Quote:
Originally Posted by thefro526
Yes, we are able to back drive our arm while the robot is un-powered, it takes a light push to get it to start going down and then once it starts going it usually goes all the way down by itself.
Our current setup is as follows: 1 RS775 Motor in a 256:1 P60 Gearbox on each side of our tower (total of two), each with a 15 tooth sprocket that drives a 48 tooth sprocket on our arm for an effective ratio of 3.2:1 from the transmission or an 819.2:1 reduction from the motor. We also have a decent amount of surgical tubing on our arm as an assist which also makes the mechanism harder to back drive.
We're swapping out out the 15 tooth sprocket on our transmission for a 10 tooth sprocket tonight, which makes the ratio 4.8:1 from the transmission or 1228.8:1 from the motor. I'll report back tonight or tomorrow if this changes the ability to back drive the arm.
Also, how much, if any, assist is on your arm? Enough springs or gas struts would make the arm nearly impossible to back drive by hand. You can also look for sources of inefficiency (binding, improper shaft alignment, etc.) and see if that is adding extra resistance which would make the arm harder to back drive. FYI, as the banebot transmissions start to fail, they will become nearly impossible to back drive without power. Check your transmissions too.
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Thank you very much. We have fixed it. It was a shot transmission that was likely messed up somewhere in very early prototyping. And now it has a burnt motor too
Incase you want a comparison (in no way am I trying to brag):
We are running a 256:1 w/ a 550 motor and a 12:25 after giving ~533:1.
Our arm will hold its position in about 30 degrees of motion only from the surgical tubing. It holds fine in all parts with the motor connected.
We also upgraded to aluminium arms with the same OD (1") and half the wall thickness. They are slightly heavier (~20%) than the pvc setup we had.
BTW, your bot looks great. I hope to see it sometime in person. I am also a fan of anything orange too.