

Spider Silk Can Halt a Train - geeknik
http://news.discovery.com/animals/insects/spidey-silk-can-actually-halt-a-train-130225.htm#mkcpgn=rssnws1

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packetslave
Former vice president Gore spoke at Google a couple of weeks ago (promoting
his new book). One of the research projects he mentioned was "spider-goats",
goats that are genetically engineered to secrete spider silk along with their
milk.

Some details in a news article here:
[http://www.guardian.co.uk/science/2012/jan/14/synthetic-
biol...](http://www.guardian.co.uk/science/2012/jan/14/synthetic-biology-
spider-goat-genetics)

Given the value of the silk (and presumably the difficulty in mass-farming
spiders), this seems like an attractive idea -- as long as the scientists do
the math right and don't end up with spiders the size of goats or something.

~~~
smegel
Sounds like an unacceptable risk to me

~~~
eksith
Exact line used in criticism of vaccines, air-travel and in-vitro
fertilization.

All new technology carries unacceptable risk... until they don't. But that's
why science needs a constant feedback loop to improve understanding and
safety. We can't make safe what we don't understand.

~~~
marvin
He was making a joke about the risk of goat-sized spiders.

~~~
Djehngo
I don't think drawing attention to the fact the comment wasn't short sighted,
merely inane will gather much more sympathy for the poster.

~~~
adlpz
It might be interesting to introduce you people to the concept of humor.

~~~
nrser
the joke here is that there are no jokes. that's what makes it funny.

------
phreeza
The article is a bit misleading in that it states that a spiders web could
stop the train. The paper is clearer in this respect. Of course it should say
the fictional web in Spiderman could stop the train, if it were made of the
material of the actual spiders web. They assume a thread diameter of 5mm, as
opposed to probably about .1mm in a real spiders web.

~~~
sageikosa
My take on Spider-Man stopping the train was that the first several anchor
points failed as anchor points in the web/anchor/train system (they underwent
systemic collapse due to loads past their design tolerances). Therefore,
Spidey increased the number of anchor points to more even distribute the load.

------
habosa
<http://what-if.xkcd.com/18/>

So can AK-47s.

~~~
pyre

      | air rifle fires [...] at a muzzle velocity of
      | 100 meters per second
    
      | The GE Genesis Series I locomotive [...] travels at   
      | around 45 meters per second
    
      | If you bounce a single BB off the front of the
      | locomotive [...] you slow it down by about a foot
      | per day
    

Why is everything in meters per second, then we jump to using feet all of the
sudden? Isn't this just asking for conversion errors? :P

~~~
Deestan
> Why is everything in meters per second, then we jump to using feet all of
> the sudden?

Metric is easier to do calculations in, while imperial is used for the "layman
terms". The intended audience is mainly american, and feet are more familiar
to them than meters.

~~~
lucian1900
But that's precisely the sort of practice that causes conversion errors. Non-
metric units should only ever be used in addition to the metric ones, in
parentheses, if at all.

~~~
Avshalom
If you're trying to stop a train with a BB gun conversion errors are not going
to be your primary worry.

------
pyre

      | We were surprised to find out that the webbing
      | was portrayed accurately.
    

They are forgetting that in the movie the strands of web were not all
connected together. They had Spiderman at their center, holding on to them. It
would seem that his body and/or his grip on the web strands would be the
weakest link in trying to resist the force of a train.

~~~
maxerickson
There's also some issues with conservation of mass.

Poor Peter would at least be thirsty after all that web shooting, if not
wildly hungry.

------
p1mrx
Anything can halt a train, if you put a lot of it in one place.

------
RyanKushner
This is related to biomimicry (using nature as the inspiration for design). If
you're interested in learning more, I helped start a local group:
<http://bayareabiomimicry.org/>

\- Ryan

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minopret
What about the materials and structure of a train car - can they sustain
instantaneous force required to stop a speeding train? RRRIP! Oops, maybe not.

~~~
NamTaf
They mention 300kN in the article, and in the design of trains that isn't a
lot at all. For example, the AAR [1] standards require a railway vehicle to
take up to 1.8x 1560kN longitudinal force - that is, the force imparted down
the length of the train through the couplers in to the body structure -
without causing bulk yield [2] of the body material. A second design
requirement is for the body structure to take 4450kN 'collision' force without
exceeding the ultimate strength of the body structure material.

Other design criteria include, for example, crash protection of the driver's
cabin if it's a locomotive where the drivers sit at the very front, so that
part's often very strong and rigid as it needs to preserve a 'survivability
space' for the drivers.

For passenger cars, the body structure tends to have a lot of strength against
longitudinal loads in order to combat the phenomenon of climbing. That is, in
a railway collision with passenger cars, as the vehicles ride in to one
another, there is the tendency for one to pop up/down and try to 'ride
up/down' on top of/under the one in front. [3]

This was demonstrated rather tragically in a particular accident (I can't find
its name, sorry) where old wooden passenger vehicles did this. Their
comparatively strong underframe simply sliced through the comparatively weak
cabins like horizontal blades and caused huge fatalities. This is because old
passenger cars used to basically be flat-top wooden vehicles with a cabin
placed on top, so the body structure was very strong compared to the weak
cabin. Since then, passenger vehicles must be specifically designed not to
climb up on one another and do that.

So really, in the sense of railway design, 300kN is minimal, especially when
placed longitudinally down the length of the vehicle structure. They are far
weaker against lateral collision so I guess if you ever want to cause a huge
railway accident, hit a train side-on rather than end-on.

[1]: Not the standards themselves, as they're not publically available -
<https://www.aar.org/Pages/Home.aspx>

[2]: By 'bulk yield' I mean yielding over a significant portion of the
structure. This is a legacy of the AAR standards originally being targeted
towards hand calculations, where you couldn't easily inspect every particular
section of every particular beam but rather you calculated it as a whole. With
the advent of finite element analysis you can now do that, so it's permissible
to see slight yield-levels of stress in certain small parts so long as the
overall section as a whole remains under it.

[3]: This will give a brief example of anti-climbers on rail vehicles:
<http://www.oleo.co.uk/products/rail/anti-climbers>

