Hi Dirk,
I like your idea and think it has real potential. As I understand it
you make a jig/former of non structural material and then reinforce it
for tension and compression.
I have been working with a RepRap for 3-4 years along with Sketchup
(freeware 3D modeling), Slic3r (freeware layer generation) and
Pronterface (gcode machine manipulator freeware).
Please notice the use of FREE software.
In the past I have designed and built recumbents from scratch in
steel, aluminium, and composites. I have also designed and built Super
Mileage cars in reinforced polyurethane foam, and carbon/Kevlar.
I also built a body for a trike, for a long distance ride 5,000 miles
in 100 days, that was made from PVC tubing, PVC foam. zip-ties and
polypropylene fabric.
There are a couple of things I have learned, carbon fibre/epoxy is
very stiff and extremely brittle. It will break with no warning and
shatter on impact.
PLA (Poly Lactic Acid) the most common 3D printing plastic is brittle
but light. ABS is more high temperature but is much stronger.
PVC tubing 25-40mm shatters but can make a light core former.
If it is okay by you I think I will try a test using PLA, PVC
reinforced with epoxy/silk fabric and thread. Chinese Silk is
extremely strong in tension.
Regards
Ken Stewart
On 22 Aug 2017, at 14:19, Dirk Bonne wrote:
Hi Philip
My idea was to be able to provide "python kits".
1) A designer would provide a list of tubing (sizing and length) +
files to print kind of "inner lugs".
2) A builder would get the tubes and cut them to length.
3) Then she would print the lugs. These lugs would then act as
connectors for the tubes.
The lugs were to fit *into* the tubes. These lugs would not give
strength. It would just make hold the tubes in the correct place. The
builder would then need to use epoxy and carbon fiber to strengthen
each joint. As a sidenote, you can get carbon fiber in tape rolls
(they are not weaved).
Advantage would be that with minimal workplace/tools somebody would be
able to make a bike. Furthermore one could provide the tubes and lugs
further making building accesable for the builder.
I have no tried it in practice because I had trouble getting access to
a printer.
greetings dirk
Gesendet: Montag, 21. August 2017 um 20:25 Uhr
Von: "Philip Hahn" <hahnpv@xxxxxxxxx>
An: python@xxxxxxxxxxxxx
Betreff: [python] Re: 3D printing
As much as I love the idea - as someone who both cycles as a primary
vehicle and has melted 10+kg of plastic in his printer over the last
year - this will not be a robust or safe idea in any available
plastic. The deposition of layers in the X-Y plane results in weakness
in the Z plane, highly susceptible to both shear and tensile loading.
Think of it as separate laminations which have a weakness in bonding
between laminas.
I would suggest perhaps that idea of tubes and connectors aimed at the
CNC community. Homebrew hobby CNC machines are built for under $1000
or about 3x the cost of a decent printer. They are driven by the same
gcode so you can prototype on your printer and then make metal parts
with the same code. I'm currently working on such a CNC conversion at
the moment.
philip hahn
On Mon, Aug 21, 2017 at 11:17 AM, Jürgen Mages <jmages@xxxxxx> wrote:
I think, it is about time to reanimate an idea, made by Dirk Bonné in
2011: The 3D-printing of a python frame. I guess, the printing
technology has advanced in a way, we can seriously start to work with
it.
Thus I have set up a wiki page:
http://en.openbike.org/wiki/3D-Printing
Here we can gather all useful information and hopefully one day the
first prototype will be made.
Everybody interested is invited to contribute ...
Cheers,
Jürgen.
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