5 Bicycle Structural Dynamics by VélUS

Mechanical Engineering researchers Y. Champoux, S. Richard and J. Drouet from the University of Sherbrooke (Canada) aim to help bicycle manufacturers study the dynamic behavior of bicycles so they can understand the real implications of their design in actual riding conditions.

The trio belong to the VélUS bicycle research team, and I had introduced them to you a couple of months back through a post on estimating bicycle fatigue. (See HotSpot Method For Bicycle Fatigue Life).

Presented below is a paper they did on structural dynamics and it had appeared in the Sound and Vibration Control Magazine. The components and the frame of a bicycle are subjected to time-varying force excitations imposed by the cyclist and by the road. Its dynamic behavior becomes an important issue, because it is directly linked to the bike lifetime, maneuverability, efficiency and comfort. The researchers describe the bicycle structure in terms of its natural characteristics which are the frequency, damping and mode shapes - its dynamic properties.



Preliminary Resources You May Find Helpful :


Size, Rattle and Modal Analysis - An article in the Machine Design magazine

Experimental Modal Analysis : A simple non-mathematical introduction

Modal analysis explained in simple terms

Basic steps involved in experimental modal analysis

Modal analysis - Mathematical introduction



Additional (Engineering 101) :


Vibration and Waves

Machine Vibration Basics

Introduction To Statics And Dynamics (An Excellent Online Book From Cornell University)

Damping Ratio

Transfer Functions

Strain Gages : Back to Basics

How Accelerometers Work

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Additional Resources For Reading :

1. Bike Think : Frame Flex And Strain Energy
2. AluMatter : Bicycle Frame Design Requirements

3 Bicycling Isn't Easy In The West Bank

For 350 riders, consisting of Palestinians, Israelis and foreigners, it was a nice joyful time bicycle riding from Ramallah to Jericho when men in uniforms stop them at a checkpoint and ask them to get lost.

When simply having fun through freedom of movement within your own territory is curbed by overwhelming foreign presence, I can see why even 9 year old Arab kids would take to the streets to fight it or die trying.

5 A Cycling Enthusiast Among 9/11 Victims

I was on Liberty Street in Manhattan the other day.

It is the location for the Tribute WTC Visitor Center where personal stories, artifacts and images from the disaster are on display. The quietness in the room is striking, as visitors look at photos of victims, messages from children, and objects taken from the actual scene. The melancholy tune playing in the background of the Center might just make you break down, even if you knew none of the victims personally.

Now on one corner of the Center, there are these two big walls with well over a thousand photos of 9/11 victims. I can't count them. Its innumerable. Most of them are nameless smiling faces and so many are simply revealing what each one enjoyed doing in their lives, just like the most of us.



A visitor, like me, could spend well over 10 minutes just standing there scanning these photos. They are overwhelming, yes. But could it be possible that you could spot someone you knew, perhaps even remotely? Could you identify someone's photo and relate their life with yours, and appreciate that life is not guaranteed? Or its meaning? Well, you wouldn't know that until you stood there and kept looking.

Which is what I did.

Now on this little corner, on the first wall (of two), there's a photo of a young female.


She appears to be in a Giro bicycle helmet.

On closer inspection, she's looks to be in a cycling jersey as well.


What struck me most was this smile. Just a full blown, innocent, 100 watt smile while perhaps enjoying the simple pleasure of being on a bicycle. Or whatever it was that she was doing when this photograph was taken.

But a nameless face, in the end.

Now that I have gotten to this point of actually taking this photo and displaying it here, curiosity compels me to dig a tad deeper. I don't know if it'll make a difference to anyone at the end of the day, but should we leave such an assemblage of pictures just to sit there on a wall in some museum?

Who was this person? What was her name? And what did she like doing in her life? If its not getting too privy into the life of the deceased, pray tell us some more. If anyone can help out in identifying this 9/11 victim, do post a good comment.

16 A Distingerated Bicycle Helmet

Thanks to Sandra from Australia (of Competitive Cycling fame) for sending me an image of a helmet involved in a crash. Its branded Tioga. Her friend was descending from Mt. Coot-tha when the person took a bad spill that ended up putting some serious cuts and bruises to the face and breaking a couple of vertebrates as well.

The lid is completely destroyed. Whether a helmet saves your life or not may be still moot, but keep staring at the picture above. 

What do you think? Did it do its "as designed job"? Does it look too fragile? Perhaps one of the commentators, Richard Keatinge, from my "How a Bicycle Helmet Works" post will be very interested in this image. Comment away.

14 Inspection of Dave's Carbon Fiber Road Bicycle

Disgruntled user : David Kina, NY - Cat 3 USCF Racer
Bicycle : 2005 Specialized Roubaix Elite
Frame material : Carbon Fiber Reinforced Plastic (CFRP)
Time in service : 3 cycling seasons


Check these pictures out. A primary aim of this post is to help you as a carbon fiber bike owner relate with these incidents and give you an idea of a couple of things to watch out for while on and off the bike.

Last weekend, after I rode with my amigo David Kina, I decided to inspect his machine. His specialized Roubaix Elite was supposedly designed with the "Paris Roubaix" in mind, and the frame geometry is pretty slack for a racing bike. Its fork has a very subtle curve to it and the bike is adorned with Zertz' inserts for vibration reduction in more places than you have fingers to count. Ofcourse, he claims that they make practically no difference whatsoever to riding comfort, and he may be right. But that's the topic for another day, perhaps.



1. Now Dave has crashed on his bike a couple of times in the past. He did not say whether the damage to his bike was a result of the crash, but he did notice resin cracks appearing on a couple of spots on his top tube. He thinks its the resin chipping away. I think it may be the clear coat. anyway, he ensured that air and water do not get into these 'cracks' by applying a fine layer of nail polish (remover?) on them as per the advice of another expert. This acts as a binder/sealant when cured but I have nothing else to back up its advantages.

These two appear to be two different (?) cracks on the same top tube and pictures were taken from both sides of the tube. The cracks appear very subtle in thickness, but not in length.

2. Dave also happened to skip his chain on an occasion, causing its metal links to fall and scrub against the chainstay. He did not have any piece to prevent the chain from hitting the frame, so his bike suffered another blow.






3. One day, Dave was rushing to get to a race on time and hurriedly placed his bike into the back his car. He realized later that day that this exercise had caused the metal alloy front brakes to impact the downtube of the frame when the handlebars were turned. Check them out.




A closer look :




To give you an idea of how this happened, I had to take the following picture with the handlebar turned. Look at my red arrows. Makes sense?


The practicalities on how to avoid this situation is under your discretion. The bottom line is, take caution when placing your bicycle into the back of a vehicle or bike case. You may use bubble wrap or layers of rags or anything such as that between the parts. Its these kind of impacts you're looking to try and avoid.



4. Dave generally likes to keep his bike clean. However, he thinks the design of this bottom bracket-chainstay junction along with the vertical internal cable routing hole creates a perfect storm for clogging of dirt. He thinks the dirt may be so deep as to suggest that it runs through a portion of the chainstay itself, like as marked below. The question he's now asking is : "How do I clean this crap?"




I'm not sure whether that is truly the extent of the clogging, but I certainly can see how the design allowes for it to happen. Generally, I'm not in favor of internal routing. (Weightweenies, I think all this dirt could weigh as much as the mounting bolt of a water bottle cage. Area for caution!)

Conversely, Dave has prevented water and dirt from seeping through his seatpost clearance and into the seat tube by sealing that off with insoluble grease. Its not a bad idea, but be prepared to take some grief from your riding friends. Hey, there's a reason behind everything! If he or she can't understand that, just go ahead and attack them on the next climb.




All in all, Dave is keeping his fingers crossed while he sits on this bike and is generally not very happy. Durability issues have cropped up just three seasons into his racing. The worst part is the feeling that even if he chooses to sell his bike as a second hand, no one may be ready to buy it from him. That surely is a bummer and I can understand that.

We certainly didn't go to great detail here, but I hope this simple case study helped give you some more perspectives on how to care for your carbon fiber bicycle - an investment that you shouldn't be ready to lose before its actual expiry date.

Besides, better safe than sorry, aiy mate?

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14 Adventures Closer To Home : A Little Deeper Into Allegany County

50 MILES
4400 FT OF CLIMBING
TEMP ---> 6 Deg C (43 Deg F)
SUNDAY OCT 19





Here's another day of beautiful riding in the Allegany and Cattaraugus Counties, visiting the little towns and hamlets of Portville, Genesee, Bedford Corners, Mill Grove and Barnum.

I realize that the last set of pics from Saturday were a little dull. I changed the settings manually on my camera so I could capture images better. Note that all of these have been taken while riding, in the true spirit of ciclofotografica!

Riding towards Mt. Herman to get out of Olean

Steam Valley Road

Short and steep may be a good warm up for the ride

Cows doing what cows do..

Scenery by West River Road

Promised Land Rd, Portville

Riding a dog? This is the way to do it!

Unpaved steep sections + dead end, nice

Lets go to Butternut Brook

Community of Genesee, very peaceful out here

Unpaved

Gradient kicks in

Probably 6% at best

Top of Butternut Brook

Deer Creek Road

Nouvoo Unpaved

Locals warned me of 5 black bears around this area

The fact that they knew their numbers made me turn back, dang!

Climbing Deer Creek again

Deer Creek turns into mild dirt


Deer Creek is 4-5 miles long, with average 3%. It was a great road to ride on!

Deer Creek Road peak

Deer Creek and Coon intersection is an apparent switchback

The sun is bright, but the cold gets into you somehow

Downhill on Coon Hollow

The beautiful Rt 305 back to Bedford Corners and Portville

Exiting Allegany County to Cattaraugus

Mill Grove.. we'll take a right turn here....

River Road is a serene cycling experience

Turn right onto Barnum Road


Barnum Road takes you up to Rock City Hill, so it gains elevation with a 3.1% average slope for 4 miles or so

I don't like this road since there's hardly a shoulder to ride on

But thats what makes it challenging. Its windy, so you better be seen climbing by a motorist

The gradient here is a constant 5%, for 1 or 2 miles

The top of Barnum. "Its all downhill from here"

Barnum gets us to Rt 16. If you go left, you get to Rock City Hill. If you go right, its all downhill for 3 miles. Time to take the downhill this time and go home!!