Slightly grindy sounding DEC axis at certain speeds (EQ6)

[rnobleeddy]

I have an EQ6 mount that I got 2nd hand without GOTO, and added the GOTO motors and a new motherboard panel (probably the only black and white mount out there!). I'd resigned myself to having to strip it down and regrease etc when I bought it, but it turned out to guide pretty well, and so I figured I'd leave it for now.

Always controlled via EQMOD/INDI until tonight. In a failed attempt to find focus with a new camera/barlow/assortment of extenders and adapters, I was using a handset I bought from another member recently, and found the mount is making a rather unpleasant grinding noise at intermediate speeds, on the DEC axis only, when used with the handset. It's not there at slow speeds or at full speed. 

Realise it's hard to hear on a video but wondering if anyone had heard a similar noise and diagnosed it? It sounds a bit like gears grinding, but then it's only happening at a certain intermediate speed, so wonder if something is loose and this is resonance? I'll pop the panel off and have a look anyway at the weekend, check grease etc, but from memory when I installed the motors, there wasn't a great deal of play available in the motor positions.

For the video, the first short move is in RA. I then tried a few times to modulate the DEC movement to maximize the noise.

 

 

 

 

 

[jonathan]

From your description it does sound like there may be some slack somewhere that slow speeds don't 'activate' and fast speeds overcome.  If the motors are identical then you could try swapping them over and seeing if the noise follows the motor, or if it's possible to do so then swap gears over one at a time.  It could be the motor spindle that has some play, not sure what you could do if that was the case.

[rnobleeddy]

Should anyone find there way here with the same issue - I was able to get rid of the noise by adjusting the motor so the gears were further apart. Not sure why it only happened at certain speeds but all fixed now.

[faulksy]

5 minutes ago, rnobleeddy said:

Should anyone find there way here with the same issue - I was able to get rid of the noise by adjusting the motor so the gears were further apart. Not sure why it only happened at certain speeds but all fixed now.

the distance is called backlash, they should be set when there at there tightest spot. this due to gears etc being bored slightly off centre or the shaft being slightly smaller than the bore ( not a interference fit) 😑