Stupid helmet question

"J.A.M." wrote in message
...
Nope. Instant acceleration and deccelerations occur, and then the time
tends
to zero and the forces tends to infinite. It's called percussion in
physics.
Classic example are the snooker balls. Also hitting a golf ball. No time
between the club hits the ball and it goes flying.

If you watch a slow motion image you'll find there is in fact a delay and
elastic deformation, small to be sure, occurs in both ball and cue/club.
Trick shots rely on this interaction, for example if you want to jump
the cue ball over another you strike down onto the top surface of the
ball, its the elastic rebound that makes it jump.


By definition the percussion is a sharp impact, where time is zero and
force
infinite.

Thats a simplification, to be true in real life this would require materials
that were completely inelastic. These do not exist.

Keith



----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Ok. That's right. Evidently that's a theoric approach to a real life
evolution.
My point was that while the forces are not infinite, they are very high
indeed.
Not very relevant to the discussion, though. English is not my craddle
language, so sometimes I have problems getting across...

Anyway, back to the topic, helmets (HGU-series) are not impact resistant,
just save your head from ocassional bumps, while manoevering, preflighting,
etc... and as stated before, provide a secure place to hang mics, oxigen
masks, NVG's, earphones, noise attenuation... etc...
And they look cool with the visor down. That must count for something.
Anyway they weigh a ton when pulling G's.

"Keith W" escribió en el mensaje
...

"J.A.M." wrote in message
...
Nope. Instant acceleration and deccelerations occur, and then the time
tends
to zero and the forces tends to infinite. It's called percussion in
physics.
Classic example are the snooker balls. Also hitting a golf ball. No time
between the club hits the ball and it goes flying.

If you watch a slow motion image you'll find there is in fact a delay and
elastic deformation, small to be sure, occurs in both ball and cue/club.
Trick shots rely on this interaction, for example if you want to jump
the cue ball over another you strike down onto the top surface of the
ball, its the elastic rebound that makes it jump.


By definition the percussion is a sharp impact, where time is zero and
force
infinite.

Thats a simplification, to be true in real life this would require
materials
that were completely inelastic. These do not exist.

Keith



----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet
News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption
=----

Greasy Rider© @invalid.com wrote:
I was browsing a newsgroup just now and saw a gentleman flying a P-51
Mustang with what appears to be just a common ball cap. I got to
wondering if he is that secure in his abilities and crash worthiness
of the air frame to simply wear a ball cap?

As a motorcyclist I feel very strange if I'm not wearing the very best
helmet that I can afford. Why would a pilot operate a high performance
aircraft with anything less?

I know that a high dollar helmet and other protective gear has no
guarantees whether it's a car, motorcycle, pony or aircraft.

Am I missing something? Is the pilot simply exercising his freedom to
take his chances? (The law won't let me do that in some states.)

In high performance aircraft, like the P-51, the thing on your head is
just something to hold the earphones and mic. An O2 mask if ya need that.

The high dollar helmet that I wore would protect in case of an ejection
but in the case of a crash, the helmet will just make it easier to
recover your head...it'll look better in the coffin.

Greasy Rider© @invalid.com wrote:
On Tue, 05 Apr 2005 14:14:08 -0400, Ragnar
postulated :


Top speed of a P-51 is over 400 mph. Exactly which helmet is going to
help him in a crash?


So... all crashes occur at top speed?


A crash and roll when landing would still be 150 mph or so...in a
cockpit not designed to protect in a crash with roll cages and such. A
helmet helps when you bang your head on preflight, again, a place to
mount the headphones, mic/O2 mask, little else. Also something that is
reflective when you are in the H2O for the helo...place to attach the
strobe. No protection in a crash.

"J.A.M." wrote: .

Anyway, back to the topic, helmets (HGU-series) are not impact resistant,
just save your head from ocassional bumps, while manoevering, preflighting,
etc... and as stated before, provide a secure place to hang mics, oxigen
masks, NVG's, earphones, noise attenuation... etc...
And they look cool with the visor down. That must count for something.
Anyway they weigh a ton when pulling G's.

Dunno about G's but they certainly weigh a ton after a 28 hour
flight.
--

-Gord.
(use gordon in email)

"Dave Kearton" wrote:


"Gord Beaman" wrote in message

| "Dave Kearton" wrote:
|
|| "old hoodoo" wrote in message
|| news:NfF4e.33$fn5.19@okepread01
|
||| Oopps, didn't put a smiley face after "pussy". Someone is going to
||| get their feelings hurt so here it is. :-)
||
||
||
|| A smiley face after pussy is assumed.
|
| Of course...some just smile, others smile AND smoke...
| --
|
| -Gord.
| (use gordon in email)




Gord, you've got to slow down ......

I know! I know!, my wife keeps saying that too (thank God)
--

-Gord.
(use gordon in email)

Pilots in my day, 50s to 90s, wore helmets because they were required
safety items. Had they not been required most jet fighter pilots would
have opted for a ball cap. Why? you might ask. The standard helmet
issued to Vietnam era fighter pilots weighed around 5 pounds. Pull max
G's and you got several things due to the helmet. One, your O2 mask
went down below your chin making it hard to talk to anybody. Two your
head was pulled into your lap and forget about twisting around to clear
your six. Why were these helmets so heavy? because we (USN) had a
helmet spec that required it to survive 40G's and resisit a 2 pound
spike dropped from ten feet above. No pilots had a voice in creating
these specs. Guess who did? Right, the helmet manufacturers.
Pre-Vietnam we wore Orange flight suits. Better to find your body
after a crash. One good thing the Vietnam war did for us was send all
these "Safety" pukes scurrying under their desks and for the most part
out of our hair. We wore really hot, sweaty, stinky Nomex flight
suits. Why? fire proof of course. I never heard of a cockpit fire in
a jet airplane but I'm sure there were some somewhere.

I don't own a P-51 but if I did I assure you I would not wear a nomex
flight suit or some damn over-speced helmet. If safety was really
paramount (the often chanted parable) I'd stay the hell out of a P-51
or anything which got me so far above ground thqt a fall might hurt. A
motorcycle? Forget that! More dangerous than smoking three packs a
day in a gasoline refinery. I'm for choice. You want a helmet, be my
guest. Just don't tell me I must also.

"Bob" wrote:
I'm for choice. You want a helmet, be my
guest. Just don't tell me I must also.

Then give up social health-care rights. Pay high premiums.

"Ed Rasimus" wrote in message
...
On Tue, 05 Apr 2005 16:36:18 GMT, Greasy Rider© @invalid.com wrote:

snip

But, they do make you feel cool when you put it on and drop the
visor--at least until the hot spots start showing up forty-five
minutes into a ten hour ocean crossing.


Ed Rasimus

On my first ride taxiing out in a Tweet in UPT, I noticed the mirror and
casually moved it inboard (to not draw attention to the fact that I wasn't
paying attention to the droning from the right seat) and moved my head
outboard. I swear, it was the coolest looking reflection I had ever seen of
myself. I laughed at myself later in my Q when I thought back that the most
exciting thing I did that day was not the flight, (even though that was very
exciting) but the image of myself in a helmet, dark visor down and oxygen
mask up. Later, I got to hate wearing that huge, heavy white helmet. It
was a real blessing when the lighterweight, fitted ones came along.

Jim Baker

Greasy wrote:

On Tue, 05 Apr 2005 18:32:09 -0500, old hoodoo
postulated :


Some pilots and motorcycle jock's I know utterly lack imagination and
have no conception of getting hurt. It may be due in part to extreme
self-confidence and perhaps a little ego boost at not being a pussy.


Been riding since the early 50s and by the grace of God only had one
serious rag doll. I'd have to disagree with the "utterly lack
imagination and have no conception of getting hurt" part in my case.
As I cruise down the concrete ribbon I am more than aware of the
delicacy and insanity of my position. Just inches from some very hard
and abrasive substance not to mention the brain dead cagers talking on
their cell phones. I’ve never talked to a motorcyclist who didn’t know
he was skating on the edge of survival and most will tell you that in
almost any event the motorcyclist will have his life forever changed.
The freedom that removing the state mandated helmet and simply
enjoying the breeze is almost intoxicating. Kinda like cruising in an
open helocopter two feet AGL.

Don’t think I’ve ever considered the ego aspect of not being a pussy
but I hear that you are what you eat.


Greasy

The great thing about P---- is that unlike cake, you can eat it and have
it too.