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Aluminum Is More Elastic Than Steel

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Aluminum Is More Elastic Than Steel

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Old 11-21-18, 10:51 PM
  #126  
Kimmo
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Originally Posted by McBTC View Post
All of them had CF forks.
Carbon forks were the hot ticket upgrade item in the 90s... Which is a bit funny, because IIRC they used to be a lot heavier; as I recall they were flat out matching the weight of a Sub One. But the point wasn't weight; the ability to engineer different amounts of stiffness in different directions meant a good carbon fork handled better.

Of course, given that many of these forks weighed about half a kilo, they should have been far stronger than a nice steel fork.
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Old 11-21-18, 11:06 PM
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Originally Posted by SHBR View Post
How many different bikes have you ridden?.
I dunno, 6 or 7. The two mentioned, one or the other every day, maybe 40K miles on the "light" one and 10K on the heavy one, on the same route daily, a couple of thousand times, so I do have a pretty good basis to compare. More miles on both in general and maybe 15-20K on a third bike that is considerably heavier. And yeah, sometimes the load makes the "heavy" bike weigh more than 50.



Less momentum is lost, and its usually easier to make course corrections, etc.


It might be that your lighter bike doesn't ride all that well, I have ridden many (somewhat light, 8-12KG) bikes that don't, they often have a harsh ride with poor line tracking, excessive flex, etc. There are many variables to consider, unless we are exactly the same in terms of size, rider ability, and bike style, we will have different results.

It's not the bike, but even if it was a horrible handling bike that couldn't roll over bumps right (however that's supposed to work) you're saying that the weight of the bike makes it harder to roll over bumps. It's not subjective, and it would logically apply to ANY bike. More weight on the bike would make it harder to roll over bumps.


But that hasn't happen in my experience. I don't see a physical reason why it necessarily would - I'm going with my suspicions that 1, you get thrown around on the rougher roads more than I do and have the bring bike back to path, and 2) you are confusing weight with some other artifact of the "light bike" such as frame compliance and better tires. What you should do is, using the same bike, coast down a gentle slope (so that terminal velocity is not involved) where the surface is irregular, with the same bike and adding weight some of the times, and see what your actual speed difference is at the bottom.
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Old 11-21-18, 11:07 PM
  #128  
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The intro of CF forks followed the same course we saw with alloy frames-- the manufacturers copied the look of the traditional a steel forks, which probably did not take full advantage of the properties of carbon, e.g., my Icon Air Rail Forks looked like vintage cromo forks whereas nowadays you mostly see modern-looking blade designs which is a good look for modern hydro-formed aluminum frame designs.
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Old 11-22-18, 07:33 AM
  #129  
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Originally Posted by wphamilton View Post
What you should do is, using the same bike, coast down a gentle slope (so that terminal velocity is not involved) where the surface is irregular, with the same bike and adding weight some of the times, and see what your actual speed difference is at the bottom.
Riding down a gentle slope is pointless, any cyclist will know that a loaded bike will out coast an unloaded one, basic physics.

Bumps be damned.

Try going uphill or accelerating over an obstacle, (like up over a curb etc.) extra weight won't help.

Its not quite as complicated as you think.
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Old 11-22-18, 02:25 PM
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Originally Posted by SHBR View Post
Riding down a gentle slope is pointless, any cyclist will know that a loaded bike will out coast an unloaded one, basic physics.

Bumps be damned.

Try going uphill or accelerating over an obstacle, (like up over a curb etc.) extra weight won't help.

Its not quite as complicated as you think.
What I think is that "basic physics" has just been mangled and I don't much care what "any cyclist" believes so I'll bow out of the conversation at this point.
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Old 11-22-18, 05:23 PM
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Originally Posted by wphamilton View Post
What I think is that "basic physics" has just been mangled and I don't much care what "any cyclist" believes so I'll bow out of the conversation at this point.
...and, on that note-- I'm ready for my next custom build to be an alloy frame made out of recycled aluminum cans of the craft beer I enjoyed over the last year...!!!
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Old 11-22-18, 07:59 PM
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Originally Posted by wphamilton View Post
What I think is that "basic physics" has just been mangled and I don't much care what "any cyclist" believes so I'll bow out of the conversation at this point.
Fair enough.

I have noticed that a lot of "highly educated" users here seem to lack common sense, its quite a shame.
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Old 11-23-18, 07:59 PM
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Seems to me that working around the weaknesses while taking advantage of the characteristics of aluminum and CF materials to build bicycle frames follow similar design considerations. As a result, you see bikes from Felt and Trek, to name just two, with various essentially identical-looking models but with the more expensive model being CF. Trek is pretty forthcoming as to the results in its Émonda ALR marketing, e.g.,

It's right for you if...

You're building up a road bike for club rides or races, and you want an advanced aluminum frame with the sleek looks and handling characteristics normally found only in carbon models.

The tech you get

A lightweight 300 Series Alpha Aluminum frame with shaped tubes....
T
The final word


Carbon looks and ride quality, aluminum price point. If you thought alloy couldn't contend with carbon in beauty and performance, think again..


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Old 11-23-18, 08:20 PM
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So, we're seeing pretty much identical-looking models (with invisible welds you can hardly tell the difference) with CF being ~$500 more. Alloy, however, has gotten good enough to where paying more for CF, even to get more in the way of comfort, isn't a good enough trade-off (especially if you're running 25s or even 28mm tires) because, despite what people think about the longevity of alloy vs. steel, alloy still seems more robust than CF.
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Old 11-23-18, 10:21 PM
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Originally Posted by McBTC View Post
alloy still seems more robust than CF.
Depends. Carbon doesn't have great impact resistance, but ally isn't great in that respect either, at least on light frames. Carbon is otherwise incredibly strong and resilient, and a crash that would turn a metal frame into a crumpled mess can leave a carbon one unharmed if the frame doesn't suffer a direct impact. Then there's the fact it's the most easily repaired material, while ally just isn't practical to repair due to heat treatment.

I scored a 330g Time fork for $0, because one dropout was twisted. The bike it was on had been violently removed from a roof rack. The dropout was ally, so it wasn't shattered and I was able to bend it back, but the rest of the fork simply wouldn't have survived if it was anything but carbon.
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Old 11-24-18, 04:24 AM
  #136  
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So ... has BF finally decided on the best-sounding color ... once again?

Don't worry, a new version of this thread will be back in a few months regardless of what people post in this version.

Two days ago I rode my steel bike. Yesterday I rode one of my CF bikes. I didn't ride any of my four Al bikes.

That's why I am alive to type this.
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Old 11-24-18, 05:49 AM
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Have to admit the 'aluminum asploding' concept in the name of 'undefined fatigue life'...every blue moon, this topic seems to show up on a bike forum.
Used to be more of these sudden explosions related to carbon fiber...like the fear of it more than the reality... but now carbon fiber is becoming a bit more mainstream and of course, what bike now doesn't have a carbon fiber front fork at least?

So, I will put my final take on it. Aluminum is good, and carbon fiber is king. That's all.
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Old 11-24-18, 09:35 AM
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Originally Posted by Campag4life View Post
So, I will put my final take on it. Aluminum is good, and carbon fiber is king. That's all.
I hate to quibble, but: steel is good, aluminum is great, and carbon is king.
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Old 11-24-18, 10:15 AM
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aluminum is recyclable...
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Old 11-24-18, 10:22 AM
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Originally Posted by McBTC View Post
So, we're seeing pretty much identical-looking models (with invisible welds you can hardly tell the difference) with CF being ~$500 more. Alloy, however, has gotten good enough to where paying more for CF, even to get more in the way of comfort, isn't a good enough trade-off (especially if you're running 25s or even 28mm tires) because, despite what people think about the longevity of alloy vs. steel, alloy still seems more robust than CF.
who are you to declare that paying more for the comfort of CF isnt a good enough tradeoff?
absurd.

but coming from someone who has this next to every post, it isnt a surprise- Alloy is Real

Keep on keepin on.
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Old 11-24-18, 10:41 AM
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Originally Posted by Racing Dan View Post
And you can find at least 100 articles claiming carbon fibre have near limitless fatigue life as well. Does that mean all carbon fibre frames last forever? No.
I had a Kestrel that l bought in 1992. That frame wouldn’t last a season before it would break. They had a lifetime warranty replacement back then. I would send it back and they would send me another one.
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Old 11-24-18, 11:04 AM
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Originally Posted by Kimmo View Post
Depends. Carbon doesn't have great impact resistance, but ally isn't great in that respect either, at least on light frames. Carbon is otherwise incredibly strong and resilient, and a crash that would turn a metal frame into a crumpled mess can leave a carbon one unharmed if the frame doesn't suffer a direct impact. Then there's the fact it's the most easily repaired material, while ally just isn't practical to repair due to heat treatment.

I scored a 330g Time fork for $0, because one dropout was twisted. The bike it was on had been violently removed from a roof rack. The dropout was ally, so it wasn't shattered and I was able to bend it back, but the rest of the fork simply wouldn't have survived if it was anything but carbon.
Big believer in the strength of CF and not worried a bit about the reliability of a CF fork-- even so, it is interesting and perhaps a bow to reality that Trek went with an aluminum fork for it's '19 520 tour bike. No doubt CF could be used to make a fork that also can carry the weight of loaded paniers but... I guess it'd be too expensive for relatively inexpensive steel road bike.
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Old 11-24-18, 11:13 AM
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Originally Posted by Trakhak View Post
I hate to quibble, but: steel is good, aluminum is great, and carbon is king.
even better said.
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Old 11-25-18, 03:11 AM
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Old 11-25-18, 10:35 AM
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Originally Posted by colnago62 View Post
I had that same crack (at the bottom of the head tube) on my Salsa scandium hardtail mtb frame. Pretty much know when it must have happened (fell over from a height) and scandium in addition to being amazingly light, I think may be a bit too brittle to take a lot of abuse. Even so, I wouldn't expect that to occur on my road bike's 6061 alloy frame with it's tapered headset and squoval downtube.
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Old 11-27-18, 06:13 PM
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Originally Posted by colnago62 View Post
A good take it is. Zinn is a very smart bike guy. A credit to the industry.
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Old 11-27-18, 09:05 PM
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Originally Posted by DrIsotope View Post
I'm talking about (and here it is again) the fact that the failure point of aluminum is indistinct. At some impossible to determine point, an aluminum frame will fail. That is the nature of aluminum as a material. By the nature of that material, the failure stress point gets lower and lower as the part is subjected to more stress cycles-- until eventually, just a bump or bang, no matter how small, will trigger that failure point. No one can ever say when that will happen.
Originally Posted by Campag4life View Post
No airplane rides for you...lol. Flat earther? Just curious. Don't tell Shimano, I hate it when those Al crank arms fly off and Al wheels fail precipitously. Glad it only happened to you...lol. Don't put the wammy on us.
And guys, watch out for Al ladders. That last step is a duessy. Also start wearing a hard hat around the house. Those gutters can fall causing imminent death.
Originally Posted by Leonard Zinn
Aluminum does not have a distinct fatigue or endurance limit, so its S-N graph curves down from the upper left to the right and continues to curve down lower and lower toward the lower right corner of the graph. This illustrates that it will eventually fail even from low stress applications, given enough of them. I of course have no way of predicting when your bike frame will fail; I only know that, since it is aluminum, it will eventually fail from fatigue, if it is ridden enough miles.


Originally Posted by Campag4life View Post
A good take it is. Zinn is a very smart bike guy. A credit to the industry.
Just... fantastic.

Edit: I would like to point out that I had not read the Zinn articles prior to my posts. I've just umm... worked with aluminum for about 25 years.
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Old 11-27-18, 11:15 PM
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In other words, alloy does not have a, 'fatigue limit' although, as has been pretty well discussed, in the real world, a life expectancy of 10000000000 stress cycles is for all intents and purposes, a lifetime and then some... such that, worrying about sudden catastrophic failure due to frame fatigue is not rational.
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Old 11-28-18, 06:22 AM
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Originally Posted by DrIsotope View Post




Just... fantastic.

Edit: I would like to point out that I had not read the Zinn articles prior to my posts. I've just umm... worked with aluminum for about 25 years.
You didn't learn much.
Aluminum is a 'real presence in the bike industry'. I have owned several. Zinn nailed the dynamic relative to Fatigue life...yield strength of Al relative to SN curve and number of cycles. Engineers understand this. I am an engineer. Designs are created based upon material properties. An Aluminum frame could weigh 650g like an Emonda SLR carbon frame. It would likely fail. Yield strength matters. SN curve matters. No. of cycles of loading matters. Engineers understand these things. Its why airplanes are deemed safe by the FAA.

You need to get over 'yourself'. The industry ignores you.
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Old 11-28-18, 06:28 AM
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Originally Posted by McBTC View Post
In other words, alloy does not have a, 'fatigue limit' although, as has been pretty well discussed, in the real world, a life expectancy of 10000000000 stress cycles is for all intents and purposes, a lifetime and then some... such that, worrying about sudden catastrophic failure due to frame fatigue is not rational.
That's right. With average loading, no corrosion, no crashing etc, an Aluminum bike can likely go 100K to 200K miles without failure. If you increase the payload...300 lb rider who rides with 60 lb panniers, the frame will likely fail sooner.

Take an aluminum beer can and cut it into a coupon. Flex it. You can flex it more aka greater displacement or less. If you displace it more aka greater loading it will fatigue in fewer cycles.

Every time a painter gets on a 30 ft aluminum ladder it flexs. When a 250lb versus 150lb painter gets on the ladder, it flexes more. A ladder will have a longer life with a 150 lb painter on it versus a 250lb painter.

Btw, I have a friend who was a good painter and he didn't like to get down off the ladder so much to relocate it. When he was young, he would pogo an aluminum ladder from one place to another. For some reason, chicken little wasn't around to tell him the ladder was going to fail with this kind of treatment.

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