Open Source DIY Strainwave Mount

[garymck]

https://astrophilos.com/blog/

cheers
Gary

[Leo.G]

Thanks Gary!
I've long contemplated a project along these lines not wanting to try and machine and mill the gearing required (plus having a friend who runs an engineering shop who does jobs for me extremely cheap) and I have long searched Aliexpress contemplating trying to get some bits together.
Now I'm going to go through this article and strongly consider replicating it.
Now I just need the clouds to ease up for more than half a night.

[bojan]

Hi Gary,

Interesting project..
I have read comments on other forum from someone who tried it.
The GoTo precision was not tested (OnStep is known to be OK so if there are issues, they will be mechanical).
I am somewhat suspicious about maximum load..

[BillR]

Hi All,
I did contemplate this approach but in the end bought a Juwei 17.

I have the gear needed and the time. However, backlash specifications for strain wave gears on Aliexpress vary from < 30 arcsecs to zero with prices varying from a few 100 dollars to a few thousand dollars so what do you use? At the cheap end you could build a mount for around $1000 that would have significant backlash or at the expensive end a mount that would cost more than an Zwo AM5!

Bill

[garymck]

Bill,
I did the same, bought a Juwei, was thinking about buying a Wave150i or AN5N, but after reading a number of threads decided that they were no better than the cheap options. One comment I saw was that the tracking was equivalent to to a mount that was a quarter the price and that you were paying for light weight. I can for example get guiding as good as an AM5 when I use similar guide settings using an my AZGTi! The strain wave mounts are in many ways a marketing triumph. Pay lots for less performance….
Gary

[rising]

HBK-17 SW gears are fairly inexpesive and have been used in DIY mounts. You probably want a type where the input is fully located by bearings so that the wave generator longitudional position and alignment is not dependant on bearings in whatever is attached to the input.

There is a long thread on Cloudy Nights for Laplase's design.

https://www.cloudynights.com/topic/901018-diy-3d-printed-harmonic-drive-mount/?hl=%20diy%20%20harmonic%20%20drive

The main issue is probably not backlash but the magnitude and shape of the periodic error curve.