Introduction: Mechamo Inchworm Hack: Crawl Along a String

This instructable shows how to hack your Mechamo Inchworm to make it crawl along a suspended string. It's surprisingly easy, and should take about 10 minutes!

Here's a video of my hacked Inchworm cruising along upside down, suspended from some nylon string:



But how does the inchworm normally work? This article has a general overview, and the video below is a good example of normal operation.
http://blog.makezine.com/archive/2010/05/in_the_maker_shed_mechamo_inchworm_1.html

Step 1: Parts: Rubber Band, Coat Hanger

Get your self a nice little rubber band. Mine is one of those teal ones they wrap around your eggs when you checkout of Whole Foods.

Get a metal coathangar, and cut two pieces about 10" long. Ben them into Ws as show. Make the outside arms of the W about 2 inches long, and the inside arms ( the upside down V part) about 3 inches long. When you suspend your inchworm from the string, this will position the string right between the bottom of the inchworm's two feet.

Step 2: Attach Coathanger Ws

Insert the W's into the holes closest to the bottom of your inchworm's feet (or the top, if it is upside down).

Make sure the tines of your W stick close to the inchworm's legs, so that the edges of the legs keep them trapped and stiff.

Step 3: Wrap Your Rubber Band Around the Inchworm's Foot

Place your rubber band around one side of the foot, over the string, over the other side of the foot. This tension will be important later when you make your inchworm walk the wire. When the foot is "up", it should be loose enough to slide across the string. When it is "down," it should hold onto the string so that the inchworm can move its legs along further to get another grip. See the video or final picture for a better sense of how this works.

Step 4: Walk the Wire!

Now run a string through the W, and the loops formed by the rubber band. Now drive your inchworm forward and back!

You'll notice pretty quickly that if you rotate the foot with the remote, it will increase the tension of the rubber band and snag, so you have to be careful to only tell your inchworm to go forward and backward (Although, if your rubber band is too big, this might be a good way to increase the tension a little. See what works best for you!)

Comments

author
TheMONKEY made it!(author)2010-12-27

Wonder How this would work as a line following robot?

author
AmosLightnin made it!(author)2010-12-27

I don't know! Seems like it could be done with an infrared sensor... That might be cool!

author
TheMONKEY made it!(author)2010-12-27

Can you tell me how far the bottom foot travels with each leg movement?

author
AmosLightnin made it!(author)2010-12-28

Uh, sorry, read that wrong. Basically, about a couple of inches. I can get a more exact measurement next time I hang it on the string if you need it.

author
TheMONKEY made it!(author)2010-12-28

Would like more exact measurements of it on the ground Im really thinking of makeing a line following robot from this

author
AmosLightnin made it!(author)2010-12-28

You mean the foot that the inchworm normally rests on when it's right side up? I'll call that the main foot.

Basically, when it pulls down, it increases the tension on the rubber band and holds onto the string, so the other "feet" can get a grip farther along the string. Then, as the foot goes up, the tension on the rubber band is relaxed, allowing the main foot to slide along the string.

The video makes this process somewhat clearer. Btw, I've just managed to make a version of this that just uses coathangers bent into hooks, for the main foot and the outside feet. It makes it easier to put it directly onto a string that's tied off, rather than having to thread the string through the Ws of the current design.

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Bio: I develop tinkering activities that invite people to experience and reflect on creativity and learning through play. Previously I ran the Scratch online community in ... More »
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