Here is what I have learned over the last few years:
You can view some of my projects on JsFiddle.
My brother and I also love to build K'nex. You can read about us on K'nex's website! On August 14, 2015 at 5:30pm, we finished out latest K'nex ball machine project as of this writing -- Impossible which you can watch by clicking this link. This project used 23,000 pieces and took over 10 months to create. We started October 2, 2014 at 4:30pm and finished August 14, 2015 at 5:30pm. Despite the number of pieces available to us to build, they aren't as expensive as you might think. We once found 1,000 pieces on Ebay for only $25.