Mathematical prediction of synchronizing multiple cams.

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I am not a mathematician so be gentle with me but what kind of math equations (or what field of mathematics) would be needed for the following:

I have designs for an old-style mechanical device I am creating with a complex set of cams -- a total of 62 of them! and I am trying to figure out how to predict how frequently the cams will all synch simultaneously to their starting position (i.e.: how often the overall complex pattern will repeat).

animated cam illustration

  • Each cam has its own unique rotation speed (generally the larger diameter ones are slower to complete one full rotation) but that speed is 100% reliable as all of the cam shafts are fed by a single MAIN drive shaft that is then geared to the various cam shafts. Essentially each cam rotates at a percentage of the MAIN shaft's rotation speed. That percentage can be over or under 100% of MAIN.

  • Each cam has a "starting position" or "zero point" and when the device is first activated each cam is reset to zero point.

  • Each cam is built as a simple circle with a different/unique radius (there "cam" effect is caused by a wavy groove on the side of each cam that transmits a pattern to an embedded armature).

So what is the required math to take these various cams's data and predict how long (i.e.: how many rotations of the MAIN drive shaft -- one full rotation = one heartbeat if you will) it will take for all of the cams to return simultaneously to zero point? For simplicity's sake lets talk about the math for only a few (3? 4?) cams (I assume this math can be expanded later to address 62 cams or more).

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You want to work out the lowest common multiple of the periods of rotation of each cam.

Mathematically you are trying to solve:

$$p_i\times n_i=t \text{ for } i=1\to62$$ where $p_i$ is the period of cam $i$, $n_i$ is how many times it rotates (an integer) and $t$ is the time taken. You are looking to minimize $t$.

Consider an easier problem as an example: One cam take 2 minutes to rotate and a second takes 3 minutes to rotate and a third which takes 4 minutes to rotate. The lowest common multiple of 2, 3 and 4 you get 12. After a total of 12 minutes the first will have done exactly 6 rotations and the second done exactly 4 rotations and the third done exactly 3 rotations. No smaller amount of time will satisfy the problem.

EDIT: If you aren't sure how to find the lowest common multiple of 2 or more numbers just post a comment.