30 Defective SRAM Brakes Not Recalled

This story is an interesting one and if true, shows how certain bicycle companies, as I have always believed, are negligent about customer safety or educating people about the same. I already proved a few months back how Shimano displayed this attitude with their Ultegra chain issue, which snapped and caused a serious safety concern for many riders yet they did not issue a recall. Its not just me who holds this belief. Notable personalities like Jobst Brandt and Professor David Wilson believed it. Its not going to erode away easily.

Last week, a reader of my blog, ordered a pair of new SRAM Force caliper brakes for his road bike. As you may know, SRAM revised the design of these brakes recently as the 2010 version has a gunmetal finish to it.

When his local bike shops’ mechanic went to install the first brake calliper, the quick release lever housing broke in half. Surprised, the mechanic then proceeded to install the other very carefully - you know - being cautious not to twist the housing when he attached the cable and careful about torque and all that.

Nevertheless the other one broke in the exact same way. About a third of the lever and the housing around the lever snapped off in both brakes, leaving a weakened part behind. This plastic housing is directly connected to the brake cable attachment point, something that could be a serious safety hazard. No brakes, no safety.

The mechanic told the reader that he had called SRAM and asked about this problem. To his utter surprise, the person answering the phone actually said :

"Yup we’ve had a whole batch of bad ones. They injected too much air when they molded the part.” 

It is a bit strange that SRAM, having complete knowledge about the defect, chose to still ship the parts to their various distributors and haven’t uttered a word on the issue or recalled the product. This is inexcusable and unethical!

I'll leverage the power of my blog to get responses from you readers. Please be aware of this problem and take action but while we're at it, have you experienced any similar issues? Please report it here and please feel free to be honest about your thoughts.



CONNECTED READINGS :

A Petition To Bicycle Companies On Safety Of Products

2 Cadel Evans And His Book 'Close to Flying'

I can't believe this was on Youtube and it garnered just 400 views. Here it is again, ABC Radio's interview with a fantastic athlete. (Recall I wrote before on how both his power to weight ratio and VO2 max were greater than Armstrong's when both were at their peak). His new book sells for 70 dollars and change on Amazon. I hear he's a good cook so there better be some tasty recipes in there for that price.

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15 Forces In A Sprint Crash

An object in motion tends to stay in motion with the same velocity unless acted upon by an unbalanced force. Unbalance can easily come in the way of a gentle sideways push during a sprint, such as that from Haussler yesterday which planted half a dozen riders including the Boy Racer himself straight down into the Wettingan straightaway like a bunch of toy pieces.



The sideways fall of a cyclist on his bike at rest can be simply modeled as an inverted pendulum, with the center of gravity inscribing a circle from θ=0 to θ=π/2 before hitting the ground. If g is the acceleration due to gravity for earth and r the height of the center of gravity, the acceleration of the fall in the tangential direction is then a function of the angle of fall - gsinθ - and the force is mgsinθ. Integrating acceleration for velocity, you'll find impact velocity at θ=π/2 as v = √(2g/r).

r = 0.8m is not a bad assumption for the center of gravity of a small sprinter like Boy Racer. Plug and chug and you find v = 4.95 m/sec ~ 10 mph!

But in the case of the sprint, Cavendish is not stationary but has an inherent velocity in the direction of the finish line of approx. 45 mph (assumed).  The impact velocity can be considered a resolution of these two orthogonal velocities and what you get is a round about impact velocity of 46 mph or so.

This velocity is reduced to zero by the unyielding bitumen, but due to impact at an angle, its effect is slightly different from a more dangerous free falling vertical collision as the deceleration is spread out over more "seconds".

Looking at the video above, it seems like Cavendish lost most of his velocity in a little less than half a second after hitting flat on the ground on his back. I obtained 200 milliseconds using a stopwatch. Assuming constant deceleration, that would be about 100 m/s². Which is 100/9.81 ~ 10 g's of impact force spread over the surface area of his back.

Is that a lot of force? Depends whom you talk to and which industry they belong to. But for the Boy Racer, it would really seem he were getting slapped hard on his back by a Sumo wrestler applying 10 times the former's body weight in force, roughly about 6 Kilo newton or 1300 pounds. Only for a fraction of a second, but certainly enough to have shocked him and given some nasty bruises to take home.

Well distributed G-forces can be handled by the body in several times more in magnitude than what the sprint crash has seen (see below). But the human head is slightly more complex and this sensitive system does not tolerate very high peak forces, especially in the rotational sense.  I have put a perspective on the peak G forces on a head with helmet before. You should also read about Head Injury Criterion. Ride safe.

Survivable abrupt positive +g impact. Source.

Strength of vertebrae and inter-vertebral discs in impact. Source.

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15 Speedplay Light Action Platformer Failure

One of the tricky aspects to catch in product design is the amount of true value in it between its stages of evolution. Sometimes, last year's model that you bought could have negligible difference in it as opposed to this year's. Its marketing might say its improved, with a new recipe, new look, new shape and so on and in the end, you would probably pay a premium for it as well, all for the same exact thing.

On the other hand, as a credit to product design, it could also be that last year's model could be insufficient for use compared to the current year's release. Dangerous too. So is this really a credit if people are still using last year's product?

Subsystem design is very dependent on the performance of the parent system.  Today's illustration is a case in point.

Speedplay's marketing line for the "Platformer" brand of pedal adapters is this : "The innovative Speedplay Platformer is a user-friendly, tool-free platform cover for Zero and Light Action pedals. The Platformer makes it easy to convert from clipless pedals to platforms for riding with street shoes."

But reality is different. Last year's clear "Light Action" pedal adapters are really light action, apparently.  As the internet will show, quite a number of people are disappointed with the quality of material used in its design. Durability issues notwithstanding, riding your bike with one of these installed could be a danger just waiting to happen

Among the disgruntled is an individual (who doesn't wish to be named) whose adapters broke just as he was pulling out of a traffic light last summer. Casual riding wasn't light enough for Platformers. The plastic adapter on his right pedal broke catastrophically with an audible snap. Because of little warning, he lost his balance very quickly and ended up crashing on his tailbone and elbow, right in the middle of a road during rush hour traffic. A crucial red light to one side gave him enough time to get back up in pain, pick up the pieces and vacate the road.

Thanks to light action pedal adapters, he is in miserable condition today. Because a fractured coccyx is an injury with no form of available treatment other than time, five months later he still is in immense pain on a daily basis and can’t sit for more than an hour without feeling discomfort. He calls the sensation "intensely searing". For the weekend racer and an enthusiastic bike geek that he is, this is not exactly the good life.

The gravity of the injury and the possibility that someone else could be hurt in similar fashion made him contact Speedplay on many occasions. To make sure this wasn't some freak event, he even installed a set of the old Platformers on his girlfriend's bike as well. The product lasted approximately 16 minutes before they cracked. Some insults are better off when they come with forewarning. This one was even recorded on video by him.

Speedplay took back his pedals for inspection and has stuck by the quality of their brand. They chose to deny his theories of why they broke and didn't feel much need to return them back to him. They have claimed no responsibility for his injuries and other damaged personal articles. The user has now fixed a date with a Small Claims Court to settle the matter in the interest of full disclosure. He has also had a meeting with the Consumer Product Safety Commission.

Interestingly enough, this year's design, with the new "recipe" doesn't seem to have had as many problems since it does not use the same plastic clamshell (see right). The user ordered a pair from Competitive Cyclist, rode them on his girlfriend's spin bike for 50 minutes (the approximate lifespan of the broken ones) and they seemed to hold up just fine.

I suppose somewhere, someone found out the trouble with the old pair, fixed it, moved on. Meanwhile, old units are still being used by riders.


A Plausible Theory

The concept behind the Speedplay Platformer is to allow the user the option of riding a bicycle equipped with Speedplay brand pedals without having to wear dedicated cycling specific shoes. By creating a larger, stable platform around the pedal, Speedplay Platformers, allow the user to ride in “regular shoes."

A set of Speedplay Platformers consists of six pieces. A complete, individual unit is comprised of two seemingly identical pieces of clear plastic. The difference between the two pieces is found on the “inside” where four tabs fit together in a male/female manner. A metal retaining clip slides through these tabs and locks the Platformer in place around the Speedplay pedal.

Because of this design and the fact that the Platformer is molded to be compatible with only one specific type of pedal, it is virtually impossible for the Platformers to be installed incorrectly. They are either locked in place or they aren’t and this is very obvious to the user. To remove a Platformer, a key, coin, or screwdriver is used to remove the metal retaining clip by sliding the clip from the Platformer. The edge of each Platformer is concaved to facilitate the easy removal of the retaining clip.

At the time the user tried the product, he was 210 pounds and stood a height of 6'1". While this isn't typical of your featherweight climbing maestro, he told me that he's never broken any products before and he's always careful with cycling equipment.

Now clipping in and clipping out of Speedplay pedals cause substantial wear on these high performance pedals as most of us have learned. The right pedal, more so due to clipping bias in start-stops. The user's had between 3000-4000 miles of usage on them. For most people, this is a season's worth of use.

This leads to a plausible theory for why the pedals failed. He wrote to me :

My theory for why they broke is because design of the Platformer didn't take into account worn pedals as they are molded around a brand new set of pedals. Since the pedals I was using were worn down, there was some open space between the Platformer and the pedal itself which lead to much more stress on the Platformer particularly on the "outside." 

The following two images show a  3.2% reduction in right side pedal dimension between a brand new and the user's old one.

New right pedal

Used right pedal

The following image, of the used left side pedal, shows a 1% difference in pedal dimensions when compared to the right side pedal. This shows that the right pedal wears more due to clipping bias.

Please be aware of this problem and report any of your personal mis-happenings in the comments section. If you also wish to offer any kind words of advice to the user with regards to a broken tailbone, please share your thoughts.

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25 GRUBER Assist Made No Sale To Cancellara

GRUBER Assist, an e-bike drive train company in Austra, has (fortunately or unfortunately) found itself at the center of rumors regarding illegal motor use among the peloton.

I covered the story two days back and wrote about my feelings of what a motor should be capable of to help someone win the Paris Roubaix or the Tour of Flanders. We took for granted that this motor could be the GRUBER Assist. In the comments section of that blog post, I agreed with posters that at high cadences and power outputs such as Cancellara's (see Anatomy of a Cancellara Attack), the rider can "dilute" this motor, if you will.

Don't get me wrong. I'm also very impressed about the product's capabilities. I suppose one good thing that has emerged out of this controversy is that it is showing people a neat little technology for use in bicycling and potential use in bike racing.

BikeBiz already reported that the motor involved in the controversy in fact comes from Hungary, not Austria where GRUBER is based in. But hey, Hungary and Austria share a border.

Just to get the record straight about the product and its alleged use in the peloton, I had a chat with Julia Timmerer, a representative for the company. The following is what she told me in reply. I quote her :

"We are pleased about your interest in our product.

GRUBER Assist is an ultra-light drive for bicycles, invisible and built into the seat tube of the bicycle. The auxiliary drive supports with 200 Watt engine power (100 Watt Output) and weighs just 900 grams (plus 1 kg battery).

You can store the frequency of the pedals between 30 and 90 rpm. And so it gives the difference to your frequency. For example: You pedal 60 rpm, the motor is stored to 80 rpm, he supports the 20 (as far as it’s possible with it’s 100 Watts). BUT, if you pedal faster than the motor (you pedal 80, motor is stored 60) you overrun the motor and have no support.
For installing the GRUBER Assist into your bicycle, please note the requirements for the bicycle frame:

• - Aluminium or steel bicycle frame
• - Straight, continuous seat tube
• - Seat tube inner diameter of 31,6 or NEW 30,9 mm
• - Shimano Hollowtech II crankset – with outer bearing shells
• - Seat tube should be as central as possible on the bottom bracket
• - Minimum length of 62 cm from the middle of the crank to the saddle or 57 cm at a shorten seat post
• - Installation by a certified GRUBER Assist dealer

On our homepage you can find 3 spots which explains the GRUBER Assist exactly: http://www.gruberassist.com/english/downloads/spot-gruber-assist/

Please note, that neither the GRUBER Assist, nor the battery is admitted in the USA.

Please note, that the GRUBER Assist has not installed a blocking. For example in Austria an E-Bike needs a blocking at 25 km/h, otherwise you cannot drive legal on a public street. If one wants this blocking, the customer should let us know with their order. A later installation is very complicated and more expensive.

We never sold the GRUBER Assist to Fabian Cancellara and we don’t think that one of our dealers did this. And I don’t know anything about the using of our product in any races. At the moment our product is unique and we also have the patent for it. I don’t know anything about a similar product. There are many other E-Bikes (hub dive, bottom bracket motor,…) but those bicycles are not only very heavy but you can also see the motor."

Fabian's race winning bike posted by Jered Gruber. Where's the motor?

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85 The Anatomy Of A Cancellara Attack

Writeup updated slightly on June 3, 2010


So dear readers, quick recap : there's this idea floating around of Swiss rider Fabian Cancellara using an electric motor at the classics. It seems to have originated at the rumor mills of il Italia and a couple of journalists, an ex-pro cyclist and a little known e-bike maker are in the thick of it. Meanwhile, Fabian tossed out a statement today in the press calling hogwash to these claims. Hey, the truth is out there...

Last evening, I spent some time re-watching 2010 Paris Roubaix clips. My focus was upon the attack from Cancellara with 48k to go. To me, there were three segments to this attack :

"..can we dissect this attack and see its parts to get a perspective of what's happening?"

1) At 55K remaining, there were a lead group of 40 favorites at the front. They included Tom Boonen (Quick Step), Fabian Cancellara (Saxo Bank), Filippo Pozzato (Katusha), Adam Hansen (HTC-Columbia), George Hincapie (BMC Racing Team), Leif Hoste (Omega Pharma-Lotto) etc.

2) In the next 2 or 3K, the group splintered. Leif Hoste, Björn Leukemans, Frederic Guesdon and Sébastien Hinault pushed to the front.

3) At 49 K to go, Fabian Cancellara surged ahead from the bunch to join the four leaders. In a few seconds, he took one sideways look behind him, saw that the title defender Boonen had decided not to mark him down. Riis, the team manager, radioed to him. "Go". Yup, it was a bad move from the Belgian champion. Fabian was then gone and the rest is history.

The jump Fabian put forth was strong and decisive. To most of us, watching the surge (see video below) may seem almost like, well, like he had a motor somewhere on the bike. How on earth can he pull away so quick, right? Well the Italians asked that hard question and came up with the answer - 'Oh mio dio, he has a motor on his bike!'

But regardless of whether he used a motor or not, can we dissect this attack and see its parts to get a perspective of what's happening? I think we could.

So I used a physics analysis software and some basic physics to get an idea of the speed and acceleration involved in this attack. This may seem pretty ghetto to some of you but perspective is what ultimately matters.

STEPS

1) First, I downloaded the above video of the action from Youtube. I cut the video segment only to the points of interest, from 2:07 to 2:22 or so. I eventually a few hundred frames at 25 frames/second. I decided a timestep of about 0.03-0.04 seconds would be more than adequate to the capture the stages of the action.

2) I scaled the segment with a known dimension of some entity. That entity was going to be Cancellara's 58cm Specialized bike. I looked up its specs and found out that the wheelbase of the frame is pretty close to 100 cm or 1m. Good enough.

3) I imagined myself seated inside the TV helicopter, shining a path co-ordinate axis down at the action below, somewhere in the middle of the screen. I reckoned that the zoom and pan from the helicopter camera would create complexities, but luckily for me, there was not much. The cameraman in the helicopter had kept his focus remarkably steady on the racers, without much shaking and distraction. There was a bit, but I knew exactly where it was. Then I positioned the axis angle to be somewhat parallel to the direction of motion on the road.

4) I then stuck point mass trackers on Fabian, spectators and motorcycles. These trackers would give me position vs time information of the object as the cross-hairs of the camera sped past them.

I finally had distance vs time plots from objects to plug into MS Excel. Since velocity depends on the observer, and since the observer is in a moving state in a helicopter, any relative motion between the observer and the cyclists is either a surge or a deceleration.

Let's explore the stages of the attack :


A) At what speed was the peloton with favorites moving initially?

Here, helicopter camera was very focused on the action with little shaking. Hence, a spectator appearing and flying out of view may give an indication of the speed of the riders. The position time graph was a straight line. The data was exported in Excel and a "linest" operation on the data yielded a slope, as shown below.

25 mph is not hard to believe.

B) What was the speed of the lead group that surged away?

Here's another spectator! Let's catch him!! So we place a tracker on his bosom.

This is how fast he flies away from the camera. The slope tells me 29mph. Hence, the leaders broke off with an extra 4 mph relative to the peloton.

C) The attack : How fast can Fabian put a 5 second gap on others?

This pic shows a tracker placed on Fabian, and the graph shows his position changing wrt to the origin due to relative motion. This relative motion is the attack!

Fabian was to the right of camera's origin (purple axis) before he attacked. The camera was focused on the lead group and did not follow Cancellara when he attacked due to the "lag" in reaction time from the cameraman. The downward slope on this graph indicates Cancellara moving towards the negative left side of the origin with his surge. In a little over 4 seconds, the brunt of the attack came, when the slope of the graph dips further, indicating acceleration. The area of interest is limited to 12 seconds because the cameraman suddenly finds out what's happening and shifts his focus to Fabian. This is why the red line begins to curve back up again.


So I exported that graph into Excel, inverted the graph so I would get nice positive numbers. Then I cut the graph to the area of interest.

Presto! This shows us that Fabian puts in a 5" gap very quickly. But how quick is "quickly"?


...this gives us an idea of Fabian's relative speed from the camera focus. So what happens in this 5" gap that Fabian puts relative to peloton? In the first 2 seconds, he manages +1.6 mph. In the next half second or so, he increases that to +3.3 mph, which then bumps up to +6.5 mph until at the second before the camera catches up with Fabian, he's riding at an impressive +7.4mph.

Since I wrote before that camera's focus was traveling at 29mph, this means that the Fabian's respective speeds are 30.6 mph (49.2kph), 32.3 mph (52.3kph), 35.5 mph (57kph) and finally 36.4 mph (58.5kph). This corresponds to an acceleration of around 0.7-0.9 m/sec^2. Ordinary cars have an acceleration of 3-4 m/sec^2. Fabian musters close to 25% of a car's acceleration. Vroom!

D) A reality check :

I stuck a tracker on a passing motorcycle as it sped past Cancellara to "get out of the way". Perhaps it was Graham Watson in the back seat as the flashes of a camera went off. Nevertheless, I found it had a relative speed of +25mph from similar analysis. Adding this to Cancellara's speed of 29mph gives a roundabout motorcycle speed of 60mph (96kph). Its believable.

Also, if I were to plug in the speed I obtained and Cancellara's weight and cadence into Analytic Cycling's "Forces on Rider" calculator (with generic parameters), it gives me about 680 Watts of power. Still believable by STATIC riding standards.


But since I said that he's accelerating with 0.9m/s, given a weight total weight of 87kg (80 kg Fabian and 7 kg bike) and a final speed of 16m/s, we should really calculate his power output and crank torque in a dynamic situation. For the crucial 5 seconds of attack time, I calculate all those below.

I assume Fabian was on his 53-11 gear, which I'm sure he could easily pedal.



Onto the propulsive force required.


Work done then becomes :


So what is his power output to accelerate for those first 5 seconds?


Though not very relevant, also notice that this power output equates to a rough 5 sec power to weight ratio of 1200W /80kg = 15 which is nothing out of the ordinary based on a power to weight ratio chart for male cyclists (See Power to Weight Ratio).

Using a stopwatch, I figured Cancellara increased his RPM from his previous 100 to 110 RPM for his attack. The average torque required for this acceleration at the crank is then :


That value is within the realm of competitive cycling. Since I said this is an average, it would be the average of the "sine-curve" of torque on the y-axis and crank angle on the x axis. The crank torque is scaled down at the rear wheel by a factor of the gear ratio, calculated earlier, since it rotates faster.

For readers on both side of the Atlantic Ocean, I put this all together in one table with units :



My sanity check is over. The numbers are believable by DYNAMIC riding standards. Any doubt? Note that some data from the recent Tour of Flanders indicates that he put in 1450 Watts during the attack on the Muur. That number came after a very long day of riding. If he can manage that, he can surely manage 1200 Watts in the initial moments of his breakaway.
This is my two cents.


CONCLUSION

It is the first 5-10 seconds of an attack that is most crucial and most tricky. Attackers must be able to speed off from an already high pace, and the objective is to dig in to hell, gather the firepower and deliver the maximum blow without suicide.

It is the rapid rate at which Fabian Cancellara increases his speed that is mind boggling to see in the video, even though such speeds are pretty normal for him.

Don't get hung up on the numbers presented here, which is all approximate. But we know from historical data that Fabian is someone who can out-sprint the best by simply staying seated on his saddle, even after 230K of racing. The following is one of those spectacular moments of Tour de France history that will not erode away with time. Watch :

ADDITIONAL READING :

Some Probability and Statistics of the Individual Time Trial

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