TD replications

[gotoluc]

Thanks Carroll for your input.

If the suggestion was to be used I was thinking of a very large scale like 20+ inches in order to allow for toleration differences.
Do you still think it's not possible?

Regards

Luc

[citfta]

Making it that large will certainly help with the precision problem.  Most of the ones on the machines I worked on were about 15 to 20 inches in diameter as I recall.  Of course they were used to move some pretty heavy tool change equipment so that made them more susceptible to problems.  With your skill at building I think you can probably make a 20 inch one work.  I would like to see one made from plywood.  That would be impressive.  They are pretty interesting to watch them work.  Once they change to the next position they hold that position very accurately until told to change again.

Respectfully,
Carroll

[Cairun]

Hi Alex,

User name TinselKoala made a suggestion of using a Scotch Yoke (1st pic) to convert the linear output to rotary.
The problem with it is there's no rest time. However, I thought there could be a way to modify the Scotch Yoke to create a pause time and found a variation that does exactly that (2nd pic)   Link to animation: http://www.mekanizmalar.com/uk012.html

The same site also has an Indexing mechanism (3rd pic). Link to animation: http://www.mekanizmalar.com/four-slot-two-pin-geneva-mechanism.html
This mechanism may do what we need to turn the rotor in four segments of rotation, stop, lock and pause.

As it is my magnet rotor only has 2 sets of magnets but I could add a second set without too much work and expense to advantage of the 4 position of this indexing mechanism.

I like both of these mechanism instead of gears since I could cut them out of plywood with a router.

Food for thought

Luc

Luc,


I've modeled a track follower setup which captures the stop and go motion.  This is a linear reciprocating design with both input and output magnets moving linearly.
This video shows a the basic idea of a track follower setup.
https://www.youtube.com/watch?v=wsqyiLaUw5g&feature=youtu.be
This setup does not take advantage of the self reset(because I just wanted to model quickly and show the basic idea), however, a self reset design can be achieved.
I will have to think a little more about how to mechanically loop your latest build/setup.


Regards,
Alex

[gotoluc]

That mechanism looks great Alex

This kind of cam follower design I can make with a router. So that's the best to start with.

Thanks for taking the time to help!

Luc

[Cairun]

That mechanism looks great Alex

This kind of cam follower design I can make with a router. So that's the best to start with.

Thanks for taking the time to help!

Luc

Luc,


Thank you, I am glad I can help!  The geometry of the track/cam may need some tweaking to enable a smoother motion, but this is a minor problem.
The one thing that bothers me is that I am not sure of the efficiency of a cam and follower, more specifically the one that I've shown in the video.
If anyone is familiar with the efficiency of a cam and follower, please chime in.


If you print the cam/track out and glue the print onto a piece of plywood and then you can cut the track with a router.
With your workmanship, I am sure you can make it .
But, if accuracy becomes too much of a problem, I can make the cam/track with my CNC mill after I get back from my travels. 
However, my CNC mill is quite small and can only make small parts.  But I can always break larger components into smaller parts and assemble into a larger component later on.
Let me know how you would like to proceed.  I can design a cam/track with info provided by you and send you the drawing so you can attempt to make it, or I can make it when I get back.


Regards,
Alex