Unless it is terribly cold, I always run a small crack at low speeds. My helmet has a notch that is just a half inch of crack. At high speeds the vents pull air through. It is funny because I never thought about CO2, just that it is too freaking hot.
Just 18mph of wind is enough to cause permanent hearing damage. Windshields and helmets don't block enough of the air (the rider needs some air ventilation for defogging in cold weather and cooling in hot weather.)
If a helmet cracks, it's absorbed energy, cracking is simply how it's designed to dissipate that energy. Whether it cracks or not, it should be replaced when it absorbs energy from a fall.
You could switch to a ski helmet, those have removeable insulation pads. Otherwise a tight fitting thermal cap should do if you are huffing and puffing.
A helmet protects you by being crushed - it dissipates the kinetic energy of your head in the process. They’re not very strong in tension at all - a cracked helmet is a helmet that failed to do its job properly.
If it crushed first & then cracked then that’s different of course.
Yeah, in racing they have vests with tubes sewn into them and they circulate cooled water though them. They also have blowers that blow cooler cleaner air directly into the helmet, you can buy special helmets with the air intakes built right in.
They are definitively designed to crack as that's a core way for it to absorb the energy of the hit. Similar to how a car crumbles in an accident. Otherwise it's just transferring the kinetic energy straight to your head.
This is also why you should replace helmets after a fall and every few years since the material they are made of degrades with age.
Helmets? That's interesting; I tend to open the visor a bit when at a stop, it gets really warm in there really fast. I know you shouldn't try to take off a helmet in case of an accident, but is opening the visor at least okay?
1. Humans cannot always interact with their surroundings at 100% mental clarity. Stupid mistakes can and will be made even by the most careful and skilled person. Fool-proof or defensive design features are very well embraced by engineers and the results have been a resounding positive.
2. Some interventions are probably not as benign as people assume, and this could become a confounding factor when it comes to analysing the outcome. Some motorcycle helmets, for example, have been found to trap CO2 at concentrations known to have a negative cognitive effect.
Why not? Given every helmet I've seen in a significant crash was split somehow, my assumption is that splitting is an important part of the energy absorption.
I cracked two helmets hitting my head on iced slopes. Every time I was able to stand back up (although dizzy and with a headache) and bless my initiative to wear a helmet. As they say, your mileage may vary.
I once crashed head-first at 20 mph into hard asphalt. Point of impact was at my right frontal lobe. My helmet cracked. If I wasn't wearing one I'm sure it would have been my skull instead.
reply