Get Gnarly On Your Own Homemade Gravity Bike
Written by mike on September 23rd, 2011
Take a bike with no pedals and a super low center of gravity, head to the top of the tallest hill you can find, and let gravity do the rest. Gravity biking, kissing cousins with downhill skateboarding, is a niche sport that attracts extreme racers who are happiest when they average 50mph and peak out as high as 80mph.
Instructables user Harlan Whitman posted a thorough writeup on how to build your own mean gravity machine from scratch. I dig the kneeling pad assembly and his use of hole saws to mate the tubes.
The details from his writeup:
The basic standards are:
Wheel size – 51cm / 20” max
Bike weight – 34kg / 75lbs max
Axle to axle length – 127cm / 50” max
Many more rules can be found in the rule book. But where we race, none apply
Tools needed or have access to:
Welder
Metal cutting tools of some kind – Angle grinder and cut off wheels, metal band saw, hacksaw, hole saw.
Assortment of wrenches
Drill press
Vise
The more the merrier!Materials:
We dig through metal scrap bins for most of our metal material and then let the material inspire.
We did buy 8ft of .75″ x 1.5″ x .125″ mild steel for this project.
Paint
Rim Brakes
Brake Levers
Brake cable/housing
L200 foam
Wheel cover
x2 20 inch wheels
Old bmx bike to pluck any tid bits from
Shaft collars
Lead
More resources can be found here:
Gravitybike HQ
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