Build a Friction Welder (2012) [video]

If you want to see the effect of friction welding you only need 7 hexagonal plastic pencils:

https://www.youtube.com/watch?v=Fn3VFXBTsDU (it's in German but captions should work well)

Related: https://www.youtube.com/watch?v=pF1mOTsYB0Q

Fran rocks.