Building a Simple Mini-Sumo Ring

Tom Dickens
October 29, 2000

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I've built a few sumo robots and one of the keys to getting the robot working well is to have access to a good sumo ring. The 3Kg class has a 5-foot diameter ring, which takes up a bit of space. The mini-sumo contest has become very popular. Dimensions are cut in half from the 3Kg specifications, and the weight limit is cut down to 500 grams.
Figure 1. Tom with the 3Kg sumo, Leo.

The specifications and rules for mini-sumo in a nutshell are:

Look here for a complete rundown of the mini sumo rules.

Building The Mini-Sumo Ring

I recently found a perfect 30"-round 3/4"-thick nicely finished board at Eagle Hardware (just renamed to Lowes). Both sides have a formica-like finish, and the rim has a nice plastic rim for protection. No cutting needed; perfect for us software types! The cost was something around $14.99 for this. Add in the tape and paint, and you have a mini-sumo ring for less than $20 and very little work.
The bar-code tag on the item is:
   3/4 30" ROUND

  7   18793 12512   0

Figure 2. 30" white board.

I also picked up some 1" masking tape and a can of flat black enamel epoxy spray paint.

Figure 3. The spray-paint, masking tape, and barcode.

Using the tape, I masked-off 1" at the permiter of the ring. I then applied about 20 coats of the paint in very thin coats, applying it in different directions to avoid any lines.
Figure 4. Board masked off and ready to paint.

The masking tape I used was not flexible, so the curve was a bit choppy and the paint got into the folds in the tape. Fellow SRS members suggested using wider tape (1.5"), and then marking and cutting the tape at the 1" circle. This is a great idea and would make the edge much better. But for a home practice ring this is good enough. I could scrape and/or sand this; perhaps later--I would rather use the ring to fine-tune my 'bot.

Figure 5. Close-up of the border--a bit rough.

I let the paint cure for a couple of days just to be sure it was hardened, then I threw my mini-sumo robot on it for testing. The robot worked great, and the surface was very robust. I was worried about the paint chipping off with the sharp from scoop. No problem, it looks like my choice of paint was a good one, and the adhesion of the paint to the white surface is also very good.
Figure 6. Mini sumo "Domey" running on the new ring.

Now I've got the platform I need to build a few competive mini-sumo robots for the next Seattle Robotics Society Robothon.

Someone at SRS also mentioned to me that the Lego sumo contest uses a black ring with a white border. The backside of this ring is also white, the same formica-like material as the topside but the finish on the edge is a little rough. Paint a 1" black border on the backside and the same board can be used for the black/white mini-sumo ring, or the white/black Lego sumo ring.

References: Home of the NorthWest Sumo Contest.

I hope this is helpful. Please e-mail me with questions, problems, and hopefully success stories...