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Old 08-30-08, 04:35 PM   #1
blazera
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Gears

I'm looking to create a speed beast, but first, I need a beastly transmission. I'm looking for a very large crankset. I'm also curious what transmission setup the record speed holder had, that Varna Diablo. all I hear is that the lowest gear is like a typical high gear, I have no idea about the high gear. Lastly, is there a calculator to figure out the resistance of higher gear ratios? Gotta p-p-p-push it to the limit.
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Old 08-30-08, 10:03 PM   #2
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Here's a link that shows the gearing, although it doesn't give technical details:
http://www.recumbents.com/WISIL/whps...rna_detail.htm

What exactly are you doing? The premise behind a fared recumbent is that it only has a fraction of the air resistance that a normal bike has, so they can step the speed way up with the same amount of power. If you're not using a fared recumbent, you don't need that gearing- you'd just wind up with something that you couldn't pedal in anything but low gear.

I've noticed that none of these people setting world records have ever asked me to ride for them. I can only conclude that setting world bicycle speed records takes an inordinantly good cyclist as well.

I've heard of people getting oversized sprockets off certain exercise bikes, but not sure which ones that is.

If you're seriously in contention for a world speed record, you can probably get someone to custom build a larger sprocket as well.
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Old 08-31-08, 12:41 PM   #3
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No I'm not going for any records, I'm too poor for that. But I do wanna do the best with what I have. I was thinking a fully enclosed trike. My ultimate goal is a man powered long distance machine, fast enough for highway travel. Plus it would just be fun to make something like this.

But I still need a large sprocket, who makes custom sprockets? Thanks for the link, I wonder how many teeth it has.
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Old 08-31-08, 12:57 PM   #4
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Oh boy, another fully enclosed trike. I had a tadpole version back in 1983 and planned to ride it from Colorado to California. In the winter the clear plastic cover I could see through frosted over and in the late spring I had serious heat stress problems passing through the Mojave Desert and the San Joaquin Valley. If I opened the hull to get ventilation the air drag wasted energy. The fiberglass fairing was half the weight (70 pounds) of the whole thing. I dumped the shell in NorCal. The fairing was 39 inches wide and caused problems on the San Gabriel River Trail, the Golden Gate Bridge, in Marin County, and near Georgetown in Colorado. Each time other cyclists helped me lift the thing over barriers. The most dangerous problem was inadequate brakes. Cut the weight, use a partial fairing with cloth side panels, and have serious brakes. Be sure the shape does not give you lift at high speeds, that nearly killed me twice.

Gears: With 16" rims I had a transfer gear or jack-shaft that gave me a 120" high and 30" low. Spun out at 40 MPH. With only the 30" low and a full touring load I damaged my right knee going over the Grapevine in SoCal.

Last edited by ken cummings; 08-31-08 at 01:00 PM. Reason: gearing
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Old 08-31-08, 01:07 PM   #5
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Originally Posted by blazera View Post
No I'm not going for any records, I'm too poor for that. But I do wanna do the best with what I have. I was thinking a fully enclosed trike. My ultimate goal is a man powered long distance machine, fast enough for highway travel. Plus it would just be fun to make something like this.

But I still need a large sprocket, who makes custom sprockets? Thanks for the link, I wonder how many teeth it has.
53x11 road gearing with 700x23 tire will give you 45mph at 120rpm.


Why not toss in some sort of jackshaft to change the gearing, it would be fairly easy to make if you have the fab skills to scratch-build a trike and fairing.


edit, post above beat me to jackshaft idea.
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Old 08-31-08, 01:24 PM   #6
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Thanks for the advice. I'll keep it in mind when I get to the fairing. This is my first bike building experiment.
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Old 08-31-08, 01:38 PM   #7
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53x11 road gearing with 700x23 tire will give you 45mph at 120rpm.


Why not toss in some sort of jackshaft to change the gearing, it would be fairly easy to make if you have the fab skills to scratch-build a trike and fairing.


edit, post above beat me to jackshaft idea.
Thank you for the encouragament because I ever said I had fabulous skills.
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Old 09-01-08, 12:24 PM   #8
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Thank you for the encouragament because I ever said I had fabulous skills.
fab. = fabrication.
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