Time limit

5 minutes

Control method


Aim of the challenge

Robots will propel a light wooden ball, 74.3mm in diameter and weighing 114g, attempting to roll it towards a set of 9 "pins". Each robot will attempt to knock down three sets of pins with up to two rolls per set. If the first ball roll knocks down all 9 pins then that finishes that set of pins.

The skittle set we are using was found on eBay.

We recommend that robots have some kind of bumper on the front so that impact with the ball causes no damage to the chassis or other parts of the robot.



Special rules

Robots are not allowed to push the ball all the way to the pins. There will be a line halfway down the course beyond which the wheels of the robot are not allowed to travel.

You may push or propel the ball using a mechanism attached to your robot. However, the ball must be on the ground when it first moves - you may not pick the ball up to attach it to the mechanism.

The mechanism can extend reasonably beyond the limits of the robot (perhaps exceeding the size category) but must not be so long that it touches the pins (obviously).

You will be allowed to handle your robot after each roll to reset it to the starting position. This can also be achieved via remote control if you wish.

Ranking and points

5 points will be awarded for each skittle knocked down.

Additional points:

  • 10 points will be awarded for knocking all 9 pins down with one roll of the ball (i.e. a Strike).
  • 5 points will be awarded for knocking all 9 pins down with two rolls of the ball (i.e. a Spare).


  • Any robot who crosses the "stop line" will forfeit the points for the current set of skittles.


50 thoughts on “Skittles

  1. Will we get some more details about the pins/skittles? I assume its not going to be the traditional wooden ones, as a tennis ball would just bounce off them.

    1. Hi Leo. Yes, you’ll definitely get more details about the skittles once those details are known. My guess would be something either 3D printed or plastic skittles. 🙂

      1. Something we can easily get for testing would be good!
        I never did manage to find last year’s ‘golf’ ball anywhere… Luckily I still have the tennis balls I picked up instead, so that’s good for this challenge.

  2. Similar to Keith’s question. Can the robot have a catapult/cannon to give the ball more speed/momentum to knock skittles over, or does the robot have to rely on its own speed to push the ball towards the skittles?
    Will we know the dimensions and weight of the ball?

    1. Hi Andy.
      I’ve added another special rule to address your first question. There can be a mechanism to propel the ball, but the ball must be on the floor – so a catapult is out, for instance, but a ram-cannon is okay.
      Yes. Dimensions and weight of the ball will be confirmed as soon as we know it. 🙂 At the moment, we’re thinking a standard tennis ball would be appropriate – good weight, good size and easy to replicate for practice.


  3. A couple of rule clarifications: so we get 3 sets of pins and *up to* 2 balls at each. Presumably if we get a strike, we don’t get the second ball.

    Are we allowed to handle/adjust/reset the robot between balls? Or is the robot alone until we’ve done all (up to) 6 balls?

    1. Oh, yes, sorry. Basic rules of bowling apply. If you knock ’em down in one go for a strike, that’s your lot for that set of pins.
      Yes, you can reset the robot manually (or remotely) after each roll. The ball will be reset for you.

  4. Is the ‘mechanism’ to propel the ball allowed to exceed the A4/A3 size restrictions? (Assuming its only attached for this challenge)

    I think for Robot Golf last year that was allowed.

    1. 7.5cm diameter. I can weigh it for you next week ? Or you could estimate from the density of what’s is made of. I reckon ours is made of pine or some other softwood.

  5. What will the running surface be? Hard flat floor, office type carpet tiles? This will effect how fast the wall rolls.

  6. I’ve been following the stories about PiWars and even though I won’t be able to be there, I had to check this out as I wasn’t sure what a “skittles contest” was. I’m from the U.S. and to me skittles are those wonderfully flavorful and colorful (colourful) candies that make your tastebuds dance a jig. I noticed though that your diagram shows nine skittles and and your rules talk about knocking down ten skittles. You might need to adjust your diagram. I’m hoping to catch highlights/ videos of the competition on the internet. Have a good weekend.

    1. Really? *checks* Oh, you’re dead right. Well spotted. Thank you. The diagram is actually correct so I’ve amended the text! Doh!

  7. What is the pin spacing / grid which the pins will be spaced on? Presumably there will be a square 3 by 3 grid but how far apart? For repeatability I am guessing there will be spots to reposition the pins on?

      1. Hi 🙂 Any update on the Pin spacing? Has a decision been made? Preferably a measurement of pin centres for the placement spots rather than inter pin spacing if possible please?

        1. All we can say is that the pins will be approximately 2 inches apart. Apart from that, it’ll be a(nother) surprise.

  8. Which side up will the hardboard be? Smooth or rough/textured? This kind of applies to all the arenas which ise hardboard. Also how will the sheets be joined together? Tape? On the running surface or on the back face?

    1. It will be the smooth side, painted.
      Ideally, we will join them on the underside but if that fails on the day we’ll have to tape it on the top.

  9. Hi Mike,
    More questions ;). It isn’t clear if there is a starting position for this challenge. There is a box on the diagram but the description doesn’t say.” The robot will start from the start box.” Is there a “start box” the robot must start it’s bowling run from or can the robot be positioned anywhere in the arena as long as it isn’t over the “foot fault” line?

    1. The robot can start from anywhere before the ball on the right hand side of the foot-fault line. So you can have a run-up if you want to.

      1. Thanks for the answer 🙂 Does that mean that there is an imaginary line, parallel to the foot-fault line, passing through the centre of (or just behind/to the right of) the ball which the robot must be placed behind? Or can the robot, or parts of the robot, be placed over/around the ball (without touching the ball) when placing the robot at the start of each bowling run?

        1. The robot can literally be anywhere. It can be to the side of the ball, it can have parts around the ball, it can be wholly behind the ball. Nothing matters, essentially, except the fault line, beyond which no part of the robot can be situated.

    1. It’ll either be as simple as drilling a hole so the ball uses gravity to stay in place or Tim will 3D print something. I’m hoping for the drill, personally – simpler and less finicky.

  10. Let the ball roam free, it was not an issue for Golf last year. We to not want blue tac getting stuck to the ball, or having to push it off something first. at the very most a small hole which the ball can settle into, but only 10mm diameter, no larger.

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