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Thread: custom sprocket

  1. #1
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    custom sprocket

    Does ne1 know if there are any places that will make a 250 tooth sprocket?

  2. #2
    Forum Admin lotek's Avatar
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    just out of curiosity, why would anyone want a 250 tooth
    sprocket?

    and no, I have no clue as to where to get one.

    Marty
    Sono pił lento di quel che sembra.
    Odio la gente, tutti.

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  3. #3
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    I am planning on building a bike that has a 250 tooth sprocket on it. SPEED!!!!!!

  4. #4
    The Cycling Photographer SipperPhoto's Avatar
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    Speed ? yeah after you blow up your knees turning that thing around

    Jeff
    Jeff

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    I have spent a year of researching a way to make it work. If I have about five different gears in front, then I should have no problem. And I have been training myself for it, so when I get it made I can then get a fiberglass body, and roll cage if I wreck.

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    Senior Member djbowen1's Avatar
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    since you seem to have to much time on your hands why dont you make one yourself.

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    I do not have the equipment to make a sprocket like that. You got to use extremely strong metal for the sprocket, and the crank shaft. I do not have anything to do this with so I am looking for someone who can.

  8. #8
    Victim of Circumstance mightypudge's Avatar
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    Originally posted by djbowen1
    since you seem to have to much time on your hands why dont you make one yourself.
    OUCH!

    Andrew

    "The Scalpel climbs like a monkey on crack." - BAC5.2

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  9. #9
    Senior Member djbowen1's Avatar
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    it wasnt meant to be taken so strongly.

  10. #10
    road siklista dexmax's Avatar
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    any machine shop with a milling machine can do that for you...

    It will cost you though.. Here I can have it made for $100 US.

    Machine shops don't design sprockets, you must prepare the design for it.

    Likewise, hard materials are a bit hard to find... What material are you planning to use?

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  12. #12
    Can't ride enough! Da Tinker's Avatar
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    Michael, great links! A good source for custom chainrings stirs some ideas for experiments. Also makes me wonder if Shimano's patent for BioPace rings is still active.........
    Happiness begins with facing life with a smile & a wink.

  13. #13
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    I was thinking about using titanium for the sprocket. My dad works at a machine shop so I got the metal to do it with.

  14. #14
    60mph in the 42 ring! Dave Stohler's Avatar
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    Well, FWIW, I think about 100 teeth is the largest ring that will allow sufficient ground clearance. I remember seeing a picture of the famous speed record holder Major Taylor with a specially made bike used to do a 70+mph motor-pace run, and it had a 96 (if I remember correctly) tooth ring. It just barely had clearance, even with a high-mounted BB. Needless to say, a 250 tooth ring would be useless for anything under about 100 mph velocity.

    The second problem with your idea is that of machining what will prove to be an extremely large piece of titanium. Not only will you need about $500 worth of stock metal to start with, but the process of machining something like that will take many, many hours. Add to that the problem that titanium is notoriously hard to machine, and you have a job that will probably take 30-40 hours to complete. In the end, such a ring will cost about $6k to make. This doesn't include CAD drawings, or any type of FEA strength analysis.

    Once you end up with this silly piece of metal (with a BB mounted about 4' in the air, BTW), you will find out first-hand about something called mechanical advantage, or, more precisely, the lack thereof. In the end, you will spend more money than a decent car would cost (don't forget that you will need a custom frame to fit this thing in), and you will have a bike that is entirely useless.

    If you don't believe me, ask any engineer on this board. I'm sure they will all agree that this idea is pure folly.
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  15. #15
    Senior Member bentbaggerlen's Avatar
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    Use a schlumpf mountain drive and a 100 tooh chainwheel see http://www.schlumpf.ch/schlumpf_engl.htm

    The speed record for HPVs is held by Sam Whittingham. 80.55 miles per hour
    http://www.wisil.recumbents.com/wisi...tsSaturday.htm

    There are some great photos of the bikes used to set the records at
    http://www.easyracers.com/racing.htm

    I know its kind of guolish but check out Rob English and the Mango crash at 70 mph
    http://www.easyracers.com/multimedia.htm
    Bentbaggerlen
    "When the spirits are low, when the day appears dark, when work becomes monotonous, when hope hardly seems worth having, just mount a bicycle and go out for a spin down the road, without thought on anything but the ride you are taking." - Arthur Conan Doyle

  16. #16
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    It is possible.
    Nothing is impossible, we just don't know how to do it yet.

  17. #17
    60mph in the 42 ring! Dave Stohler's Avatar
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    [quote]It is possible.
    Nothing is impossible, we just don't know how to do it yet.[/b]

    DS's corollary: Sometimes, we need to know whether something is possible, or is just plain idiotic.
    Cycling Addict
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