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Thread: Drag bike

  1. #1
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    Drag bike

    I was just thinking, what could I do to convert a wal-mart mtn bike into a bike to be used to go from 0-20mph really fast. lol i know it sounds stupid but i wanna try to do it.

    What should i add/remove? I know the front gears and deraillaur(spell check) lol

    What kinda tires and wheels?

    anything else?

    thanks
    http://www.NickReynolds.net

  2. #2
    Senior Member Brian's Avatar
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    Depends on how strong your legs are, and how fast you want to spin. Someone should come to your rescue with the math for the gearing. In the meantime, you will want to remove an excess weight.

    It is not our place to ask why, only to help you achieve your goal, as dubious as it may seem.

  3. #3
    Non Tribuo Anus Rodentum and off to the next adventure (RIP) Stacey's Avatar
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    You might want to look in to energy storing mass such as a flywheel. Spin the flywheel up, engage the rear dirve and off you go.


    Don't forget to hang on!

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    Radfahrer Rincewind8's Avatar
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    Quote Originally Posted by highspeedcycle
    I was just thinking, what could I do to convert a wal-mart mtn bike into a bike to be used to go from 0-20mph really fast. lol i know it sounds stupid but i wanna try to do it.

    What should i add/remove? I know the front gears and deraillaur(spell check) lol

    What kinda tires and wheels?

    anything else?

    thanks
    http://www.NickReynolds.net
    I don't know what exactly you want to do. Do you want to just want to go from 0-20mph and then stop or do you want to keep going at 20mph. What kind of surface are you planning to do that on, closed parking lot with smooth pavement or bike trail or...? In general, to make a bike accelerate fast, get fairly narrow high pressure tires and small diameter wheels. Possibly just one gear and possibly the gear range, so that you just not spin out at the highest speed you want to reach. There is a pretty good gear calculator here:
    http://sheldonbrown.com/gears/
    TH 1.81 (133kg*62)

  5. #5
    Senior Member Sir Lunch-a-lot's Avatar
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    Maybe add on some sort of a fairing to cut down on wind resistance.
    Pythagorean Theorum: 24 words. Lord's Prayer: 66 words. 10 Commandments: 179 words. Gettysburg Address: 286 words. Declaration of Independence: 1,300 words. U.S. Government Regulations on the Sale of Cabbage: 26,911 words.

  6. #6
    Ride for Life wearyourtruth's Avatar
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    find a steep hill
    before posting, a "noob" should always ask themselves "could this have been answered by first visiting Sheldon Brown

    -Tim-
    www.velocipedebikeproject.org

  7. #7
    Recumbent Evangelist
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    get two very large, industrial-sized elastic bands......

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    Senior Member biodiesel's Avatar
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    You need one of these.

    An xtracycle without racks. You can't possibly wheelie this thing and will almost never endo. On a rig like this you look like a drag racer. Then you just need a can of NOS.

  9. #9
    You know you want to. Eatadonut's Avatar
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    for the gearing, I would use probably a 34-25. That's the granny gear on my roadie, and if I remember correctly it gets to 20.4 mph at about 150 rpm, and I can spin it up pretty quickly.

    I'm liking the flywheel idea. How do you rig up a clutch for your bike, though? Think about the usefulness in traffic situations. No more angry drivers when a red light goes green and you're working to get to speed.
    Weather today: Hot. Humid. Potholes.

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    FLYWHEEL, omg, why did i not think of that. i love it.

    Lets work on this now!... What parts should i start with and whats the basic design, i love it.

    thanks
    Nick

  11. #11
    Non Tribuo Anus Rodentum and off to the next adventure (RIP) Stacey's Avatar
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    Gee, all I have is concept, and that's free. You want design? That's $250 an hour

    Seriously. I'm thinking of the flywheel from an old Schwinn Excersize bike. Drive it from one of the sprockets on one of those old Front Feewheel systems Schwinn used on their gaspipe lightweights. Use the other sprocket to drive the rear wheel. With the bike up on a drop stand (back wheel up while you get the mass up to speed)you crank the snot out of it, the ffs will let the rotational mass spin without the cranks beating the crap out of your legs. Just a starting point.

  12. #12
    Senior Member Brian's Avatar
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    Flywheel? Chainguard. When that chain snaps, it's going to be dangerous.

  13. #13
    You know you want to. Eatadonut's Avatar
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    why would the chain be any more likely to snap than a normal chain, also, why would it be more dangerous?
    Weather today: Hot. Humid. Potholes.

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    Senior Member Brian's Avatar
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    With a flywheel? Stored energy + bike chain = accident.

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    You know you want to. Eatadonut's Avatar
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    ...much like dropping the clutch at 8k rpm in a truck. I gotcha. That's why you gotta keep the chain spinning as you release the clutch.

    Also, remember that there's no way you'll be applying more force to the chain this way than a fixie would skidding.
    Weather today: Hot. Humid. Potholes.

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    Quote Originally Posted by Eatadonut
    Also, remember that there's no way you'll be applying more force to the chain this way than a fixie would skidding.
    How so? Weight transfers off the rear wheel on decelleration and onto it on accelleration.

    Regarding gearing for drag racing to 20 mph;
    Most of the recommendations have been for a single gear.
    I entered a double elimination 50 meter drag race a couple of years back at an HPV event. Most of the 12 other racers used one or 2 gears. I used 155mm cranks, a 34t chainring and 5 gears in the rear, shifting every couple of seconds. I think the cogs were 24-21-18-16-14. I never stood on the pedals, just sat and spun.

    None of the runs were even close. I was always able to ease up before the finish to conserve energy for the next run. I needed to because at 57 years old I was at least twice the age of the average competitor.

    "Old age and treachery always overcome youth and strength"

  17. #17
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    did you beat everyone?

  18. #18
    Senior Member Brian's Avatar
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    Of course he did, he's old and treacherous.

  19. #19
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    Quote Originally Posted by Stacey
    You might want to look in to energy storing mass such as a flywheel. Spin the flywheel up, engage the rear dirve and off you go.

    A low racer recumbent would be a good platform. The link has an extreme example. It's the third bike down. I wonder if anyone's learned to ride it yet?

    http://www.dclxvi.org/chunk/meet/outside/index.html
    Last edited by Hal Hardy; 10-13-05 at 11:09 PM.

  20. #20
    Senior Member cranky's Avatar
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    How about a Trebuchet Bike? Using the same principle of storing energy into a flywheel, only you put it into a weight. Pedaling in a low gear with pulleys lifts a heavy weight, release the weight to propel the bike.

  21. #21
    old codger icithecat's Avatar
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    Quote Originally Posted by biodiesel
    Then you just need a can of NOS.
    Or a chilli burritto.

  22. #22
    You know you want to. Eatadonut's Avatar
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    Quote Originally Posted by MnHPVA Guy
    How so? Weight transfers off the rear wheel on decelleration and onto it on accelleration.

    True. Obvious solution: someone try it, and we want pics!
    Weather today: Hot. Humid. Potholes.

  23. #23
    Non Tribuo Anus Rodentum and off to the next adventure (RIP) Stacey's Avatar
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    Quote Originally Posted by Hal Hardy
    A low racer recumbent would be a good platform. The link has an extreme example. It's the third bike down. I wonder if anyone's learned to ride it yet?

    http://www.dclxvi.org/chunk/meet/outside/index.html

    That's exactly what I'm talking about.

  24. #24
    Senior Member duckliondog's Avatar
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    You need to be able to put all your energy into the rear wheel. Including arm power.

  25. #25
    Dog is my co-pilot 2manybikes's Avatar
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    You mean a bicycle that is a dragster ??

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