Ah, memories.
My dad didn't make my cars. His dad did.
The last year of Cubs my car made it to the final and was in the lead when it got to the flat. Then it bounced on a gap between track sections and a wheel came off. It was the only time they didn't reprimand a scout for cussing at a uniform event.
One year in boyscouts they decided to have an Unlimited Class Derby, not BSA Unlimited, mind you. Anything was legal as long as the car was within the standard dimensions and didn't weigh over 16oz. Most put electric motors attached to oversized rear wheels. They tended to fail wonderfully. Mine used a single motor that turned on when the gates dropped and was connected to all 4 wheels. One guy ruined it for everyone and used a similar starter system with a model rocket engine. It burned up the track a bit too literally.
The Unlimited Class Derby was discontinued until the troop could acquire a metal track. They still didn't have one when I made Eagle and got out.