Why Steel Will Always be Real

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Steel is real everyone says it no one really knows why steel is heavy it rusts and it could Dent or crack just like any other material so why is it real in order to understand we must dive deep into Steel's mechanical properties and investigate how the tubes are made as a frame buer and mechanical engineer let me break it down for you let's educate ourselves on material properties when you are engineering a bike frame you are trying to balance three things stiffness strength and  weight to understand stiffness and strength you need to understand the stress strain curve the stress strain curve is a generalized method of visualizing how a material acts under a load on the y- AIS you have stress which is the amount of force that the material experiences on the x-axis you have strain which is the amount of elongation or stretch that the material experiences as you apply load to any material it starts to stretch or compress as long as you keep it under a certain amount of stress it will bounce back to its original shape this is known as elastic deformation the stress threshold is known as the yield strength let's break this down the more force or stress you apply to a material the more it deflects or strains the slope of this line the stress divided by strain is the stiffness of the material the elastic region is where all normal riding occurs far away from the yield strength if we keep pushing the material past its yield strength it starts to permanently deform this is known as plastic deformation the material no longer bounces back to its original shape in the plastic deformation region the material is not broken in fact it can get stronger in a process known as work hardening finally if you keep pushing the material it will eventually break this is known as the ultimate strength steel has a very large plastic deformation region the plastic region is what allows you to manipulate steel to Form buted Tubes bends and dimples now that we understand the stress strain curve let's use it to  understand the differences between frame materials let's start with 4130 chromal steel as a baseline it is pretty stiff has decent yield strength and a large plastic deoration region next is heat treated steel it has the same stiffness as 4130 so it shares the same slope on the stress strain curve Heat Treating increases the yield strength but decreases the plastic deformation region this is why you should never try to bend or dimple hardened steel tubes carbon fiber is slightly stiffer than steel so it has a steeper slope it is also stronger but it has almost no plastic deformation it just fractures finally titanium is a little bit less stiff than steel but is just as strong as the heat treated Steels it has a short plastic deformation region which which is what makes it notoriously difficult to work with steel is neither the strongest stiffest nor the most compliant material its true magic lies in its large plastic deformation region more on that later one final note and then a quick break to let your brain marinate stress strain curves do not factor in the weight of a material otherwise we could keep adding material to make something stiffer or stronger because bikes are human powered weight is always a consideration to understand the stiffness and strength to weight ratios  of material we must look at the specific strength and specific modulus I won't spend too much time here but if we zoom into the chart we can see that the composits have a better stiffness and strength to weight ratio than all metals that means if you were to design two bikes of the same stiffness and strength carbon fiber would be lighter I know that was a lot of  information to take in so let's take a break and visit a tubing manufacturer and supplier in California fairing [Music] Italians have Columbus the British have Reynolds and the Americans had True Temper until 2016 when they stopped producing tubes due to the shrinking Market of Steel bikes to fill this Gap and support the American frame Builder fairing begin sourcing the American raw material and draws them into tubes in Taiwan these tubes are called velec Rita is one of the owners of Fairing and velc here's a quick chat what is fairing fairing is a tubes and a b frame part supplier and we produce material of Steel aluminum titanium in our Taiwan Factory what is velc VPC is the highest quality American Steel formed into buy tubes in Taiwan to serve the high-end custom frame Builders this material is a high strength seamless material allow to form thinner wall for lightweight and stronger tubes the main reason why we use vpec tubing is that fairing is open-minded and listen to us frame Builders to create the tubes that we need like these 35mm down tubes with an extra long butt that allows us to bend for fork clearance thanks for uh showing me around today I would love to come visit taian and see how tubes are actually made in your factory yes you certainly welcome now pour your your third cup of coffee and let's dive back in to talk about bike specific steel tubing All Steel bike tubes in the front  triangle are budded this means that the tubes are thick at the ends and thin in the middle this is the Cutaway of a bike tube the thick ends of the tubes are typically 7 to9 mm thick the thin section is typically between 4 and 7 mm thick when we say a tube is 969 budded it means that it is .9 mm thick on the ends and 6 mm thick in the middle the reason why is the highest stress happens where the tubes join earlier this year I visited Aura  Engineering in Taiwan where I learned how steel and titanium tubes were [Music] made they first start out as a large and thick seamless mother tube a hydraulic ram forces the mother tube through a die with an internal mandrel to form the inner and outer diameters this process is known as budding butting cold works plastically deforms the material making it stronger it is repeated multiple times to form the final geometry of the tube how does  budding contribute to ride quality a bike wall being ridden is subject to all sorts of different loads let's simplify this complex interaction into an easy to understand problem the canti lever beam imagine you have a tube of known length L clamped at its end you apply a force F and the tube deflects a certain amount Delta the tube's deflection is given by the equation displacement Delta equals the force * length cubed / 3 * e * I throwing back to part one e is the modulus of elasticity it is the slope of the stress strain curve for steel this value is 2 200 Gap pascals I is known as the area moment of inertia don't let the name scare you away the area moment of inertia is a number that describes the contribution of the tube's geometry to the stiffness it is the parameter we tune with tube diameter and buding in order to achieve the stiffness we want this is the area moment of inertia equation for a hollow tube the key takeaway is that the diameter is quartic to the fourth power this means that small changes in tube diameter will result in large changes of stiffness let's look at some real world  examples with a quick experiment I clamped one end of the tube placed a 24 kg Mass on the other end exactly 520 mm from the clamp and measured the deflection of each tube here are two 28.6 mm velis spec tubes one is hardened and the other is not I need to emphasize again that all Alloys of Steel are the same stiffness regardless if they are heat treated or not in practice Heat Treating makes the material stronger which allows manufacturers to use thinner butts which actually makes heat treated tubes more flexible now let's compare three velec Elite tubes with the same butt thicknesses but different diameters each step up in diameter is roughly a 15% increase in stiffness if you understand these principles you can design strong lightweight bikes with great ride quality this is why when Nolan of fik sauce tested our new house hummingbird it was noticeably more compliant than a steel Hanzo it replaced now that we' properly educated  ourselves why is steel real first is ride quality you can build steel bikes with more compliance the secret is in Steel's large plastic deformation region of the stress strand curve that means when steel goes past its yield strength it bends it does not fracture you do not need to overbuild a steel bike to ensure that it's safe to ride instead you could focus on ride quality the second reason is Steel's ability to innovate it is not a coincidence that the first mountain bikes gravel bikes fat bikes and 29ers were all steel bikes once again this is because of Steel's ability to plastically deform and work Harden which allows you to shape and bend tubes to clear tires and drivetrains without having to resort to expensive tooling and equipment and I'm just getting started with 3D CAD metal 3D printing modern Steels and advancements in casting I know steel has way more potential and I'm excited for the future finally the biggest reason of all a simple material that is easy to understand inevitably inspires you to design and build bikes that are simple and fun to ride Trends come and go but steel bikes are Timeless no gimmicks just simple reliable and fun bikes for that reason steel is real if you learned something new leave a comment like the video thanks for watching