There is a piece sold that will fasten on a BSA block. I simply cut the block down to about 1/2" and drilled holes for the axles. It's good to have an adult watching the kids because they push hard when building their design. An adult can make sure the block is sitting on another block to take the stress off the wheels while the kids are building. I weighted the cars to 5 ounces and then added weight so all the cars would reach the finish line about the same time. We had 4 cars set up so an adult comes in handy so the kids take turns.
I'm happy I did not cut up and burn my obsolete 2 lane wood track. It was set up out of the way and the kids used it all day while we were running the Regulation races.
Lots of FUN!
There is a veggie car derby ...
And a Valve cover car derby as well..
https://www.derbytalk.com/viewtopic.php ... car#p60167
Plus: Belt sander Racing: