Crash-pro needs for hispeed HPVs?

Jeff Potter said:

Can someone help me do some physics here?

Quoted message said:

I suspect the carnage we've grown used to hearing
about with car wrecks HUGELY relates to the heaviness
of the cars.

The 'simplest' view of this that I know of gives:

Kinetic Energy = 0.5mv^2

(units SI) Joules, metres/sec, kg

Without taking anything else into account, that shows a
direct proportional relationship between kinetic energy and
mass, but velocity^2 is the big factor.

L
🙂
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Counter No. 275325 *Remove Spamcatcher and x for email reply

"Jeff Potter" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Can someone help me do some physics here?

When a car crashes at 30mph there's a certain amount of
impact that the people inside have to be protected from.

Can we compare that to the forces that have to be overcome
when an HPV crashes?

A car and passenger weighs, what, 2000 pounds?

An elite HPV and rider might weigh only 200 pounds.

I had been thinking that a 30-pound titanium HPV, full-
fair, that can average 30-40mph would offer a stuntman's
danger level if ridden frequently on open roads. But maybe
that's not so. Sure, there's crush worry, but if an HPV
was made of strong reinforced lightweight metal and carbon
it might stand up to LOTS of impact damage or
strategically crush. A rider could wear a seatbelt.

Anyway, how do the common forces generated by crashing 2000-
lb cars compare to 200-lb HPVs?

I suspect the carnage we've grown used to hearing
about with car wrecks HUGELY relates to the heaviness
of the cars.

Maybe bike impact energy at similar speed is HUGELY less.
And so perhaps the modest protection offered by a fairing
might be sufficient for significant safety.

--

Jeff Potter

Jeff,

One of the too-many variables in your question is what it is
you run into. For example, if you run into a ground-hog,
(gofer) while doing 30 MPH in your automobile you will
hardly notice the impact. If you hit one while doing 30 MPH
on a mountain bike you may end up in the emergency room of
the local hospital.

Not physics, just experience....

Jack

PS...It is not as bad as hitting a large dog while going 80
MPH on a motorcycle.

Quoted post said:

Originally posted by Jack Davis
"Jeff Potter" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Can someone help me do some physics here?

When a car crashes at 30mph there's a certain amount of
impact that the people inside have to be protected from.

Can we compare that to the forces that have to be overcome
when an HPV crashes?

A car and passenger weighs, what, 2000 pounds?

An elite HPV and rider might weigh only 200 pounds.

I had been thinking that a 30-pound titanium HPV, full-
fair, that can average 30-40mph would offer a stuntman's
danger level if ridden frequently on open roads. But maybe
that's not so. Sure, there's crush worry, but if an HPV
was made of strong reinforced lightweight metal and carbon
it might stand up to LOTS of impact damage or
strategically crush. A rider could wear a seatbelt.

Anyway, how do the common forces generated by crashing 2000-
lb cars compare to 200-lb HPVs?

I suspect the carnage we've grown used to hearing
about with car wrecks HUGELY relates to the heaviness
of the cars.

Maybe bike impact energy at similar speed is HUGELY less.
And so perhaps the modest protection offered by a fairing
might be sufficient for significant safety.

--

Jeff Potter

Jeff,

One of the too-many variables in your question is what it is
you run into. For example, if you run into a ground-hog,
(gofer) while doing 30 MPH in your automobile you will
hardly notice the impact. If you hit one while doing 30 MPH
on a mountain bike you may end up in the emergency room of
the local hospital.

Not physics, just experience....

Jack

PS...It is not as bad as hitting a large dog while going 80
MPH on a motorcycle.

I think the physics would corroborate your experiences.

Maybe Fe b2 is a good day to stay off bikes.

Jeff Potter said:

Can someone help me do some physics here?

When a car crashes at 30mph there's a certain amount of
impact that the people inside have to be protected from.

Can we compare that to the forces that have to be overcome
when an HPV crashes?

A car and passenger weighs, what, 2000 pounds?

An elite HPV and rider might weigh only 200 pounds.

I had been thinking that a 30-pound titanium HPV, full-
fair, that can average 30-40mph would offer a stuntman's
danger level if ridden frequently on open roads. But maybe
that's not so. Sure, there's crush worry, but if an HPV
was made of strong reinforced lightweight metal and carbon
it might stand up to LOTS of impact damage or
strategically crush. A rider could wear a seatbelt.

Anyway, how do the common forces generated by crashing 2000-
lb cars compare to 200-lb HPVs?

I suspect the carnage we've grown used to hearing
about with car wrecks HUGELY relates to the heaviness
of the cars.

Maybe bike impact energy at similar speed is HUGELY less.
And so perhaps the modest protection offered by a fairing
might be sufficient for significant safety.

The force imparted to the rider will depend on the rate of
deceleration; therefore what we want is the maximum length
of "crush space" possible. In addition, the sacrificial
structure should deform at a rate below the serious injury
threshold. To rapid deformation will not absorb sufficient
energy to protect the rider after deformation is complete,
while too slow deformation will transfer too much energy to
the rider.

Tom Sherman - Quad Cities (Illinois Side)

As a Flying Safety Officer, I'm pretty well read on what
hurts and kills people in crashes.

Mechanical trauma: Some object traumatizes your body, such
as a fender wounding you like a baseball bat. For example,
years ago, they gave cars have collapsible steering columns
and padded dashes, so you don't get impaled or bash your
brains out on the dash.

Excessive de/acceleration: Beyond 10 Gs (the equivalent of
zero to 33 feet per second in a tenth of a second. Depending
on what is being affected and how, 20-50 Gs will kill you.
Seatbelts function by holding you against the seat while the
car decelerates comparatively slowly. Without them, the car
stops while you fly forward and smack into a much slower or
even stationary dashboard. Airbags take this one step
further by keeping your head and neck from suffering impact
or high G forces.

I'll skip "car proofing" a bent due to obvious reasons.
Recumbents have lots going for them in a crash sequence. The
minor discomfort of landing feet first from a small drop
would kill you if you fell head first. The frame and fairing
of a bent (and to some extent your legs folding up) could
absorb even more impact.

If you are doing 33'/sec (22.5 MPH) at impact, and have
3.3' of fairing and frame to collapse (using simple linear
math) you stop in a tenth of a second and experience 10 Gs.
The trick is to have a uniform deceleration rate.
Restraining the rider is mandatory for this, and to avoid
groin spearing.

You could engineer the frame to telescope under impact
forces, and crush foam inside the frame. You could increase
the crush distance by building a long skinny nose made of
foam and composite. As to protecting from other impacts,
make the shell out of Kevlar for puncture/cut with a foam
liner. The liner should fit the rider very closely, with
just enough room for airflow.

Another not so serious option is external airbags like the
Mars rover. You would pop them upon realizing you are going
to eat it.

"Jeff Potter" <[email hidden]> wrote in
message "]news:[email hidden]...

Quoted message said:

Can someone help me do some physics here?

When a car crashes at 30mph there's a certain amount of
impact that the people inside have to be protected from.

Can we compare that to the forces that have to be overcome
when an HPV crashes?

A car and passenger weighs, what, 2000 pounds?

An elite HPV and rider might weigh only 200 pounds.

I had been thinking that a 30-pound titanium HPV, full-
fair, that can average 30-40mph would offer a stuntman's
danger level if ridden frequently on open roads. But maybe
that's not so. Sure, there's crush worry, but if an HPV
was made of strong reinforced lightweight metal and carbon
it might stand up to LOTS of impact damage or
strategically crush. A rider could wear a seatbelt.

Anyway, how do the common forces generated by crashing 2000-
lb cars compare to 200-lb HPVs?

I suspect the carnage we've grown used to hearing
about with car wrecks HUGELY relates to the heaviness
of the cars.

Maybe bike impact energy at similar speed is HUGELY less.
And so perhaps the modest protection offered by a fairing
might be sufficient for significant safety.

--

Jeff Potter
****
*Out Your Backdoor * outyourbackdoor.comoutyourbackdoor.comOpen ↗
publisher of do-it-yourself culture ... bikes, skis, boats
& more! ...

... offering Vordenberg's XC ski tales in "Momentum"!
... ... "The Recumbent Bicycle": the only book about
these bikes! ... ... Rudloe's "Potluck": true-life story
of workingclass smuggling! ...

... with radical novels coming up via
LiteraryRevolution.com! ... ... music! ... articles! ...
travel forums! ... WOW! 800-763-6923

All of this assumes you run head-on into a fixed object
without decelerating first, which is not a typical
crash scenario.

Consider the kinds of crashes you're likely to
have...they're a lot like motorcycle accidents.

The typical roadgoing motorcycle accident that is
survivable at all generally consists of falling a couple of
feet to the pavement and sliding to a stop. Often, when an
object is hit, it's after a lot of speed (and kinetic
energy) has been dissipated by the initial fall to the
ground and the ensuing slide.

Full roadgoing motorcycle safety gear consists of a helmet,
leather gloves, and a full suit. The best suits are made of
leather because it slides along the pavement easily and
doesn't wear through in a hurry. There also are very well
engineered suits made of multiple layers of ballistic nylon.
( aerostich.comaerostich.comOpen ↗ )

Motorcyclists have walked away from 70 mph crashes thanks to
this gear, provided they don't hit something like a bridge
abutment while they're still moving fast.

Tune in the Speed Channel and watch a motorcycle race (one
on a paved track, not motocross). You'll be amazed at what
that leather suit will let you walk away from.

What often happens to motorcyclists, however, is neck
injury. Makes sense...you're wearing a heavy helmet and your
head already weighs a lot, so your neck snaps. Of course,
without the helmet you'd split your skull open.... Race car
drivers wear thick foam collars to prevent whiplash injury.

This kind of safety gear is utterly impractical for cyclists
because you'd overheat so fast you wouldn't be able to ride
the bike. It's also heavy. So it's a moot point.

Regarding vehicle design...a 30-lb streamliner isn't going
to happen, especially if head-on-impact crashworthiness is
taken into account.

The lightest streamliner I know of is John Tetz's orange
foamshell, which weighs about 32-35 lbs total. The fairing
alone weighs seven lbs. (See the projects pages on the MARS
website at recumbents.commarsOpen ↗ ). It's actually
interesting from a crashworthiness standpoint and might
serve as a model for crashworthy designs.

The bike is carbon and the shell is Zote foam. He's crashed
foam fairings many times, and the foam actually does offer a
surprising degree of protection against road rash and the
impact of falling over...the same sort of thing that those
motorcycle suits are designed to protect against. I have his
first foam fairing in my garage. He crashed that one at 40
mph when his Sachs hub locked up. He came out of it only
bruised and the fairing is still serviceable. But it would
not have done much for him had he run head on into a
telephone pole at speed.

Andrew Douglas said:

Regarding vehicle design...a 30-lb streamliner isn't going
to happen, especially if head-on-impact crashworthiness is
taken into account.

I don't see why not. 7 lb hard shell fairings are possible -
the End-to-End Windcheetah one, for example, and 20 lb
bikes, while not commonplace, are possible. Only a matter of
time and/or money before someone combines the two.

--

Dave Larrington - legslarry.beerdrinkers.co.uklegslarry.beerdrinkers.co.ukOpen ↗
===========================================================
Editor - British Human Power Club Newsletter
bhpc.org.ukbhpc.org.ukOpen ↗
===========================================================

"Dave Larrington" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Andrew Douglas said:

Regarding vehicle design...a 30-lb streamliner isn't
going to happen, especially if head-on-impact
crashworthiness is taken into account.

I don't see why not. 7 lb hard shell fairings are possible
- the End-to-End Windcheetah one, for example, and 20 lb
bikes, while not commonplace, are possible. Only a matter
of time and/or money before someone combines the two.

"The one time World Record Holding Cheetah HPV, with a
sprint to 68.73 mph. The composite bike weighs 21lbs., the
fairing 8.5 lbs. The rider was Chris Huber, and the design
team (pictured behind the Cheetah, left to right): James
Osborn, Fevin Franz, and Jon Garbarino."

recumbents.commiscellaneous.htmOpen ↗

... although I wouldn't want to crash in it.

Jeff

Consider an all titanium bike/fairing. 30 lbs reasonable
maybe for this future bike. What would the forces be on a
rider in some bad kinds of collisions at 30mph? It seems
like a total vehicle weight of 200 lbs compared to 2000 of a
car would make a difference. It's different from motorcycle
wrecks because it's enclosed, can have a seatbelt. And a
motorcycle scenario also involves maybe 600 lbs crashing mass----
to mess with your legs, fall on you, etc.

I've slid out a few times in fullfaired HPVs---not even
a roadrash.

I'm thinking that maybe a robust HPV---especially hightech
with titanium, say---might readily handle many kinds of
crashes without hurting the rider. Of course there will be
exceptions, but still...

A ti HPV might be 3X as safe as my fiberglass model...which
is already offering me pretty darn good crash pro.

Comparing data might show better crash energies than with
any car or motorcycle at 30mph. ??

--

Jeff Potter
****
*Out Your Backdoor * outyourbackdoor.comoutyourbackdoor.comOpen ↗
publisher of do-it-yourself culture ... bikes, skis, boats & more! ...
... offering Vordenberg's XC ski tales in "Momentum"! ...
... "The Recumbent Bicycle": the only book about these bikes! ...
... Rudloe's "Potluck": true-life story of workingclass smuggling! ...
... with radical novels coming up via LiteraryRevolution.com! ...
... music! ... articles! ... travel forums! ... WOW! 800-763-6923

The Dupont Prize winning Gold Rush weighed 31 lbs, complete.
19 lb chassis, 12 lb faring. Steve Delaire of Rotator has
built a 29 lb Coyote, titanium frame, carbon shell.

Regarding crash worthiness. Consider this...

In all of HPV racing there has never been a fatality and
few, if any, serious injuries. There has certainly been no
lack of crashing so one must draw the conclusion that HPV's
protect their riders.

Gabriel DeVault Easy Racers

"Andrew Douglas" <[email hidden]> wrote in
message news:180320040743298525%aNO-
[email hidden]...

Quoted message said:

All of this assumes you run head-on into a fixed object
without decelerating first, which is not a typical crash
scenario.

Consider the kinds of crashes you're likely to
have...they're a lot like motorcycle accidents.

The typical roadgoing motorcycle accident that is
survivable at all generally consists of falling a couple
of feet to the pavement and sliding to a stop. Often, when
an object is hit, it's after a lot of speed (and kinetic
energy) has been dissipated by the initial fall to the
ground and the ensuing slide.

Full roadgoing motorcycle safety gear consists of a
helmet, leather gloves, and a full suit. The best suits
are made of leather because it slides along the pavement
easily and doesn't wear through in a hurry. There also are
very well engineered suits made of multiple layers of
ballistic nylon. ( aerostich.comaerostich.comOpen ↗ )

Motorcyclists have walked away from 70 mph crashes thanks
to this gear, provided they don't hit something like a
bridge abutment while they're still moving fast.

Tune in the Speed Channel and watch a motorcycle race (one
on a paved track, not motocross). You'll be amazed at what
that leather suit will let you walk away from.

What often happens to motorcyclists, however, is neck
injury. Makes sense...you're wearing a heavy helmet and
your head already weighs a lot, so your neck snaps. Of
course, without the helmet you'd split your skull open....
Race car drivers wear thick foam collars to prevent
whiplash injury.

This kind of safety gear is utterly impractical for
cyclists because you'd overheat so fast you wouldn't
be able to ride the bike. It's also heavy. So it's a
moot point.

Regarding vehicle design...a 30-lb streamliner isn't going
to happen, especially if head-on-impact crashworthiness is
taken into account.

The lightest streamliner I know of is John Tetz's orange
foamshell, which weighs about 32-35 lbs total. The fairing
alone weighs seven lbs. (See the projects pages on the
MARS website at recumbents.commarsOpen ↗ ). It's
actually interesting from a crashworthiness standpoint and
might serve as a model for crashworthy designs.

The bike is carbon and the shell is Zote foam. He's
crashed foam fairings many times, and the foam actually
does offer a surprising degree of protection against road
rash and the impact of falling over...the same sort of
thing that those motorcycle suits are designed to protect
against. I have his first foam fairing in my garage. He
crashed that one at 40 mph when his Sachs hub locked up.
He came out of it only bruised and the fairing is still
serviceable. But it would not have done much for him had
he run head on into a telephone pole at speed.

Quoted message said:

If you are doing 33'/sec (22.5 MPH) at impact, and have
3.3' of fairing and frame to collapse (using simple
linear math) you stop in a tenth of a second and
experience 10 Gs.

The problem with simple linear math here is that distance
while accelerating is not linear with respect to time;
instead, distance is the integral of velocity over time, so
that under uniform acceleration, you get

x = (a * t^2)/2, where x = distance, a = acceleration, t =
time

Substituting v = a * t, where v = velocity, you get

t = (2 * x)/v

Plugging in the numbers, you stop in two-tenths of a second,
with an acceleration of 165 ft/sec^2, which is about 5 G.