Mechanics and Construction > Mechanics and Construction

Simple tripod walker

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--- Quote ---The prototype is going to be about four inches long and an inch and two inches wide, but in later versions I intend to make them as small as I possibly can.
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That is definitely a good size for muscle wire, just be aware you will only get about .5 Hz or 1 Hz maximum speed from it. Roaches run at like 10 Hz? I forgot . . . You might want to calculate how much force the wires need to apply to move the bot. You may need to double or triple up the wires to get enough force. Also make sure that they deflect as much as you need - muscle wire usually doesnt shrink more than ~10% (varies a lot on what type you get).

Know that muscle wire fatigues over time if you push it too far, and will stop working in as little as a few hours.

--- Quote ---The legs will be made of steel wire.
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Consider carbon fiber rods - lighter weight than steel and wont absorb the heat from your muscle wire.

Everything you mention sounds doable without too much effort. That e-spider that dunk showed is a very common walker design I have seen. I almost did something similar myself but got lazy and didnt want to assemble that many parts . . .

--- Quote ---I intend my roach to be more of a spastic walker than a deliberate one, trading control for speed
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I think the same way! Actually, roaches use less brain power the faster they run. The roach uses the most brain power when they walk very slowly! At high speed, the roach relies on chassis stability and the nervous system controllers located at where the legs are. So I think you are on track.

This is a high speed robot leg I built awhile back, watch the vids . . .

Yeah, my research so far has made me shy away from muscle wire ideas for the moment, because I don't think I could get the speed I want. I was originally thinking of using them to control the torso twisting, for which the speed would not be a problem, but I've discarded that approach. I might play around with them later on another project, as I'm sure I could make some incredibly tiny critters using them. How cool would a little robot snake the diameter of a pencil be? The slow activation cycle would lend itself well to undulation. But for the roach, I think they're out, the failure rate and slow cycle time are just unacceptable. So the smallest motors, and the battery to power two of them, dictate a minimum size for the chassis of the first version.  The complexity of the logic might become the big factor before I'm done, but I've got plenty of time to optimize the logic circuit modules as I go along.

I redesigned the insect structure based on two motors with gearing to connect the legs on each side. It worked out nicely, I have two identical pieces that can be separately assembled and tested for left and right, and a third, top piece that joins them, on which the sensors and circuitry will be mounted. This top piece will also have the guide holes for the knee spurs.  I could potentially add another piece of the same size for the bottom, to double the space for electronics.

Thanks for the suggestion about carbon fiber; I'll look into it.


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