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Old 08-29-03, 02:01 PM   #1
Anderson3250
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custom sprocket

Does ne1 know if there are any places that will make a 250 tooth sprocket?
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Old 08-29-03, 02:17 PM   #2
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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.

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Old 08-29-03, 02:24 PM   #3
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I am planning on building a bike that has a 250 tooth sprocket on it. SPEED!!!!!!
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Old 08-29-03, 02:28 PM   #4
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Speed ? yeah after you blow up your knees turning that thing around

Jeff
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Old 08-29-03, 02:31 PM   #5
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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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Old 08-29-03, 02:33 PM   #6
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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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Old 08-29-03, 02:35 PM   #7
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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.
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Old 08-29-03, 02:43 PM   #8
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Quote:
Originally posted by djbowen1
since you seem to have to much time on your hands why dont you make one yourself.
OUCH!

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Old 08-29-03, 08:32 PM   #9
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it wasnt meant to be taken so strongly.
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Old 08-29-03, 08:33 PM   #10
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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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Old 08-30-03, 04:39 AM   #11
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Do you mean chainring or rear cog?
check out
http://www.argonet.co.uk/highpath/cycle_/eggs.htm
http://www.bikebrothers.co.uk/ultimatebike.htm
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Old 08-30-03, 05:29 AM   #12
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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.........
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Old 08-30-03, 09:25 AM   #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.
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Old 08-31-03, 08:41 AM   #14
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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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Old 08-31-03, 07:15 PM   #15
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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
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Old 08-31-03, 08:34 PM   #16
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It is possible.
Nothing is impossible, we just don't know how to do it yet.
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Old 09-01-03, 08:50 AM   #17
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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.
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