B.I.O. Bug Waist Motor
Adding an extra degree of freedom to a "Predator B.I.O.Bug"
Dave Hrynkiw - Feb 25, 2002

I had the privilege to participate in a impromptu "BIOBug Hackfest" not long ago. Among other projects, I managed to finish an experiment in adding a waist (or neck, as the case may be) to a red "Predator" BIOBug. Fortunately, we had extra motors on hand, so I had the ability to use "BIOBug Certified" gearmotor for this function. I think I used a 200:1 offset gearmotor in this modification.

Step 1: Rip out the innards, and saw it in half


This is Scotty (aka: ScottyDogma) showing off my almost complete jeweler's saw cutting of the neck from the body of the BIOBug, right through the battery compartment. (This is the only picture that isn't a link to a bigger one. Scotty's evil grin and magnified eyes just have to be a highlight of this whole project!)


Step 2: Mount the waist motor in the battery compartment

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I roughed up the gearmotor's plastic with a file before epoxying it in place. The nut on the output shaft is Mark Tilden's technique hack of installing a solderable mount onto the plastic shaft.


Step 3: Reinforce the mount; fit battery cover.

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That neat black stuff used as a shim to fill in the gap is called Sintra. AKA: Expanded PVC sheet. Neat stuff. Cuts well, glues fabulously, and is easily shaped. A wee bit flexible, but manageable in thicker sections. Note how I cut the battery cover to fit the motor too - really stiffened up the installation.


Step 4: Add body cap, join halves together.

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Here's more of that cool sintra stuff. I used a sheet of it on each half as a low-friction bearing surface. The 2nd picture shows it a bit better. The last picture is the final joining of the halves, using a bar through the head, then through the nut, and out the other side. It was a pretty snug fit (intentionally), so the bar only protrudes out a bit of each side on the head. Kinda like the bolts sticking out of the side of Frankenstein's head...


Step 5: Reassembly, wiring, and finale!

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One of the trickier tasks was to thread all the body wires out of the body and over to the head. Fortunately, there was enough slack to do this without splicing in wire. Call it an exposed spinal cord.

The waist motor was slaved directly to the front motor outputs, so when the front legs went clockwise, so did the waist motor.



It was really, really, an interesting hack to do. The final increase in mobility didn't warrant the hack (in my opinion), as the increase in vertical step height was 15%, and battery life was reduced noticeably.

So *where* did I put the batteries? I stuck a pair of nicads on each side of the rear motor...



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