[hpv] Re: Plastic Bicycle Frame Building

[Charles J Knight]

On Wed, 12 Feb 97 18:39 MET Timo Christ <agn...@smaug.netwave.de>
writes:
>Hi Chuck, fellow DIY-freak!

hehehe I love *trying* to do things myself. Many times I don't succeed.
(I'm the real life "Tim Taylor") I'm trying to design a model airship
right
now...future plans may include a full sized one which could be human
powered.

>triangle yet. since welding is difficult (i'm a beginner in that)
>plastic
>materials with glasfibre/carbon reinforcements seems to be a cool
>alternative.

If you're talking about "simple" materials, here's a suggestion.
(One I don't know much about, I'm sorry to say) Foam core
with glass fiber. Basically, you get a cheap piece of structural
foam and carve it...it's styrofoam so it's easy to shape. You then
take it and cover it in fiberglass cloth and paint over it and the
cloth with the resin. Then you repeat the process for a couple'a
layers...builds up strength.

Alternately, you take it in to a fiberglass manufacturer and have
it glassed...there's a material called "chop" which is glass fibers
in a resin...it's sprayable fiberglass.

>do you use standard epoxy (like for glider aeroplanes or surfboards)
>to stick the pipes together?

Depends on what you're using. Personally, I like to use plastics
for a lot of things. But I also use paper (YES), wood, cloth,
mylar sheet, rubber, and anything else I have lying around.

If I was building something out of PVC pipe, I would use PVC
solvent. It actually welds the pipes together...melting both surfaces
and literally combining them into a single piece.

>how thick (wall thickness) must the tubes be to resist the abuse?
>i think fat tube diameters will add rigidity (like to Alu Frames).
>what material is to use? really conduit pipes??

I like using materials I can get "anywhere" instead of requiring
myself to use expensive stuff like bicycle tube sets. Of course
I've not yet built a bicycle...a fairing is a simple wind deflector.

One thing I'm working on is a design for a bike where none of
the rigid members touch. It's a tensegrity design...but I don't
have much experience with them, so it's been slow going.

>why pay thousands for so-called thermoplast frames when you can go to
>the local store and get conduit pipes for little bucks...

I *never* said you could or should build bikes from plastic
conduit.

However, with proper engineering, there's no reason that
it shouldn't be possible. If we can build PVC furniture with stuff
from the hardware store, we *should* be able to beef up the design
and use the same material for a bike frame.

-- Chuck Knight