are some of the funnest things to build with Knex. The challenge in building a roller coaster is keeping the car moving downward so it doesn't stop on the track. Build your Knex roller coaster as high as your chain will let you or you can hand release your cars as high as you want. The key to a fast roller coaster is the gold rod, gold connector, and tight track tubbing.
New Knex roller coasters are also availible that allow your to build inverted and twisting roller coasters. Some models include the Serpent's Spiral Coaster, Renegade Run Coaster and the Vertical Vengence Knex Roller Coaster.