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single speed efficiency,why?

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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

single speed efficiency,why?

Old 02-26-08, 03:33 PM
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dwarner1
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single speed efficiency,why?

Single speed drive trains are said to be more efficient than derailluer systems. I think it's true, but I'd like to know exactly why. Commonly listed reasons include: fewer moving parts = less friction, shorter chains = less chain mass and less friction, straight chainline = less friction(?), less angular momentum change since they don't have to zigzag through the derailleur (?), ,,, Must be lots of opinions about this. List the reasons in rank order.

Last edited by dwarner1; 02-26-08 at 03:34 PM. Reason: misspell
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Old 02-26-08, 03:41 PM
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Please read the article from page 3 to page 12.

The mechanical efficiency of bicycle derailleur and hub-gear transmissions


When you have read that, do you have any more questions?



I warmly recommend to anyone posting in this thread to read that article.
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Old 02-26-08, 04:34 PM
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That was a nice read. Thank you.
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Old 02-26-08, 04:39 PM
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friction
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Old 02-26-08, 05:26 PM
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Originally Posted by dwarner1 View Post
Single speed drive trains are said to be more efficient than derailluer systems. I think it's true, but I'd like to know exactly why. Commonly listed reasons include: fewer moving parts = less friction, shorter chains = less chain mass and less friction, straight chainline = less friction(?), less angular momentum change since they don't have to zigzag through the derailleur (?), ,,, Must be lots of opinions about this. List the reasons in rank order.
You pretty much started and ended the thread in one post there. All of that is true.

One extra thing that's true for fixed is that the momentum of a fixed drivetrain pushes your feet through the dead spots. But that's not applicable to ss.
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Old 02-26-08, 05:45 PM
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Unfortunately there is nothing mentioned on the efficiency of a fixed gear drivetrain. Most of the drivetrains measured an efficiency of around 92 to 94 on average in the article, which is lower than I expected. I had the assumption that all drivetrains were nearly 100 percent transfer of energy, and that all the differences were miniscule. Plus when you add in dirt and old chain and everything else that modern bikes develop, I'm guessing these numbers would be even lower.
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Old 02-26-08, 06:13 PM
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I have been assured that it is Zen Effect and Perpetual Motion, and who am I to doubt it?
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Old 02-26-08, 06:14 PM
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Fascinating reference. Thanks for the heads-up.

But it doesn't address the question at all, except for a short textual note about smallest derailleur sprockets being the least efficient.

I guess am most curious about which features of a singlespeed (or derailleur for that matter) drivetrain are most or least likely to be detrimental to efficiency, and to what comparative degree---especially as to what 'mistakes' in setups may be most damaging to performance.
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Old 02-26-08, 06:20 PM
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No such thing as a 100 percent transfer of energy in a mechanical system.
An off kilter chainline can affect efficiency with more friction compared to a straight chainline. With constant rubbing the parts wear faster... and the noise will make you nuts. In a single speed context, the chain being too tight can affect performance as well.
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Old 02-26-08, 06:27 PM
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Originally Posted by kjohnnytarr View Post

One extra thing that's true for fixed is that the momentum of a fixed drivetrain pushes your feet through the dead spots. But that's not applicable to ss.
This has nothing to do with mechanical efficiency and everything to do with halfassed lazy pedaling technique. A fixed gear drive train does not have a magical extra energy source that ss drive trains lack.
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Old 02-26-08, 10:49 PM
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Originally Posted by mihlbach View Post
This has nothing to do with mechanical efficiency and everything to do with halfassed lazy pedaling technique. A fixed gear drive train does not have a magical extra energy source that ss drive trains lack.
That's what I said: It makes my lazy-ass technique more efficient.
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Old 02-26-08, 11:35 PM
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But it's true! It is about perpetual motion. I just know it!

On a fixed gear bike, your legs turn the pedals. But as anyone who has ever tried to stop pedaling a fixed gear bike knows, the bike makes the pedals go around.

So the faster you pedal the bike, the faster it moves the pedals around for you. So the faster you go, the more the bike starts pedaling itself. If you go fast enough, it just takes off like a rocket.

The oil companies and the Big Three auto makers do not want you to know about this unique feature of fixed gear bicycles, and that's why a brown GMC Suburban with Texas plates now follows me everywhere I go on my bike.
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Old 02-26-08, 11:47 PM
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(custom cadence x best power) (centrifical force + perpetual force - friction) = [fixed gear]
(varied cadence x varied power) (intermittent force + friction) = [geared]

thats why some time trialists use one gear
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Old 02-27-08, 01:22 AM
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Originally Posted by jgrant75 View Post
(custom cadence x best power) (centrifical force + perpetual force - friction) = [fixed gear]
(varied cadence x varied power) (intermittent force + friction) = [geared]

thats why some time trialists use one gear
ugh...
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Old 02-27-08, 04:34 AM
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Originally Posted by kjohnnytarr View Post
That's what I said: It makes my lazy-ass technique more efficient.
no it does not.
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Old 02-27-08, 04:52 AM
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Originally Posted by kemmer View Post
ugh...
Dont ugh Kemmer, it's science.
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Old 02-27-08, 05:15 AM
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dude, its just like you're one with the bike, and like you're connected with god in a way, like he's pushing you along with his magical powers. it's very spiritual. especially when you're baked.
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Old 02-27-08, 05:32 AM
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its like you're swinging your sword
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Old 02-27-08, 05:58 AM
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Originally Posted by ThunderChunky View Post
dude, its just like you're one with the bike, and like you're connected with god in a way, like he's pushing you along with his magical powers. it's very spiritual. especially when you're baked.
The first time I experienced this baked, dude it was magic... aaaah.
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Old 02-27-08, 06:12 AM
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Originally Posted by mander View Post
Dont ugh Kemmer, it's science.
Maybe he was ugh-ing at "centrifical".
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Old 02-27-08, 07:10 AM
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My Ultegra rd pulleys use 24 teeth in total that do not transmit any chain force into forward movement of the bike. Thats exactly where the friction is.
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Old 02-27-08, 07:24 AM
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Great article! I have not read it all but I will.

I have been looking for an article/study on the difference in efficiency between fixed and geared drive trains. We have talked about his several times on this forum. I have never found information/study directly relating to this question.

What comes to mind for me is the Sturmey-Archer three speed fixed gear hub. The major downfall of these are the efficiency of the gears. There are many positives to them but the efficiency is lacking in all internally geared hubs.
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Old 02-27-08, 08:34 AM
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Originally Posted by captsven View Post
Great article! I have not read it all but I will.

I have been looking for an article/study on the difference in efficiency between fixed and geared drive trains. We have talked about his several times on this forum. I have never found information/study directly relating to this question.

What comes to mind for me is the Sturmey-Archer three speed fixed gear hub. The major downfall of these are the efficiency of the gears. There are many positives to them but the efficiency is lacking in all internally geared hubs.
Exactamundo.
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Old 02-27-08, 12:05 PM
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Originally Posted by TRaffic Jammer View Post
An off kilter chainline can affect efficiency with more friction compared to a straight chainline. With constant rubbing the parts wear faster... and the noise will make you nuts.
Yes. That's something I really noticed when I went ss/fixed. The constant ticking, clinking, and mild grinding sounds of the few geared bikes I've had bugged me ever since I graduated from my old BMX to a 10 speed mountain bike at around the age of 13 or so.

Now I'm back to a straight chainline and the (near) silence is golden.
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