape, well maybe more like giant marker. Point is it fits in hand, easy to hold but has a short stroke and offten a perpendicular motor. I prefer it to be parallel. Did find another example, wish it showed the unit together. lynnslids.wordpress.com/2014/10/19/toys-and-tools/amp $\endgroup$
    – Espey127
    Nov 25, 2021 at 14:07

1 Answer 1


The sewing machine mechanism is a possibility.

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which is an extension of the slider crank mechanism.

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Figure: slider crank mechanism (source Britannica)

The skotch yoke mechanism which:

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Figure: (source: grabcad)

Also another solution from another question.

enter image description here

Figure (source this question)

There are many variations of this.

  • $\begingroup$ To narrow down my dilemma, transferring direction of orginal rotational source. Maybe by adding a worm gear or beveled gears. Would this effect the original input shaft speed? In all examples like scotch yoke, the motor would be perpendicular to the mechanism. I need it parallel. Hope I'm descriptive enough. $\endgroup$
    – Espey127
    Nov 25, 2021 at 13:47

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