Fwd: Re: Folding liquid fiberglass bicycles

[Kragen Javier Sitaker]

Forwarding comments on the bicycle idea:

Date: Wed, 20 Sep 2006 21:10:03 -0500
From: "Michael Leonhard" <michael206 at gmail.com>
To: "Kragen Javier Sitaker" <kragen at pobox.com>
Subject: Re: Folding liquid fiberglass bicycles
Message-ID: <21f8b6e20609201910x12f676edk95beff683fc2acce at mail.gmail.com>

Please feel free to forward my replies to the mailing list.  I suppose
I could have done this myself by replying to kragen-tol at canonical.org?

Perhaps flexibility in all directions is not required?  I'm imagining
a closed cylinder, made of a stiff material with many straight folds,
allowing the cylinder to collapse and expand.  Like an accordion.
Perhaps the machine could be manufactured in its proper useful shape,
and then collapsed via vacuum to a pocket size?  Then the user would
release the vacuum and watch the machine self-inflate and return to
its rigid shape.  It would be like a flattened coke can where you
crack open the lid to let the air in, and watch as it returns to a
proper coke-can shape.  I guess this would be a likely application of
super-strong materials like carbon nano-tube composites.

What material may be used for the hinges?  It must be flexible at the
dimples/vertices.  It would probably need extra internal pressure to
be rigid enough.  Unless there was a very clever way to have the hard
plates fit together and lock in place.  This sounds like a topic ripe
for research.  But not by me; I'm no mathematician. :)

Powerisers look very cool!  I wonder if one could use them every day
instead of a bicycle?  I suppose they could cause health problems in
the legs over time.  The powerisers site says:

> To stop running, take it slow and easy. Gradually slow down to a walk,
> and then stop when you are to a place you can hang on to something.
> (remember, you can't stand still without support on the Poweriser)

I wonder if they could improve the design to allow stability for
walking and standing?  I definately want to try Powerisers out once I
get a proper job and non-temporary health insurance. :)

-Michael

On 9/18/06, Kragen Javier Sitaker <kragen at pobox.com> wrote:
> You write:
> > Hi Kragen,
> > This is an interesting idea.  What kind of material did you have in
> > mind?  Glass fibers can be embedded in many kinds of materials, some
> > flexible and others stiff.  I've used very light weight fiberglass in
> > radio controlled models.  First, I must cut the fiberglass cloth and
> > lay it over a form.  Then I apply epoxy, which soaks into the cloth.
> > For added strength, several layers of cloth may be applied
> > successively and soaked in epoxy.  After the epoxy hardens, I destroy
> > the form, leaving a thin fiberglass-epoxy composite shell.  The
> > flexibility of this shell depends on the kind of epoxy and the number
> > of layers of fiberglass cloth.  A single layer of very light weight
> > cloth can yield a part that is about as flexible as the cardboard from
> > a cereal box.  It's not the kind of thing you would roll up and stick
> > in your pocket.
>
> Thanks for your thoughts!
>
> It doesn't sound impossible to roll up the single-layer material and
> stick in your pocket (especially with a dowel or something to roll it
> around) but it does sound difficult --- and that's only a single
> layer, which presumably has very little strength.  (I think I
> calculated that the glass part of the thing would need to be 0.12 mm
> thick --- roughly how many layers of glass cloth is that, before you
> apply the epoxy?)
>
> To keep it flexible with greater thickness, the material holding the
> layers of fiberglass together would have to be one of the following:
> - very yielding to shear (say, rubber) which implies that it would be
>   thick or heavy;
> - nonexistent --- maybe you'd wrap the glass sheet around the water
>   many times
> - very thin indeed (although I think the required thickness of the
>   glass alone would prevent this)
>
> > I suppose there must be some very flexible plastics that could be
> > mixed with fiberglass to make very strong and flexible cloth.  Have
> > you heard of anything in particular?
>
> Indeed not; I know very little about the material, just what my
> ex-co-worker Matt told me about his airplane models.
>
> > If the frame will be filled with water, perhaps osmosis create the
> > necessary pressure?  According to Wikipedia, ocean water has 27 atm of
> > osmotic pressure.  That is about 400 pascals, three orders of
> > magnitude less than you estimate is needed.  But I suppose it would be
> > difficult to make a semipermiable membrane that is strong enough to
> > contain the 300-650 kpsi necessary for the structure.
>
> That's the tensile strength of the glass, not the necessary pressure
> of the water.  I think I calculated the pressure needed in the water,
> but apparently I failed to translate that into the electronic version
> of the post.  A 46 cm^2 cross-section is 7 in^2, and I was saying we
> could probably get by with 300 pounds of bending strength (i.e. being
> able to support 300 lbs. in the middle of a strut), which gives means
> we need 1100 lbs. of pressure to prevent the "under compression" side
> of the glass from going below zero tension when it's under bending
> stress.  That's almost 160 psi, which is about 10.6 atm.  Achievable
> with a bicycle pump, and if most of the internal space is full of
> water, it won't even be that much work.
>
> > How about a scooter?  The wheels could be shaped like shallow bowls
> > that fit together, holding the deflated frame and axels inside.
>
> That's a great idea!
>
> > Have you read Neal Stephenson's book The_Diamond_Age?
>
> No, although I've read a lot of the extropian and Foresight source
> literature it's based on.  But Neal's writing is a lot more riveting
> than Drexler's or Merkle's, so people read him more.
>
> > He describes a future where nanotechnology facilitates cheap and
> > perfectly recyclable machines.  An automated manufacturing machine
> > is called a 'matter compiler'.  While the automated recycler is a
> > 'decompiler'.  Recycling is then 'deking'.
>
> Suppose the technology described above comes to pass.  What
> institutions are needed to allow human beings to continue to enjoy
> some kind of privacy and day-to-day security?
>
> > A common mode of transportation is the 'velociped'.  It's a pair of
> >  robotic stilts or bionic leg extensions.  They allow the person to
> >  walk comfortably while taking enormous strides to travel very fast.
>
> Powerisers are a non-computerized version of this that go about 30mph.
>
> > One character in the book uses a new velociped for every commute.
> > His home compiler produces them every morning for him to take to
> > work.  When he gets to work, he dekes them.  At the end of the day,
> > he compiles a new pair for the trip home.  The velociped is created
> > by a computer so each one is identical.  It is very enticing to
> > always have perfectly new machines.  Dropped your PDA?  Just deke it
> > and compile a new one!
>
> Better make sure you have a backup of the data, though.
>
> > I dunno about fiberglass though...
>
> Presumably, in the glorious molecular nanotech future, we'll be able
> to use diamond fibers, anchored together into sheets with more diamond
> fibers, instead of settling for glass and epoxy.
>
> By the way, may I forward your comments to the kragen-discuss mailing
> list?
>
>


-- 

-Michael
michael206 at gmail.com