what motor did you use(arm)

[ducttapedude]

Team 233 used one large CIM through a custum gear box to rotate our arm, and another large CIM through a custum gear box to extend the arm

[pythagoras]

We used a CIM motor to drive te arm with the help of a andy-mark planetary gear system. we also used two globe motors on our end effector. We had to save our fisher-price motors for our lift.

[Doug G]

Originally Posted by ChrisH

Power = force x distance / time
...
As an example let's run the numbers:

We want to move a 0.5N object approximately 3 meters in 4 seconds. That will take 0.375 watts.
...
If we assume a 2m arm, we only actually need 0.5N *2m = 1Nm.
...
I puposely left out the power required to move the arm itself as that can be adjusted by using counter balances or springs.

So it really does not matter too much which motor you use as long as you use it correctly and keep all hardware within its operating limits.

Excellent points, Chris. I'm a physics teacher, so I get all geeked up when this stuff comes up. I see a mistake some teams make is under-estimating the amount of torque required to move not the game piece, but their robot's ARM! True any motor could be used to pick up the 1 lb tube, but what about that 1x1 box tubing and the grabber assembly at the end? 16 W Mabuchi motor?? Well, if the arm weighs a modest 10 lbs with its CM located 2 ft from the pivot = 20 ft-lbs (27 N-m)... That means that mabuchi would need to be geared down at least 1800:1 and moving 0.033 rps or 12 degrees/sec. Yikes or better yet, Yawn!!

I know Chris was simply making a point to look at the physics, specifically mechanical advantage of gearboxes. Hmmm... maybe we could re-write the Archimedes quote ... "if I had a big enough gearbox for my 16 W mabuchi, I could move the world". Another hmmm.. makes me think of an off-season project!!!

[Alex.Norton]

Then again you could also consider the arms moment of inertia because many of these arms have a large weight at the end of a long stick. So even if the motor can move the arm fast, it might take too long to get up the speed.

We didn't use an arm this year but we used one in 2005 and each joint was powered by a fischer price. I forget the reduction on the lower arm but the upper arm somehow got to 1157:1. Not by design, but hay it was a highly entertaining fluke.

Alex

[Gabe]

Quixilver used the window motor for the shoulder joint and a globe motor on the elbow joint.

[cgredalertcc]

1741 used five motors on the arm assembly of our first robot. One keyang to move a shuttle up and down. Two fischer prices and one that ended up having to be changed multiple times (started as a keyang, then went to a globe on a custom worm drive gear box, and finally the banebots planetary on that same gear box). Finally we used one globe to adjust the pitch of our gripper via a screw drive. This system was extremely complicated and we chose to build an entire new robot for IRI. This new one used two banebots planetarys one on either end of a worm gear that moved the arm around a fixed gear on the shaft which was also fixed to our tower.

The moral of the story simple is almost always equal to better.

[Qbranch]

1024 Used both large CIMs for the manipulator... worked out well, 0->12ft on the elevator in 0.9 seconds.

-q

[joeweber]

We used the large CIM motor with 3 to 1 belt drive to a 2 in pully to wench up 8020 slid on a slide. The claw we used was large enough to grab a tube from the outside. When the tube was in the claw it took no time for it to go to the top spur. We did not want to wait for it to crank up so we made sure it would get thier fast. For the claw we used pneumatics pulling steel cables to close the claw and springs to open. http://team1322.org/DESIGN1.jpg

[Schnabel]

We used a CIM motor straight into an AM Gearbox which drove the arm.

[Ben Martin]

We raised and lowered our arm with the Keyang window motor. We attached the motor to the arm itself, so we could use it as a counterweight. Originally, we planned to use another window motor to telescope our arm, but we swapped that for pneumatics late in the build season.