Bike handling

[cyclintom]

Quote from here:https://en.wikipedia.org/wiki/Fatigue_limit

Ferrous alloys ...have a distinct limit, called the endurance limit... below which there appears to be no number of cycles that will cause failure.

...Aluminium ....do not have a distinct limit and will eventually fail even from small stress amplitudes.

How can this make steel "the worst"?



Never said that it couldn't. Only that materials properties and engineering restraints makes it easier/more likely that a Ti frame comes out flexy.



In engineering terms, that statement makes about as much sense as writing "What does the flammability of gasoline has to do with the risk of fuel fires?"

So either you didn't understand what I wrote, or you choose to ignore it, or you're being knee-jerk contrary. Which is it?

Because in order to have a "light" steel bike you have to make the steel tubing lighter than the end of that endurance limit. Likewise the aluminum frames are constructed with material heavy enough that they never reach their stress limits. Early titanium bike were also built too lightly and would fail. It was common for the Colnago Bititan with dual downtubes to break the welds of the downtubes or break the tubes year the welds because of stress multiplied by leverage.

This is all engineering 101 so why are you questioning it? I used to see Reynolds 531 frames come in relatively often with tubes with crystalline fractures around the lugs. I didn't see one case of Columbus SLX frames breaking because they were heavier gauge tubing. Likewise you can find really high stress levels breaking anything

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In this you can see every material break. Does that mean that all materials are inappropriate for bicycle design or that the material has to have the proper design for the expected stress and material properties?
View: https://www.youtube.com/watch?v=QoV2yliPmK4

 

[Froze]

TOM, WAKE UP and COMPREHEND, you DON'T have a CLUE about engineering which several of us forum members have proven time and time again because of your complete lack of knowledge and understanding of simple stuff, so I wouldn't be so snarky if I were you towards others here.

And Reynolds never had the issues you speak up except on rare occasions just as did ALL other steel tube manufacturers including Columbus because I saw those break...BUT I never saw a Reynolds break either, so what does that prove? It proves that you and I never saw thousands of frames from all the tubing manufacturers that ever existed; and this had nothing to do with Reynolds but had everything to do with the builder applying to much heat in the brazing process. I've gone over that before with you.

Brazing is like glue, it holds the pieces together, silver brazing has a lower brazing temperature than brass has, and when builders first started to work with brass instead of silver because it was cheaper they overheated the tubing at the lugs to high of a temperature which would lead to fracturing; and I explained that to you before, but due to your lack of engineering knowledge you obviously didn't understand that or otherwise we wouldn't be having this discussion again.

I have a Trek 660 with 531cs tubing that was brazed with brass and done so by robots, and after over 160,000 miles later there are no issues with frame weakness...but then again no bike I have ever owned ever suffered from that EXCEPT for a Ridley Scandium bike I had where the headtube cracked at the top which Ridley denied the warranty due to fatigue after just 8,000 miles!

And again you are wrong about Reynolds being lighter than Columbus and that's why it failed, because Columbus actually had LIGHTER tubing then Reynolds had their 531 tubing thicknesses between 0.5 to 0.8mm Columbus with the Spirit tubing got it down to .38...yet Ishiwata had it down to .22! Neither of those steels if built correctly by the builder ever had issues with fracturing.

And since you have a huge engineer brain read this: http://www.thetallcyclist.com/2016/09/theoretical-framebuilding-part-3-metals-heat/ If you can't understand what your reading, which about 99% of the time you can't even understand what others are saying on this forum not alone more complicated stuff like the above site, then I suggest you find someone who can read it to you in simple terms.

 

[dabac]

This is all engineering 101 so why are you questioning it?

I'm questioning how you can say that steel has the worst fatigue properties.

Seems like you're intent on mixing materials properties with design properties, using characteristics of a marginal design as "proof" of your opinion about a material property.

I'm done with this thread. I'm not going to become the cartoon guy.

 

[Froze]

I'm questioning how you can say that steel has the worst fatigue properties.

Seems like you're intent on mixing materials properties with design properties, using characteristics of a marginal design as "proof" of your opinion about a material property.

I'm done with this thread. I'm not going to become the cartoon guy.

Wait don't go, you're discussing engineering principles with one of the foremost engineers of our time.

 

[cyclintom]

Wait don't go, you're discussing engineering principles with one of the foremost engineers of our time.

Oh wait, froze wants to tell us that bikes are all correctly designed and take engineering into account for endurance limits regardless of the materials because his Trek was designed by the space shuttle design crew.

 

[Froze]

Oh wait, froze wants to tell us that bikes are all correctly designed and take engineering into account for endurance limits regardless of the materials because his Trek was designed by the space shuttle design crew.

Oh please tommy boy PLEEEEEESEEEEE show me where I said my bike was designed by the space shuttle design crew, I'm dying to see where I posted that. I know one thing for sure, I am extremely grateful my bikes weren't designed by Tommy boy! I would have been killed by a tragic frame failure if Tommy boy had done the design work.

 

[cyclintom]

Oh please tommy boy PLEEEEEESEEEEE show me where I said my bike was designed by the space shuttle design crew, I'm dying to see where I posted that. I know one thing for sure, I am extremely grateful my bikes weren't designed by Tommy boy! I would have been killed by a tragic frame failure if Tommy boy had done the design work.

I don't know what you ever did for a living since the only thing you talked about is being a landlord. You and I have disagreed about a number of things, most especially helmets and your absolute belief in the safety increase from using a helmet.

Be that as it may, I'm an engineer and have been for over 40 years. While not a mechanical engineer you have to have a good working knowledge of it for the research and development work I've done.

If you look in Wikipedia you'd find this under Fatigue Limit: "The concept of endurance limit was introduced in 1870 by August Wöhler. However, recent research suggests that endurance limits do not exist for metallic materials, that if enough stress cycles are performed, even the smallest stress will eventually produce fatigue failure.

For polymeric materials, the fatigue limit has been shown to reflect the intrinsic strength of the covalent bonds in polymer chains that must be ruptured in order to extend a crack. So long as other thermo-chemical processes do not break the polymer chain (i.e. ageing or ozone attack), a polymer may operate indefinitely without crack growth when loads are kept below the intrinsic strength.

The concept of fatigue limit, and thus standards based on a fatigue limit such as ISO 281:2007 rolling bearing lifetime prediction, remains controversial, at least in the US."

I am not saying this - the engineering manuals are.

In short, contrary to most experience, steel has the lowest fatigue limit while carbon fiber is unlimited under certain conditions.

The REASON that this seem contrary is because this assumes that the total strength limits of the material are not exceeded. 100 years of experience with steel frames gives them the advantage of knowing what their material will take. Aluminum and carbon fiber are fairly new and were used to reduce weight and their limits were not really known by the lower engineering experience of the modern generation of bicycle builders. Hence they have much less experience with the fatigue limits and they were passed all of the time. Also until recently they didn't use the appropriate polymer to hold the carbon fiber into a structural component.

 

[king bily]

Each sort of material has its own specific pluses and minuses. And the feel of a bike using those different materials can be pretty dramatic.

Steel was the original high end racing bike and they were extremely well engineered by the mid-90's. You can hear people talking about how steel has a limited fatigue life but be that as it may, since it is EXTREMELY rare to have a frame of any material fail because of fatigue you can just assume that they never wear out.

The steel failures are in most cases from overheating and "hardening" high grade steel while brazing lugs. For this reason many frame builders that used very high grade steels would silver solder the tubes into the lugs which requires a lot less heating.

The weaknesses of bike handling of the lower grades is a "wiggle and bounce" reaction from the steel tubes bending under stress and then acting like a spring and rebounding. Reynolds tried to cure this with stronger grades while Columbus developed the SL and SLX which were thicker and so stiff that they were almost impossible to wind up to bounce. In the days when a 23 mm tire was considered monstrously large this made for a tough ride.

In the early 80's in order to lighten the bikes and yet not let them rebound all over the place they started using mild aluminum tubing. Rossin, Vitus and Allen were examples. These were lighter and rode pretty well but you couldn't do things like sprint or climb hard on them and keep control because their bending was not good for that sort of thing. Later companies started using higher and higher grades of aluminum culminating in aircraft grade. This allowed them to be very light and strong but they often also had the bending problems unless the tubes were heavier or the cross sections were very large. I think that Eddy Merckx company peaked this material with the Premium. This one made the strongest steel frames feel flexy.

Then Carbon Fiber came onto the scene after experimentations with Fiberglas failed to have any advantages. This material has had a great deal growing pains since you cannot build bicycles using any of the last century's methods. All of the thousands of years of combined experience building bicycles had to be thrown to the wind. On sure, originally you had some bicycle frames build in the older manner of lugs and straight CF tubes. These sorts of tubes are easy to make and you can in general go down to your local plastics store buy these tubes and then make up some aluminum lugs and made a workable frame. Look did a really good job of insulating the carbon from the aluminum and all of their early CF bikes are running to this day though if you didn't insolate them the least water would cause corrosion and failures.

Finally the Indian, Chinese and Taiwanese started real assembly lines for monocoque frames that didn't use lugs or any sort of thing and that could spread the loads over very wide areas and reduce peak forces instead of focusing them. When you use this construction method you can REALLY lighten the construction up.

Composites also have problems with the fact that they are fibers held together in a resin carrier. Earlier resins as were used in fiberglas composites had the property of continuing to harden over a very long period. Boat builders solved this problem by simply making the wall thicknesses so great that no matter how long it cured it always had far more strength than brittleness. But bicycle frames are light under any comparison and so they would grow brittle and the resin would fracture, breaking the carbon fiber under layer.

Various resins were tried until we presently have a thermoset resin that can but may not use a catalyst. At this point in time they seem to be very reliable. Boeing uses their entire aerodynamic sections composed of carbon fiber composites with thermoset resins. If you're afraid to ride a carbon fiber bicycle now you should be frightened into never flying again.

Advantages of carbon fiber is that it has a very low modulus of elasticity - it absorbs rather than bounces. And it has a low coefficient of expansion - it doesn't change size with even major changes in temperatures.

While you CAN find carbon fiber failures they have grown increasingly rare as the material and its production methods mature.

What is my opinion? I like the way that steel handles. But I don't like the way it bounces when you get it light. Now, with frames forks and wheels and tires you can tune the bike so that it is a very good handling bike for any particular course,

Aluminum and it's snootier cousin who is always looking down its nose at you - titanium - are in general simply so stiff that they must be tuned with tire sizes and pressures. But they are not bouncy and once tuned they are pretty good for all purposes.

Carbon fiber is presently pretty well developed. I had most of the carbon fiber Colnagos and they were mostly conventionally build using the "lug" system. Just Tuesday on a ride a friend brought his Colnago Precision which was a cyclocross bike with disk brakes but MAN - that thing was heavier than my steel Pinarello.

Now I have a middle of the line Colnago CLX 3.0 and I haven't ridden a better bike. It has every possible advantage of the composite materials though being Colnago it is a little bit heavier than it could be - 17 lbs in my XL size.

There is another material on the horizon - graphene. This makes lighter weight still possible and MUCH stronger strength. Graphene is more than 10 times stronger for its weight than steel. So when they really get to using it in composite frames you can pretty much discount them ever breaking. But that is still quite a ways off - though you can presently buy tires with Graphene armor on them to prevent punctures.

Now the most substantial difference between all of the materials is cost to the buyer. You can get a good steel bike for a reasonable price. You can get a great used steel bike for a CHEAP price off of Ebay. There was never a very large production of racing aluminum bicycles so they are a bit hard to find and medium priced when you find them. Let's face it - carbon fiber bicycles are just too damn expensive. But today more and more people are converting to it. Even those who had bad experiences with them in the past. This should help to bring the price down somewhat but that will probably take quite a bit of time because companies have to pay for equipment and engineering costs. Research and development is never cheap and companies can pull that money out of thin air.

Tell that to Sean Kelly. He won classics out the yin yang and the Vuelta France on early Vitus aluminum frames...and multiple stages (5) with his powerful sprint. He won the green jersey FIVE times!

The soft aluminium Duralinox fork was no detriment either. The glued together frame proves, once again, you're clueless.

ALAN not only had considerable success with the glued and screwed aluminum frames starting around 1972. They went to pioneer carbon fiber construction with great success. Jeezus! So stupid it hurts

 

[cyclintom]

Tell that to Sean Kelly. He won classics out the yin yang and the Vuelta France on early Vitus aluminum frames...and multiple stages (5) with his powerful sprint. He won the green jersey FIVE times!

The soft aluminium Duralinox fork was no detriment either. The glued together frame proves, once again, you're clueless.

ALAN not only had considerable success with the glued and screwed aluminum frames starting around 1972. They went to pioneer carbon fiber construction with great success. Jeezus! So stupid it hurts

You really should work on that reading comprehension.