25Seven

Seven Cycles Collaborative

During the past couple months, 25Seven has been fairly quiet, to say the least.  I have lots of reasons—as always.  Fortunately, the primary reason for this radio silence is a positive one; recently I’ve been focused on another blog.  That blog just went live a couple days ago—although I’ve been posting there since September.  The blog is called the Seven Cycles Collaborative. 

 

A few people have already been checking out the CoLab; we’ve received a lot of interest and enthusiasm about the Collaborative project, and some confusion about what we’re hoping to accomplish.

 

Outcome:  Product or Process?

 

As with so many projects on which I participate, the product is rarely the only important focus.  Often times, as is the case with the Seven Collaborative, the process is the point.  The product’s primary purpose is to bring focus to the process, and to get our employees excited about the process; tactile items are often more fun and engaging than process charts and boring conversations with me.  And as a great storyteller once said:   

 

“It is good to have an end to journey toward; but it is the journey that matters, in the end.”  - Ursula LeGuin

 

True that.

 

The Collaborative’s focus on the process as our primary measure of success has been confusing for some.  Spectator confusion is probably caused by a cursory glance at the CoLab blog, or from reading just one or two journal entries.  Unfortunately, it’s a bit difficult to get a complete picture of the Collaborative’s mission by a brief perusal because the project is large—probably too large, moving fast, and we’re making a couple posts a day recently—weekdays at least.  Because of all this, I think it’s easy to lose sight of the overall project purpose.  I’m here to try and explain:

 

Seat Post Fatigue Testing

Recently we’ve been doing a lot fatigue testing; many times it goes on 24-hours a day—and even on weekends.  This happens when we’re in heavy R&D product cycles.  In order to get through our backlog of testing we often run Tessie—our in-house designed fatigue testing machine—overnight.  We run through the night because, on average, it takes about a week to do one industry standard DIN test cycle—if we’re constraining the testing time to a standard work day.  That’d be about 50 tests a year.  This isn’t nearly enough.  We have slated over 200 tests for this fall and winter.  And, we use the fatigue tester for other work, too—proprietary, for now.  So 24-hours, and weekends, it is.

 

I think our fatigue testing system is pretty cool:  our testing machine, our methodology, and the intensity with which we do testing.  For example, currently we have a team of three engineers, plus me, that are working on testing projects.  Each person brings a unique and valuable critical thinking element to the work.  And each person manages separate testing projects.  This enables us to apply what we learn from each test cycle in a very effective and diverse way; we’re able to improve overall results and the process itself very quickly.

Strategic Application of Carbon in a Titanium Bicycle Frame

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.

Bicycle Frame Fatigue Testing

We do a lot of testing at Seven Cycles:  fatigue testing, destructive testing, product testing, real world testing, and some test riding once in a while.  Even our sponsored riders are expected to perform product testing; it’s a tough life.

One of the more interesting testing tools we employ is our fatigue testing machine—named Tessa.  Not many bike companies have in-house fatigue testing equipment.  In fact, I don’t know of any US companies of similar size to Seven that have invested in designing full fatigue testing equipment that can cover the breath of testing that we do at Seven; although there may a company or two that has.

If you’ve never seen a fatigue testing machine in action—bicycle or otherwise—it’s a pretty cool sight. I have some video of our tester in action; I’ll post it once I figure out how to edit and transfer it…  Most fatigue testing machines are designed to accelerate fatigue failure results.  In other words, the equipment usually pushes the stressed part to extremes.  Seeing a bike frame on a test apparatus is impressive; 

Definition: Material Fatigue and Failure

What I experience every day.

Fatigue, when discussing materials, is structural damage caused by cyclic loading that exceeds the lower threshold of the material’s fatigue endurance.  This damage accumulates and progresses during cyclic loading to the eventual point of failure.

Definition of industry standard fatigue testing for bicycle frames can be summarized as follows:

Olin College Visit: Human Powered Vehicles – Part I

Last week Seven Cycles had a visit from some students of the Olin College of Engineering.  Actually, we had two visits from them. 

Olin College is an interesting school.  It is a new engineering school, very cutting edge, and employs a project-based curriculum.  I remember when the Olin Experiment began in the early naughts—before it became an accredited college a couple years ago.  It sounded very innovative back then and it has clearly kept its promise.  It’s the kind of school that I might have survived at—well, aside from the engineering requirements.

Last week’s visiting groups were from Olin’s Human Powered Vehicle Team.  It’s a student led organization with the goal of rethinking human powered transportation from the user’s perspective.  They are working on their 2009 HPV design—to be entered in the annual ASME HPV Challenge—and the Olin team is in the midst of evaluating their preliminary design. 

Engineering: Buckling Limit of Frame Tubing

In the last post, I began to address Yoshi’s interest in understanding how Seven Cycles goes about determining bicycle frame tube diameter and tube wall thickness.

I’ve already discussed a bit about how we adjust ride characteristics; I then talked about how we think about ride characteristics.  Here I’ll address one of the most fundamental engineering parameters of any thin wall shell structure—like a bicycle frame tube, for example:  unstable shell bucking.

The concept of shell bucking is simple.  And the simplest example of unstable shell bucking is seen in the result of holding a soda can at both ends and twisting the ends in opposite directions—the can buckles.  It buckles because the can is an unstable shell.  In the case of a soda can, this instability is fine—in fact it’s a good feature—because the can engineers did not optimize the design around an open and empty can.  The can is designed to function when full.  When it’s full, it is not unstable.  When it’s empty, it’s very unstable.

Some Factors in Bicycle Frame Tube Engineering

Recently, Yoshi posted a statement and question on 25Seven regarding my post about tuning ride characteristics.  I’m paraphrasing his comment here:  

“I want to know how you made the average…  and the relation of diameter and the thickness?”

Yoshi’s questions are important and fundamental for frame builders.  Without giving away any Seven Cycles secrets, I can explain some of the interesting basics.

In the above mentioned post, I talked about how we adjust the ride characteristics on each individual frame.  Here’s I’ll provide an overview of how we think about ride characteristics—at least as relates to tubing.  In essence, I’m talking about why we bother with tailoring the ride characteristics and why it’s worth the bother.

Interview: Road Bike Action Magazine - Part III of IV

Back in January of 2008 Zapata Espinoza of Road Bike Action Magazine interviewed some frame builders about the future of frame and component design.  Seven Cycles and I were fortunate enough to be included.

I posted the first and second parts of the interview already.  Here's the third part of the full transcript.  The magazine edited the interview in order to fit into the magazine—and probably to reel in my rambling. 

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Zapata:  What do you see in the new world of frame design, materials, and components and where are we heading?

Results of Fire Damage to Titanium—and Other Materials

A good friend of Seven had a really bad New Year’s Eve night.  The house where he and his family were storing a lot of possessions, burned to the ground.  His family is safe and no one was injured in the fire.  The house and all the belongings were not so fortunate; one of those possessions was our friend’s Seven Aerios.

This is not the first time a Seven has been through a fire.  Nor the first time we’ve seen the remains of a Seven post-fire.  In a clinical sense, it’s a very interesting sight; our friend brought us the frame because he was amazed at the results.  Here’s a series of photos that show the surviving skeleton.