Now that the season is over, I am curious to how everyone approached rotating their turrets (if you did).
What kind of hardware and motors did you use? What were its advantages/limitations? How much did it cost (money & weight)?
I’ll start off: We were a bit unsuccessful (partly why I’m asking about other solutions) using a directly-mounted solution. We didn’t pick up balls from the ground, so the entire turret was mounted on top of a rectangular board, which was in turn mounted on a lazy susan bolted on to a second board below. The window motor was then directly attached to the bottom board, and when it was turned, the whole assembly would rotate.
Only once it was assembled (doh!) we realized that it was impossible to have the wires come up through the center, so we had an umbilical cord of wires come up through a corner, leaving enough slack to rotate about 90 degrees off center in either direction. Suffice to say, with all those connections and the slight “play” in the motor, it wasn’t a very stable rotation platform, and we ended up just bolting it down and turning the robot to aim.
So how about you all?
Unfortunately we approached the problem the same way but used a fisherprice motor with gearbox. We used an umbilical type cord as well and just like you guys did, just ended up bolting it down and using the robot to aim.
Similar problems with a window motor mount, though our shooter was supported by a single axle at the top and bottom, so we just ran wires along the sides up to it. It was never intended to turn more than 120 degrees.
It was too wobbly for a while, but we eventually fixed the problem towards the end of our regional by using a spring to keep it from shaking.
The spring slipped during shipping and caused problems of turning too fast one direction like we had experienced the first time we tried a spring, so we took it off again because we haven’t gotten it to work right a 2nd time.
We made our own 4 point contact V grrove bearing so it could support both thrust and radial loads. It came out very nice. It was able to take considerable amount of load without binding up at all. It was something like 12 inches in diameter. The V groove was filled with steel and delrin balls (alternating). It was driven by a globe motor with a 4.8:1 sprocket and chain reduction. Picture here http://www.team696.com/blog/images/06/IMG_0143.JPG We were able to pas from 90 to the left to 90 to the right and tilt from about 15 down to 50 up.
As Joel said above were were quite unsuccessful in our methods of creating a turret but i did see one quite interesting method at championships this year.
I forget what team it was or even if they were on newton with us but what i do remember is that they were a row or two behind us near the wall, and that they used sprockets layed out flat to function as gears. It consisted of one very large sprocket on which the actual gun was mounted which was then driven by two around 12 tooth sprockets mounted 60* from each other. ill try to figure out who it was and get a pic but if anyone else knows that would be great.
We found an awesome lazy susan bearing at the local Reno Depot. It had a 12.5" outer diameter, and viewing from the top it had a 3/4"-wide fixed ring, encircled by a slightly higher 3/4"-wide rotating ring.
Our turret was all mounted on an extrusion frame, so we bolted that to the rotating ring. A Globe motor mounted on the turret drove a rubber cylinder against some belt we glued onto the fixed ring, for turret rotation by friction drive.
All the wires ran up through the middle of the bearing (the balls went in the front).
Here’s a picture of the robot, if that helps make things any clearer.
We were quite pleased with our turret… it had 300+ degrees of rotation and about 45 degrees of tilt, and worked flawlessly all season.
If only the mechanism that loaded balls into it had done the same. Sigh.
In any case, we used an aluminum lazy susan bearing from Lee Valley Tools
The balls were loaded by a belt drive through the centre of the lazy susan.
Oh… yeah… we used a globe motor (with a 1" dia. pulley on it) to turn the turret using a 1/4" thick 15" dia. o-ring stretched around the outside of the lazy susan.
We used a globe motor and 25 chain - we actually “attached” 25 chain around a lazy susan purchased from mcmaster carr to rotate - could have went 360 but we limited it to 180 just to be on the safe side. wires for the shooter CIM motor were tethered. We had no problems with this, our loader was also our demise. Anyway we used the same lazy susan last year for our arm and it worked really well.
Our original plan was to have a shooter on a turret, using a lazy-susan bearing from Mcmaster. Well, we got the shooter on the bearing, ran out of time, locked the bearing and eventually ended up just ditching the thing. But, the Mcmaster bearing was rated to a very high weight load, only 30 dollars, light, large ID, very tight for the price, and seemed very tolerant to side thrust. Very similar to the Lee valley bearing, and probably the same one UCGL_Guy’s team used. Overall, nothing but good things to say about it, especially with a little weight on it.
Last year, we used an aluminium wheel hub for our arm. (I thought it was a great idea this year, too.)
This year, it was a turntable similar to what you would find at Home Depot for swing-out tables. (about 6"~8" diameter)