Gravity racer - Calling all daredevils!

[S.I.N. CYCLES]

Nice! Really looking forward to seeing what everyone comes up with! If anyone has any questions about our instructables build in the OP or gravity bikes in general please feel free to ask. We just picked up 84lbs of cromoly so we'll likely have a new bike pretty soon. Until then, here's all the ones we've built so far:

Wasp

Red1

S1

And footage of us getting the S1 to 58mph:
http://www.youtube.com/v/7pkDxQK3bDc?ve ... p;hl=en_US

There is a road by us where we can likely hit 65+ that we need to go ride and get footage of. Stay tuned!

 

[snydur]

question:whats a good weight to have on the bike? i was thinking about two 5 pount weights where the crank was. should this be enough?

 

[S.I.N. CYCLES]

The more weight you have and the closer to the ground you have it, the more stable your bike will ride. If you can get more weight than 10lbs, do it. The max weight, in accordance with IGSA, is 75lbs. So try to shoot for that. On that note, if anyone is interested in complying with IGSA rules, here is the quick and dirty version:

Wheel size - 51cm / 20” max
Bike weight - 34kg / 75lbs max
Axle to axle length - 127cm / 50” max

Long and thorough version: http://www.igsaworldcup.com/rulebooks/2 ... _final.pdf

 

[snydur]

hmmm . . maybe i could fill the frame with sand.

 

[snydur]

well, got a some more done. not all the psint is done, but most it. also cut the brake mounts, look like its shoe brakes (yes im serious)


011 by andrew snyder, on Flickr
why i left that huge gap, i dont know


019 by andrew snyder, on Flickr
so people will see me, and so it adds some dorkiness


020 by andrew snyder, on Flickr


015 by andrew snyder, on Flickr



022 by andrew snyder, on Flickr

hoping to get the other rim redone tommorow, and mount matching tires. tubes, and then drill some holes for the pegs. getting close. willl probably make different bars for it to.

 

[snydur]

:shock: you were on a freeway

Nice! Really looking forward to seeing what everyone comes up with! If anyone has any questions about our instructables build in the OP or gravity bikes in general please feel free to ask. We just picked up 84lbs of cromoly so we'll likely have a new bike pretty soon. Until then, here's all the ones we've built so far:

Wasp

Red1

S1

And footage of us getting the S1 to 58mph:
http://www.youtube.com/v/7pkDxQK3bDc?ve ... p;hl=en_US



There is a road by us where we can likely hit 65+ that we need to go ride and get footage of. Stay tuned!

 

[ossum]

That video was insanely cool!

How do you measure your speed? Sounds like you need a little bicycle computer or GPS phone running something like Endomondo. If you had a speed logger you could overlay a speedometer on the footage for those of us who like living vicariously through your videos :mrgreen:

 

[S.I.N. CYCLES]

ossum: I was riding along side Harlan on my motorcycle and judging the speed based on my speedo. It isn't the most exact reading, but it's pretty darn close. I love the overlay idea and I think it will be necessary we incorporate that into our following videos.

snydur, are the hills in your area mild and straight enough for flintstone breaking? The reason I ask is because a lot of the corners we take require us to feather the breaks, choose a solid line, and use body english all well before entering. If you were to foot brake prior to the corner it would mess up your positioning on the bike and likely result in entering the corner all wonky like. Beyond that, public roads are unpredictable and breaks are really useful to combat that.

Also, what modifications do you have left on your front end? If you hit a manhole cover at speed does your front wheel have the potential to lock up into the fork?

It may not necessary seem like we are really safety conscience given us racing down the freeway during the day. However, we try to control as many variables as we can. Especially because neither of us have insurance. =P

Anyway, build on! We really like seeing new g-bikes and new riders!

 

[snydur]

ossum: I was riding along side Harlan on my motorcycle and judging the speed based on my speedo. It isn't the most exact reading, but it's pretty darn close. I love the overlay idea and I think it will be necessary we incorporate that into our following videos.

snydur, are the hills in your area mild and straight enough for flintstone breaking? The reason I ask is because a lot of the corners we take require us to feather the breaks, choose a solid line, and use body english all well before entering. If you were to foot brake prior to the corner it would mess up your positioning on the bike and likely result in entering the corner all wonky like. Beyond that, public roads are unpredictable and breaks are really useful to combat that.

Also, what modifications do you have left on your front end? If you hit a manhole cover at speed does your front wheel have the potential to lock up into the fork?

It may not necessary seem like we are really safety conscience given us racing down the freeway during the day. However, we try to control as many variables as we can. Especially because neither of us have insurance. =P

Anyway, build on! We really like seeing new g-bikes and new riders!

the straight away is a half mil long strip of road, only about half of itis downhill. the other side is slightly uphill, (the street floods in the winter) ive went down it afew times on bigger biks and they'l stop without any braking. ill make som slowr test runs somewhere alse, dont really want to die :mrgreen: . as for the frontend, its only there for a mockup, im looking for a lowrider springer forks, or even just bent 20" forks.

 

[Gravitate]

Built this one from a DK SOB frame. 75LBS. Top speed around 75. I regularly hit 63+ mph on the run in this vid. The only video I have that proves I have hit these speeds without power I would have to upload.I got a speeding ticket in that vid doin 60 in a 30. $256 ticket. http://www.youtube.com/watch?v=sbBRxnJw9_s

 

[snydur]

002 by andrew snyder, on Flickr
my new handles. parted out a scooter yesterday, these are some of the parts. Schwinn grip stays are from and old cheap bmx bike.

003 by andrew snyder, on Flickr
the clamp on the forks is also off the scooter, there's a matching one but bare on the other side. how they will attach it via a long bolt through the grip stay, handlebars, and into the clamp. so to tighten it, it will be at the end of the bar. its hard to explain, but pretty much the same setup as a second handle on a grinder or cement drill.


005 by andrew snyder, on Flickr
figured out some brakes


007 by andrew snyder, on Flickr

everything kinda got reversed since this is all for the front of the bike, it was on the left, well it got flipped since im right handed. note the strap because the original wasnt ratty enough (and because it had been cut) but this works better and holds tighter.


009 by andrew snyder, on Flickr

rough mock up before i remembered that i was right handed.

 

[snydur]

006 by andrew snyder, on Flickr
25 pounds of weight put this bike right at. . . a rough 52 pounds.
so now i need to mount the pegs, drill the holes for anti pivot bolts, and get the handles done.

also! i painted the panels grey, put them on . . .and realized they were ugly. so i'm keeping the flag, but the panels went.

 

[dmitri11]

Nice, i love the idea of the handlebars on the forks

 

[breakurnees]

Looking good. Glad you decided to go with brakes.

I can't find my camera battery, so no pics, but I am working with a crappy next full suspension bike. I have a springer front on it, and just bought some Avid Arch Rival brakes to help slow it down.

 

[snydur]

i mounted the brakes on the back today, wasnt to bad, have enough slack to turn pretty well. ive come on a dilema: the pipe the weights are on wobbles when i sit on it. . .hmmm. im guessing ill need to figure something else out.

 

[snydur]

bars, brakes, and turtle are mounted. sat on it, and realized. . . im a 6'1" white lop on a 60 pound pocket rocket that when leaned on edge is only up to my elbow. aka- its will be very interesting to ride :mrgreen:

 

[Philphine]

i wish i had come across this sooner. i might have tried something. i just found it doing a bing search for gravity bikes looking for ideas.

i'll probaly try building something anyway. been trying to figure out what to do with extra 20" parts that would be interesting.

 

[fixmyride]

this is my bike from scratch to latest evolution, great bike on the twisty stuff but loses out to bikes that use the full wheelbase available. hope it helps

http://www.youtube.com/watch?v=ZSEJaVfX ... ideo_title

 

[Philphine]

those are the first bikes i noticed with suspension, but i might not have been paying enough attention before. right after my last post i walked out to the garage and picked up a 20" suspension fork. now i see i can use it. i guess being from a kids bike it would probaly be to mushy for something serious (unless there's a way to get into them and change springs). but it's a style exercise for me, so i'm going with them.

 

[Philphine]

well, i don't know how far i'll get, but here we go

some mountain bike bar ends i was able to force over the fork tubes i hope i didn't over stress them or something, cause i like how they look. added some brake levers once i got them in place.

side view. if you can't read the writing on the fork, it says "gravity games". i planned it that way.... er... yeah. the forks are from where i used the rear suspension on another experiment (soft tail bobber i played with some time back).

and the planned front and rear more or less in position, wheelbase about 49" (in case i mess up a little)

a girls mountain bike i need the main body from, so the rear suspension was there to use. the tube holding up the front is what i'm going to use for a frame. gutted conveyor roller from where i work. i'm meaning to just do a simple triangle, from the rear pivot point up to the shock mount, then two tubes from those points up to the head tube. if i get that far i'll work out seating and foot positions from there.

we'll see what happens.