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Old 20-06-2020, 11:03 PM
Ilmenite (Nick)
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3d printed gear or timing pulleys...

I am planning to convert a 100mm reflector to an ALT-AZ goto system in preparation for doing the same to a 300mm reflector. It seems that getting 359 or 360 tooth worm gearwheels is out of my price range. So, I was considering trying to 3d print something which could be used for this application.



The options seem to be either a gear or a timing pulley. From what I have read, gears need to be very high precision to get good tracking, so that would be too hard to do. It seems to me that the much higher number of teeth meshing with a timing belt arrangement would overcome imperfections in individual teeth by averaging them out.


The drive would be stepper controlled, possibly with encoders.



Has anyone tried to do this? How did it perform? Is there a better way of doing this without access to a lathe, mill etc?


Would I be better trying to find a nonfunctional motorised mount and strip it for parts?
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Old 21-06-2020, 05:50 AM
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bojan
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I printed timing gears for eq3 mount (post #32) it is sufficiently accurate even for tracking of 200mm lens.
There are number of parametric design available on Thingiverse, I used (for ALTAZ encoder) and commented this one, there was an issue with code, read the comments and correct the code accordingly:
https://www.thingiverse.com/thing:36568/comments
It is definitely worth a try to print the pulleys and gears.. any inaccuracies will be sorted out with guiding anyway.

Perhaps you should consider friction transmission, like this one (inspired and driven by Mel Bartels' software) or similar

Bigger wheels can be made from plywood, without access to "real" lathe, with relatively simple jig (using router).

See here: https://www.bbastrodesigns.com/mechanic.html
and here:
https://www.instructables.com/id/Con...arium-Arduino/


For electronics, I highly recommend OnStep (https://onstep.groups.io/g/main/topics)

Last edited by bojan; 21-06-2020 at 06:10 AM.
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