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?

>
> >
> > Where does the energy go that represents decelerating a 220 pound
> > person from   terminal velocity to zero?  Hmmm.  100Kg x 50m/sec
> > = 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
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)?

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.
>
> > 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?
>
> > >
> > > 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?
>
>
> >
> > 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
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?
> >
> >
> > 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?   ;-)

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


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.

Mark Borgerson



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