Originally Posted by
joejack951
I hope you are not proposing that the changes to or advancements in the manufacturing of helmets are in any way comparable to that of the advancements in computers/science. You listed three basic changes in helmet design: vents, rear thickness, and adjustable circumference head bands. As far as I can tell, improved airflow through a helmet has nothing to do with how well it protects. The thicker rear sections of bike helmets seem to be a controversial feature (note the lack of this rear thickness on motor cycle helmets). Not all bike helmets have adjustable circumference headbands, which while possibly acting to keep the helmet in place during a fall, are mostly a bonus to the helmet manufacturers as they can get away with fewer sizes (less tooling and manufacturing costs). I haven't looked at every children's bike helmet made but I have never seen one with an adjustable circumference headband, so if that feature did make a big difference in safety during a minor fall, the helmet manufacturers are missing what should be their main target.
Science and computer technology have made great leaps in the past 20 years. Look at the advancements in medicine for fighting cancer and aids. Look at hard drive capacity/size and processor speeds. There is no comparison to the minor changes made to helmet design (unless we consider cosmetics of major importance). It's almost laughable that you would try to apply the "old studies are invalid" attitude.
Joejack951,
Are you telling us that there has been little or no advancement in the science of foams since the late 1980s? Here is the helmet, the Skid Lid, that I was using in the 1980s:
http://www.helmets.org/history.htm
The Skid Lid is the second helmet down, the yellow one. My brother was still using his Skid Lid a year and a half ago, and I told him to throw it away and get a good bicycle helmet. It had about 10 mm of open cell foam neoprene "protecting" the rider. Here is an account of a person who was wearing one when he crashed:
http://www.helmets.org/crashmor.htm
Look at the story that was added on March 6, 2006.
I have found my wife's Bell V1-PRO hard-shelled helmet from that time period. Inside, it states that the helmet shell is made of "injection molded thermoplastic." The liner is "expanded polystyrene." The foam is 15 to 18 mm thirk, with the thinnest part on the sides. In the front, over the temple area, the foam is reduced to about 12 mm because this is where the strap must fit underneath the hard shell. The helmet is uniformely symetrical side to side, and end to end. It is thickest on the right and left front, at about 18 mm. And yes, it is tested to the Snell Standard. It has no adjustable headband, but the strap system is adjustable. Open cell foam is used to adjust for head fit. There are 8 vents in this helmet, all symetrical oblongs oriented in the direction of travel on the top of the helmet.
My wife now rides with a Giro Mojav '02 helmet. It is not symetrical front-to back, as the back extends down about 2-3 cm further than the Bell V1-PRO. It has an adjustible headband, the Giro Roc-Loc. Thte sides of the helmet are 18-20 mm thick, the front 28 mm thick, and the top and rear are about 30 mm thick. This helmet uses an expanded polystyrene (EPS) foam, which is also known as a "glassy foam." There is another foam in more expensive helmets called a expanded polypropylene (EPP), which my son uses in his helmets (he's a racer now). This helmet has 13 top vents, 2 side vents, and 4 rear vents. It has a more complex shape than the Bell V1-PRO, and a series of vertical foam supports that are 38 mm thick. The shell is a molded-in plastic shell.
All in all, her newer Giro Mojav '02 helmet is much more sophisticated, more comfortable, more secure, and looks to be a better head protection system than the older Bell V1-PRO. And, of course, my Skid Lid from the 1980s would not hold a candle to either of these helmets.
John