Nice Gearmotors & Wheels!

erco

Eureka! I finally stumbled across the 120:1 gearmotor & wheel combo I've been asking for these past years. Every other wheel/gearmotor I've found uses a 1:48 ratio: too fast with no torque. This one is vastly superior and actually usable for robotics. I'll make a simple diff-drive bot with them. Might be good for a lightweight 4WD rover too. Both motors demoed at 3 volts in video below. Gearmotors look identical from the outside. Can't tell from the item description, no mention of the gear ratio. Hopefully US seller cenn2010 has plenty more just like these. $7.29 OBO for the deuce w/free ship. He didn't take any of my lowball offers, but he might go $7 if you tell him erco sent you.

http://www.ebay.com/itm/360812723413

Martin_H

You are always recommending parts faster than I could ever use them in a project.

erco

Martin_H wrote: »

You are always recommending parts faster than I could ever use them in a project.

"All right, guys, uh, listen. This is a robot riff in hacking, watch me for the parts, and try and keep up?"

erco

I bought 6 pairs so far, Martin. C'mon in, the water's fine!

Martin_H

Erco, I'm furiously building a robot for the golf tee challenge. No need to get side tracked!

Although I am planning to try to build a DIY servo using the open servo firmware, a 10k pot and a gear motor. I want to see if I can build something more accurate than the RC servos I am currently using. I want to see an end to servo dead band.

erco

There's gotta be a musical group called the Deadband... at least the Grateful Deadband...

JasonDorie

How much gear slop is there in those? IE, could they work for a balancing bot?

erco

Little to no backlash, excellent quality IMO. Def balancer potential.

erco

Here's a useful fact about these gearmotor modules which have their output shaft extended on both sides. One side is much stronger than the other, because the torque goes through all large diameter plastic/delrin parts. The other shaft is pressed on using a small knurled metal shaft which I have found to strip out under load. The photo below is of these particular 120:1 modules, but is likely true for similar-looking gearmotors of varying ratios. The stronger shaft sticks out the side which has a molded shaft boss below (on the right side as shown here).

There's actually a too-strong clutch on the strong side which will never give on the 120:1, much less on the 48:1. Well, maybe at 75 volts.

erco says be sure to put your drive wheel on the strong side and encoder on the weak side.