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  #21  
Old 30-10-2018, 04:48 AM
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Quote:
Originally Posted by Wavytone View Post
...complete with period errors arising from such a small pinion.

Would have been much better if the teeth had been helical, or use a toothed belt between the two.

Yes, I know.. but I had only this one in my drawer....
If ever I stumble on the suitable helical gear, I will print the new matching sector - it is easy enough to do.

And it can't be belt (in conventional configuration) because I keep the OTA and mount separate when not in use (when put together they are too heavy to handle)... and I do not want to complicate assembly - this way, I simply put the OTA in place and encoder (and drive) is automatically engaged.



BTW, period of PE (due to teeth engagement) is a bit less than 1, not sure about amplitude...

Since encoder inputs are used to calculate the tracking rates for EL and AZ motors, even 1 accuracy is good enough for visual.

If I need any better, I simply sync the system with observed (or photographed) object from data base (which is a bit fiddly process, not wanted when in dark and people around waiting for next object to have a look at).
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  #22  
Old 30-10-2018, 02:05 PM
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Quote:
Originally Posted by Wavytone View Post
... Would have been much better if the teeth had been helical...
Prompted by your comment, I went to have a look at Banggood... and found there metal helical gear, of apparently right size.
Being a metal part, I will be able to "lap" the gear sector (printed with ABS filament) in boiling water, to improve gear matching even further.

And, on Thingiverse this contributor made available designs suitable for helical sector (and much much more).

Thank you for suggestion!

Last edited by bojan; 30-10-2018 at 03:46 PM.
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  #23  
Old 30-10-2018, 09:04 PM
sharpiel (Les)
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Bojan, I really like the things you do.
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  #24  
Old 31-10-2018, 08:01 AM
Wavytone (Nick)
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great. Bojan !
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  #25  
Old 02-11-2018, 06:59 AM
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Banggood has suitable pinion gear as well.
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  #26  
Old 21-11-2018, 11:30 AM
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After 20 days of waiting, gears arrived.
I am pleased with smooth match with previously printed test gear sector.
Now I have to print the whole sector (110)... and remove a bit of material from the neck of the small gear (where the hole for grab screw is now).

As the gears are modulo 0.6, I will have up-gearing ratio of 365/10 = 36.5, and with 40 ppr (and quad decoder implemented in Ek' box) I will have 5840 tics/rev which results in 3.7arcmin resolution.
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  #27  
Old 21-11-2018, 04:02 PM
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Gear cut to size...
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  #28  
Old 27-11-2018, 05:58 AM
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Yesterday afternoon I experimented a bit with two other options - both gears printed, and cheap 360ppr encoders (~$13 at ebay).
Final decision depends on preliminary assemby, maybe this coming weekend.
I am looking forward to holidays... I really need a week or two away from work to sort out all that I started recently...
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Last edited by bojan; 27-11-2018 at 06:38 AM.
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  #29  
Old 09-12-2018, 05:59 PM
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Encoders transmission in place...
(rusty spring goes on first occasion..)
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Last edited by bojan; 09-12-2018 at 06:24 PM.
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  #30  
Old 25-02-2019, 10:01 AM
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This is the final solution for elevation encoder.
The load is now on ball miniature bearing (3mm), and encoder shaft is parallel to horizontal shapt of th etelescope (not that it really mattered for good functionality...)
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