verslagen1 wrote on 08/10/11 at 09:58:16:




You see that? Huhh? You SEEE that? Thats how I qualify that statement! & Im Danged glad someone else did it, cuz I wasnt gonna waste my time..

OHH,, & dont read that 1st sentence like Im really being mean,, Im just goofin off..


OHH,, & Thanks Versy.

I think I read somewhere, on the snell site, maybe on the dot site, that helmets must be able to sustain a drop of 3 maybe 5 feet onto concrete without the helmet losing any ability to protect the wearer.

I was once a student of physics. Or, rather, I went to physics class a lot when I was in college. Actually, I was a physics major, transfered to another university, changed from nuclear to antenna, lost interest after my junior year, became an acountant, now I am a welder, I love it when the architect or engineer comes out and starts throwing math my way,, I can send most of them crawling back to their office.

Anyway, at 1.5 feet and say maybe 2 or 3 pounds,,,thats about 4.5 ftlbs of energy. When the helmet hits the ground it has about 4.5 ftlbs of energy it needs to dissapate. I don't know, as I am not associated with any helmet testing organization, how long it takes the helmet to come to a stop from the time of ground contact until the energy is dissapated.

On a low energy impact, let us assume, that the impact time is about .001 seconds.

4.5 ftlbs/.001 = 4500 ftlbs/sec

That is a pretty big number, might be a tenth of a second, about 450 ftlbs/sec, still a pretty big number. About a horse power, ,,,

The foam in a helmet is not protecting by compression, it protects by absorbing the energy of the impact itself.

A shock wave of energy, a fairly high energy wave, has been generated by the impact.
The foam has elastic bonds, the shock wave breaks these bonds, dissipating the energy within the helmet, before the energy can be transmitted to your skull.

High energy impacts will destroy the foam, the helmet is designed to do this one time.

Check with the company that rated your helmet for the answer to your question.  

Yea, I wear a helmet, always,, the energy levels from head to concrete impacts is on the order of several magnitudes larger than a 1.5 foot drop, and helmets are designed to absorb a tremendous amount of this energy.

Compressing the foam = allowing the foam to absorb the impact, like crumple zones on a car.

Johansson wrote on 08/11/11 at 03:11:30:


All this talk of "the head"....  kinda' makes me uncomfortable... ...

Myself, I wouldn't replace it.
From that distance, a little
drop is nothing like slamming your head
down on the pavement.  Now if you
were riding and went down, hitting your
the helmet (head) against the pavement,
then yes I would. In fact I did..
I slammed so hard my shielf flew off. Helmet
was replaced before I ever rode the bike again.
I never had any doubts about replacing it.
Then again, your helmet, your choice to whether
you replace it or not..
You need to feel comfortable that your helmet is
going to do the job, if it is ever needed to do.
Hopefully that never happens to you. kim

mine fell off the handle bars, onto the black top, bounced, and then rolled 3 times.. should i get a new one?? Fulmer D5