From what I read, tape decks auto-reverse by having a sensor keep track of an encoder. When the take up pulley stops turning, the logic board reverses the direction of the motor (and does some other stuff to pickup different tracks on the tape).

In my art project the rotating reels are the only necesseary parts, and the exact speed of the tape doesn't matter. All I want to do, is rotate one reel and then move the input gear to the other reel when the tape has run out on one side. It just needs to rotate forever.

I assume it would be somewhat similar to this mechanism:

Mechanism for converting two-way to one-way rotation

I would like to use as few parts as possible, and no electronics (except for the small motor that drives the mechanism). Is this at all possible?


I have not yet seen the perfect solution, but I did find this cassette tape adapter:

Cassette tape adapter

From the Wiki page on this type of adapter:

To simulate tape movement, a system of gears or a drive belt connects the tape player's drive motor (via the take-up spindle) to a wheel inside the adapter. This wheel rides against the detection wheel to simulate tape movement. Because the wheel never stops spinning, the deck never senses an end-of-tape and never tries to reverse the tape.

I think my solution would look similar to the inside of that adapter, but then stuck to the back of a normal cassette. It will provide the drive motor, also rotate the spindles that the reels are on.

What I'm looking for is a gear mechanism that will 'walk' to the reverse gear when the first gear stops turning (like in the image above). Does that make sense to anyone?


2 Answers 2


You could have the orange and green gears permanently in mesh mounted on a plate.

Then if you rotate that plate then the orange gear become un-meshed from the blue gear and the green gear comes into mesh - this will reverse the direction of the orange gear. The rotation may be achieved by a small solenoid...

Turning the motor off then on may also be good.

  • $\begingroup$ Thank you. I am not sure I can picture it though. How would the plate be rotated, and how would the mechanism know when the solenoid needs to push? And what does turning the motor off and on do? I was hoping there would be a way to use the inertia of the stopped reel to have a gear move to the other side or something. $\endgroup$
    – Tjaap
    Dec 23, 2019 at 19:44
  • $\begingroup$ The plate can be rotated by the solenoid - if the plate pivots around a point and the solenoid can move it. Turning the motor off allows the gears to mesh without damaging teeth... $\endgroup$
    – Solar Mike
    Dec 23, 2019 at 21:12
  • $\begingroup$ This is more clear to me, but it would only work manually or with a movement sensor. I would like to do it without any electronics if that is at all possible. $\endgroup$
    – Tjaap
    Dec 27, 2019 at 14:41

Old tape decks had a rather simple gear-only auto reverse system. The take up pulley kept pressing a lever and when the tape ended the pulley stopped thus the lever got stuck in another gear to cause tape reversal.

The opto system was designed later on for logic contro decks.


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