James Fergusons Mechanical Paradox Orrery

[Sunset Machine]

Okay- one gear apparently cut normal and the other two have more teeth than normally used on a given OD, making their teeth smaller and moving in smaller increments for each tooth as they engage a common pinion.

But the text describes something else:  one gear moving backwards. So many teeth that its mate misses the peak and instead pushes it away? Do we have tooth counts for doing this? A pointy tooth form is indicated, yes?
Fascinating, thanks Chris.

[craynerd]

Morning guys,
I'm currently cutting the brass frames and progress is slow. I'm also trying to figure out how to motorise this and maintain some decent looks as sticking a motor under it is clearly going to increase the size of the base.

The tooth form is not cycloidal like a true clock but instead a standard involute form. My understanding is that this tooth form would have a little more freedom in meshing. They actually mesh with no problem at all. As I mention in the video, I used a different cutter module on one tooth count than I did for the others, again to try and get a better fit. It worked fine but I would have hand filed any issues down if they had have been apparent. I also thought I may have to run them in a little on the lathe and although I did try them on the lathe, it didn't need it.

Quote:But the text describes something else: one gear moving backwards

It's all in relation to one another! All three are driven off a common gear. One of three has the same teeth and therefore turns at the same rate. One wheel has more teeth and therefore does fewer revs per rotation and another wheel with less teeth and therefore more revolutions in relation to the driving wheel. Consequently, when you stack these up, in relation to each other, one stays still, one goes forward and one goes back (they are just turning slower). That is my understanding of it all.... Haha I'm building it but I really could be wrong!

[Sunset Machine]

I remain skeptical of the backwards movement.
By the way, I like your videos. Thank you.

[TomG]

Think of it as falling behind, rather than backwards.

Tom

[Sunset Machine]

An illusion?

[MikeWi]

(04-10-2016, 09:54 AM)TomG Wrote: Think of it as falling behind, rather than backwards.

Tom

From the text: "what would you say if I should say that, turn the thick wheel whichever way you will, it shall turn one of the thin wheels the same way, the other the contrary way"

Seems like there's no wiggle room here.  Love to see it!