On Sat, 18 Jan 2020 17:38:23 -0800 (PST), Sir Ridesalot
wrote:

The trick would be designing the release so that it stays attached
in an accident yet releases if the pressure on it stays beyond a
certain time.

That would probably be acceptable for a bicycle helmet. However, I
can imagine situations where a premature release would cause
additional injuries. For example, I was the first on scene at this
automobile accident:
http://www.learnbydestroying.com/jeffl/pics/drivel/slides/Accident-2013-05-10.html
Instead of backing out of the handicapped parking space, the driver
accidentally floored the accelerator, drove onto the roof of the
Nissan, and then fell off the roof onto it's side. The driver was
duly strapped into the car seat, but couldn't release the seat belt. I
arrived, climbed up onto the left car door and quickly determined that
it was best to leave the driver strapped into the car seat. If the
seat belt was suddenly or improperly released, the driver would have
fallen onto a pile of broken glass and some junk that was in the car.
So, we waited about 5 minutes for the fire department to arrive. They
threw some padding onto the glass, and slowly lowered the driver onto
the padding. If the seat belt had automatically released because it
had been under excess tension for too long, the driver would have been
shredded by the glass.

The same might happen with a bicycle helmet strap release. The child
could end up suspended off the ground by the helmet in playground
equipment. An unexpected and sudden release of the strap could cause
more harm than good. It's difficult to predict this one. My
guess(tm) is a rope pull release would be acceptable, but having the
strap release without warning would not work.

What bothers me is how the helmet strap could end up around the
child's neck and kill by asphyxiation. If the helmet were suspended
vertically (from the center of mass), the strap would remain under the
child's chin. That would cause some damage, but would not strangle
the child. However, if the helmet straps were loose, and the helmet
slid towards the back of the head, the child could conceivably be
strangled by straps. However, the helmet would be in a very odd and
unusual position. Try to visualize where a helmet and straps would
need to be positioned into order to wrap around the neck.

I have a friend who was pulled off his MTB whilst riding off-road,
when a branch snagged in one of his helmet vent holes. Fortunately,
other than being a bit stunned o=upon impact with the trail he was okay.

Buy your friend an aluminum wire screen to cover his helmet. That
should keep the branches out of the helmet holes.

I wonder how many injuries are caused by a helmet strap not releasing
when the helmet is snagged by something? I think it would be filed
under "freak accident".

I don't know. It might be a rather large number that appears to be
small because only the fatalities are reported. Or, it might be so
unusual as to be statistically insignificant. Either way, it's very
difficult to protect against any and all forms of real and potential
injury.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558