Instructables
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Brett Phillips - Gravitybike HQ

A Gravity Bike is a specialised two wheeled bicycle propelled by nothing other than gravity. Without pedals or a chain, Gravity Bike riders rely on steep gradients and gravity to reach incredibly fast speeds. Historically, Gravity Bikes evolved from modifying a traditional BMX where a rider would add weight, alter seating and handlebar positions and change a bikes aerodynamic characteristics in the pursuit of greater speeds. More recently, Gravity Bikes have evolved to become highly specialised and purpose built machines capable of reaching speeds over 130kph from a standing push start.

Gravity Bikes are ultimately built for speed. The steeper and more technical a road or dedicated racing circuit, the greater the adrenaline rush for riders. Fitted with full protective gear including leathers, helmets, gloves and boots, Gravity Bike riding combines the thrill of speed with a love of bicycles.

In 2009, I designed and built this purpose built and highly specialised Gravity Bike. The first of its kind, the bike is a quantum leap in Gravity Bike design and fabrication. The bike is a combination of hand fabricated and CNC (computed numerically controlled) components. The bike was designed from scratch and had to accommodate existing components such as 20'" wheels and mountain bike brakes. The bike has reached speeds of 136kph from a standing push start and assisted me to win the 2009 World Gravity Bike Championships. The only Australian to do so to date. I hope you guys like the build!

For more: www.gravitybike.com.au
 
Wroger-Wroger4 months ago

My ONLY complaint about all of this is that the bikes lack engines - to get back up to the top of the hill again......

Yeah, yeah, yeah, legals and all that - but a 200W petrol motor, running back up a big hill at 5Kmh,- 15Kmh is a lot better than walking it...

Still I suppose that is what cars are for..

There is a hill crest about 5 or 8 Km out of Marysville in Victoria. Heading away from Marysville, towards Narbethon - I clocked about 130Kmh and rising on a bog bike - good quality high pressure tyres - with a heavy trailer behind it....and crouching down some.

The other way back into Marysville, it's SO steep and the hill is so long - I THINK in a really crouched down position like that - that there is a VERY steep bit of hill, that if you come to it at a great speed and then hit that drop - someone MIGHT be able to crack it for 200Kmh - maybe 240Kmh...

(I used an asterisk as the keyboard has no degrees symbol)

Google Earth: 31*31'59.11 S ---- 145*43'10.85 E

The hill continues on, at a very steep angle (generally) for another 4 or so Km, all the way into Marysville - which has it's main street running at 30* down hill - with traffic and round abouts etc..

But be careful - I am not sure that blowing out past 200Kmh - is within the realms of anything other than a special bicycle tyre and wheel - and dumping that amount of energy through the brakes - might result in the inability to stop....

The other way to Narbethon is pretty good though.... but not much windy stuff and once your hit the turn off, back towards Lillydale and Melbourne - the road has various grades - mostly downhhill but some uphill - and the log trucks - which actually are faster around car racing tracks, than the cars, because their built more like go carts with some flimsy cabin on top - well race up and down that road - and there is no where to go besides the embankment or off the edge or worse, under the truck wheels - it's a fantastic road to have race on - but you would EITHER have to find a great all down hill section and race between vehicles with a place to pull off at the end - or not at all.

But the Marysville to Narbethon road - that is as far as I know, one of the steepest and longest racing grade roads in Australia.

"The first of its kind, the bike is a quantum leap in Gravity Bike design and fabrication."

You're probably going to want to change that. A quantum leap is the smallest measurable change.

Atomic Electron Transision 

Yeah I think the statement "That is a quantum leap forward" was originally meant in the most sarcastic of ways., sort of like calling it, "An Epic Failure".

However Quantum is a big and important sounding word that must mean great things...

I think humanity (minus dictionary) just got confused along the way.

i see your in australia, do you know lithgow?
if you do, there is a huge steep windy highway there, which would be great for this, but, there is a cliff on the edge, not too high but still a cliff
Aron3132 years ago
Can you say it in mph?
just divide by 1.6 ;)
or multiply with 5/8 if that suits you better
Ok thanks.
Oldbear2 years ago
Odd question - but do you have to counter steer at a certain speed? (my motorbikes have been anywhere from 25kmph to 35)
mr fat2 years ago
Is there any gravity bike racing in Queensland?
Dedlee3 years ago
I want to find someone to build me a gravity bike. As of now I ride a BMX doing downhill. Any suggestions?
gravitybike (author)  Dedlee3 years ago
Hey Dedlee
shoot me a email at brett(at)gravitybike(dot)com(dot)au and we can have a chat about it! cheers Brett
how much would you ask for one built just like that?
afleming23 years ago
looks comfortable
calcooper53 years ago
This would be cooler if you put up some instructions on how to build this bad boy
there IS one.
http://www.instructables.com/id/Gravity-Bike/
ive seen that one but it is a completely different grav bike. i would love to build THIS one
tyoung63 years ago
whats the song
TheMaker8883 years ago
dont get pulled over for speeding mate haha
nice bike too, you build it?
russvan3 years ago
that is amazing
TwistyTIE3 years ago
oh my that design is just asking for a small bike engine to be put on it :P
Ceiling cat3 years ago
I love that you're wearing Converse high-tops in the video. Probably some of my favorite shoes. I've been wearing mine a lot lately.
gravitybike (author)  Ceiling cat3 years ago
Hey CC, they are the best shoes and have followed me all over the world on the bike! :)
rimar20003 years ago
WOW! That is wonderful! It is a pity that my area be totally plain.

The bike seems very strong. Good design.
muy diferente a la planilandia de La plata, no se puede andar ni en patineta, por el empedrado.
Sí, la pendiente más alta y pronunciada que tengo a 200 kilómetros a la redonda es el acceso a la autopista...
jajaja, es verdad. Aunque descubri que todas las calles son planas hasta que te subis a la bici y te das cuenta que estan todas en subida.
notingkool3 years ago
is awesome, i wish i live in a place with that road. it's ideal to longboard and to back home without efford