Although it’s a game that can trace its origins back over 700 years, most people know Dominoes as a fun chain reaction toy that’s actually only fun when it comes to knocking them down, not the stressful process of stacking them up. With that in mind, Grant Davis built a self-stacking and self-toppling domino machine using nothing but Lego, and it’s an engineering marvel.
Building machines that can stack domino tiles in long chains is relatively simple. In fact, there have been battery-powered toys that can do that since the ‘80s, driving along and dropping dominoes one by one until they run out. Even Mark Rober designed and built an automated domino machine that can stack 100,000 tiles in 24 hours, far outperforming even the most talented human stackers.
Where all of these automated machines fail, is when it comes to resetting a domino chain after they’ve all fallen. What’s usually left is a mess of scattered tiles that needs to be cleaned up, and manually re-loaded back into the stacking contraptions. Where’s the fun in that? Davis wanted a better solution: a machine that both stacks dominoes and knocks them over all on its own, again and again, in an infinite loop requiring no human intervention. And to make things extra challenging, they limited themselves to Lego to make it happen.
There were many layers of complexity to building this machine, from designing the lifting mechanisms to reliably raise the individual dominoes after they’ve fallen, to a clever floor structure that opens to allow the reset mechanisms to do their thing, but quickly closing afterwards so the brick-built dominoes have something to fall on. Further complicating things is the fact that dominoes never fall and end up in the same position twice: a problem that Davis solved using magnets borrowed from Lego’s train sets (used to couple train cars together) hidden inside each domino causing them to perfectly realign themselves with magnets in the floor when raised back up.
All-in-all, Davis estimates they used over 4,000 Lego pieces to build this machine, and spent 300 to 400 hours over evenings and weekends perfecting its design. It topples and raises a set of 10 dominoes every seven seconds, which means that if left running for 24 hours, it would potentially set a world record with 120,000 dominoes stacked in a day’s time. If you’re nursing a turkey hangover today, this 12-minute video is a fascinating look at just how far the engineering limits of Lego can be pushed.