It’s been a while since I’ve had at technical rant on this blog about bicycles. Most of the wind has been taken out my negative drag sail-like wheels due to the fact that we’re now sponsored by said dimpled company, plus they have gotten a little more scientific it seems. The rest of the wind has been taken out by all the techno bable going on at the 9-5. But fear not since most of my job involves Excel spreadsheets and simple arithmetic I’m ready for some real Engineering bull shit.
So, on to another pet peeve I’ve had concerning the bike industry. Particularly the lack of communication between the MTB world and Road world.
No I’m not talking about the most stupid recent fad:
Ok so there are a few things terrible fad-dy things about this bike, first stupidly large headtube (they’re called spacers dumb-ass, learn to use them), but I’m talking about road bike disc brakes. Get it through your thick little heads: BRAKING POWER IS LIMITED BY TIRE TRACTION. You’ll be locking up this bad boy so much on wet descents, you might as well just be doing this sick fixie skid
down the mountain. Given the fred-tastic nature of this bike’s headtube and disc brakes, the only wet or dry road it’ll ever see is the garage floor.
What I’d really like to tackle is the road industries terrible misunderstanding on how or why suspension works (which the MTB guys have totally figured out, probably borrowing knowledge from motocross). This lack of understanding has produced a few terrible bikes, like this:
I’ll admit this is well done and an interesting new idea to tackle a familiar problem: how to transfer the load of rider and pedals to the wheel. The bike’s mission is to absorb bumps and smooth out the ride, the problem is one of those pesky laws of thermodynamics, that energy cannot be destroyed (or is that Rebecca Black
‘s music, I can’t remember). Anyway the problem is really encapsulated in this video:
They wizened up and used some pretty generic looking FEA system to show how springy their bike is.
The problem with these guys and the rest of the bike industry is they’re treating the bike frame as a static system with the axles being fixed. This is exactly the problem, when was the last time you were riding along and looked down at the axles of your wheels and saw them just rolling along perfectly smooth…NEVER. This is because of the nature of the roads we ride on; which we cannot change, are usually a shitty mess of potholes and broken pavement (if you live outside the midwest…you’ll just have to trust us that there are shitty roads out there).
Back to the second law of thermo, when you ride this bike over the shitty roads it does a great job of absorbing the energy, but it does a terrible job of DISSIPATING that energy. A singular bump that you ride over will get absorbed by the bike and just get transmitted right through the saddle, although in a slightly slower fashion than a stiffer bike. And that’s the problem bikes need to be modeled as dynamic systems that can move rather than fixed system. For instance let’s pretend you ride up a curb, which is represented below by the stepped black line and your saddle (the important part in the circle bike’s case) is the red.
Mountain bikers long ago figured if you just put a spring on a bike, you’re going to be bouncing all over the place unless you have something to dissipate the energy into another form that isn’t kinetic energy. Usually suspension dampers convert this kinetic energy into heat, but you could turn it into sound, charge a battery for your bicycle speakers, maybe pump some water to a higher location. Regardless of where it goes, if it isn’t dissipated from kinetic energy within the structure of the bike, it’s going into your butt (oh yeah!)
When a nice damping device is applied you get a lot less overshoot and a system something like this:
The problem with road bikes is that they’re usually pretty minimalist systems that don’t lend themselves weight or stiffness wise to a full blown suspension system. What you really need to make a realistic road bike that can not only be fast and light but also absorb bumps is some type of damping within a system. In fact it would be great if there was some kind of magic material that just naturally had something of a high Viscous Damping Ratio, but was still lightweight and stiff.
You’ll notice composite is only at 0.002 at worst vs. 0.001, this may not seem like much but it means that carbon dampens any movements twice as much as steel (and all other metals). There are a lot of very complicated types of damping that can happen in materials, but I don’t really understand them so I’m just going to go ahead and ignore the complicated stuff. Plus I think we’ve reached the point of diminishing returns in terms of this blog’s length vs. fidelity of crap I’m talking about.
So it turns out the cycling industry has already fixed the problem of damping out frame deflection without really even knowing it, that ‘smooth’ feeling you get from carbon fiber is really due to the damping properties of composites. It also explains why steel bikes are typically so much more noodle-y than modern race bikes. In order to absorb the bumps, they have to be weak enough to move around a lot. However, with the shaping capabilities of carbon, you can configure the bike to have strength where you need it (gigantic steerer tubes and BB) and weakness where you also need it (seat stays).
You could almost realistically build a very comfy and stiff bike without seat stays and just a really stiff downtube….
Ladies and Gentlemen, I give you the worlds absolute, without a doubt, perfect bicycle:
The downtube should really be more like a torque tube but I think at this point in my blog post I’m so off point I’m just going to say that’s it.
I gotta say though this is one of the great things about the bike industry, they’ve been around, largely unchanged for the past 100 years. Yet people are still trying innovative and unique ideas, although sometimes not well thought out, to tackle problems that have already been solved. It gives bikes character and the initiative is defiantly lacking in a lot of other design industry that have a lot of heritage…maybe like another 100 year old industry where you build propulsion devices, you know for things that fly, possibly airplanes. While most the idea’s are goofy one-of designs that never really do what they were created to do, every once in a while some new guy will come along without any preconceived notions and be all like “why don’t we try doing it this way” and the industry will be changed for ever…too bad we all just like playing with shiny things.
*If I’m wrong on any of this stuff just let me know. I’m not pretending to be correct, or to have correct grammar, or spelling, or sentence structure, or logical arguments.