How to make a Sumo ring in 30 minutes

In recent weeks my children and I have been having lots of fun making and fighting Sumo robots with LEGO MINDSTORMS NXT. However, I wanted to make the fights to resemble the official Sumo rings used in competitions similar to how it is suggested in the LEGO NXT Sumo web site.

Making a simple Sumo ring for the family is really easy. The following explains how a Sumo ring can be built in 30 minutes with easy to find stuff.

Things you need:

· Few sheets of A3 paper
· 1 x pair of Scissors
· 1 x can of white paint
· 1 x can of black paint
· 1 x knife / box cutter
· 1 x bottle of mineral turpentine (just in case you have to wipe any drips)
· 1 x piece of wood
· 1 x hard board
· 1 x masking tape
· 1 piece of string about 1 m
· 1 x PVA bonding / Glue



(1) Make a stencil with paper

Step 1 - make a giant square of paper: Join up few sheets of A3 papers together with masking tape to make a giant square just over 4 feet by 4 feet [1.25m x 1.25m]

Step 2 - Draw a giant circle: Rest the giant paper on something solid (like a wooden deck) and hammer a nail into the middle of the paper

Tie a piece of string on the nail with a bit of slack so it can freely rotate around the nail. Tie a pen or a pencil to the other end - you now got a poor man's compass.

Using the stretched string as guide, draw two concentric circles – the outer one 2 feet (61 cm) radius and the inner one 22 inches (56 cm).

Step 3 - Cut the stencil: Use a knife or pair of scissors to cut along the mark. You will have three stencils: a round circle, a ring, and a outer bit.

(2) Painting
Step 4 - Paint the outer bit white

First use the smaller circle template – place the stencil on the hardboard - you may use a glue stick to prevent it moving while spraying. Spray the can of white paint around the stencil. Wait for 10 mins for it dry.

Step 5 - Paint the inner bit black

Using the ring stencil, spray the inside black – being careful not to get any drips / spray on to the outer white bit. Wait for 10 mins for it to dry

(3) Cutting and finishing

Step 6 - Cutting the hardboard

Using a very sharp knife cut the hardboard along the outer edge of the ring stencil. The hardboard is pretty hard to cut with the knife - If you are not comfortable using the knife, then get an adult to help. If you are using a thicker material (such as plywood), then you are better off using a Jigsaw - as you will get a much better finish.

Place the painted circular hardboard on a piece of wood so the edges will be raised Glue it so it is firm and solid. Leave for another 2 hours for the paint to harden and the glue to dry.

You are now ready to have some fun with your sumo robots:

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