816 - 90% Complete (Video inside)

[Madison]

Originally Posted by thefro526

Madison, the gearbox failure happened during initial testing of the Aluminum link. That being said, we were never able to work the PVC link as hard as we were the Aluminum link because we were afraid that the PVC was going to snap. It's a bit hard for me to say that the aluminum caused the failure, but at the same time it's difficult for me to say that the aluminum didn't cause the failure.

Sorry I can't be of more help.

No worries -- I just want to keep an eye on things as we continue testing and our robots are very similar. I think the PVC is absorbing a lot of the shock loading we've imparted into the system by rapidly stopping and changing direction. The aluminum won't do that nearly as well and we'll likely need to be kinder to the gearbox.

I just ordered a 1.25" OD x .083" wall 2024 Aluminum Round Tube. We'll swap it in on our practice robot tomorrow and see how things go. Also, for what it's worth, we've been running our motor at 40% of its full power. It's otherwise too fast.

[thefro526]

Originally Posted by Madison

No worries -- I just want to keep an eye on things as we continue testing and our robots are very similar. I think the PVC is absorbing a lot of the shock loading we've imparted into the system by rapidly stopping and changing direction. The aluminum won't do that nearly as well and we'll likely need to be kinder to the gearbox.

I just ordered a 1.25" OD x .083" wall 2024 Aluminum Round Tube. We'll swap it in on our practice robot tomorrow and see how things go. Also, for what it's worth, we've been running our motor at 40% of its full power. It's otherwise too fast.

Cool, once we get our robot back together tonight, I'll try to get some more data for you.

What speed does 40% power (I'm assuming 40% signal) equate to? I know that at 100% signal our arm goes up in ~1 - 1.1 seconds (90* per second), but we usually go up in around 2 seconds because it's more controllable.

[ZeroGAdam]

Great Job Guys! I am always amazed at what your team is able to come up with every single year! Its always effective, simple , and a marvel among all teams. I wouldn't be surprised to see you guys go very far into Saturday like every year. Awesome job!

See you at The NJ Regional!!

[Jeffy]

We are running a similar mechanism with an rs550 motor in a 256:1 gearbox with a 2:1 reduction after the gearbox. Are you able to backdrive the gearbox when the robot is off?
It does not seem possible with our robot.

[thefro526]

Originally Posted by Jeffy

We are running a similar mechanism with an rs550 motor in a 256:1 gearbox with a 2:1 reduction after the gearbox. Are you able to backdrive the gearbox when the robot is off?
It does not seem possible with our robot.

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.

[Jeffy]

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.

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.