One mechanical engineer at Frankfort was always trying to
design things and could never get everything right. One
time he designed a box full of gears, one of which was a
big, eight-inch- diameter gear wheel that had six spokes.
The fella says excitedly "Well, boss, how is it? How is it?"
"Just fine!" the boss replies. "All you have to do is
specify a shaft passer on each of the spokes, so the gear
wheel can turn!" The guy had designed a shaft that went
right between the spokes!
The boss went on to tell us that there was such a thing as
a shaft passer (I thought he must have been joking). It was
invented by the Germans during the war to keep the British
minesweepers from catching the cables that held the German
mines floating under water at a certain depth. With these
shaft passers, the German cables could allow the British
cables to pass through as if they were going through a
revolving door. So it was possible to put shaft passers on
all the spokes, but the boss didn't mean that the machinists
should go to all that trouble; the guy should instead just
redesign it and put the shaft somewhere else.
http://www.drgoulu.com/2005/12/29/eviteur-daxe/
The mine application seems to be a subset version. If that is the best example any one has of this design in practice it suggests that its not possible to build a working version of the whole thing. A mechanically weak proof of concept might be possible, but a solid use-able version seems to me to be impossible.
Might work if the outer rim is supported or guided on some way. I still think loading is a problem though.
I love to see some one try to build it....
For something like this to even have a chance, it would probably need many more, thinner teeth than these diagrams illustrate.
EDIT: @analogwintermut I think this addresses your question.
[1]http://drgoulu.com/wp-content/uploads/HLIC/849e60a7d99c30c2a...
Wish I knew the name of the mechanism they used, it looked interesting enough to get me talking to one of the workers about it.
Edit- the best I can find is either something called a 'starpass glider' mentioned on page 14 of http://s7d9.scene7.com/is/content/minesafetyappliances/Horiz...
or http://www.saferack.com/lifeline-cable-systems-fall-protecti...
The system I saw at the locks seemed like a better engineered system, from what I remember.
"The device works by using a spoked, rimless wheel that allows cables to pass through as it rotates. The ends of the spokes are widened, and the cable is held together by a short curved sleeve through which these spoke ends slide."
I've cut each stator into two parts vertically so it can actually be assembled by gluing them around the rotor, and I've also cut the rotor so it can be printer without support.
The device used in mines is somewhat similar in that it seems to allow solid objects to pass through each other, but it is not a shaft passer as it is not a wheel with "penetrable" spokes.
They were used on the mines. http://drgoulu.files.wordpress.com/2007/03/minesweep.jpg
Here's a video demoing it.
head cut ... without letting ... go.
> One mechanical engineer at Frankfort was always trying to design things and could never get everything right. One time he designed a box full of gears, one of which was a big, eight-inch-diameter gear wheel that had six spokes. The fella says excitedly “Well, boss, how is it? How is it?”
> “Just fine!” the boss replies. “All you have to do is specify a shaft passer on each of the spokes, so the gear wheel can turn!” The guy had designed a shaft that went right between the spokes!
> The boss went on to tell us that there was such a thing as a shaft passer (I thought he must have been joking). It was invented by the Germans during the war to keep the British minesweepers from catching the cables that held the German mines floating under water at a certain depth. With these shaft passers, the German cables could allow the British cables to pass through as if they were going through a revolving door. So it was possible to put shaft passers on all the spokes, but the boss didn’t mean that the machinists should go to all that trouble; the guy should instead just redesign it and put the shaft somewhere else.
Yes, it rotates and passes shafts successfully :)
Based on this model[1] with some modifications for printability. I've printed it in 6 parts and glued it together. It's barely holding though, because apparently super glue is not the best way to bond ABS ;)
EDIT: I just figured out that to use it as a shaft passer inside a wheel just like on the Wikipedia article, the rotor would need some plastic removed so that the shaft can get through without having to move up and down.
Anyone who has done the bridge climb over Syndey Harbour Bridge has used one too. Unfortunately I couldn't find a good photo of the harness and connector.
My answers to some of your questions:
Yes, my own images are free ( https://en.wikipedia.org/wiki/File:Shaftpasser1.jpg and https://en.wikipedia.org/wiki/File:Shaftpasser2.jpg ) . The scan from the mine cable was sent to me by email but I don't know its exact reference and status
Clearly the wheel would be extremely difficult to produce and to operate, especially if torque has to be transmitted. I intended to model a version with the german cable design, i.e. one of the half-spoke attached to the star wheel axle, but I leave this to the most fanatic of you ;-)
Congrats to ambrop7 for the printable model !
..though i get the implication of design vs engineering
[1] http://upload.wikimedia.org/wikipedia/commons/thumb/1/16/Bal... )
