This is not my project. It is by a guy I see around. I interviewed him and took some pictures. There is enough information here to get you started if you have some hand tools and curiosity.
Remember to leave a comment :)
Step 1: What you need
Wrenches and screwdrivers
Hacksaw or maybe an angle grinder
Welder. Oh, you don't have a welder? Now you do.
Electric scooter, or maybe any bicycle would work fine.
~1/4" x 2" angle aluminum
~3/4" steel square pipe
Angle iron (you decide how strong it should be)
Scrap steel pieces
Front suspension from a small "quad" 4 wheeler.
Wheels with a thick (14mm?) axle. The axle must be strong enough to be supported on one side only.