Howdy, We are S.I.N. Cycles builders of gravity fueled machines. This is our most recent build, hope you enjoy! Just want to add that if you are interested in some of our other machines check out http://sincycles.blogspot.com/
A Gravity Bike? It is what it sounds like, a bicycle that goes down hill and otherwise has not much use. These machines are a joy to ride almost soothing; just the sound of the wind and road. Speed varies depending on the hill. We regularly get up to 50mph but speeds up to and beyond 80mph can be accomplished. While the speeds may be questionably legal, these machines are legal on all public roads where bicycles are allowed.
If you ever care to race in an organized race. Conforming to the IGSA standards might be a good idea. Listed below are the three rules we build loosely around and have not found the need or desire to go out side of those bounds. The rulebook can be found at http://www.igsaworldcup.com/rulebooks/2009_igsa_rulebook_final.pdf
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
We truly hope you enjoy this inside look!
S.I.N. (Sir Isaac Newton) Cycles
A Gravity Bike? It is what it sounds like, a bicycle that goes down hill and otherwise has not much use. These machines are a joy to ride almost soothing; just the sound of the wind and road. Speed varies depending on the hill. We regularly get up to 50mph but speeds up to and beyond 80mph can be accomplished. While the speeds may be questionably legal, these machines are legal on all public roads where bicycles are allowed.
If you ever care to race in an organized race. Conforming to the IGSA standards might be a good idea. Listed below are the three rules we build loosely around and have not found the need or desire to go out side of those bounds. The rulebook can be found at http://www.igsaworldcup.com/rulebooks/2009_igsa_rulebook_final.pdf
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
We truly hope you enjoy this inside look!
S.I.N. (Sir Isaac Newton) Cycles
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Signing UpStep 1: Prototype
This is a critical step to create a comfortable ride. Everyone has there own body length and preference of how something should feel. So play around. We joke sometimes saying every bike is our prototype for the next bike we build.
As you can see in the photo our prototype is super high tech utilizing a chunk of wood, rope, zipties, a fork, and some wheels. It was just together enough that we could carefully straddle it. Pretending where the handle bars, kneelers, and rear pegs might be. Card board boxes milk crates and other random items come in handy at this stage.
Be sure to take more measurements than you think you need. Also plenty of photos sure don't hurt. Documentation is a wonderful thing.
Sometimes we will draw over the photo to play with the overall aesthetics and frame layout. It is cheaper to learn things on paper than steel.
As you can see in the photo our prototype is super high tech utilizing a chunk of wood, rope, zipties, a fork, and some wheels. It was just together enough that we could carefully straddle it. Pretending where the handle bars, kneelers, and rear pegs might be. Card board boxes milk crates and other random items come in handy at this stage.
Be sure to take more measurements than you think you need. Also plenty of photos sure don't hurt. Documentation is a wonderful thing.
Sometimes we will draw over the photo to play with the overall aesthetics and frame layout. It is cheaper to learn things on paper than steel.
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Just need little help plese guys i want to iknow the measurement of the frame full frame.
what is the size of frame and lower frame. plese
VBrake rear, 160mm Disk front, fully suspended. Total build cost, about AUD$100 but that uncludes 3 donor bikes (from my local scrap yard). The bottom bar is full of lead. The only thing really left to do is put a seat on it. Rides well, spring rates are perfect. Now i just have to find some hills to run it on (and make some brackets to strap it to the roofracks on my car). Still trying to source some wheel covers at a reasonable price but with my feet further forward, they tend to stay out of the spokes anyway.
Thanks Harlan for such an awesome inspirational instructable!
On another note, I recall carrying a 200lb., two person, elephant costume down Main St. that your company designed for the Lion King Celebration back in 94. I remember meeting Michael a couple of times. Seemed like a nice guy. Was attentive to our puppeteers.
I especially like the "bomb" between your legs. You should add a fuse on top to complete the picture...
Have you ever considered using solid wheels? (for weight but for a very strong gyroscopic effect and thus stability as well).
We did build a 16" racer though and it is certainly a fast and interesting ride.
thanks anyways
video please.
also, how do they dismount at the end of the hill? or do they just wipe out? video also please.
not a lot of people doing this it seems. i heard Portland is a good place for downhillers of all breeds.(something about zoo bombers?) if you're ever in the SLC area shoot me a message and i can point you to some good hills.
Just a note that Barge is a brand name of glue. The generic name is contact cement, though I believe Barge is superior.
nice landscape btw!
do you think that you could use arc welder to weld the old bike frame to steel?
if so normal rods and normal current?
Good Luck
http://www.youtube.com/watch?v=uo7bFgO9_f4&feature=related
Also, just saw pic 3, Be carefull with your shoelaces :)
honestly ive never heard of gravity bikes before, but it isnt a surprise since im from the prairies :P
Building a suspension version would be really cool. I've got a couple of old pull shocks out in the garage- high pivot, rearward axle path with a low leverage ratio and a short linkage fork.... I might have to draw that up!
Now if they only did GPV sidecars...THAT would be crazy!
Urban Assault from Lugepunk on Vimeo.
I will keep this idea to, who knows, any day build one. Another project I intend to do is the Mono Wheel Bike: http://cms.obviousmag.org/mt-search.cgi?IncludeBlogs=2&limit=28&search=mono+wheel
I use good old spit on the inside of grips. You don't need too much and you have to be careful for a couple of days until it dries out fully, but I usually don't have any problem finding spit.
It also works a treat for getting old grips off. Pull them out a bit and force some spit in the gap, then slowly work the grip back and to, forcing the spit down and the grip will just fly off.. It works a treat.
Has my vote..
Add some EL panels and you have the envy of the neighborhood. :)
It's a pity that the tallest hill near my home is the highway bridge...
I didn't know it was known as a sport somewhere else in the world.