[python] Re: no weld python
- From: Kevin Bailey <ke-python@xxxxxxxxxxxxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Tue, 3 Jun 2008 10:18:21 -0700
On Tue, Jun 03, 2008 at 06:38:52PM +0200, Uipko Berghuis wrote:
>
> Please correct me if I'm saying stupid stuff..... my only composite
> experience is making a kitesurfboard. Before doing that I read a lot
> about and I find it a really interested metarial. One of the projects
> on my list is making a composite tail faring. The ultimum would be to
> make my own (light weigth) carbon bike ;). But I think Jaculus has a
> point changing a steel frame sounds way easier to me. So I first have
> to learn to weld to make a steel prototype, adjust it till its the
> perfect bike for me and than make a carbon version.
Agreed. You'd pretty much have to get it right the first time
or allow lots of ways to adjust it.
> Don't you have to use a vacuum pump, bag breeder etc. if you want to
> make round shapes?
A vacuum certainly makes lighter parts with no chance of bubbles
but its not that difficult to make decent parts. Just laying on
some plastic sheet and squeegeeing the bubbles out works.
> And I think you also need to make molds or not?
> Or do I make things to complex? Is it possible to make a foam frame
> and just wrap around the composite?
What I would do if I were building a bike would be to get some
spray foam (or glue together better foam), make something roughly
the correct shape and start carving it. (If using spray foam,
wait optimally a couple days for it to finish growing.) This
is where composites shine. You can make really beautiful, flowing
shapes with just a knife and sandpaper.
Once it was the shape you wanted and smooth, you could start
wrapping it. You'd probably want to read a bit about composites
at this point to learn all the steps, and to learn how to best
lay the cloth. You're also going to have to embed your pivot
and drop-outs, etc. That's something that steel can add after
the fact.
> I think the "problem" is that glas is more flexibel and you want your
> frame as rigid as possible. Probably you can solve this by using a
> more rigid core, for example a foam wood combination (like the
> stingers in a surfboard). Or you can make a sort of sandwitch of foam
> and glas to build a more rigid core.
You can make the frame as rigid as you want simply by putting
on more layers. For example, take out a credit card and bend it
but glue 2 cards together and try to bend it. Its my understanding
that most (all ?) production bikes have no core.
As I said, the hard part really is joining cloth to non-cloth
materials i.e. metal.
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