New From the Cozy Beehive...

This is a post from the Cozy Beehive discussing a specific bike crash and a potential carbon fork failure.


Safety Moment : Crashing Into Pine Needles

Lets get no illusions about our sport.It can get dangerous. Losing just a moment's worth of concentration may be enough to unseat you off your saddle smack into danger.Our second safety moment for the year is Liz Hatch's latest injury report on her blog. As it turns out, she was enjoying the breeze on a fast downhill in a fundraiser ride for the Women's Tour of California Criterium when she approached a corner full of pine needles at more speed than was actually safe. She rode right into the guardrail at 45K and landed face first into the area of needles. Thankfully, she made it but the bike was sheared off at the fork on impact.

For the rest of this post go to http://www.cozybeehive.blogspot.com/.

What to look for from a Bike Accident Expert Witness

When a bicycle accident occurs, the resulting litigation can have serious ramifications for both the Plaintiff and Defendant. Choosing the correct expert for either side is crucial. These are the basic criteria for choosing an expert that should be carefully considered.
· Is the individual a Professional Engineer by examination? This can usually be determined by the initials P.E.” after their name. The Professional Engineering Examination is 16 hours long and the requirements even to sit for the exam are fairly extensive. Some individuals have the initials “P.E.” and were never required to sit for, or pass, the National Examination. The question that should be asked is “have you ever sat for and passed the NCEES examination for registration as a Professional Engineer?” If the individual has the Professional Engineer designation they are required to conduct themselves under the direction of the Board of the State in which they are registered. This provides the Client the knowledge that the PE, will conduct him or herself in a ethical manner and is bound by the Engineering Code of ethics.

· Is the individual an advocate? Often times a simple examination of the persons website will determine if they espouse some “over the top” opinion. There is no place for an advocate in the court system. If someone is constantly exposing “cyclist rights” or, designated bike ways over bike paths, they are not objective in their opinions. Cross examination is not the place for a “hired gun” mentality- if the individual is constantly talking about cases he “won,” then you do not want them involved in your project. If someone qualifies as an “expert” in a court room they are given wide latitude in what they can say under oath. While the court may allow a hired gun mentality during testimony, the verdict will probably be over turned on appeal ,resulting in large expense for the client. The Forensic Engineer’s role is to be a Friend of the Court and assist the Trier of Fact not brag about “winning” cases.

· Publications. Has the individual published in the Engineering Literature and has the article been subject to peer review. There is a lot of literature in the cycling world on various issues. There is very little literature that has made its way into the Professional literature and is relied upon by other Engineers. A simple inspection of the individual’s web site will determine whether the person just writes in the Cycling Publications or actually publishes in Engineering Journals.

· Racing Background Has the individual had an extensive cycling background? Certainly, having a racing background is a definite plus. Equipment and bike handling capabilities are stretched to the maximum during racing. That “hands on” knowledge is essential for reconstructing bike accidents. However, just because someone “rides a lot” or belongs to the League of American Wheelmen does not make then an expert in Engineering areas such as; trajectory calculations or force of impact on the human body.

· Professional Engineering Organizations. Professional Engineering organizations vet their candidates extensively. If the PE is a full member, or Fellow, in the following organizations their qualifications have been subject to peer review:

o American Society of Civil Engineers
o Institute of Traffic Engineers
o National Society of Professional Engineers
o National Academy of Forensic Engineers
o Practice Division of the State of Registration
o American Society of Mechanical Engineers.

I have been reconstructing bicycle accidents for 35 years. Nothing pleases me more on a project than to have a highly qualified Professional Engineer on the other side of the issue. In these instances, the matter usually gets resolved with a minimum of cost and effort for both sides. There is nothing more difficult than having a “nut case” on the other side that will not take the facts of the matter into account, has a personal agenda, is not qualified, and attacks anyone who disagrees with them on a personal level.

Bicycle safety in bicycle to car accidents

Go to

http://media.fietsersbond.nl/botsvriendelijkeautos/bicycle_safety_in_bicyle_to_car_accidents.pdf

for a report on why there were more people in the Netherlands getting killed on bicycles than as pedestrians.

Carbon Fork Testing

Carbon Forks: Testing has shown that these forks are a problem. When the forks are stressed beyond the yield point, catastrophic failure occurs. The forks do an unusually good job of improving handling for a modern road bike. They are light and enable the bike to absorb road vibration and hold a line extremely well. But, when stress is placed on the forks, beyond the yield point, by running into the side of a car or curb (or equivalent) the forks completely break leading to collapse. The “chrome moly” forks that were on bikes for several years do not collapse but bend under similar forces. I will be glad to share data that I have available if anyone is interested. There is peer reviewed data on front fork failure in my Engineering Text – go to http://bikereconstruction.com/aboutthebook.aspx.

LED Lights on Bikes

Preliminary field results indicate that LED lights on bikes, or used by pedestrians, increase the recognition distance to over 2000 feet at night. LED lights appear to be more effective that none LED lights or retro reflectors at night.

Cyclist Trajectory

Recently on Cozybeehive.blogspot.com I was highlighted with this article.

On Reaching Dizzying Heights In Bicycle-Vehicle Collisions

"If a car traveling at 46.5 kph hits a cyclist, the force of impact would be sufficient to send the cyclist up to the thirteenth floor of a building."

- Traffico, a journal by the Directorate General of Traffic of the Spanish Ministry Of The Interior

I happened to come across this quote on some helmet advocacy website a few days back. I forgot to bookmark the darn site but had copy pasted this statement exactly as it was into a word file on my computer. Anyway, I was struck and bothered by such a bold claim. While it sounds scary, is there any real truth in it? 46.5 kph is around 29mph, which is a low speed for a vehicle. Despite this, the momentum of the vehicle is a hell of a lot considering its high mass with respect to the cyclist. So can the momentum transfer in the above collision really rocket the cyclist up to as high as thirteen floors before crashing to the ground? If such were the case, the cyclist could be in serious condition, even dead.

If you know your college physics, the topics to recall would be Newton's laws, impact and momentum transfer, conservation of energy, collisions and projectile motion. But hold on. Its a tricky challenge. There are many variables to consider : the masses of the three bodies, height of the cyclist, the gradient of the road, point on the vehicle first struck, orientation of the bicyclist before impact, the launch angle, coefficients of restitution and friction, and victim's behavior post impact (wrap, vault, forward projection, somersault etc).

Physicists and engineers across the world have come up with all sorts of equations to study vehicle-pedestrian collisions. They're interested in things such as - how one can devise a good comprehensive mathematical model that will approximate well the speed with which the vehicle first impacted the victim, or what the total throw distance of the victim would be given other data, or would the model ultimately validate real world behavior - questions of that nature. Such models could then be incorporated into manuals and computer tools that could be used by police officers and forensic investigators to catch criminals and help serve justice.

Example of a Post Impact Scheme Adopted By Bogdanovic and Batista, 2004

Anyway, coming back to my first question based on the initial quote : Can a cyclist really be projected that high, where max height h=height of 13 storeys, about 130-150 feet? We may never know exactly, because not a single bit of data is provided by Traffico other than the car's speed at impact which is given to be 46.5kph=29mph. But lets make an effort to find out.



1. LOOKING AT VIDEOS


Forget the theoretical part for a moment. Lets look at a couple of real collision videos involving a two wheeler and a car.

Here's a guy on a bicycle getting hit by a car. The latter was decelerating hard after the driver spotted the rider coming into his view but it was too late to stop an impact. Note how the right corner of the car impacts the cyclist first. The rider then hits the windshield and bounces off it before falling onto the road on the right side.



The victim is pretty lucky. He just gets up and immediately starts yelling his frustrations. I'm so surprised he didn't smash his head onto the ground. But hey, neither did he fly any higher than the car itself. Just a few feet. The car itself could have been doing 15 or 20 mph before impact.

Here's another video. This time, its a vehicle colliding with a motorcyclist who fled a red light only to meet his deadly fate.



If it had been a bicycle in the video, which is much lighter than a motorbike, it would have been thrown off a farther distance. The car was moving much faster than the first video. It could well have been doing 35 or 40mph before coming to an abrupt stop after the collision. The airbags must have surely deployed since the driver appears disoriented. The motorcyclist is shown spinning in the air at a stomach sickening angle before landing onto the hood of the car and bouncing off it straight onto the road, right in front of the stopped vehicle. Its anyone's guess how many bones he could have broken that day.

And finally, here's a simulation of a car-bicyclist collision. It was done by Crash Teams, the largest crash reconstruction company in the world.




All three of these videos don't show the cyclist being propelled to dizzying heights after the collision. At least not thirteen storeys high.



2. FIELD EXPERIMENTS

Jim Green is a triathlete and Professional Engineer with over 20 years of experience in reconstructing bicycle accidents. In the 19th chapter of his book "Bicycle Accident Reconstruction For The Forensic Engineer", a table of vehicle-bicycle collision data is presented to us. The analysis was done on the field by Rusty Haight and Jerry Eubanks who set up an experiment in which different kinds of motor vehicles were used to strike an exemplar bicycle with a dummy cyclist at various speeds.

Here's the field data that shows the linear throw distance of the dummy cyclist after impact.

Determination of the throw distance of a bicycle and cyclist at various impact speeds

I have highlighted some rows of data for cars close to 29mph. For example, a 1979 Honda Accord hitting the dummy cyclist at almost 27 mph in a 60 degree orientation would throw the rider some 58 feet. Although the field experiment did not measure for the maximum height of the cyclist in the air, I highly doubt that the dummy really went as high as thirteen floors for a throw distance of 58 feet. I don't believe that's what the researchers really observed.



3. PROJECTILE MOTION

Coming back to physics, the cyclist on impact would be a projectile because his motion is only governed by gravity. But can we use the equations from projectile motion to find out what his height achieved could be in an ideal case scenario?

Lets use some simple assumptions like : a) the cyclist is a particle of mass 70kg , b) the head-on collision is elastic, c) the bike is immediately separated from under him after impact, d) the cyclist hits the windshield and is launched forward at an angle, e) during the collision between him and the car, there is zero effect on the velocity of the car itself due to its very high mass and that all the car's impact velocity is transferred to him, f) and the car comes to a complete stop just after impact, leaving the cyclist with the forward motion velocity.

Using the equations for a projectile, we can apply a simple applet to solve for height. Note : This is strictly a 2 dimensional scenario which is not the real case. We're completely neglecting the Z dimension.

For head-on elastic collisions, the velocities of the car and cyclist would be :



Assume the car has mass m1=2000kg, and the cyclist has mass m2=70kg.

v(car) = 13m/s (46.5kph, given by Traffico).

So, v(cyclist) = 25.12 m/s.


According to the equation for maximum height in a trajectory, we find that range is shortest and peak height is maximum when the launch angle is exactly 90 degrees with respect to the horizontal. This is because sin(90) = 1.



Since we assumed that the cyclist hits the windshield, lets give him a launch angle of 80 degrees. Solving :

With air resistance factored in, the cyclist would make a 30.82 m max height, or 101 ft. Add the height of the car's impact point to this figure and it still gives us something under 105 feet. This is not what happens in real at this speed. This is an ideal case scenario where we haven't accounted for the losses in the kinetic energy in the collision. Moreover, a cyclist is not likely to be launched like a cannon, following a perfect ballistic curve . At least that's not what real world vidoes or simulation show us. Lets remember that the cyclist also sits on a bike and that fact coupled with how he impacts the car are very likely to influence how far or high he's thrown. Hence, I cannot validate the calculations above. I may believe it if you're talking about a collision on the surface of the moon where the acceleration due to gravity is 1/6th that of the earth. Ha.

CONCLUSIONS


I won't declare the myth as BUSTED just yet because I have used a number of simple equations with attached assumptions. This is NOT the way to an actual crime scene investigation. I'll be interested in seeing further research data from bicycle-vehicle collision studies investigating multiple accident scenarios. But for now, the idea that a cyclist will launch as high as 13 storeys seems like a wonderfully wacky proposition. I support the wearing of helmets for protection but don't support the spreading of false information by agencies in putting together a helmet wearing agenda.

As an end note, I just thought of something in my hindsight. Maybe Traffico is right. What if, in Spain, the 13th floor of a building is considered so unlucky that there is no 13th floor at all in its elevator's options.

What Traffico then must have actually meant through their quote is : You're one unlucky bastard to be hit by a moving car at 46.5kph!



Concluding video presentation : James Green, PE discusses bicycle accident scene investigation from the perspective of a forensics engineer.

Pollinated by Ron

John Forester's Background Including His Stay in a Mental Institution and His Failure in Calculus

Here is some more infrmation on Forester including his stint in the mental institution

My research, much of it involving the C.S. Forester papers at the Humanities Research center at the University of Texas,shows that John Forester came from a somewhat dysfunctional household, much of it the product of his father's obsessive womanizing.

He (John) started as a physics major at UC-Berkeley about 1946. He failed a second-year calculus exam and dropped out of college and worked in a warehouse in Boston for about nine months, then returned to UC-B as an English major, graduating in August, 1951. He went into the Navy in December 1951 and received a medical discharge in August 1952 after being hospitalized for several weeks at the psychiatric unit at Bethesda Naval Medical Center in Washington DC.

He married an Englishwoman, Jean Labada Clough Nicholson in September, 1953. A son, Geoffrey R. Forester, was born on 4 June 1954. He now lives in Muncy, PA. John Forester went to work in a steel fabrication factory about the time of his marriage and studied at night at UC-B for a certificate in industrial engineering. With this certificate, he received his P.E. from the State of California, probably in 1956. California no longer licenses P.E.s in industrial engineering, which is primarily a business methods discipline, but does maintain the licenses of those who received their P.E.s before they were eliminated.

In March or April, 1958 a daughter Pamela was born. She died in April (probably 11) 1962 of natural causes. Forester and his family moved from Berkeley to Fullerton in the LA metro area in late 1958. He worked at North American Aviation, and probably other places, got his master's in industrial engineering from Cal State Long Beach in 1964 and started to teach there part-time in the business school. He claims that he was an assistant professor, but his textbook, which came out in January, 1968, just before he moved back north, lists him as a "lecturer."

C.S. had a major stroke in 1965, and he and his second wife Dorothy moved to Fullerton in late 1965. C.S. died in April, 1966. In his will, he left John and his brother each $5,000. About twenty other individuals received testimonial bequeaths worth a total of $25,000. The bulk of the estate, about $700,000, went to Dorothy. John and his brother did receive all the literary properties. Dorthy soon returned to England and severed relations with the Foresters.

The will appears to have tripped him out. Within a year or two he quit his job, left his wife and family (he says because she discouraged his cycling, fearing it would bring the opprobrium of their upper-class neighbors) and moved back north to Palo Alto, where he became a bicycle racer, randonneur, and sports car enthusiast. He wrote an incredibly viscous biography of his father detailing every moral and personality shortcoming.
He could not get it published then and sat on it to 1987, when be had a brief excerpt published in American Scholar. In 2000 the whole thing was self-published in a 2-volume set limited to 250 sets. This is the last sentence in the 2000 postscript, which closes out the 800-plus pages:

"I can honestly write that I am better known in my field than my father was in his."

He worked at Xerox in 1970-71, but got fired in 1971. He was working at another high-tech firm in 1972. In 1972 he met Dorris L. Taylor, a cyclist and biochemist visiting from Minneapolis. he apparently talked her and her two daughters into moving to California. In late 1972 he became involved in cycle advocacy and in 1973 he quit work for what he says he thought would be two years full-time work in cycle advocacy while Taylor supported him.
He has, apparently, never worked as an employee since. In 1998 he and Taylor split up (she moved to Fort Collins, CO) and he moved to the San Diego suburb of Lemon Grove. He may be in financial straights; the Sunnyvale house he sold in 1998 had an assessed value of $390,000, while the sales price of the Lemon Grove house was only $143,000; it has only two bedrooms, one and a half baths, and 1043 sq. ft. and was built in 1950.