0 A few bicycle FEM samples

Possibly every changing, dynamic system in the world depends on a host of other factors. These relationships can get pretty complex. They are united by equations. Thats called mathematics. :) And most equations are differential type. Some can be solved. But what happens if you find youself with too big of an equation that there is no way on earth you can do it yourself. Unless you were a scientist in the early days working on solving the subsonic and supersonic issues of an airplane wing or nose tip. I hear these guys would sit down with papers and pencils and spent hours trying to solve equations with matrices and what not, which they did. But its their work that helped revolutionize the FEM field. Nowadays, computer processing technology has changed everything. One depends on computers to solve these equations and run simulations. Some of these simulations can run well into hours, or days!

Knowing the factors also might not tell you how it would affect the design unless you test it out. These days, many companies resort to an FEM analysis of their design. That helps study complex relationships, and helps for a sturdier design. It helps in studying complex models and thermodynamic properties of materials as well. The idea behind it is to discretely solve complex equations bottom up, using boundary conditions.

Good bicycle companies that have the IT resources for such endeavors also resort to such testing. TREK, for example, uses Solidworks.

Aah, the beauty of partial differential equations. Like sunflowers on a breezy day...

I haven't come as close to simulating anything on an FEM application yet. Sadly, I opted not to take the FEM or Pro Mechanica course in the Pro/E series at school, I chose Virtual Reality instead. I think I'll just learn it myself on Solidworks or something. The closest I have come to FEM was in a computational fluid dynamics course that taught us about finite difference and Runge Kutta methods. In the end, all we used was MATLAB.

But here are a few FEM clips that sort of show you the forces at work and the effects on a bicycle. You'll now appreciate the deflections in the various regions of a frame, although I think the ones in these clips are slightly exaggerated. Which is good, because we can learn! Thank you, mmagnasco. These clips show what happens on minute scales in your bike as you ride. Now you will apreciate the meanings behind a downtube, which I think is the most important in a frame, and the seat stays. Check it out!

Ciao amici!

2 Tokyo Cycle Show 2007

I'm not sure when this took place, but here is a link with lots of "white", totally Euro products in the glitz.

And what's more interesting than learning today that people at Compagnolo should work a bit with their English.



Speaking of grammer, I hear quite a lot of people pronouncing it as "COM-PAN-OLA". Whats the deal with this? Totally destroyed it there. As much as we all love their products, we could hold some reverence to getting their name right in the first place.

CAMPAGNOLO.

Just like French names are not messed around with, this Italian name is pronounced "CAM-PAN-YOLO". There is no "A" at the end, and the "gn" in the word produces a distinct "nye" sound. Try it out. I just had to correct a long time cycling buddy of mine last week on this.

5 CSC bike on sale

Yes, on Ebay is Carlos Sastre's Tour ridden R3 for auction. All proceeds to CSC are supposedly going as charity to a South African cycling center. Save some of that Christmas money for this one.

Its raining and snowing out here in Buffalo. Seems like that misleading winter has finally kicked in. Its beautiful to watch. When I get cold, I hop on the trainer. Speaking of trainers, there isn't any in the market to which you can fix your fixie to, can you? I've a bunch of ideas..

3 A History and Development of the Carbon Fibre Bicycle

0 My Bontrager Wheel

Its funny how you miss little things. I took out my Bontrager Race X-lite tubulars and noticed the lacing pattern of the spokes into the hub. I then took an old Alex Rim and saw how each spoke was fitted into different slots, as opposed to the Bontrager's where two crossing spokes are laced into a single slot. Just from observation it seems as if those spokes are serving to tear apart the hub flange instead of fighting each other in normal spoking pattern. Moreover, in this low spoke wheel, the angle made between opposing spokes is so much greater (almost 180 degrees) than the Alex rims, which is less severe since its a 32 spoke wheel. Thats like two spokes trying to shear the flange from a single slot, an area with high residual stress. Ouch..





And thanks to Arthur Shapiro from RBT, we now have a picture of a failure that can happen in hubs like these, although the cause of the flange failure is being debated.





And another from RoadBikeReview.


I'm very much confused as to why a hub would be designed like this. Accident waiting to happen?

4 Car Chaos

A Little Off Topic here, but if you're on a bike, don't ride like I drive my car in this computer game :) [Dug it up from my google video archives...] The music is set to some sweet Fat Boy Slim. Actually, running away from the cops (i don't recommend it) is kind of like bike racing. You're trying to tear away from everyone's leash anyway... breakawayyyy!

2 Sticker of the Z

Photo courtesy Lennard Zinn

No, this sticker doesn't say which bike shop Dave Z's bike came from...

This is a Tour earned special sticker for the blitz speed he set at the 2005 TDF 19 km time trial, 54.676 kmph!! Its still only 19, but what is remarkable was that prior to setting this record, David had never set foot in a wind tunnel. Until he joined Team Slipstream, which was this year!

0 Wheel Rotational Inertia Testing - 3

The wheels we tested had a pretty close range on inertia's so I doubt its going to make that much of a difference. Yet, I have to say that Dave is a CAT 3 racer and he has had some solid results for the past 4 years with the FSA's. So I'm wondering what the test results show for those wheels. How to Interpret the Resulsts : Since we have only the rear wheels, you might be thinking what the number represents. Rotational inertia or moment of inertia is the rotational analogue of mass in the linear F = m.a equation.

So according to what I believe (I could be wrong), more inertia means more of the mass of the wheel is concentrated around the rim as opposed to the center. When that happens, the wheel can be a little more sluggish at acceleration than a wheel with a considerably lower inertia. But again, only starts, stops and accelerating while racing count, otherwise I don't think moment of inertia hardly makes a difference. On flats at constant speed, aerodynamics has far more advantages than wheel weight. On long climbs with a grade of 3% or higher, wheel weight can factor into the speed you can attain for the same power input, so unless you're doing super long steep climbs on races, one doesn't have to worry about inertia.

Besides, when you take something on a climb that rolls, its generally agreed that its just overall mass that matters, not really on how that mass is distributed. One can do as much number crunching as he or she wants, but I warn you that you'll be dealing with extremely low numbers and you'll at once understand why the differences are so small as to be negligeble.


What's Next? I hope to test the corresponding front wheels, retest the Jets, and also form some kind of error analysis, because I fully understand this is not the most accurate way. For example, the final result could be affected more due to error in some parameters (as opposed to others) such as the distance from the ceiling to the center of the wheel. Again, if time allows me to do this, I'll come up with something. Sayanara!

0 Best Post? Wheel Rotational Inertia

One of the best posts on any bicycle forum I've come across. Thank you Mark MCM.


I can't believe that people keep arguing that rotating mass climbs slower than non-rotating mass under the same power. When you are working against gravity, mass is mass, it doesn't matter if it rotates or not. The idea that micro-accelerations due to pedal force fluctations make a difference in the overall picture is a strawman. During pedal force fluctuations, accelerations are decelerations cancel out. All that really matters is average power output vs. gravity.

Since Ras11 complained that no math has been offered, I decided to set up a model to simulate the accelerations/decelerations due to pedal fluctuations. The equations and variable values were taken from the Analytic Cycling web page. Pedaling force: The propulsion force (from pedaling) was modeled as a sinusoidal.

Since it is assumed average power is constant, the nomimal drive force will vary inversely with velocity. So, the propulsion force is modeled as: Fp = (P/V)(1+Sine(2RT))

Fp = Propulsion force (pedaling)

P = Average power

V = Velocity

R = Pedaling revolution rate

T = Time (Note: The angle in the sine term is double the pedal revolution rate, since there are two power strokes per revolution)

The drag forces on the rider are aerodynamic drag, rolling resistance, and gravity. These three terms together are: Fd = (1/2)CdRhoAV^2 + MgCrrCosine(S) + MgSin(S)

Fd = drag force

Cd = Coefficient of aerodynamic drag

Rho = Density of air

A = Frontal area

M = total mass of bike and rider

Crr= Coefficient of Rolling Resistance

g = Acceleration of gravity

S = Slope of road

The total force is thus: F = Fp - Fd

From Newton's second law, the equation of motion is: dV/dt = F/I

I= Inertia

Because there is both rotating and non-rotating mass, total mass and total inertial will not be the same. Because mass at the periphery of the wheel as twice the inertia as non-rotating weight, the total mass and inertia of a bike are:

M = Ms + Mr

I = Ms + 2Mr

Ms = Static mass

Mr = Rotating mass

The complete equation of motion is thus: dV/dt = {(P/V)(1+sin(2RT)) - [ (1/2)CdRhoAV^2 + (Ms+Mr)gCrrCosine(S) + (Ms+Mr)gSine(S) ] } / (Ms + 2Mr)

This equation is non-linear, so I solved it numerically with a 4th order Runge-Kutta numerical differentiation. Borrowing the default values in the Analytic Cycling web page for "Speed given Power" page, the values used are: P = 250 Watts, Cd = 0.5, Rho = 1.226 Kg/m^3, A = 0.5 m^2, Crr = 0.004, g = 9.806 m/s^2, S = 3% (= 1.718 deg.)

(http://www.analyticcycling.com/ForcesSpeed_Page.html)

For this simulation, the pedal revolution rate was selected as 540 deg/sec. (90 rpm cadence) To solve this equation, a 4th order Runge-Kutta numerical differentiation was set up using an Excel spread sheet. Step size was selected at 0.01 sec., and the initial Velocity was 1 m/sec. The solution was calculated for 3 cases of equal total mass, but different distributions of static and rotating mass, calculated over a 200 second period, by which time each case had reached steady state. As expected, the velocity oscillated with the pedal strokes.

The average, maximum, and minimum velocities during the oscillilations during stead state were:

Case 1: Ms = 75 kg, Mr = 0 kg (0% rotating mass)

Average Velocity: 7.457831059 m/s

Maximum Velocity: 7.481487113 m/s

Minimum Velocity: 7.434183890 m/s

Speed fluctuation: 0.047303224 m/s

Case 2: Ms = 70 kg, Mr = 5 kg (5.33% rotating mass)

Average Velocity: 7.457834727 m/s

Maximum Velocity: 7.480016980 m/s

Minimum Velocity: 7.435662980 m/s

Speed fluctuation: 0.044354000 m/s

Case 3: Ms = 65 kg, Mr = 10 kg (10.67% rotating mass)

Average Velocity: 7.457837584 m/s

Maximum Velocity: 7.478718985 m/s

Minimum Velocity: 7.436967847 m/s

Speed fluctuation: 0.041751139 m/s

These results agree very strongly with the solution on the Analytic Cycling web page, which predicted an average speed with constant power of 7.46 m/s (16.7 mph) The results show that as expected, the smaller the percentage of rotating mass, the greater the magnitude of the velocity oscillations (which are quite small).

But a more interesting result is in the average speed. As the amount of rotating mass decreased, the more the average velocity _decreased_, not increased (at steady stage). This result is actually not unexpected. The drag forces are not constant, but vary with velocity, especially aerodynamic drag (Because aerodynamic drag increases with the square of velocity, power losses are increase out of proportion with speeds - so, for example, aerodynamic losses at 20 mph are 4 times as much as they would be at 10 mph). Because speed fluctuates as the propulsion force oscillations, in the cases of the low rotating mass, the maximum peak speeds reached are higher than for the cases with the high rotating mass.

This means that when a lower percentage of rotating mass there will be greater losses during the speed peaks. Because of the total drag losses will be greater over the long run, the greater momentary accelerations with lower rotating mass actually results in a lower average speed.

To see what happens at a steeper slope, which will have a lower speed (and presumably larger speed oscillattions), I ran the model again with a 10% (5.7 deg.) slope. Here are the results:

Case 1: Ms = 75 kg, Mr = 0 kg (0% rotating mass)

Average Velocity: 3.217606390 m/s

Maximum Velocity: 3.272312291 m/s

Minimum Velocity: 3.162540662 m/s

Speed fluctuation: 0.109771630 m/s

Case 2: Ms = 70 kg, Mr = 5 kg (5.33% rotating mass)

Average Velocity: 3.217613139 m/s

Maximum Velocity: 3.268918539 m/s

Minimum Velocity: 3.165997726 m/s

Speed fluctuation: 0.102920813 m/s

Case 3: Ms = 65 kg, Mr = 10 kg (10.67% rotating mass)

Average Velocity: 3.217618914 m/s

Maximum Velocity: 3.265921742 m/s

Minimum Velocity: 3.169047012 m/s

Speed fluctuation: 0.096874730 m/s

This data follows the same pattern as above. The speed oscillations (micro-accelerations) are greater with the lower rotating mass, but the average speed is also slightly lower with lower rotating mass. So next time you want to claim that lower rotating mass allows faster accelerations, remember too that the greater speed fluctuations (due to greater accelerations) will also results in greater energy losses due to drag forces. But, in reality, the differences in speed fluctions and average speeds are really very small between all these cases. For all practical purposes, when climbing, it is only total mass that matters, not how it is distributed. I'd be happy to send the Excel spreadsheet to anyone that is interested.

1 Wheel Rotational Inertia Testing - Part 2

Before I start, I'd like to point out that the pendulum method is pretty simple, but its not the most concrete way to get inertia. Also, slight reading errors could have creeped in while measuring r0 (distance from the ceiling to center of wheels), and there could have been errors with starting or stopping the watch (which is why we took averages of two times), and there could have been errors with the wheels not swinging in one plane. I believe the 100 swings smoothed that out and our estimates should be pretty close to the real thing, unless something is drastically wrong with the results.

REAR WHEELS and RESULTS




Name : Compagnolo Proton Training Wheel, 24 spokes
Tire : Conti Ultra Sport Trainer Specific (Yellow)
Cassette : Compagnolo Centaur 10 speed
Weight = 3.58 lbs = 1623.860 grams

Time for 100 swings = 204 seconds.
Time for 1 swing = 2.04 sec
ro = 98.5 cm = 0.985 m
Ic = 0.0779976 kg m^2



Name : HED Jet 50 mm, 24 spokes
Tire : Conti Ultra Sport Road
Cassette : SRAM PG 970 9 speed
Weight = 3.39 lbs = 1537.678 grams

Time for 100 swings = 202 seconds.
Time for 1 swing = 2.02 sec
ro = 98cm = 0.98 m
Ic = 0.0506224 kg m^2


At this point, I thought let me switch to my race tires and see how the results are affected.

Name : HED Jet 50 mm, 24 spokes
Tire : Michelin Pro Race 2 Blue
Cassette : SRAM PG 970 9 speed
Weight = 3.19 lbs = 1446.959 grams

Time for 100 swings = 202 seconds.
Time for 1 swing = 2.02 sec
ro = 95.3cm = 0.953 m
Ic = 0.0835551 kg m^2

Hmm, that's a little strange. As I changed the tire to something lighter, the inertia increases from .0506224 to 0.0835551, which is an increase of roughly 39%. The next time we do this test, I think I'll retest this wheel again. I'm taking this with a pinch of salt, but again how off could we be?




Name : FSA RD-600 30mm, 24 spokes
Tire : Michelin Pro Race 2 Lite
Cassette : Compagnolo Centaur/Chorus (not sure) 10 speed
Weight = 3.19 lbs = 1446.959 grams

Time for 100 swings = 204 seconds.
Time for 1 swing = 2.04 sec
ro = 99cm = 0.99 m
Ic = 0.062691 kg m^2



Name : Arraya SuperHard CTL - 370, 32 spokes (I haven't even heard of this brand, it was on my commuter Bianchi)
Tire : Hutchinson Carbon Comp
Cassette : Shimano Ultegra 7 speed
Weight = 3.42 lbs = 1551.285 grams

Time for 100 swings = 206 seconds.
Time for 1 swing = 2.06 sec
ro = 100.4cm = 1.004m
Ic = 0.0780815 kg m^2




We can sort of compare these with what some of the values for wheels analytic cycling had on their website. I mean, our values are not so bad are they?

Rotational Inertia and Mass for Various Wheels

Wheel	Details	Ic (kg m^2)	Mass (gm)
Wire Spoke	Rear, Std Rim, 700, track, 36 spokes, w/o tire, w/ axle, nuts	0.0528	1177
Wire Spoke	Front, Std Rim, 700, 32 spokes, w/ tire, tube, rim strip, axle, skewer	0.0885	1264
Wire Spoke	Rear, Std Rim, 700, 32 spokes, w/12-21 cassette, tire, tube, rim strip, axle, skewer	0.0967	1804
Specialized tri-spoke	Front, 700, w/ tire, tube, axle, skewer	0.0904	1346
Specialized tri-spoke	Rear, 700, w/ 12-21 cassette, tire, tube, axle, skewer	0.1032	1771
Specialized tri-spoke	Front, 650, w/ tire, tube, axle, skewer	0.0683	1207
Mavic	Front, Std Rim, 650, 28 Bladed Spokes, w/ tire, tube, rim strip, axle, skewer	0.0632	1179
MTB	Front, 32 Spokes, w/ tire, tube, rim strip, axle, skewer	0.1504	1847

0 Wheel Rotational Inertia Testing - 1

The day before Thanksgiving was one spent with our wheels, since we SOO had nothing else to do. Getting a break from the university can also be a boring time for students.

A friend of mine, Dave Kina, and I sought out to investigate what the moment of inertias would be for some rear wheels we had. We raided his grandma's basement, which is sort of Dave's cycling playground, with couple of bikes, a pool table with hundreds of cycling items, weights, shoes and what not. The overhead pipes gave us a nice support from which we could do the tests.





We chose rear because, well, we didn't have time for the front ones, and we aim to test them at a later time.



The test setup was a simple pendulum, we hung our wheels from the ceiling using a rope for hanging clothes. The setup is described on analytic cycling in the wheels and inertia section, so I'll spare you the details.


We weighed the wheels with the Ultimate Digital Scale. The wheels had everything on them in as ridden condition except for the QR skewers since that's not rotational.

We timed 100 swings with two stop watches, a Suunto and a Polar. We then averaged those two times out, and divided it by 100 to get the the average time per swing, or the TIME period of the pendulum. This is our Tau or T in the equation :


We measured the vertical distance from the ceiling and that was our r0, or r not.

We then simply solve for Io, or Io, which is the moment of inertia of the pendulum about the ceiling support. The second equation relates the rotational inertia about the ceiling with that about the CG of the wheels which is Ic, so we used that to arrive at what we wanted. Instead of plugging in all the numbers on our calculators, we just saved time and plugged it into the calculators on analytic cycling. The results are on Part 2.

0 Road vs Tri

There, a picture that speaks a thousand words. Notice the steeper seat tube angle made for better body positioning when you are bent over on the aerobars.

Happy thanksgiving holiday everyone!

Vacanza felice!

0 Bicycle efficiency boosters

Photo courtesy Keith Weller

Shimano supported a study on efficiency through John Hopkins University in the late 90's. Just got hold of it via Earth Times.

Just like driving in cruise control increases fuel efficiency, riding in bigger sprockets with less chances for cross linkage and using good chains with high tension ups the efficiency of the drivetrain as the article points out. Read on, the bicycle and the chain drive is tremendously efficient! (Assuming you, the rider, pedal without choppiness in circles, you have decent rims that are true, and the tires and bearings in your equipment are smoothly functioning.)



Pedal power probe shows bicycles waste little energy

When it comes to efficient use of energy, it's tough to beat a bike.


provided by Johns Hopkins University

That's what Johns Hopkins University engineers learned when they aimed an infrared camera at a computer-controlled bicycle drive train in a campus lab. The camera detected heat generated by friction as the chain moved through the sprockets under varying conditions. This heat represented wasted energy, and by measuring it, the engineers were able to identify sources of inefficiency.

In the best test, the chain drive posted an energy efficiency score of 98.6 percent, meaning less than 2 percent of the power used to turn the front sprocket was lost while being transmitted to the rear one. Even the worst test turned in a respectable 81 percent efficiency score.

The results surprised faculty member James B. Spicer, who supervised the studies. "This was amazing to me, especially when you realize the essential construction of this chain drive hasn't changed in more than 100 years," says Spicer, an associate professor of materials science and engineering. "The modern safety bicycle with fixed front and rear gears came about in the 1880s. There have been modifications to make the chain work better and last longer, but essentially, it's the same type of drive."


Test Drive


To approximate real-life riding in their lab tests, the Johns Hopkins engineers used magnetic brakes to mimic the friction of tires touching the road and the air resistance created by a rider. An electric motor was adjusted to change the speed of the chain drive, simulating slow, moderate and fast pedaling. Although the tests focused on a bicycle drive, the results could have implications for other chain-driven devices, including cafeteria conveyor belts, factory production lines and the movable clothing racks found in dry cleaning shops.

The researchers found two factors that seemed to affect the bicycle chain drive's efficiency. Surprisingly, lubrication was not one of them.

"The first factor was sprocket size," Spicer says. "The larger the sprocket, the higher the efficiency we recorded." The sprocket is the circular plate whose teeth catch the chain links and move them along. Between the front and rear sprockets, the chain links line up straight. But when the links reach the sprocket, they bend slightly as they curl around the gear. "When the sprocket is larger, the links bend at a smaller angle," Spicer explains. "There's less frictional work, and as a result, less energy is lost."

The second factor that affected efficiency was tension in the chain. The higher the chain tension, Spicer says, the higher the efficiency score. "This is actually not in the direction you'd expect, based simply on friction," he says. "It's not clear to us at this time why this occurs."


Greasing the wheels


The Johns Hopkins engineers made another interesting discovery when they looked at the role of lubricants. The team purchased three popular products used to "grease" a bicycle chain: a wax-based lubricant, a synthetic oil and a "dry" lithium-based spray lubricant. In lab tests comparing the three products, there was no significant difference in energy efficiency. "Then we removed any lubricant from the chain and ran the test again," Spicer recalls. "We were surprised to find that the efficiency was essentially the same as when it was lubricated."

The researcher speculates that a bicycle lubricant does not play a critical role under clean lab conditions, using a brand new chain. But it may contribute to energy efficiency in the rugged outdoors. "The role of the lubricant, as far as we can tell, is to take up space so that dirt doesn't get into the chain," Spicer says. "The lubricant is essentially a clean substance that fills up the spaces so that dirt doesn't get into the critical portions of the chain where the parts are very tightly meshed. But in lab conditions, where there is no dirt, it makes no difference. On the road, we believe the lubricant mostly assumes the role of keeping out dirt, which could very well affect friction in the drive train."

Spicer cautioned that the chain drive is not the only place on a bicycle where energy can be lost because of friction, but it is an important one. The Johns Hopkins engineer wonders why bicycle manufacturers don't advertise the energy efficiency of their products, especially considering that the source of this energy is a human rider. "When you walk into a store and look at appliances, there's usually an energy guide on them, telling you how much it will cost to run the machine for a year. That allows you to make comparisons," Spicer says. "And if you go to an automobile dealer, you can see how many miles per gallon a car is expected to get, and that's essentially a measure of efficiency. So why shouldn't bicycle manufacturers post their energy efficiency?"

Participating in the testing program with Spicer were Michael J. Ehrlich, a former Johns Hopkins associate research scientist, and Johns Hopkins engineering graduate students Johanna R. Bernstein and Christopher J. K. Richardson. The tests were supported by a grant from Shimano Inc., a maker of bicycle components.

x . x . x

If only we could have a glimpse of those infra red videos. I tried following the link to the clips but since this stuff is so old, I couldn't find anything on the John Hopkins page. If anyone finds anything let me know.

0 Altitude and cycling world hour records

Why were most hour record locations at altitude?

At high altitudes, aerobic capacity decreases since atmospheric pressure and the partial pressure of oxygen is pretty low. This is because atmospheric pressure decreases somewhat linearly with height. So does density of air, or the number of air molecules packed in a cubic feet or whatever unit of volume of air you want to consider. In aerodynamics, lift and drag depend linearly on density of the fluid (air in our case) So if density if going to decrease with altitude, so is the drag or wind resistance. Air density is a direct multiplier in the equation for drag!

Which is why (well, not entirely the reason but it counts in), most venues for famous hour records (Eddie Merkcx etc) were located at altitude, so the cyclists would have to face lesser drag than at sea level. Chris Hoy's recent attempt at the kilo record was, according to PezCycling News, was venued at some stadium in Bolivia, which is 3500 feet above sea level. Wow! If you play around with this applet on a NASA website, you'll see how such an altitude change affects barometric pressure, and air density (consequently, drag). Click here for density effects on drag (its for the wing of an aircraft but you'll get my point).

Another epiphany I had. Tail winds might not help THAT much at altitudes. :)

0 Bike Furniture

Talk about creative business ideas! This furniture company started by Andy Gregg and based in Michigan makes chairs, tables, stools and loveseats with bent (sometimes trashed) bicycle rims. Bellissimo! Do they look classy! This may be a way to get your disagreeable wife to think bicycles are indeed 'cute'! And how better than adding a few bike furniture to complement your cycling lifestyle.

3 Tubulars Exploding and Peeling Off

In high speed crashes, the intense heat generated due to braking and friction can heat up the rims of the wheels. If one has tubular tires on, the glue can soften and the tire as a whole can peel off leaving the rims exposed to more damage. I think this can be made even more worse when its a hot day and the asphalt is scorching.



Two videos I looked up to show you this. The second one pointed by Ryan Cousineau from RBT, thanks Ryan!


Video Clip 1



On stage 8 of the this year's tour de france, Australian Michael Roger's from the T-mobile squad had a spectacular crash along with David Arroyo who went over the safety rails and plunged into some trees. Sad for Rogers, who simply lost the tour right then and there... a more spectacular event from a mechanical standpoint was Roger's rear tire peeling off due to the crash... or maybe its whatcaused it.. considering that he's a good descender. Look at 0:40-43 secs. Again, except for Roger and his mechanics and a few others,we are not really sure how this happened. Perhaps it was the tire deflating prior to the crash and the braking that made it peel off? This can happen and I've seen it in clincher tires.


Video Clip 2



During the descent into GAP in stage 9 of the 2003 Tour, Beloki takes a horrendous spill. It was a scorching day and the tarmac was literally melting, the corners were dangerously slippery. Beloki slipped, braked hard, locked up his rear wheel and then the bike's control slipped away from him. The heat was so much, it made his tubulars peel away and explode, and at that point he was on his rims. Lance's escape route is stuff of legend.

One more reason to show you how tough and risky the sport of cycling is, probably the toughest of all.

Solutions ?

1. Go with a slightly wider tire for steep descents? I've read Jobst Brandt saying this will prevent a small volume tire from heating up so quickly.

2. Inflate the tires maybe 10 psi less than max?

3. Take a more deeper section metallic wheel to your high speed descents (?) since more surface area quickens the heat dissipation to the atmosphere.

4. There's no substitute to keeping one's head up, and anticipating a misfortune down the road. This way, one need not apply sudden, continuous braking. He or she can pump the brakes to stop well before the danger spot.

* * *

3 Servizio Corsa

Quite a few cycling names like Veloflex, Deda, Michelin etc brand their products (tubulars,clinchers,stems) with the term "servizio corsa" or "servizio corse" which in English translates to "Service Course" . Whats the whole deal with this word?

1 Magnesium Wheels, worth it?

I'll try to keep this small.

The primer for today's post is yesterday's PezCycling News article on a test run done by Chris Manatan on the Extreme Power bike...Click to read.

In this setup, you would think Chris should really be satisfied with the setup he has, instead he chooses to switch his Fulcrum racing wheels (690 gram front, 850 gram rear) with a pair of American Classic Magnesiums (1150 grams or so per pair...) and makes the following statement :

"Now in fairness to Fulcrum they make a slightly better wheel than their Mavic cousins the Ksyrium but I am not a sloppy guy that will notice that the American Classics do have more side flex. I am not a low power guy either, and simply notice the FAR snappier acceleration and better, quicker handling of the lighter American Classic and Zipps (even Zipps CSC training clinchers) more than I notice any better stiffness of the Fulcrum. This was a great example of how important wheels are to a bike. I would say that wheels are more important than most of us give them credit for…"

True and true... but I think this statement has been grossly overestimated, for the simple fact that today (forget about Pro's , they're given what to ride) most of us ride 600-2000 dollar pair of wheels that are quite light and aero... and the differences between them are very small. Magnesium wheels maybe 200 grams lighter, but you will pay the high premium due to its insane production costs (its a rough one to weld, and it can catch fire)...

And we also know that due to the small weight differences between the two sets of wheels, the difference in rotational intertia (or rotational weight) is going to be pretty small. Try measuring rotational inertia, you'll get something like 0.1 or something, something you can't even count ! Any lightweight wheel today requires both energy to move it linearly, and a still smaller component of energy to move it rotationally. I'm pretty sure the difference between that second component for both these wheels is negligibly small. In energy tems, it might require a rider to put for 2 or 3 more watts of energy to accelerate, but then think about it. How much time do we spend on the bike actually accelerating? And are our pedal strokes really smooth, like a motor driving the cranks? People are being fooled. Think about this. You're paying probably a 1000 dollars more to shave off a one digit number of Watts from your efforts. That's a load of crap.

Magnesium may be slightly less dense than aluminium, but its less stronger and less stiffer. Its Young modulus is quite small. And durability issues? It corrodes, its pretty unstable with heat, and I'm pretty sure no one needs Magnesium to win races.

But bike companies, and some people who don't think, like to fool you with junk and ask you to pay more to cover its production costs and profits. This is another reason I stopped reading reviews :) I only look at them for the pictures.

So top wheels in today's market have hardly much difference between them. To say that a 1000 dollar wheel has "FAR" snappier accelaration than another 1000 dollar wheel is just making fun of us readers. How much is FAR? Obviously designers from a top wheel company like Fulcrum aren't foolish to drop all mass into wheel rims.

Subjectiveness and false reports have always been a part of bike reviews and I believe it requires engineers to come up with specific numbers (which being very small for today's high standard products).

:) ... I guess all of this does not matter when you have the money, right? Still, its all for little which is my point. I guess inadequecy of training, and poor performances make people think that buying high priced equipment can actually help them someway.

6 Enlarged Heart = Cardiac Arrest? Improper cool down?

I sure don't want to sound like an alarmist, but hell, I was quite alarmed after reading news from an Olympic event some weeks back.

We all enjoy pain, training stress, body adaptation. We all at some point want to be like pro's on TV or glitzy-glossy bike magazines. This is a sport where pain and as much pain as possible is happily glorified through mass media.

And so we push ourselves. But the simple fact is that we're not pro's. We're mortals. And I've seen quite a number of folks who push themselves way too much. Think about it. Elite cyclists and runner have doctors for a reason (assuming dope doesn't exist). They have a free license to regular medical checkups. Since we aren't so privileged, is it time to rethink how much we push ourselves and how we condition our bodies for this pain? What is my point?

Endurance athletes who have years of training and racing in their belts have large hearts, this being a direct adaptation of training stress. Doctors have noticed this phenomenon for many years, and recently it was made famous after Lance Armstrong's Discovery Channel documentary.

Athletes' hearts hypertrophy to become larger, more powerful pumps over time, acquiring siginificantly higher stroke volumes per beat. The human body is simply marvellous. Essentially, with the higher stroke volume, the heart doesn't have to beat that fast and it can throw out the same output with a lower heart beat. They even have a lower resting pulse. Average humans have 70-75 bpm while athletes could have 50 or less. This, ofcourse, is a simplistic view of the adaptation and there is perhaps much more going on at the microscopic level.

The fact is kind of intuitive that as you stop stressing your body out that much, it can return to its past level. I'm not sure by how much. Would endurance athletes after a string of stressful seasons be able to get back to what they were before? Eddie Merckx and Hinault are probably doing very well these days.

Recent news of elite distance runner Ryan Shay collapsing and dying 4 or 5 miles into an Olympic marathon trials event has exposed the hazards of being an elite at the top of your game. I'm not sure how much percentage, but a certain number of elites develop what is known as ventricular arrhythmia (VA). Just google it out.

Studies have shown that most diagnosed (by birth of through endurance activity) with VA have dysfunctional right ventricles that could in the future lead to heart murmurs, irregular heart rythms which could result in sudden cardiac arrest. This is what may have happened with Ryan, but we dont know if its VA. We do know, as his doctors have said, that his death was caused by his enlarged heart.

With sudden cardiac arrest, the body's electrical system becomes defective and the heart is not able to form an organized beat and is plunged into rapid or chaotic activity.

Its probably a one or two in a 100,000 probability (or more, non lo so), but it sure is scary, and that's what happens when you push yourself way way too much. The scarier thing I've read about is this article from a Swedish Medical Center website that suggests that younger athletes have higher risk of cardiac arrest than collegiate and other older athletes. The article also suggests the importance of getting an electrocardiogram (EKG) checkup for young athletes but since this isn't very cost effective, other solutions are to teach young athletes about proper body conditioning for the sport, proper cooling down protocols after exertion and having pre competition checkups.

"Without a cool-down, the toxic wastes accumulate and may create such irritation and electrical instability that the heart will develop a fatal arrhythmia," he says

We live in a culture where being slim and hearty and healthy is just over emphasized. Not that many people follow it, since U.S has some of the highest percentages of obesity in the world, which is a fact. But the ones who aren't in this equation can also get trapped in a mindless, addictive world of over-fitness.. to gain acceptance, personal satisfaction or to win laurels for a team, school and perhaps state.

Perhaps it no reason to jump but its a relavant thought for today. If you're an amateur endurance athlete, how much are you pushing yourself and to what aim are you doing it? Are you stressed and tired, do you have little energy? How much do you know about your own heart? Have you ever had a screening or a checkup? Do you even care to go to a doctor or do you like to wait before its too late to turn back? Think about it. Fortunately, these conditions may be so rare we don't even have to worry about it. But my point is, an early diagnosis could save a life.

2 Chain Tool Failure

My chain tool is broken. Its a fatigue failure, the crack started at the top surface of the broken piece and propogated down, taking a chunk of metal with it. I got it second hand from a person in the club. It has no brand name but the "Made in Taiwan" is more than sufficient evidence for me. The chain pushing against that piece caused a lot of stress, besides the sharp inside edges probably also created a stress riser. Poor manufacturing.. ? Seems to me as if this tool was made using powder metellurgy, looking at the inside cleavage and the grains, if so perhaps it was not heat treated enough I think.

0 Il Pirata

I'm a few days away from actually seeing this movie, but a small trailer. This also calls for brushing up my Italian to even actually understand a word in the movie.




Did you know? Pantani was one of the few cyclists I have seen in videos who descends in a strange aero position. He lowers his upper body while actually being behind the saddle of his bike. Again, stuff of legend. One must also see the tremendously fast and risky speeds he reaches descending in some of the Tours.

1 Responsorium Ciaveté

Perhaps one of the latest revolution in steel alloys is the new Columbus XCR tubing. Pretty neat. It is probably their answer to super light Reynold's "Carpenter's" tubing. I'm not here to compare and contrast, but simply to show you what Pegarotti, the famed Italian frame maker, has lately come up with this alloy. Handcrafted and handpainted for your pleasure, this thing is stuff of beauty. It'll set you back 4500 dollars, and I wonder how much we have to pay for his painting. (?) Is he a talented artist, I don't know? Find out. Anyway, interesting part of the story is that he named it Ciavete (cha-va-tay, from some Italian dialect), which literally means "f*** off", reflecting the feelings he has towards the cancer he was diagnosed with in 2006. Atleast this is what competitive cyclist as to say. So there's something for language class.

0 RBT and a video...

To be a casual browser of the RBT forums is do-able. I got so interested in a particular post about the gyroscopic action of the front wheel that I took the trouble to go through 100's of messages, some just pointless arguments going nowhere, I mean trust me. If you have been on the forums, you'll know every bit what I'm talking about. The first 10 or 20 messages are fine and pertain to the topic, and then whoa! A huge tangent off to some where else and a few more posts later, every one is fighting with every other guy. Its hilarious, but please, if you're more sane, you'll do something better on a Friday night then go through RBT.

Anyway, nothing much comes out of reading RBT other than newly found motivation to learn how the bicycle works, how this intricate mechanism steers, how it's stable. Its a marvellous invention.

But another sweet video I came upon, thanks to the post from Tim McNamara, actually disproving the notion that track cyclists have to maintain a speed above some threshold value on highly banked tracks to avoid taking a spill, and the fact that they CAN indeed do track stands. Another sweet reason to start watching some track racing in winter. Watch these monsters get to 41 mph without a train, pure muscle...they probably wouldnt be able to climb a 3 mile hill though. If I were rich enough, I would build a velodrome for myself. Aaaah...(also, did I hear Liggett just saying that the record for a track stand is over 3 hours? Masochism!)

0 Wrist and Palm

That's a small preview from Steve's DVD, however, here's a visual picture of what's happening in the cyclist's distal end of the upper limb (wow, now I recall everything I learnt in my biomechanics class). From everyday riding experience, I can say that putting too much pressure on the hands (upper body weight) is going to lead to tightness in the wrist, pinching in the nerves of the hands, and discomfort/pain in the shoulder and upper back. Another reason to check your bike position. This winter, I'm going to take my own sweet time to perfect my position.


Picture courtesy of Hughston Health Alert.

1 A Mathematical Bicycle Model to End all Models...

I was on a hunt for a certain paper written by a student under Dr. A Schwab, at the Delft University of technology in Netherlands. J. Kooijman was a Masters student in mechanical engineering, and probably still is. The subject of his research interested me. He investigated the dynamics of a bicycle and after numerous tests, wrote his engineering thesis and defended it. The topic, on a mathematical model of the bicycle to "end all models".

I finally got it!

"Experimental Validation of a Model for the motion of an Uncontrolled Bicycle" can now be read at this link. Warning, please proceed to attempt reading only if you're engineering savvy. I plan to read some right away. This will add to my 100 MB folder of bicycle related research papers on my computer. I'm :) sad (?)...but I love it!

Check this webpage for some videos and pictures on his test setups.

Here's a primer article for you folks from the University webpage itself. What this means is that a big part of the future of the bicycle industry may be in custom making, or tailoring it to the rider with the help of the computer models, and not just through the knowhow and practices of the frame maker. With the help of these models, we can stray away from conventional bicycles to modern designs, that'll achieve the same or more depending on what the rider intends to do with the bike. Soon we can gravitate towards the Toyota like way of researching customer needs : surveying what their riding styles are like! I think the future is already taking place.

Bicycles Made to Measure

For almost a century and a half, mathematicians have been racking their brains about the bike. How can a rolling bicycle be so stable of its own accord? Delft researchers now say they have completed the model to end all models. Bicycle manufacturer Batavus intends to use it to make better bikes for the elderly and disabled.

By: Tomas van Dijk

The conveyor belt passes at speed under Ir. Jodi Kooijman and his bicycle. Kooijman, an enthusiastic off-road cyclist, pedals until his speedometer indicates sixteen kilometres per hour. On the sideline, Dr Ir. Arend Schwab of the Faculty of Mechanical Engineering, Maritime Technology, and Material Sciences (3me), at the agreed upon moment, yanks a rope attached to the bike’s luggage carrier. For a brief moment Kooijman veers to the right, but his bicycle regains its balance within a fraction of a second, appearing to automatically retrace ‘the line’.

This video-recorded incident took place on a large conveyor belt at the department of motion sciences of Amsterdam Vrije University. The experiment is just one of those the two 3me researchers have carried out in the past couple of years to test a mathematical model defining all the forces that act on a moving bicycle. A publication about this bicycle model recently appeared in the ‘Proceedings of the Dutch Royal Society’, the Royal Dutch Academy of Science.

Schwab shows another video recording. Here, Kooijman is giving a bicycle a hefty push. The bicycle is laden with measuring equipment and the carrier holds a laptop computer that records the bike’s every movement. The unmanned bicycle rolls on following a straight line in the sports centre of Delft University. Kooijman runs after it and pushes the bicycle sideways. The bike wobbles a bit, the handlebars move from side to side, but the bike soon regains it’s straight course.

“The bike’s speed must be between fourteen and twenty seven kilometres per hour,” Kooijman says. “At those speeds, the bicycle is inherently stable. If it goes faster, it will wobble less, but if you then push it sideways it will lean over to one side until it topples. The data match our model predictions exactly.”

Balance in motion

Ever since the invention of the pedal-driven bicycle around 1860, researchers have been trying to determine what makes a bike fairly stable of its own accord. They added formula after formula, each one of them derived from the laws of motion as defined by Newton and Euler, but they never managed to develop a completely accurate model for predicting a bike’s riding characteristics.

“Bicycle manufacturers never knew exactly how a bike works either,” Schwab says. “They have always had to resort to experiments to improve their products. Not that there’s anything wrong with that, but now they can use our model to feed into a computer all the factors affecting a bike’s steering properties. The model then calculates how the bicycle will behave at different speeds.”

Together with colleagues at Cornell University in the u.s. and at Nottingham University in the u.k. the Delft researchers perused more than fifty publications written by scientists on the subject since the early days of the bicycle. Many mathematicians claim that the bicycle mainly derives its stability from the fact that it takes effort to change the direction of a rotating mass, the gyroscopic effect.

“The gyroscopic effect certainly plays its part,” Schwab says. To demonstrate this, he produces a wheel weighted with lead around the rim, and gives it a mighty jerk. Only with great difficulty can the wheel be made to change direction. “However, mathematicians who took this principle to heart were wrong,” Schwab continues. “When we disregarded the weight of the wheels in our model we discovered that it was still possible to make the bicycle stable. And there is no truth in the idea that bicycles with small wheels are unstable.”

Countersteering

We all know intuitively the main combination of forces that ensure we stay upright when riding a bicycle. They involve leaning over and steering and they explain why, when we wish to turn to the right, we have to first turn the front wheel slightly to the left. The action, known as counter steer, results in a force that causes the bicycle to lean over to the other side, which is the direction in which we wanted to go. This also explains why we fall over if we pass too close to a kerb. We just can’t manage to get away from it without hitting it.

As for the steering properties, the greater the angle at which the fork of the bicycle points forward, the more stable the bicycle will go in a straight line, but also the more difficult it will be to go round corners. “The distribution of mass is also very important,” Kooijman says. “Moving the centre of gravity of a bicycle forward makes it more stable.”

The Delft scientists included twenty five such parameters in their model. All of them are relate to the two connected motion equations, one for leaning over and one for steering. “It remains unclear how exactly all these parameters affect the stability,” Schwab says. “In the final model these parameters appear in fairly complex forms as coefficients to the motion equations. For practical purposes most researchers used to simplify the equations by disregarding certain parameters, but the results tended to be far from ideal. And scientists who failed to make the connection between leaning and steering certainly were on the wrong track altogether.”

Thoroughbred

A model that indicates whether a design will result in a thoroughbred racing bike or in a stable ride suitable for the elderly, is something the bicycle industry has been eagerly awaiting. Rob van Regenmortel, product development manager of bicycle manufacturer Batavus, is following the Delft research effort with an eagle eye. Van Regenmortel: “Traditionally, when designing a bike, we use three parameters: the general geometry, the distance between the axles, and the angle at which the fork points downwards. Most of these properties were established back in the 1970s. Take the angle of the tube that carries the saddle. On our old-fashioned bikes this tube is mounted almost vertically. On bikes made by Gazelle on the other hand, it is inclined slightly more backwards. These are simple design choices all bicycle manufacturers made at one point and which they then more or less stuck to for the simple reason that their products kept selling. Now that we have Schwab’s model, we hope to be able to start designing bicycles aimed directly at special target groups.”

Van Regenmortel would like to collaborate with Schwab and Kooijman on a future project that will also look at the riding behaviour of the cyclist. The ultimate goal of the bicycle research effort is to include the cyclist’s riding behaviour in the model so as to be able to investigate the combination of the bicycle and its rider. “We could then actually make a ‘tailor-made’ bicycle for everyone,” Van Regenmortel says. “People who find it difficult to maintain their balance would no longer have to ride a tricycle.”

Ultimately, the model is intended to improve customer communications. “Perhaps we could label bicycles with numbers to give customers an idea of their riding properties. People looking for a bike to carry lots of luggage on holiday could then be recommended a type two bicycle, say, and someone needing transport to work and back might be wanting a slightly more thoroughbred machine, say type four. It’s just an idea.”

But how do you measure people’s riding behaviour? On the conveyor belt in Amsterdam, Kooijman and Schwab have already collected some manned bicycle data through the simple expedient of riding the test bikes themselves. “Scary is the word,” Kooijman says. “You’re cycling at some speed inside an enclosed space without moving forward. It feels very weird. You’re constantly afraid of hitting the wall. We can’t ask elderly or disabled people to ride a bicycle that way to collect data. In future we will have to conduct our tests on the road, and then copy the cycling behaviour in a robot bicycle.”

1 Headoscopy

A pro's heart rate is 50 or below. Are these guys even going to hear anything?

1 The Lamborghini Bicycle

Before all that, I've incorporated some music on the side, so feel free to check out the day's tune. Ofcourse, you don't get to choose what you want to hear so bear with me. Anywho, let the music beginnn...!!!


Thanks to a very Euro group on facebook, I was able to learn that Lamborghini once made a bicycle under their name.

I don't want to mess with any more pictures of this bike, since its heavily copywrited with text on the website. Anyway, some highlights are that this bike was made in Germany by Lamborghini Bike International for the 1979 Frankfurt Motor Show. Now what was remarkable was that the bike was built with Titanium and Magnesium (for the wheel rims probably) and supposedly, even polyester was used (handlebar tape?).. bringing the total weight of this bike to 14.3 pounds, or 6.5 kg. That's pretty sick for a 1970's bike. The cost of this limited production baby must have run well into the 10,000's of dollars, but whatever happened to the Lamborghini bike, I do not know. It just goes on to perhaps show that auto companies can take a break from cars and produce bikes to get their name out there, and do so in the highest form of bling bling om shanti.. Good question to think about? What if the car business was no more economical in a hypothetical world where 'go go green' was the chant and any more of 4 wheelers were looked down upon. Don't you think if car companies wanted, they could make some hot bikes and put current bike companies in tough competition? Well, its also a matter of 'field of expertise' but still....

Some observations : In this picture, the wheels have no tires. And ..the brake hoods can easily give someone Carpel Tunnel, unless the position is changed. Man, can someone even ride like that? Is that EURO? And that odd looking thing to stabilize the bike is extremely fugly and industrial.

See more pictures and details here.

2 For Sale!

1.Specialized AL Alloy Handlebars 44cm

2.Easton Road Bike Stem 90mm

3.Shimano 105 9 speed Cassette - Used

4.Shimano Dura Ace 9 speed Rear Derailleur (Sold)

Check these next set of my Ebay used items. As usual, I sell these things very cheap so if you have something in mind you want for a build, check them out.

Update : Holy Crap, within 2 minutes of my posting the 4th item on Ebay, it was sold. Thats a record!

0 Daihatsu Mud Master-C

A solution to weekend warriors who don't want to travel with a truck or an SUV with four doors to races. It'll probably eat lesser fuel per mileage while getting you to your race, its completely configurable and it looks super cool with its hatches and the 16 inch off road wheels. Something like this can really get into the market. The gullwing doors swing open to fit a bicycle without having to take off the front or rear wheel. That also means not having to place it on bike racks and leaving them at the mercy of the elements. If only modified a bit more, it would be perfect.

When will the auto industry start being a little more bicycle friendly?

Read more here.

0 Merckx's Scar?

Did Eddie Merckx have a big scar/wound mark on the back of his left shoulder? I noticed this while watching the fabled movie A Sunday In Hell, towards the end where the riders mount off their bikes and get rid of their jerseys, to probably go shower or something I think.

Before I end, a word of support to all the people down in South California who had to face the devastation of forest fires. On another sad note, some beautiful and popular mountain biking trails were also destroyed in the process, and I think only Bike Mag has taken the initiative to report on the damage done. Read it here.

0 The call of the offseason

I've started running for the past one month, from 6-10 miles each session. Its the best cross sport. Especially since my resources are low, I cannot get into something where I'll have to spend money. Cycling has eaten my wallet. Yesterday I lifted at the gym, doing a circuit style workout. Today I'm a little sore and I love it.

Getting one's mind off the bike, and focusing on other aspects of conditioning before the next season is the purpose of off season. Or you'll burnout! And you may break your bones... Well, atleast highlighted by this article that I came across in LA TIMES. I like the idea of playing soccer. Sweet... Hey, scroll down and check out the "core stability exercises" link in my honeycomb on the left.

Cycling may shortchange bones

A little high-impact exercise can help prevent osteoporosis, experts say.
By Jeannine Stein, Los Angeles Times Staff Writer
October 22, 2007


CYCLING is terrific exercise, hitting the cardiovascular system and major muscle groups simultaneously -- but it may not be the best thing for building strong bones. Compared with male runners, male cyclists appear more likely to have lower-than-normal bone density.

"You would think that cyclists are very healthy because they spend all those hours training," says Pam Hinton, associate professor of nutritional sciences at the University of Missouri-Columbia and coauthor of the study accepted for publication in the journal Metabolism. "In other aspects they are -- cardiovascular health and body composition. But in this one aspect, they're not doing so well."

The study tested the bone mineral density of 27 cyclists and 16 runners ages 20 to 59 who had engaged in their sport a minimum of six hours a week for at least two years. Hinton controlled for diet, past exercise and weight training. Whole body scans and blood tests showed that 63% of cyclists had osteopenia of the spine or hip, compared with 19% of the runners.

Osteopenia is bone mineral density that's lower than normal but not so low to be considered osteoporosis, or very low bone mineral density. Not all who have osteopenia will develop osteoporosis, and treatment isn't always required.

Some of those with osteopenia were in their 20s and 30s, "and that was pretty alarming to me," Hinton says. "I thought I'd just see it in guys who were older and had been riding for years."

In general, men may not be as much at risk for low bone density as women -- especially postmenopausal women. But Hinton believes they should be concerned because osteopenia can lead to osteoporosis and injuries such as hip fractures.

Bone cells are surrounded by fluid that, when hit with an impact force, moves back and forth. That action signals to the bone cells to add more mass."You lose bone mass quickly if there isn't some kind of mechanical loading on the bone," Hinton says.

That, she adds, best comes from movement involving impact -- running, playing basketball or soccer, or doing plyometric exercises such as jumping.

Weight training can also exert force on the bone, says Hinton, but not as much as during impact, perhaps accounting for the lower bone mineral density in cyclists. Some of the study participants protested that the muscle contractions that occur when pedaling and standing on the pedals should account for some impact. "But the pedal is moving with you," she says. "You don't have the earth resisting your body."

Hinton recommends that cyclists add a little variety to their workouts to help increase bone density: running, playing basketball, jumping rope or doing plyometrics a couple of times a week.

"When you're young, you should be maximizing your bone density," she says, "and as you get older, exercise slows the rate of loss. So it's really important no matter where you are in your life to be doing some kind of bone-loading exercise."

jeannine.stein@latimes.com

0 Surprise Tour de France rider

A horse! Watch....!

I enjoy watching Ivan thrash the competition. Maybe the girls too..

0 How are you lubricating your chain?

Old topic revisited. Are you lubricating your chain right? Have you thought about what you're doing while lubing the chain? The cycling chain is marvellous, able to take anywhere from 0 to 2000 watts of power (in normal circumstances), over many miles, many hours, and if taken care of right, many months and years.




Source : Chains for Power Transmission and Material Handling - ACA, Pages 320-322