Tuesday, April 23, 2013

Vivisection of a servo

I'm redesigning the block lifting mechanism, version 0.1 (everything you've seen up till now) is too Rube Goldberg-ish (too many moving parts that rely upon the goodwill of the universe for alignment and proper functioning).  It'd probably work if I were a mechanical engineer, but I'm not, so discretion is the better part of valor.  That being said I plan on finishing 0.1 just to see it work (pictures and video will be taken and posted).  Anyway, I was struck by inspiration while I was daydreaming about a potential future project that involves a power screw to lift portions the sculpture.  Ugh, so blindingly obvious, use power screws to lift and lower the blocks.  Each block can be independently raised lowered with with power screws driven by small continuous rotation servos.  This solution would eliminate the need for a higher voltage power system just for the solenoids (to engage the rack and pinion), springs to counterbalance the solenoids (to disengage the rack and pinion) and the rack and pinion.

To this end, I've started looking at inexpensive continuous rotation servos.  One solution that +Jason Hoff suggested is modifying a Tower Pro MG90S servo (I have a couple laying around).  There are a number of tutorials claiming to modify this servo (they're usually not, people generally modify the TGY-90S which has nylon gears), so I disassembled one of the MG90S to see how difficult modding it would be for continuous rotation.  Here are some shots of the vivisected servo, I want my trusty EE to look at the circuitry before I start soldering in resistors and bypassing potentiometers (the MG90S looks a bit more complex than the TGY-90S).  So, once Jason has his ankle bolted back together and he's off heavy tranquilizers I'll see what he thinks.

(lovely, durable metal gears)

(stops that need to be ground down)

Block lifter V0.2 schematics will be forthcoming soon.  Once I've figured out how to mod this little beast I'll post a full and detailed tutorial (as opposed to a video of the the final result and vague instructions on what's needed and how to do it).

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