Someone
asked me the other day about Seven Cycles’ approach to combining titanium and
carbon together in one frame. This
conversation occurred, in part, because of our recent introduction of our Integrated
Seat Post frame model.
Part of the conversation had to do with the various approaches to combining titanium and carbon together in a single frame. And why Seven approaches it the way we do. This is a long complex conversation. Not one we could cover in one discussion; so we focused on only one facet of titanium and carbon as frame materials: vibration and shock absorption.
Titanium and carbon are interesting in the context of vibration characteristics because they behave so different from each other. This difference is one of the primary reasons that Seven offers frames that combine both carbon and titanium—as well as monolithic titanium frames and full carbon fiber frames.
One Facet: Vibration
When you hit a bump in the in the road—or off-road—one of the results is vibration through the bike. The vibration frequency’s behavior—and physical feeling experienced by the rider—is dependent on, of course, a thousand factors. Material type is certainly one of the primary behavioral dictators.
A simple example of this resonance, and how it plays out physically, can be experienced when a tube of carbon and titanium are each tapped on a table:
The sound of Titanium: The titanium sounds a bit like someone striking a bell—or really more like a tuning fork. It definitely has a sustained ring to it. I just tapped a Seven titanium tube on a desk and the sound sustained for 12-seconds—that’s a long time.
- The sound of Carbon: The carbon sounds a bit like someone knocking on a door—sort of a wood sound, or a bit plastic-like. It has, what is sometimes referred to as, a dead sound; a dampened sound. It has no sustained tone at all.
Neither reaction is inherently good or bad. As Chuck Teixeira once said:
“There are no bad materials, just bad applications.”
If we begin with Teixeira’s statement as being reasonable, we can start thinking about the right applications for both materials’ reactions. So, where, in a bike, would a rider want dampening effects? Where would a rider want to feel vibration? On one hand, it might seem logical to ask, why would a rider want to experience any vibration in a bike? A well damped bike might sound like the way to go. However, one simplified way to express these characteristics’ positive or negative flip sides is in the expressions:
Damping is isolation and deprivation
Vibration is connection and communication
An analogy could be the experience of playing a driving video game versus actually driving. In the video game, non-visual and non-aural sensory input is non-existent. The vibrations experienced in real world driving—and riding a bike—provide a multisensory connection to the experience. I don’t mean this in a philosophic sense—although it does apply; I mean this in a very literal sense. Too much damping means too much isolation from stimuli that provide valuable sensory feedback that helps improve the ride—and even safety.
So, again, where, on a bike, would a rider benefit from damping, and conversely from vibration—isolation versus connection? The answer to this question reveals a bit of Seven’s reasoning for using carbon where we do in some of our titanium frames.
Where does a rider benefit from
the isolating effects of carbon?
- Primarily in areas that impact the rider’s contact points with the bike: rear-end, hands, and feet. The rider’s rear-end is most important on this list. Feet are least important.
- Vibration, in general, absorbs the rider’s energy and causes fatigue in extreme cases—aluminum bikes can be an example of this. Vibration can also cause long=term negative effects.
Where does a rider benefit from
the connected feeling that titanium can offer?
This is
a bit trickier to describe. Essentially:
- Through the drivetrain: feeling connected to the drivetrain provides forms of feedback about body English and bike performance.
- Pedal input: a lively bottom bracket can provide feedback with which some riders connect well.
- Handlebars connectedness to the pedals.
We discussed this strategy of controlling—not eliminating—vibration through tube-by-tube evaluation—starting with the fork.
Tube-By-Tube Evaluation
Carbon Forks
For a few reasons, we started this carbon characteristic exploration with the fork.
- Longest History: Carbon fiber entered the mainstream bike market in the form of the carbon fork. The fork set the stage for carbon frame acceptance, and the early understanding of carbon ride characteristic.
- Market Dominance: Well over 99% of all current high-end road bikes employ carbon forks.
- Damping is a priority: Front end damping—vibration management—is definitely a priority for bikes. At the same time, having some road feel through the front end of the bike is critical for the rider. Fortunately, most carbon forks don’t isolate too much input because there is already too much information coming at the rider through the front end. And popular aluminum handlebars and stem certainly don’t dissipate vibration any.
And yes, carbon forks are fairly light and inexpensive—those characteristics don’t hurt. There are some other interesting reasons that carbon has become the material of high-end forks—a topic for another day.
So, even with a full carbon fork, the bike doesn’t typically exhibit too much damping. However, put a carbon fork, frame, bar, light carbon rims and spokes all together, and the rider may have an initially odd riding experience—not necessarily bad, just very different from the classic bike riding experience.
Next post I’ll get into the frame portion of the tube-by-tube resonance discussion we had a few weeks ago. Again, we isolated this one facet of the complex system, for now. We’ll meld vibration characteristics with other material characteristics later. A good challenge.
Ti+ca, Steel+ca. Is there something difference like compatibility with bond or the materials each other?
Posted by: Yoshi | April 11, 2009 at 10:35 AM