But that doesn't stop me so I decided I would construct my own, so after seeing some more videos I figured out how they work, but before I could design and manufacture an equivalent product I need to make a fast prototype for testing. This instructable is the way i made that prototype which really exceeded my expectations and you could use it to make your own and save a lot of cash.
But what exactly are this things, well to my understanding they have a freewheel mechanism between the axle of the crankset and the cranks which make each crank independent from each other so you need to actively maintain the 180 degree separation of the cranks.
This supposedly makes you go faster (hence the price tag), but I really don't care about that, they just seem fun to me.
Step 1: Materials
1.- Cheap chinese steel crankset. I used the one that came with my bike but a new one cost about $11.00. You could buy one new or salvage one from another bike if you don't want to destroy your actual crankset.
2.- 2 cheap chinese frewheels. One speed freewheel BMX type, I got these for $0.90 each at the chinese store
3.- Mighty Putty (HI BILLY MAYS HERE!!!)
4.- A handsaw, a file, a grinding stone and welding equipment.
5.- Patience. (Yoda: "The boy has no patience." Obi-Wan: "He will learn patience.")