Re: Backlash compensation/PEC #EXOS2 #VIDEO

Jerry Hubbell - Explore Scientific VP Engineering

On Fri, Mar 27, 2020 at 11:01 AM, wayne archard wrote:
This is probably a stupid question but does the Exos 2 GT with its drive belt system suffer from backlash and PEC?  Thank you.
Hi Wayne,

I was going back through the messages on the MAIN group and noticed that your question fell through the cracks. You may have already found the answer. The backlash on the EXOS 2 PMC-Eight is mainly in the worm/wheel mesh. The belt drive system smooths out the PE. There are a couple of main components of the PE in the system. The first is the 600 second fundamental of the worm period. This is based on the 144 tooth wheel/ring gear. The second fundamental is a 133.3 second period based on the 4.5 to 1 ratio of the belt pulley system. 600 seconds / 4.5 = 133.3 seconds. This is caused by any slight wobble that may be on the motor pulley. There are other harmonics of these fundamental periods caused by belt tension issues and other miscellaneous issues.

We recently did an OpenGOTO Community Live program talking about how to analyze your gear system using the guide logs from PHD2.  Here is a link to the video on YouTube:

Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at
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Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home

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