Invisible Dog

Hey, I'm working on a live stand up comedy project where the character I play has a invisible dog, I know of the old magic trick/illusion of the invisible dog lead but I want to go a step further so the lead can go slack and rigid at the pull of a trigger/leaver hidden in the handle to give the illusion of the dog sitting and then maybe pulling at the lead, I hope this is clear, I'm a complete novice at prop making and can't think of a way to achieve this, any ideas would be gratefully received :)


  • One way to achieve that effect would be to have the core of the lead be segmented plastic tubes with a cord running through them.  When that cord is pulled tight, the tubes would stack up and form a rigid line, and when the cord is slack the assembly would swing freely.

    Things to test:  How much do you have to pull the cord to transition from slack to taught and would that work with a trigger mechanism?  And how rigid is the assembly when the cord is tensioned.

    Another option would be to have the segmented tubes all connected along one side with a piece of fabric, so they can only bend one direction.   If the fabric side is facing up, the lead would be rigid, but if turned so the fabric side were facing down, the lead would become slack.

    Example A:  (side view)

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    In example A (where the "=" character would be the fabric) with the fabric at the bottom the segments could bend downward.

    Example B:  (side view)

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    In example B, with the fabric along the top, the segments would be unable to bend downward.

    While that example uses fabric, any flexible material that does not stretch would work to link all the segments on one side.

    Those are just the first concepts that come to mind.  I'm curious to see what you (and others) come up with!

  • Hey thanks for your suggestions Chris they were very helpful, they both seem like good ways but  I'm thinking something more along the lines of the first idea you suggested, my thoughts now are on generating and torque to pull the cord taught, I'm thinking at the moment a small DC brushed motor inside the handle with a button mounted on the handle, If I was to use a leash such as the one above that should give me ample space to mount everything inside as it doesn't need to be retractable but this will take some testing to see if this is feasible, what do you think?

  • edited February 2018
    A motor might work, depending on the gear ratio and how much tension it needs to provide.  I would suggest designing it so when pulled tight a braking mechanism locks in to hold things in place, so the motor is not under constant strain.

    You could possibly do it with a crank handle, which would require a second hand, but may be more reliable than motor/batteries/etc.

    I would do some small scale prototypes.

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