Mark Borgerson wrote:
> In article ,
> drawnai{at}hotmail.com says...
> >
> > Mark Borgerson wrote:
> > > In article
,
> > > drawnai{at}hotmail.com says...
> > > > I'd give it away for free, just to save lives.
> > > >
> > > > In fact they already exist. Stuntmen use them for falling off
high
> > > > buildings.
> > > >
> > > Yes, but stunt men get training and have the balls to jump off
> > > a high building.   People in a burning building certainly have
> > > incentive, but do they have training and enough courage to
> > > use the device without panicking?
> >
> > Are you telling me, that having watched the World Trade Centre live
on
> > TV, and stuck in the same situation, you wouldn't jump off?
>
> No   I would probably have died in one of the stairwells that
> didn't survive the impact.
> >
> > > > In the world trade centre bombing, practically everyone on the
> > upper
> > > > floors would have got out, had their been a cable harness,
> > consisting
> > > > of several hundred feet of free fall and 200 feet (the last bit
> > > > obviously) of governed decelleration.
> > >
> > > How would they have fared (and how would the cables do) going
past
> > > the burning floors?
> >
> > This is why there's not much speed restriction until the bottom.
>
> But how long does the cable have to hang in the flames coming
> out of the windows?

The cable doesn't actually hang in the flames until the guy stops
descending, the crucial factor is how hot flames have to be, to burn
through three eighths thick, nomex coated steel cable, in less than a
second of exposure.


>
> >
> > >
> > > Where does the energy go that represents decelerating a 220 pound
> > > person from   terminal velocity to zero?  Hmmm.  100Kg x 50m/sec
> > > =3D 5000Kg M/sec or  about 5000Watts (did I get the right
conversion
> > > factor).  Does that energy go into the cable, or into heating
> >
> > The cable will no doubt stretch, but a real of sufficient strength
> > can be easily engineered.
>
> If the cable stretches--you get a bungie-jumper effect at the bottom

No you don't because the reel allows free release below a
certain speed.

> That means that your deceleration profile has to be different for
> cables from the 80th floor and those from the 15th floor.  How
> does your system decide when to start the deceleration?  Is
> there a trigger on the cable, or does it do it by time or
> barometric altitude (which varies at the rate of about 8meters
> altitude per millibar of pressure change)?

Yes. The deceleration profile is different. The length of cable on
the reel is adjusted to reach the ground. As the reel becomes more
empty, the diameter of the remaining cable on the reel decreases.
The length of time taken to reach the bottom / the height is
definitely not linear, but it all works, Mr Hope, my primary school
teacher taught me the maths to cope with this. I can assure you it's
only first year secondary school mathematics.

>
> If the decision is made at the cable braking box, that implies a
> different length of cable and/or braking system for each floor of the

> building.  What impact does that have on production costs?
>
> Of course you have to have twice as much cable on the 80th floor
> as on the 40th floor.  That means you use up more storage space
> on the upper floors.,

But it's on a reel, the space of a three eighth cable is , while not
negligible, at least statistically insignificant.


> >
> > > the device worn by the jumper?  either way that's a lot of
> > > heat to dissipate?
> >
> > Yes. The, governor, with it's centrifugal governor, and carbon
fibre
> > clutch is completely fucked once it it used, but that's ok, since
the
> > building's just about to fall down and destroy it anyway.
>
> >
> > >
> > > Who takes the people off the cable that faint on the way down?
> >
> > The 99% of people who don't faint?
>
> What statistics do you have on the number of people who faint?

How many people have you ever heard of, passing out on a bungy jump?

> >
> > > >
> > > > In fact, a government could be considered criminally negligent
for
> > not
> > > > requiring these things to be installed in very building over a
> > hundred
> > > > feet high.
> > > >
> > > > Compared to the cost of the insurance, at 50 dollars a head for
> > 5000
> > > > people? That's 250,000 dollars. Just one guy in World trade
centre
> > 2,
> > > > cost Lloyds 25 million.
> > > >
> > > > There would have been literally no casualties on the non-hit
> > floors.
> > >
> > > Have you ever seen such a rig used from 90 floors up--on a windy
day?
> > > How much does the cable weigh and how many cables do you need?
One
> >
> > It's a once only device. Like a bunjy jump that doesn't rebound.
You
> > don the harness, and clip it onto the cable, then smash the window
and
> > jump out. It's a one way trip. The cable allows a maximum speed of
say
> > 30 metres per second until 100 metres from the ground, and then
> > decelerates at the last moment, to something like 1 metre per
second,
> > by ground level.
> >
> > This way, anyone falling through the flames wouldn't be exposed to
them
> > for more than a second.
> >
> > > per floor?  One per 5 floors?   How do you keep the cables (and
> > people)
> >
> > One per person.
> >
> > > from higher floors from colliding and tangling with people on
lower
> > > floors?
> >
> > You don't need to. Everyone's going downwards.
>
> How do you get all the people out of a few exit points---or even a
few
> dozen per floor.  What happens when a falling person runs into
another
> cable on the way down?

They get hurt, but since the person below is also falling,
the forces are minimised. The effects are much less on the human
skeleton, than actually were measured on the people in the stairwell of
World trade centre's one or two, (or even the one guy in world trade
centre 7.)

> >
> >
> > >
> > > Have you actually tested this idea with a drop of more than 300
feet?
> > > With more than 10 people using the same cable?
> > >
> > > Do you have more than one person on the cable at a time?
> >
> > No. Check out the breaking strain for plastic coated steel cable.
> >
>
> If  you have one cable and brake per person on a floor (say 200
systems)
> how much storage space do they require.  Do you need 200 mounting
> points and exit windows?  Can you only use the exit points on the

No. You need 200 reels. You could run a hundred reels across a window
area.

> downwind side so that the people don't collide with the
> building on the way down?    How does it work if the
> building face is not a completely smooth surface?

A few people will have bruises as mentioned.

> > >
> > >
> > > I think the biggest problem would be getting anyone to
manufacture
> > > the system given the potential liabilities involved.   Heck, the
> > > cost of liability insurance represents about 20% of the cost of
> > > a simple step ladder?   What would the proportion be for this
device?
> > >
> >
> > The insurers of the building would pay for the loss. I'm a
scientist, I
> > advocate murder of anyone found guilty of murder, this would reduce
the
> > net loss of innocent life, factoring in recidivism alone. The same
is
> > true here. 3000 people wire jump out of the world trade centre,
this
> > results in 2000 people bruised, 900 with sprains, 90 with broken
> > legs/arms, 5 crippled, 5 dead. This is a whole lot better than 3000
> > dead.
> >
> > > Sounds like an interesting idea---if you have the engineering
worked
> > > out properly.
> >
> > Yes. I have. A once only device is child's play to make.
>
> So how many have you made?  Or have you not bothered since you
> aren't a playing child?   ;-)

I proved the concept with mechano and a rubber band, in a winch effect
from our loft in the house I helped my dad restore, when I was 14, 25
years ago. I didn't have a governor, so used a resistor/battery effect
against a motor in the style of a telma braking system as seen on
buses.


> Your proposition sounds like one originated by a scientist.  Now
> you need to carefully consider why an engineer might not think

Yes, I love that joke. "First we assume the chicken is perfectly
symmetrical."

> it practical unless you have extensive test data to support
> your conclusions.   When you've accumulated statistics from
> a few hundred trials,  then you can talk to a lawyer about the
> legal consequences of installing the device in a public area.

I'm an ideas hampster. Some fucker else can make the money.

>
>
> You implied earlier that you could build these systems
> for 50 dollars per person.   I doubt that you can
> buy 1300 feet of cable, a clutch and harness for that
> price.   A 1000 feet of cable alone might cost over
> a hundred dollars.   A parachute-type harness---even
> for a single use, is going to cost at least 30 or
> 40 bucks.
>
> I think you're underestimating the cost per unit
> (without installation and annual safety checks)
> by at at least a factor of 10.

Lloyds could have kitted out the entire world trade centre, for less
money than was paid for a single investment banker's insurance.

Even assuming bulk purchase and construction can't gain me a third of
the price I'd pay in B&Q.

5000 people * =A3150 =3D=3D =A3750,000

The cost of the world trade centre's glass was?

>=20
> Mark Borgerson



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