Gear lash and funky noises

[jeffmar]

I recently put my CGEM mount on a CGE tripod. It is kind of like a CGEM DX with a skinny counterweight bar. It was a significant improvement in stability. When I was testing the right ascension and and declination I noticed the declination had bit of a clunky sound at medium speeds. I could not hear anything at top speed nor at slow speeds. I just couldn't leave it at that so I have been tightening up the gear lash on the RA and declination. I now have no noticeable play in the declination and less than one mm of play on the RA measured at the end of the counterweight bar. I have been testing the RA and declination functions and they are moving freely with no change in the sound. There are still few subtle clunks at speeds 8 and 7. I had never noticed any odd sounds before because I am either slewing my scope at the highest speed or making very small adjustments at very low speed. My first question is how important is it to have to gear lash on my mount? Are the motors more likely to be overloaded if there is no slack in the gears? My last question is whether this little clunking noises indicate anything significantly wrong with my mount?

[TrickySpot]

Hi jeffmar,

Having used a CGEM for many years, I've never had unusual noises at any speed, though putting a C11 with a 70mm guidescope on made it struggle, its just not made for such weight....I also had zero play in either axis, measuring at the end of the counterweight bar could very easily be just play in the bar itself....how hard are you pushing to test? The CGEM is a very noisy mount generally, so its hard to say if a "clunk" is normal or not, all I can say is mine was consistently noisy and more so when under heavy loads.

Having just worked on one of the gearboxes I can say there is no slack in my RA axis gearbox itself, though having backlash between the motor and the gearbox is virtually impossible to eliminate in a mechanism that rotates both ways. I'm not a mechanical engineer though, so hopefully somebody can advise on how much/little backlash is normal. I do know you want it at a minimum for general guiding.

Hope somebody else has more knowledge to help you out!

 

[jeffmar]

19 hours ago, TrickySpot said:

Hi jeffmar,

Having used a CGEM for many years, I've never had unusual noises at any speed, though putting a C11 with a 70mm guidescope on made it struggle, its just not made for such weight....I also had zero play in either axis, measuring at the end of the counterweight bar could very easily be just play in the bar itself....how hard are you pushing to test? The CGEM is a very noisy mount generally, so its hard to say if a "clunk" is normal or not, all I can say is mine was consistently noisy and more so when under heavy loads.

Having just worked on one of the gearboxes I can say there is no slack in my RA axis gearbox itself, though having backlash between the motor and the gearbox is virtually impossible to eliminate in a mechanism that rotates both ways. I'm not a mechanical engineer though, so hopefully somebody can advise on how much/little backlash is normal. I do know you want it at a minimum for general guiding.

Hope somebody else has more knowledge to help you out!

 

I suppose you could say that the CGEM sounds a bit clunky all the time. It certainly is noisy. My CGEM doesn't seem terribly stressed when I have my C11 with a camera and 70mm guide scope on it. If I just go by the sound level I really can't tell much difference unless I have not balanced the mount. It is good to know that gear lash is not necessarily a built in feature of this mount. Changing the tripod really made a big difference in how stable the setup is. Thanks for your input. I really appreciate it!

Jeff

[Glenn_N]

Hi Jeff

I recently purchased a CGEM II + C11. I have also noticed that the mount makes a lot of knocking / clunky noise in DEC slewing in a CW direction but is quiet slewing CCW. It's more obvious at slew rate 7 or 8. The mount is relatively quiet in RA. 

Glenn

[newbie alert]

Think the cgem are just noisy..the original coffee grinder.

Mines very smooth in both axis without any play that I can see..

Is anyone guiding with theirs..ive only just managed to get familiar with the ad bolts as compared to my AVX they're terrible..need beefing up I think..