Delay in DEC motor starting

[Peco4321]

Searched but not found anything on this. 

I have enhanced RA and DEC motors fitted to my eq3-2 and there seems to be a delay of about 4 seconds when I switch direction in controlling the DEC direction. It's fine once moving in one direction if I pause then start again it's pretty much instant but if I then switch to opposite direction it does not turn for about 3-4 seconds. The RA works fine switching direction almost instantly. This also happens when there is no payload on the mount at all. 

Is this normal?

[jambouk]

It sounds like there is a lot of backlsh in the dec. it's normal to have a bit in these kind of mounts. I don't know if the problem is the mount or the motor, but you might be able to reduce the back lash a little. 

[Peco4321]

Thought it was that but all this terminology just though I'd check . Now searched on it and found something to try. 

Thanks @jambouk. 

[Peco4321]

I have tried all the tightening as described in earlier posts about backlash but there is still s delay. If I take the DEC motor off the cog attached to the DEC axis, it performs fine. I will attach a video clip later tonight but in the meantime any suggestions welcome. Thanks. 

[StuartJPP]

I had a similar issue with a totally different mount...

It was a toothed gear that had a loose grub screw attaching it to the motor shaft. So when you changed direction the gear would slip as the grub screw was not engaged for ~1/4 turn until the grub screw caught the shaft. It would only do it when changing slewing direction.

Like in this video where you can see a delay before the worm wheel starts to move (this was at slewing speed, not tracking speed).

 

[Peco4321]

@StuartJPP is it something you just have to live with then. 

[StuartJPP]

1 hour ago, Peco4321 said:

@StuartJPP is it something you just have to live with then. 

Nope, I dismantled it to get the belt off and fastened the grub screw underneath. It made all the difference.

[Peco4321]

So here's a clip and pictures to show what's going on. Once turning it's ok and if I stop and continue in the same direction it's ok, but when I change direction there is this 4 second delay. I have done what was described but no change. 

IMG_1535.MOV

[StuartJPP]

Looks to me like there is a lot of backlash in the motor housing itself. From the video clip it looks like the parts labelled 1 & 2 move in unison but only after the mentioned ~4 seconds however you can hear the motor running during those 4 seconds after the direction change.

Not sure what to suggest...looks wrong to me. Is the RA motor identical (except that it doesn't suffer from this issue)?

 

[Peco4321]

@StuartJPP, RA motor is different design and seems to work fine.  I only bought it December so I will send video to RVO for their thoughts, thanks for your input.

[Peco4321]

RVO have confirmed "the suppliers say it is normal. The reason there is a delay is that the motor takes up the slack in the gears before changing direction. "

Anyone else have this with eq3-2 motors?

[Peco4321]

I think I have this sorted now, I simply twisted the slow motion control all the way, taking up the slack I guess, until it would not turn, then when running the DEC motor and swapping direction, the delay was gone. 

[Peco4321]

Not sure now, when scope was on there was a delay. Will test again in daylight.