The 12v gearmotor version pitched up today in the post. A set of performance curves for the motor came with it. At first glance it appears to get about half again faster rotational speeds unloaded and four times the torque at at stall compared to the 5v motor currently being used.
I did some timings on the 5v and 12v GM8 models.
Unloaded, the 5v GM8 gave about 2.14 rps at 5.43v.
The 12v GM8 ran at about 3.7 rps at 12.3v.
Sorry, that was 3.75 rps.
Interesting, if I mate that motor with National Coarse Threaded Rod 3/8-16 you get a metric pitch of .63 turns/mm. That would give you an unloaded maximum translation of 3.75/.63 or 5.95 mm/sec.
That would also give you 161 pulses/turn.
That's not bad. :-)
Great, more torque! Extra speed can be handled by your nifty pulse-bumping trick for the slow end.
I guess the gears will wear out faster though, but that's in the future!
These will make great Z axis drives, for sure. Something small and light that can crank up/down an extruder head.
I suspect that even the 5v GM8's will be more than adequate for that light-duty task.
I bought a half-dozen of the 12v motors from Solarbotics to replace the 6v ones in the GM8's that I'd bought earlier. They cost about US$1.75 each.
Yesterday, I swapped out one of the GM8 6v motors for a 12v one. It took less than a minute and I wasn't hurrying. The only finicky bit was slipping the tiny little gear off of the old motor's drive shaft and putting it on the new one.