Vertical Spinner

I was thinking of doing a vertical spinner for my weapon. Any hints from experience you are willing to share?
Thanks,
Freshman looking for ideas.

15lb class? What do you have so far? What kind of resources do you have

He's one of my kids, it will most likely be a titanium or a steel possibly s-7 based on weight. This means it will probably be water-jetted. Yes it is a 15 pound robot, and through what i have seen he has a basic outline of the shape he wants the weapon to have. It is a plate cut into a circle with sections cut out to form teeth.

Many people would say to start HERE

There are all kinds of details needed to figure a weapon correctly.
The mass and diameter are gonna limit how fast it spins up, but also determine how hard it can hit.
The tooth size and speed, combined with how fast you think the robot will move will determine your 'bite.'
Bigger weapons require bigger motors (go brushless, btw) bigger ESCs, and bigger batteries--all making weight and space demands.
You are probably gonna use a belt to drive it--go learn a bit about belt drives, and make the motor location adjustable, but strong. You will also need to figure a pulley ratio, balancing top speed with spin up time.
It may be worth your time to calculate how much power is required to spin up a theoretical disk to your theoretical full speed, and see if there is a non-theoretical motor that can do the job.
Make sure your teeth can actually hit an opponent with a low profile (i.e. the axis of the disk should be at or near the front of the armor).
Vertical disks often have gyro problems, so your robot might need a wide footprint.
I would recommend you use one battery just for weapon, and a second for drive.

Or you can just look at a bunch of other successful robots online and try to make something about the same size and design. Most people kinda 'jump in' like this and learn all the other stuff later!!