Motorcycle Crash Physics

[wobblywalrus]

Ive been close to crashes.  My own and others.  Cliff Gullet on his last ride was the bike just after mine at BUB.  Last night I watched Jason McVicar's crash on U-tube.  Something like that would kill me.  I am not young and unbreakable any more.  Jason is one lucky dude.  Right then and there, speed racing at under 150 mph started to seem like a really good idea.  My mind is made up.  I will leave the 200 mph stuff to John Noonan, Slim, Nancy, and the Amo bros.  I have no more desire to reclaim the 1000cc MPS-P record.

My current plan is to fine tune the new engine this year at BUB.  Next year I will build a set of tuned pipes to take advantage of the overlap in the new cams and I should be running plenty fast.  The BUB people have really treated us well and I want to make my lifetime best run at their 2011 meet.  Squeaking through the mile at just over 150 would be great and my speed dreams would be fulfilled.     

Werner will be close to finishing high school in 2012 and as a graduation present I want to take him to Elmo so he can see the belly tanks and roadsters.  We have not seen cars run or been to an SCTA meet.  Hopefully a club will accept us.  Then we can race, too.  There is a lot of history at Elmo and we can meet people on this forum that we would not see at BUB.  We will be down south in 2012.     

[Dakzila]

Sounds like a good philosophy to me, and I can't say I haven't thought about the same thing many times.
I might try to make the BUB meet this year, we'll see how the finances work out.

Not sure how much experience you have with exhaust systems but if you're looking for information there's an old book that will help.

The Scientific Design of Intake and Exhaust is a book written in the 1920s or 30s but is still very relevant today. You can get a copy out of the library or I believe that Amazon now carries it.

I don't think you would have a problem getting into a SCTA club. I'm a member of the Sidewinders and we have many out of State members.

Look forward to seeing you at Bub this year.

Buzz

[wobblywalrus]

Buzz, Jason's crash was the first high speed get off I saw on video.  The thing that made the biggest impression on me was the Jason's and the bike's behavior.  Both were cartwheeling and the bike was breaking apart.  Something was happening there.  Their behavior seemed out of proportion to their speed.  I did some physics calculations.  The results are something I do not want to post, but it may help someone make a decision.  It sure influenced me.

A moving person has translational kinetic energy expressed as (mass x velocity squared) / 2.  The same person at rest has a kinetic energy of zero.  They are not moving.  When you crash and your bod skids across the salt it transfers your kinetic energy to the salt as external heat and friction, and internal friction as your insides move around and bones break.  In lay terms, the faster you go when you hit the deck, the more it hurts.

That's not the full story.  The hurt is not directly proportional to the speed.  Twice as fast does not mean double the pain.  Kinetic energy is proportional to velocity squared.  200 mph is 1.3 times faster than 150 mph, the kinetic energy is 1.8 times greater.  250 mph is 1.7 times faster than 150, and the kinetic energy is 2.8 times greater.  Open bikes are running this speed now.  300 mph has 4 times the kinetic energy of 150 mph.  Someone on an open bike will be there in a few years.   A 150 mph crash is gonna hurt.  Running for 1000cc records against Japanese fours will put me at speeds that will double the damage.  One mistake and I will be a dead duck.

On a lighter note, I will find the book.  Thanks for telling me about it.

   

[Dakzila]

Interesting summary and kinda sheds some light on the "physics" aspect of crashing at speed.  I've been very fortunate in all my years of riding/racing I've only had a couple of what you'd call "bad" accidents. Both of the crashes were in the dirt while racing off road desert events. My speeds were at, or about, 70 MPH and I can tell you first hand that going down at that speed, in the dirt, is no fun! Both crashes were my fault for not paying attention or believing I could get away with a little more speed in very rough terrain. I wonder how translational kinetic energy is expressed when you throw a cactus into the equation?

My goal in running LSR, right now, is to shoot for the 1000cc A/G El Mirage record. So I'll be trying to get about 175 out of the Kawasaki. I can only hope that I've matured a little since my last "get off" and will use my head more than I use the right wrist if I get into trouble...

I haven't had the opportunity to view the video you're talking about so I'll have to try and look it up on U-tube.

Right now it's just positive thoughts and working on the bike.......looking forward to a full season of racing at ELMO and maybe getting to Bonneville and or Bub this year.

Buzz

[Grandpa Jones]

Hi all,

The Jason McVicar crash video should be required viewing for anyone contemplating throwing a leg over
a motorcycle. If I recall correctly, Mr. McVicar was "armored up". That is, full roadrace-style shoulder,
arm, knee, and shin armor, and maybe most importantly a back protector.

A new custom suit with all the bells and whistles ain't cheap, but money well spent to help stack the deck
in your favor.

Cheers,

Dave

[Jasontmc]

Hello Dave,

The only thing between me and the salt when I came off was a custom made NJK one piece leathers.

I have been a long time supporter of one piece leathers. I feel the zipper on the two piece suits is a weak link. A good tumble and the zipper breaks you can imagine the rest....

I ordered the suit without any padding or armor. As back protectors were not mandatory I choose not to wear one (I have 3 at home)

The suit was in serviceable condition after the crash. All the seams were intact and the leather was only lightly abraded on the knees and elbows. Unfortunately the medics cut the suit into a million pieces.

One week after the crash NJK sent me a new set of leathers with full armor (Thanks Kelsey!)

I agree with you Dave there are places to save money but safety gear is not one of them. Buy the best one piece leathers you can afford , the lightest approved helmet and it pays to have friends in high places!!

I have been frequently asked how I walked/limped away from the crash.

The answer is that as soon as I came off the bike I pulled my arms into my body and tucked my head into my chest. Putting your hands out is the natural reaction and a compound fracture or two awaits you. In the video you can see my legs flailing like a pair of chop sticks at a chinese restaurant. Look closely and you wont see my arms. My knees were the only hard parts that were damaged.


Dak, the bike looks great congrats on getting her dirty!

[Dakzila]

Thanks Jason.

Glad your doing well and on-line giving out some good advise.  I've always worn two piece leathers because I race mostly in Vegas.  During the summer month it's nice to be able to get the jacket off while you're waiting in the staging lanes.  I'll rethink my logic now and consider a one piece suit for landracing.  Sacrificing a little comfort is a fair trade for better protection.

Thanks again,
Buzz

[Seldom Seen Slim]

This point, Jason, brings a concern to my mind.  Nancy and I both wear two-piece leathers made by Z Custom.  The zipper is metal and goes 350 degrees around us.  The zipper is fastened to a (relatively) sturdy material, not just the lightweight liner of the jacket.  Do you believe that even such good construction is still a safety hazard -- or were you mostly referring to a common inexpensive two-piece suit wherein the zipper might be plastic, or only at the sides and rear, or whatever?  Your input is (unfortunately for you) well-tested and regarded and I'm sure other racers will give serious thoughts about upgrading pending your comments.  I might ask Z Custom if they'd be able to suture the two pieces of our suits into one -- with a heavy-enough material that separation during an incident would be much less likely.   

Thanks in advance.

[Jasontmc]

Not to hijack the thread more than I have already...
 
I think by wearing a one piece suit you are eliminating one of the variables that may seriously injure you.

The question is: Do you think when tumbling down the salt or pavement do you feel comfortable trusting a zipper(possibly off shore made) to hold together and keep the jacket from rolling up your back?

What are the advantages to a two piece suit?

Ease of entry, convenience, cost, ability to wear just the jacket for street rides, you already own one.

Know-body buys a 2 piece suit because it is safer than a one piece just more convenient.

Noonans jacket zipper came undone from the wind (Think michelin man) at Bubs. If wind can undo a zipper what can a good crash do?
You won't see 2 piece leathers in Moto GP and they are going slower than most of us.  Makes you think....

[fredvance]

I am all for one piece leathers. It seems like one of the main objections is the heat. Think white or light colors. Mine are white, at the last two Speedweeks, my first as a competitor, I never got hot. At World Finals I put them on at the hotel and wore them all day or until I was finished running.

  Fred

[Grandpa Jones]

Jason, thanks for clarifying that. I seem to "mis-remember" more things as the years go by... 

Best wishes,

Dave

[wobblywalrus]

Slim, this build diary is for Buzz to talk about his bike.  The video and crash physics post is mine and it takes attention away from the build diary.  You can move the crash physics and related stuff to a new topic.  I certainly will not object.

Buzz, it will be great to see you at BUB.  You will love it.  There is a lot of room and its a real thrill to ride flat out for a long way without slowing down.

[Jonny Hotnuts]

A friend of mine who raced GP on the Suzuki factory team said "when you fall on a motorcycle, you are only falling 3' to the ground, and a 3' fall never kills anyone". (he was saying this in partial jest)

He told me that he would rather fall at 150+mph on a track (and he had multiple times) then 35 mph on the street (where you would almost surely die).

It is true that the higher the speed the higher probability that you will get hurt based on potential energy alone...but the energy and friction are applied gradually on the salt (as apposed to hitting a stationary object) so ideally a person would skip along until they stop....and hopefully the MC wont land on you and catch on fire! The injuries sustained from violent G forces in a tumbling crash in an enclosed MC or other vehicle are the the worst.

The Ack crash on youtube is a prime example of a "good crash" where the vehicle glides gently on its side until it comes to rest, and IMO a very solid reason not to have hard angles on any exterior surface (flat bottom or other) or other elements under the body that could catch the salt in a crash and cause the vehicle to tumble.

http://www.youtube.com/watch?v=YkZjrmX3fzQ

BTW:
Rider walked away from this 300mph crash.

~JH
  

[panic]

The zipper question is important. If the amount of force required to separate the halves is lower than the tensile strength of the adjacent material, they shouldn't be legal... if they're the only point of attachment.
A simple tether (or 2) anchored to each half and joined like a helmet strap will prevent this.

The "impact = 32 f/s/s × height" argument (viz. speed is irrelevant) is closer to being applicable in LSR than anywhere else since the chance of striking a foreign object (2nd vehicle, guard rail) is very small. However, a Silver Cup crash video will show that when the smooth continuous slide to a stop is interrupted by any minor event (elbow, handlebar touching down first) the forward movement is instantly converted to tumble and the energy is separated into 2 vectors: (reduced) forward speed and spin.
The spin will tend to act first by using the point of contact (and higher traction) as a lever (with mechanical advantage) to rotate the body around it's center of mass. This will cause the limbs to flail, knees and elbows to hyperextend, and other very bad things. As the body rotates, each subsequent point of contact initiates a new spin with a different point of leverage. If the speed is high enough, just the centrifugal force will push the brain up into the skull.

[RansomT]

This point, Jason, brings a concern to my mind.  Nancy and I both wear two-piece leathers made by Z Custom.  The zipper is metal and goes 350 degrees around us.  The zipper is fastened to a (relatively) sturdy material, not just the lightweight liner of the jacket.  Do you believe that even such good construction is still a safety hazard -- or were you mostly referring to a common inexpensive two-piece suit wherein the zipper might be plastic, or only at the sides and rear, or whatever?  Your input is (unfortunately for you) well-tested and regarded and I'm sure other racers will give serious thoughts about upgrading pending your comments.  I might ask Z Custom if they'd be able to suture the two pieces of our suits into one -- with a heavy-enough material that separation during an incident would be much less likely.   

Thanks in advance.

But Jon aren't we talking about "fast" motorcycles?   


Seriously, I'm all about the 1 piece suits .....