How to build a fast soapbox/gravity racer (theory)

I couldn't find a video on TH-cam that showed me what I needed, so I did some research and put this video together. I'm not an expert of any kind so the information may not be 100% accurate but It's my best guess. Also, the battery ran out on my camera at the end so that's why it's cut short. Sorry! I was about to say that, if you liked my video and you want me to go into more detail about certain points then I would be happy to make another. Also, I will be building this design in the near future to compete in a local race and will record more stuff!
Thanks

[@tommarkhaley]

Mad Lad

[@biketech60]

If you can't figure it out yourself , steal as much as possible from Graham Chapman .