
3D printable shaft-passer: parametric shaft-passer in OpenSCAD - iamwil
https://cubehero.com/physibles/epicepee/Cable-passer
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iamwil
In case some of you were wondering, this is related to a previous post:

[https://news.ycombinator.com/item?id=6817451](https://news.ycombinator.com/item?id=6817451)

It's a device that allows cables to pass through it. As it happened, we were
talking about in on HN, and a few days later, I found this 3D printed version.

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PhasmaFelis
As I said on the previous thread, I'd really like to see actual evidence that
the thing existed, worked, and was used. Every serious discussion I can find
goes back to the mention in Feynman's autobiography, in which he presented the
thing as a friend-of-a-friend tale, and it's a bit improbable to accept on
that alone--it doesn't look impossible, but it seems like it would be very
difficult to keep the gear turning smoothly without binding.

Without convincing evidence, it's hard to see the shaft passer as anything
more than an engineer's prank. I'd love to be proven wrong, though.

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salgernon
What if you had a spoked wheel (bicycle wheel) where every spoke had a little
spring loaded collar at the location of the shaft. As the shaft hits the
collar, it is pushed out of the way while the other spokes, secure in their
collars maintain enough tension to keep the wheel attached.

spoke closed '===', the collar is '/' and the shaft '(asterisk)'.

Spoke direction of travel is s4 -> s0.

    
    
      s0c------===------
    
      s1c------===------
    
                /   
      s2o------/*-------
    
      s3c------===------
    
      s4c------===------
    
      etc.

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gmaslov
When the collar closes, its spoke will have pulled apart a little bit under
the tension and widened the gap. You'd need some kind of motorized grabber-
puller collars to make this work.

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fit2rule
The beauty of OpenSCAD never ceases to amaze me .. minkowski as a built-in?

[http://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Transforma...](http://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Transformations#minkowski)

Wow, its just so .. elegant ..

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Timmmmbob
Maybe, but it of limited use for most CAD problems - "standard" visual sketch-
and-extrude systems are MUCH easier to use for 99% of things you'd want to
model.

Exceptions are highly repetitive and mathematical objects like gears, CNC art,
fasteners and so on.

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thu
3D printed:
[http://www.thingiverse.com/thing:193022](http://www.thingiverse.com/thing:193022)

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Timmmmbob
Cool, but I'd be surprised if this actually works well - the shaft would
surely catch on the shoulder bit, and the force pushing the shaft through is
perfectly in line with the axis of the wheel, so there is very little moment
turning the wheel.

These can be fixed by:

1\. Smoothing out the outside a lot. 2\. Rotating the "guards" around the
wheel by 45 degrees about the axis of the wheel, so the shaft enters at the
top or the bottom of the wheel rather than in the middle.

I can make a drawing if that isn't clear.

Plus I haven't come across any low-friction 3D printed materials yet but
there's not much you can do about that.

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samstave
Can you please describe what this is exactly and how it works?

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iamwil
Sure, I found this blog post that describes it pretty well:

[http://somethingsurprising.blogspot.com/2011/11/feynmans-
sha...](http://somethingsurprising.blogspot.com/2011/11/feynmans-shaft-passer-
in-reality.html)

But basically, it was something that was posted recently on HN, about how
Richard Feynman (famous physicist) happened upon a mechanism designed in WWII
to avoid mines being detected by trip wires between boats, by allowing the
trip-wire to pass through the shaft-passer

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samstave
Wow - that's actually really cool.

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aeykie
Am I in the wrong for briefly wondering why 3d-printed dildos was on HN?

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jadeddrag
Yes, you are wrong. 3D printed anything is still pretty amazing, and now we
have people who are trying to disrupt the adult toy industry. A worthy hack
IMO.

~~~
contingencies
And an excellent moniker for it, _Jade D 'Drag_.

