Battling Tops
By Bob Jennings

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The game features an 18” diameter parabolic base shape with a one inch drop from the side wall to the middle.    Note:  It can be made with a steeper drop towards the middle, but that crashes the Tops together more violently and the games don’t last long as the Tops are frequently bopped out of the arena.   

My base is made from 8/4 maple, two pieces joined together with biscuits, you could get away with 1.5 inch thick pieces as well.
Bottom support ring is a 4/4 maple 12 sided segmented ring.    There are two reasons for the ring:  1)  provides some lift to the game so that when the players pull their Tops they have some clearance between the table top and their hands.     2) Cut-outs on the base allow your hands to get under the base to lift it.   There would be other ways to raise the base.
I also glued a maple block on the bottom of the base,  a faceplate can go directly on the top of the base. I turned the bottom first, removing significant material near the edge but less material in the middle and then put a tenon on the bottom glue block.

Flipped the game over, chucked it and turned the parabolic shape.   I used a narrow parting tool to put a groove in the outside wall.   This was to accommodate the Plexiglas wall that I intended to install.      This wall could be eliminated but it keeps the Tops in play a bit more.     Another approach could be to add a couple of segmented rings on the top and turn them down to a narrow wall instead of the Plexiglas.   This would also make the construction of the Top launchers a lot easier.

On my prototype game I simply glued the launchers to the outside wall, seems to have stood up quite well.  But for this game I made the launchers with a tenon on the bottom that inserts into the groove on the ring wall.     This made the launchers much more difficult to make and I ended up using a router circle jig to cut out the tenon on the launchers. 

I needed eight launcher vertical pieces. The horizontal launcher pieces are glued to the top of the vertical launcher struts. (A simpler approach would be to just glue the launchers on the side wall or make the side wall higher and cut the launcher slots out from the side wall.)
There is a 0.375” drill hole in the inside of the wall to allow the Top to sit there and a corresponding 03.75” hole in the horizontal piece of the launcher.   
The launchers are two inches tall with one inch clearance in the middle for the shafts.

The side walls are 1/8” Plexiglas which I heated up in boiling water and then curved and dropped into place.   

The Tops are 3.75” tall with outside diameter 2.25”.   The shaft diameters are 0.25”.    The little string pulleys are 0.75” diameter by 0.125” thick.     I made about 5 prototype Tops before I landed on this design.   

The Tops have four flat spots grounded on the disc to make them “bounce” a bit more.   Without the flat spots the Tops slide off each other.   You can make the Tops “too aggressive” if you put too much of a flat spot on each side.    
The pull strings are about 18” long. 

Wind the pull string between the pulleys and feed the Top into the launcher from the inside of the arena.   Hold the tip of the Top with one hand and let er rip,...  “it’s all in the wrist action”.