Mindstorms Sumo Ring (Dohyo)

I have some experience playing with mini sumo robots, but lately I discovered the fun you can have with (old) LEGO Mindstorms robots.

My mini sumo ring is a little bit small for the bigger LEGO robots and searching the internet I noticed that most sumo rings for Mindstorms are colored the other way around. (this means white in the middle and a black border surrounding it) So it was time to make a new sumo dohyo.

I didn't want to spend a lot of time making it, so I took a trip to a thrift store and bought myself the cheapest round table I could find. I wanted to buy something like a party table, that is already white. They didn't have something like that so I came home with a heavy, 90 cm, massive oak table. (I make up my own rules for the sizes I use.)

Well than we have to use just that.

You will need:

• one round table in the right size
• masking tape
• sanding paper
• matt black paint
• tape measure
• a nail
• hammer
• piece of schrap wood
• knife
• dry erase pen
• scissors
• spatula or credit card

We only need the table top, so first we need to remove the legs. (I didn't buy the legs, so for me it was easy)

I didn't want to paint the sides, so I had to mask them. (Most rules say that the sides have to be an other color than black or white, so the original brown was ok for me. Also if it was painted, it would damage very easily during transportation.)

Ik sanded the outer 10 cm (4 inch) of the table to give the paint something to hold on to.

And before painting you also need to wipe it clean again.

I used some matt black spray paint that I had.

Only the outer ring of the table needs to be painted, because the middle will be white.

Don't worry when your paint looks glossy. It will turn matt when it dries.

The most fun is always the removal of the masking tape.

It wasn't the best masking job I ever did, but more than good enough for this.

(Wait until the paint is fully dry. I surely didn't)

The middle has to be white and glossy, so I wanted to use adhesive vinyl like they use with sign making. You can probably get this at your local sign maker, home depot of maker space.

First you cut it roughly in the right size.

Cut a couple of inches (like 15 cm) from the backing paper.

Be careful to cut nicely. Every piece of dust will become a bump in the end result.

Put the vinyl on the table and stick the part where the backing is removed on the table.

To do this nicely I used a special spatula, but you can also use an (old) credit card for this.

Now you remove the rest of the backing paper little by little and stick the vinyl on smoothly with the spatula.

Always work from the middle towards the sides to prevent bubbles getting trapped.

To cut out the vinyl, we need to find the middle.

Measure half of the table and put a line on the table with a dry erase marker.

Do this from four sides.

Now it is easy to approximate the middle in the figure that is drawn in the middle.

Hammer a nail in the middle of the table and remove it again.

Hit the nail in a strip of scrap wood.

Push the nail, that is through the strip of wood, in the hole in the middle of the table.

Mark the strip 2,5 cm (1 inch) from the edge of the table.

Cut the strip where it is marked.

The strip should be able to turn around freely.

Use the strip as a guide to cut the vinyl with a sharp knife.

Remove the excess vinyl.

Remove the nail and wood strip.

The ring looks already really cool, but there is a little hole from the nail in the middle.

To cover the hole I punched a dot out of some left over vinyl and stuck it over the hole.

The dot makes the hole invisible for the robots but just visible enough for us to know where the middle is so we can keep both robots on their own half to start a battle.

Lets play!