[python] Re: crazy idea?
- From: "dirk@xxxxxxxxxx" <dirk@xxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Mon, 2 May 2011 08:19:06 +0200 (CEST)
Hi Dirk,
as was mentioned, it is the joints that take the most stress. I have had great
interest in 3D Printers an saw one in action once. However, it is a steep
learning curve to get one reliably working. There are fablab communities popping
up in various places to adresse this problem with team work. The printers are
slow and the material is not solid, rather a mesh of small tubes. Imagine a
glue-pistol you steer by hand. You cannot produce overlaps so far, so things
won't be easy, i'm afraid!
I came across a bamboo bike build for africa, with connected with sheetmetal
joints. I think you could use something like "dyneema ropes" running diagonally
across each field and reduce the torque and sheer stress greatly. In theory, the
wires only take pulling forces while the beams get the pushing forces, much like
moulton or pedersen designs. There was a danish company desiging a bike for puma
stores with a rope beam between steering pivot and pedals which could also be
used as a lock.
If you can adjust the tension of the wires, you could create universal joints
that are bolted together regardless of orientation. I'm not so sure about the
stiffness of such a concept. But if you come up with a cage-like design with a
driver inside of it, it could be working! Never stop tinkering!
I have to look at this cad-tool as well. if we could agree on a free cad
packages, that is available to all of us, i would set up a repository, so we can
share design and otehr documents!
Keep going!
Greetings,
DirkS
"Dirk Bonné" <dirk.bonne@xxxxxxx> hat am 29. April 2011 um 14:35 geschrieben:
> Attached is a drawing of such joint. It would connect 3 tubes at
> 90degree angles.
>
>
> On 29.04.2011 12:21, Dirk Bonné wrote:
> > A week ago I came across the reprap project (reprap.org), which is an
> > "open source" 3D printing machine. Such a printer can print pieces of
> > plastic, supposedly in any form as long at it is limited in size. I'm
> > very much tempted making such a machine for my self (as winter project).
> >
> > One idea I have is to build a bike (e.g. python) using the reprap. The
> > goal would be to build a trellis-framed python, like my own bike
> > (pythoon) and some others seen on the project page. I would still use
> > regular steel tubing with small diameter (8-16mm), but the joints
> > connecting those tubes would be printed plastic bits that are pressed
> > inside of the tube. The construction process would look like this:
> > 1 design all the joints connecting the tubes.
> > 2 print them -> results in "inner lugs".
> > 3 cut the metal tubes to the right length (tube cutter).
> > 4 assemble the frame by pressing the plastic joints in the tubes.
> >
> > => at this point I would like that the bike is stiff enough to hold itself.
> >
> > The next phase would strengthen the bike by wrapping uni-directional
> > carbon fiber around the joints (like using a tape roll wrapping it
> > around forming a "outer lug":
> >
> > 5 paint the tubes with a primer before wrapping the CF around
> > 6 cut the roll of unidirectional CF in long strands about 1cm width
> > 7 use a brush dipping the CF with epoxy while wrapping it around the
> > joints firmly connecting the tubes to the joints.
> >
> > What I hope the advantages would be:
> > * sharing: possible to share the design between people - anybody with a
> > 3d-printer could produce a bike. It would even be possible to make a
> > program that given some parameters can produce a custom measurements.
> > * easier/quicklier: the tubes are just cu wih a plain tube cutter tool.
> > There is much less measuring and filing involved (making a trellis frame
> > can really be horrible - especially when brazing where precision means all).
> > * easier: no need for a jig. The joints would make the frame pre-stiff
> > enough to easily adjust the frame as a whole using a measuring stick.
> > * equipement: no welding/brazing equipement needed (ok, you need a 3d
> > printer....).
> >
> > Other directions: the same process would be useful for a pure CF-bike or
> > may be a bamboo-bike...
> >
> > What is your take on the idea? Is there ny around iwth experience with
> > 3d printing product?. Could it work? Would there be a real advantage?
> >
> > DirkB
> >
> > PS: with the reprap I discovered there is a 3D CAD for programmers:
> > OpenSCAD. For those with the programming ability, it might be
> > alternative for autocad and the like.
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http://dirk.steuwer.de
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