OT : looking for info on "axis avoider" or "cable crossing" mechanism

I heard of something similar a while ago called a shaft-passer. The context was for allowing a shaft to pass through the spokes of a wheel, gear, etc. Unfortunately, I didn't get a real good idea of how it was supposed to work.

I only heard of this one time. The context was in Richard Feynman's book, "Surely You're Joking, Mr. Feynman". Engineers were joking about a "shaft passer" to allow gears to overlap. Then some mention was made of the mine warfare application.

You may need to dig deep > I heard of something similar a while ago called a shaft-passer. The context

Thanks to those who pointed me to Richard Feynman's book where it is mentioned as "shaft passer". However, If you search for "shaft passer" on Google, you won't find many useful info, so I expect my new page about it to rank first very soon ;-) I made a model of it with SolidWorks 2004, available on

at the bottom of a small article with pictures. I'll try to drive the entire construction from the blue shaft position and diameter, as it looks like the ratio between the wheel diameter and the shaft's has to be fairly high. The tolerances analysis and manufacturability of the whole is another thing... But now I meet a simpler problem as I expected to use the "physical dynamics" SW feature to animate the model, but it fails : when I try to move the wheel, I get an error saying physical dynamics can't solve it, even if I only specify one red star and the blue shaft as components... Looks fairly simple though... any idea ? Philippe Guglielmetti

"Philippe Guglielmetti" wrote in news:415bc5b0$0$21016 $ snipped-for-privacy@news.sunrise.ch:

As usual, very cool.

So it looks like a mechanism that allows a fixed position shaft to be placed inside the periphery of a large wheel and the wheel still be able to rotate. But, I don't see what is supposed to attach the hub of the wheel to the outside rim. Yes, I see the 6 small star shaped devices, but how do they transmit torque to the outer rim? Am I missing the obvious?

WT

It's easier to envision if you replace the "stars" with solid disks?

That is interesting. I'm trying to envision a similar device placed in a mine anchor cable and having a bit of trouble with that. 8~)

Cool stuff. I once saw a series of books (Ingenious Mechanisms?); wonder if they have anything on it there?

Oops! Wasn't paying attention to the details of the channel sectors. Wonder if they were ever employed.

Looks like the problem is in the component pattern for the stars. Suppress those and just the parent works fine with Physical Dynamics. Dissolve the pattern, and fix the subs and it the whole thing simulates great on 2005.

SC

Exactly.

I'm not sure that this is the intended way of using this design, but theoretically, it will work if the 'shaft passer' just transfers motion from one gear to another (rather than driving it).

Imagine a three gear scenario with the shaft passer in between the two. The hub would be stationary. Very comical!

Now all you need to do is add some electromagnets for some real silliness.

This reminds me of some attempted "perpetual motion" devices I've seen.

Mike Wilson

I was just thinking that some planetary gears and large diameter bearings would probably be a much better solution.

Yes, thanks to some unrealistic mates. In reality, the only thing that should be mated is the inner hub center hole to a shaft, assuming the rails are welded to the spokes. Gravity would not be kind to this assembly.

Upon further inspection, I see that the stars actually do transfer the load. The images on Philippe's website made me think that only one point of each star was within the rails. If two star points are in the rails at all times, then it will work.

I'm guessing that the contraption would be more stable if it were wider?

Pretty cool Philippe!

Mike

transfers

no, no! the "goal" is much simpler ! Read Feynman's story and watch the original minesweep avoiding mechanism on

I know a watchmaker who does very compact mechanisms and "complained" designs required "bars" to separate layers of wheels. (see for nice 3D anims of watch mechanisms) I mentioned the "shaft passer" as a joke, saying there was always a more complicated way to solve a problem... Please downlaod the model from there and tell me how to make it "work" using "physical dynamics" : normally, if you select the red and blue components, you should be able to rotate the wheel, but SolidWorks can't do it. Why ?

When I opened the assembly, I had mate errors in 2005. There are some in-context features and flexible subs. Your best bet is to make the this all one assembly (no subs). Don't use any patterns and use only three stars instead of six.

Try and simplify it as much as possible. SolidWorks is trying to calculate too much in your assembly.

I started to do that here...

The simulation is already set up. I eliminated many mates to give real world results, so don't drag any parts around! Let Physical Dynamics do the work.

Mike

I opened the "shaft passer demo" and let the physical dynamics do the job.....worked like a charm from start in SW 2004

Krister L

Sorry....should have been SW 2005....even the small stars move as the thouch the passing shaft (which they don't do when I try Mikes fixed assy)

Krister L

OK, I simplified it and made a motion picture (rated 'G')...

Mike Wilson

I skimmed the indexes of all four volumes "Ingenious Mechanisms" and could find nothing in reference to the descriptive names provided.

Kman

Thanks. Philippe posted a picture of the device in a cable (heck of a deal). Now, I wonder if Paul Ratajczak had that 1946 copy of Popular Science and remembered seeing the article? 8~)