# Converting Rotational Motion to Pendulum-Like Oscillation

1. May 7, 2016

### bobthebloh

Hello,

I am trying to create a mechanism that will allow for a motor to power a pendulum-like motion (but not an actual pendulum), back and forth. As shown in the picture, I need 180 degrees of rotation about the swinging part. I have researched escapement, but I need this design not to rely on gravity and to move much faster than I imagine the anchor escapement works. Ideally, such a mechanism would minimize the loss of torque on the output gear, so that I can use this oscillating motion to accomplish other tasks in my application.

I would appreciate any help you can provide!

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2. May 7, 2016

### Simon Bridge

There are lots of ways to do this - you know how to turn back-and-forth motion into circular motion ... this is just going the other way.

3. May 7, 2016

### bobthebloh

Could you please provide an example?

I'm not sure if it's clear in my drawing, but the green part is intended to rotate, not slide linearly. I could easily come up with mechanisms that convert linear to rotational or vice versa, but my problem is achieving a back-and-forth rotational motion to power another mechanism.

I would really appreciate an example name or reference site! Thank you!

4. May 7, 2016

### Simon Bridge

A reciprocating motor turns back-and-forth motion into rotating motion.

Now: none of us are going to present you with a design - this is what you pay engineers for.
What we can do is attempt to match your existing knowledge with a direction for you to do your own research, maybe some trial and error.

Imagine your green wheel has a peg sticking out of it ... that peg can fit into a groove in a rod. If one end of the rod is fixed to a pivot, then, as the wheel turns, the rod is forces to swing back and forth.

This won't give you the full 180 ... but you can put a section of toothed gear on the swinging end and use that to drive another cog that your pendulum arm is fixed to.

This is not actually a pendulum - it is a motor that waves a rod back and forth.
If you prefer to have a free swinging pendulum that can be driven by a motor, that is a different design.