Singlespeed & Fixed Gear - My new track crank.

Get a load of this ring. It's a cottered crank though so it may not be the best choice for fixed...

http://img217.imageshack.us/img217/8074/ebay026smallfn1.jpg

It's an oval, so it would be totally impossible to use on a fixed. That thing must need a massive chain tensioner

Moose is that yours? Do you know anything about it? The label makes it look like a legit mass-produced item from the old days of cycling.

It's an oval, so it would be totally impossible to use on a fixed. That thing must need a massive chain tensioner
I was kidding of course...however the chain tension does not vary as much as you'd think, in fact in theory a perfect ellipse would take up the same amount of chain regardless of rotation. The problem is that the chain would have to remain parallel in perfect tangents from the top and bottom of the ring, which'd be tough to acheive.

Moose is that yours? Do you know anything about it? The label makes it look like a legit mass-produced item from the old days of cycling.
It's on my father-in-law's old Bridgestone Kabuki, he installed it some years ago. It is coupled with a wide range 5 speed freewheel and an old Tourney derailer. The ring, if I remember, was produced by some gent in CA who made them in his garage and advertised them in Popular Science or some such publication.

The label says "Durham Elliptical" and I have not found any info anywhere.

My FIL swears by it and says when he rides a bike with a normal ring, it feels out of round to him.

that rules!

That would make for some extra-nasty chainring scars. Look at the teeth on that thing, it's just waiting for you to slip off those pedals...

however the chain tension does not vary as much as you'd think, in fact in theory a perfect ellipse would take up the same amount of chain regardless of rotation.

I'm having a hard time picturing that. I guess I'd have to see it in action.

I'm having a hard time picturing that. I guess I'd have to see it in action.

When the ring is big sideways, it's small frontways. When it's big frontways it's small sideways. Therefore, no matter what the same amount of chain is always touching the ring and tension is even all the way around.

I bet a less sloppy version of what i just said follows mathematically fron the definition of an ellipse but I'm too lazy to work it out.

do you know the supposed benefit of that? i'm assuming that it has something to do with minimizing dead spots in cadence by getting maximum benefit on the downstroke and easing up on the upstroke...or something.

When the ring is big sideways, it's small frontways. When it's big frontways it's small sideways. Therefore, no matter what the same amount of chain is always touching the ring.

I bet this follows mathematically fron the definition of an ellipse but I'm too lazy to work it out.

You got it, except that the chain has to angle towards the cog from the top and the bottom, so that throws off the whole equation and causes some difference in tension.

Hahaha, like the maker needed to write "elliptical" on a sticker... "Hey, look out, this is not a round chainring!"
:)

That is the cat's ass. Just make sure you've got a good chainline, then do it!

it could be a perfice elipse which mean the tencion of the chain wouldn't change

I was kidding of course...however the chain tension does not vary as much as you'd think, in fact in theory a perfect ellipse would take up the same amount of chain regardless of rotation. The problem is that the chain would have to remain parallel in perfect tangents from the top and bottom of the ring, which'd be tough to acheive.

how can i be more like you

how can i be more like you
Eat more chocolate.

Actually, somebody who added me on flickr recently posted a similar chainring.
http://farm1.static.flickr.com/149/369623350_066620a418_o.jpg

I'm having a hard time picturing that. I guess I'd have to see it in action.

Think of it this way - the same number of teeth should be engaging the chain no matter what the chainring's position (theoretically at least).

Mac

ryand they are made byt the same company you can barely make out the label bu they are the same

that's too wonky not to run. I suppose you would eventually tire of the gawkers, but it's worth rockin' it.

there's actually a company out there that makes them, maybe not as drastic...i cant remember the name but i know bobby julich(the CSC rider) rides one and says its the best thing in the world. and if you've ever gotten a Bianchi from the early to mid nineties and looked at the parts for a second before stripping them all off you'd see it most likely had a Shimano Biopace chainring, which is a really water down version of it. Shimano's selling point was that the human knee isn't made to go around in perfect circle, and so this was supposed to make the whole biking experience easier on the knee. The new guy doing it sells it for pretty much the reason the Radarksas said..."minimizing dead spots in cadence by getting maximum benefit on the downstroke and easing up on the upstroke...or something."

*edit* found it... http://www.osymetric.com/ and i remember him saying there was another competitor but he didn't like them as much..idk

there's actually a company out there that makes them, maybe not as drastic...i cant remember the name but i know bobby julich(the CSC rider) rides one and says its the best thing in the world. and if you've ever gotten a Bianchi from the early to mid nineties and looked at the parts for a second before stripping them all off you'd see it most likely had a Shimano Biopace chainring, which is a really water down version of it. Shimano's selling point was that the human knee isn't made to go around in perfect circle, and so this was supposed to make the whole biking experience easier on the knee. The new guy doing it sells it for pretty much the reason the Radarksas said..."minimizing dead spots in cadence by getting maximum benefit on the downstroke and easing up on the upstroke...or something."

*edit* found it... http://www.osymetric.com/ and i remember him saying there was another competitor but he didn't like them as much..idk

i can't believe they advocate grinding off part of the spider where the chainring bolt attaches. seems fishy to me. see step 8 of installation (http://www.osymetric.com/index.php?option=com_content&task=view&id=16&Itemid=31)

http://www.osymetric.com/images/serv3.jpg

I can't believe they'd have you permanently install a chainring with snaprings. As much as my bolts creak if they are just a little loose I wouldn't think this would be a good idea. Am I alone on this?