FRC 95 Shooter Turret Prototype (not a teaser)

[JamesCH95]

100% student programmed CNC machine work! I helped with the setup, but that was it.



Combo of manual and CNC work on the sprocket and window motor hub.



Student-conceived chain attachment system, from some rookie members no less, I was impressed with the elegance.

Comments? Questions? Constructive criticism?

[MrWolverine12]

I am curious has to how this thing works. Very interesting as to how people come up with these ideas.

[JamesCH95]

The main aluminum disc you see the bolts sticking out of is mounted on the inner race of a 'ring-style turn table bearing' available from McMaster, PN 18635A52. The chain is motivated by a window motor (mostly hidden) attached to a sprocket. The motor is attached to the outer race with a bracket.The inner race of the bearing and the aluminum plate to which our shooter will be attached will rotate relative to the outer race, which will be fixed to the robot.

Edit: welcome to CD! Feel free to ask as many questions as you'd like.

[Akash Rastogi]

I really hope your 2012 machine is a derivative of 95's 2006/2002 robots. Those two were nasty.

[JamesCH95]

Originally Posted by Akash Rastogi

I really hope your 2012 machine is a derivative of 95's 2006/2002 robots. Those two were nasty.

Have no fear, ancient and brilliant coaches of yore were consulted.

It is unfortunate that the massive sets of intake and shooter rollers from Feynman (2002) and Lilly (2006) respectively are no longer practical. Though we hope to show how awesome really small rollers can be.

[ENIAC]

ENVY. My school has yet to have a fully functional CNC. (I blame the stupid postprocessor)
Nice turret though. I think we have one of those rings lying around.

[s_forbes]

Very nice! We were looking at using the same turntable from McMaster, but have not ordered yet. Can you comment at all on its quality? It appears to match the CAD model fairly well.

Also, is that the KOP window motor adapter? I'm curious as to how you are retaining it... did you tap the output shaft for the Phillips head bolt shown in the picture?

Neat turntable, I'd love to see what goes on top when you get to that stage.

[Mk.32]

We just got the same turntable, as far as I can tell it seems pretty solid.
Very nice design. We have something a little different cooking up...

[waialua359]

Our 2009 turret robot utilized the same method as yours by attaching a fixed chain on the outer portion of the lazy susan.

[JamesCH95]

Originally Posted by s_forbes

Very nice! We were looking at using the same turntable from McMaster, but have not ordered yet. Can you comment at all on its quality? It appears to match the CAD model fairly well.

Also, is that the KOP window motor adapter? I'm curious as to how you are retaining it... did you tap the output shaft for the Phillips head bolt shown in the picture?

Neat turntable, I'd love to see what goes on top when you get to that stage.

The bearings seems to be of reasonable quality. There's no slop in it and the holes do line up pretty well with its CAD model.

We tapped the stationary metal shaft that the output shaft rotates about, stacked two greased washers under it, and tightened down the screw.

[THE DYNAMO]

I'm thinking of a hinged set of shooter wheels that rotate on the edge of the turntable. Some kind of belt would bring the ball up through the turntable and bend to match the shooting angle. Comments/ ideas?

[JamesCH95]

Originally Posted by THE DYNAMO

I'm thinking of a hinged set of shooter wheels that rotate on the edge of the turntable. Some kind of belt would bring the ball up through the turntable and bend to match the shooting angle. Comments/ ideas?

I think you'll find that range can be adjusted adequately by varying roller speed, which is much easier than angling the whole roller assembly. This is the conclusion we reached in 2006 and it seems to hold true based on our testing so far this year. Forgo the effort and mass of angle adjustment and apply it somewhere else where you may see a better return on investment.

[Bruceb]

Just found the same bearing from VXB bearings for $15.
http://www.vxb.com/page/bearings/PROD/Kit11279

Bruce

[JesseK]

Originally Posted by JamesCH95

Forgo the effort and mass of angle adjustment and apply it somewhere else where you may see a better return on investment.

I agree for the most part. Something else to consider...

During prototyping, the question may arise of whether or not to apply the flywheel effect to prevent momentum loss as the ball moves through the wheel (move the mass towards the outside of the wheel). If the flywheel effect is used, the question becomes "does the wheel slow down in a short enough amount of time so as to not shoot the balls too far or too hard as the robot drives towards the basket?".

If the flywheel effect isn't applied (e.g. use of light skyway wheels), then there are other tradeoffs too (spin the wheel faster than needed because of anticipated slow-down, control feed rate, less ball contact time, etc). This also makes it mostly easier to control distance with shooter wheel speed since the wheel is more responsive to [lack of] motor input.

We are still (sorta) wrestling with this tradeoff. For now, we're making the flywheel weight adjustable and forgoing the adjustable angle. Test test test .

[MrForbes]

We're going to try the "wait till it speeds back up again before feeding the next ball" approach. So we need to have good control of when the ball enters the shooter, and a student came up with a very simple way to do this using a single pneumatic cylinder and gravity.