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-   -   Interesting finds around the web (https://www.bikeforums.net/showthread.php?t=929230)

taras0000 01-30-18 11:27 PM


Originally Posted by spartanKid (Post 20141865)
Aluminum track cogs seem like a huge risk for little reward, but maybe I'm wrong.

They are ok when they are relatively new. The problem is that aluminum is soft, but it work hardens along where the fatigue stresses occur. It doesn't wear as fast as it hardens, so differential stresses build up inside the piece. As it wears, these stress lines change in the piece, and the affected area grows until it fails.

Putting a sharks tooth grind on the tooth shape helps.

http://i.imgur.com/6c96QWg.jpg

Cutting them like a regular steel cog is no good.

http://i.imgur.com/MZ2gFAt.jpg

It also helps if they are 1/8th inch and not 3/32nds.

carleton 01-31-18 12:52 AM

If it was aluminum, it's not worth the few ounces saved especially assuming he rode like a 12 or 13t. I've owned one. Used it once and tossed it.

Poppit 01-31-18 01:16 AM

I believe it was carbon

carleton 01-31-18 01:21 AM


Originally Posted by Poppit (Post 20141973)
I believe it was carbon

Wow. Definitely not worth it.

My teeth are worth more than the few ounces saved.

Poppit 01-31-18 01:24 AM

He was using a road chainset/chain combo as well

carleton 01-31-18 01:33 AM


Originally Posted by Poppit (Post 20141979)
He was using a road chainset/chain combo as well

I'm glad he's OK.

I'll bet a dollar to a dime that the next time you see him, he'll be on a proper track crankset with common chainrings and cogs.

queerpunk 01-31-18 10:55 AM

those british fellas put some power data on strava from their Minsk World Cup win.

Their TP starts with 20 seconds at 1000w, a minute at 650w, and overall, about 4 minutes at 530w.

A ****load of power, god damn.

Morelock 01-31-18 11:25 AM


Originally Posted by queerpunk (Post 20142611)

Their TP starts with 20 seconds at 1000w, a minute at 650w, and overall, about 4 minutes at 530w.

A ****load of power, god damn.

:eek:
That's wild

taras0000 01-31-18 03:04 PM


Originally Posted by queerpunk (Post 20142611)

A ****load of power, god damn.

All the more reason to use dependable equipment. Track bikes are so easily made light that one doesn't need to start using questionable ultralight components on their bikes. An average sized frame can come pretty close to the weight limit just using standard parts.

Poppit 01-31-18 03:13 PM

It wouldn’t just be about weight, it’ll be about watts and feel, e.g. http://www.peekrings.co.uk/

taras0000 01-31-18 05:47 PM

A chainring is one thing. You typically have around 3-4x more teeth in contact with the ring than a cog would, yet they both have to deal with the same amount of force being transmitted through them (via chain tension). Add the differing leverage ratios due to the differences in diameters, and the amount of force on each individual tooth is compounded many times.

To me, passing on a carbon cog would seem to be a no-brainer. On the other hand, I would test out carbon rings if they were available to me.

pierrej 02-01-18 08:15 AM

On the topic of mantis like positions, this has changed a little since the word cup.
59.759
https://www.ridemedia.com.au/wp-cont...e-Glaetzer.jpg

taras0000 02-01-18 12:23 PM

My eyeball aerodynamics say that looks like a very slippery position. It's funny, because if you rolled his torso up at the hips a little, he would look like a normal pursuiter in the mantis position, but here, the mantis is so low that his forearms are still almost level, yet still able to close off the airspace in front of the torso.

It looks like compared to his last position, his hands are basically raised "one hand width".

The crappy thing about this, only 2 news agencies have picked up on the story from what I can see.

queerpunk 02-01-18 01:53 PM

It's the kind of position that only tall people can achieve with conventional gear - no short person can have a hip angle that can still generate power while being that folded up.

bitingduck 02-01-18 01:55 PM


Originally Posted by taras0000 (Post 20143499)
To me, passing on a carbon cog would seem to be a no-brainer. On the other hand, I would test out carbon rings if they were available to me.

I'm not small (ride a 56 cm diamond frame) and I never made any effort to shave weight on the track, and I always had to add weight (sometimes just 20 grams of tape) after I stopped riding the old steel Pinarello. There's really not a lot of value on the track in going for lighter & less durable equipment.

pierrej 02-01-18 02:09 PM


Originally Posted by taras0000 (Post 20143499)
A chainring is one thing. You typically have around 3-4x more teeth in contact with the ring than a cog would, yet they both have to deal with the same amount of force being transmitted through them (via chain tension). Add the differing leverage ratios due to the differences in diameters, and the amount of force on each individual tooth is compounded many times.

To me, passing on a carbon cog would seem to be a no-brainer. On the other hand, I would test out carbon rings if they were available to me.

I'll admit I have no knowledge on the subject of carbon cogs, bit surely it's not in an effort to save weight as it would be one of the most negligible gains for obvious risks.
My thoughts would be along the lines that they might be more efficient/smoother or something along those lines, given the kgf guys do focus on small improvements

Poppit 02-01-18 02:35 PM


Originally Posted by pierrej (Post 20144908)
I'll admit I have no knowledge on the subject of carbon cogs, bit surely it's not in an effort to save weight as it would be one of the most negligible gains for obvious risks.
My thoughts would be along the lines that they might be more efficient/smoother or something along those lines, given the kgf guys do focus on small improvements

Like I said about 5 posts ago

carleton 02-01-18 03:44 PM


Originally Posted by pierrej (Post 20144275)
On the topic of mantis like positions, this has changed a little since the word cup.
59.759
https://www.ridemedia.com.au/wp-cont...e-Glaetzer.jpg

Jeez. I just realized that this is a new sea level world record. Wow.

Are there plans to take him to altitude and take a shot at Purvis' 56.303" that's been on the books since 2013?

taras0000 02-01-18 10:18 PM


Originally Posted by Poppit (Post 20144955)
Like I said about 5 posts ago

I tried to find some data on Watt savings versus aluminum cogs/chainrings, and couldn't find anything. Any leads?

taras0000 02-01-18 10:29 PM

For all the Campy fans out there (which includes me when it comes to vintage Pista Record)

https://jalopnik.com/campagnolos-408...ory-1822278077

brawlo 02-01-18 10:39 PM


Originally Posted by carleton (Post 20145074)
Jeez. I just realized that this is a new sea level world record. Wow.

Are there plans to take him to altitude and take a shot at Purvis' 56.303" that's been on the books since 2013?

Given his speed ATM you would have to think that is was a consideration. Their primary concern right now will be the Commonwealth Games in April which has the kilo TT. From there it would be a worthy consideration before the team changes focus towards Tokyo in 2020 where kilo is not included

Morelock 02-02-18 05:53 AM

I'm usually all for carbon components (ran Fibre-Lyte chainrings on the road for years) but the rear cog... I dunno if I'm brave enough to try that.
I was playing with the idea of a big ring from aerocoach... but even that makes me nervous (plus it's quite a bit more than just a metal one)

rustymongrel 02-02-18 10:58 AM

Hey Morelock, I tried sending you a PM about the IO clone you have that tested well. Do you have any info on which supplier it came from? I might be interested in getting one.

Morelock 02-02-18 01:17 PM


Originally Posted by rustymongrel (Post 20146402)
Hey Morelock, I tried sending you a PM about the IO clone you have that tested well. Do you have any info on which supplier it came from? I might be interested in getting one.

Hmm I didn't get it (or see it, I might be dumb to the forum)
AnglerWang1 was the ebay id.

Poppit 02-02-18 01:31 PM


Originally Posted by taras0000 (Post 20145667)
I tried to find some data on Watt savings versus aluminum cogs/chainrings, and couldn't find anything. Any leads?

Not really, at a guess you're probably only looking at a couple of watts, waxed chain will be around 5 watts and the carbon chainring around 3 watts so do all 3 and it could be around 10 watts. Marginal gains? https://www.shopforwatts.co.uk/blogs/news


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