HEQ5 RA gear stiffness

[Sabalias]

Hi All,

I recently took delivery of my HEQ5 Pro which I gave the once-over. I found that the Dec was good and sturdy but the RA had considerable movement (I presume due to the worm gear not being fully engaged). I followed the adjustment instructions on Astrobaby's site and, when I came to testing the mobility of the gears under the motor cover, I found that the Dec gears move quite smoothly and freely but the RA gears are quite stiff (it moves but it requires more effort than the Dec); this is both before and after the adjustment. Is this normal? I was thinking it might be because the RA is carrying more weight than the Dec (i.e. the weight of the whole mount rather than just the mounting bracket).

Thanks,

Stu

Edited July 1, 2021 by Sabalias

[7170]

 

22 minutes ago, Sabalias said:

Hi All,

I recently took delivery of my HEQ5 Pro which I gave the once-over. I found that the Dec was good and sturdy but the RA had considerable movement (I presume due to the worm gear not being fully engaged). I followed the adjustment instructions on Astrobaby's site and, when I game to testing the mobility of the gears under the motor cover, I found that the Dec gears move quite smoothly and freely but the RA gears are quite stiff (it moves but it requires more effort than the Dec); this is both before and after the adjustment. Is this normal? I was thinking it might be because the RA is carrying more weight than the Dec (i.e. the weight of the whole mount rather than just the mounting bracket).

Thanks,

Stu

Is it a new mount or used?

If the RA clutch is fully disengaged does the RA axis turn very freely or is it slightly stiff, assuming good balance (worth testing with no scope or weights on it)? 

 

[AstroMuni]

1 hour ago, Sabalias said:

but the RA gears are quite stiff (it moves but it requires more effort than the Dec); this is both before and after the adjustment. Is this normal? I was thinking it might be because the RA is carrying more weight than the Dec (i.e. the weight of the whole mount rather than just the mounting bracket).

Have you tried it with and without adding the counterweights?

[Sabalias]

2 hours ago, 7170 said:

 

Is it a new mount or used?

If the RA clutch is fully disengaged does the RA axis turn very freely or is it slightly stiff, assuming good balance (worth testing with no scope or weights on it)? 

 

It’s a new mount and the axis turns free and smooth when the clutch is disengaged. So far after adjustment I’ve not used weights or scope on it. 
 

Just for clarification, the motors work fine, I’m talking about turning the gears with my fingers as described in the link

https://www.astro-baby.com/astrobaby/help/rebuilding-the-skywatcher-heq5orion-sirius-mount/adjusting-worm-gear-engagement-motor-gears/

Stu

Edited July 1, 2021 by Sabalias

[Padraic M]

Hi Stu, I'm not sure that you have a problem. I would imagine that any resistance you feel when turning the cogs by hand will come from the motor through the reduction gearing rather than from the worm. That step is to check if you have binding caused by tightening the worm too far. If the motor can rotate the axis through 360 degrees then you don't have binding - it will be pretty obvious if you've overtightened as the motor will be forced to a halt at some point in the rotation (or at least you will hear it struggling).

The trick with backlash is to tighten just enough so that there is no binding. For my mount, there is still a small amount of backlash left in the worm but you do the best you can.

[Seelive]

I assume that when you are moving the axes by hand you are also moving the stepper motor via the preceeding gears.  Depending upon the gearing ratios, where you try to turn the axis can make a big difference to the apparently required torque.  Ideally, you need to 'feel' the torque needed to turn only the worm and wheel when the axis is balanced (and as the RA axis wheel will have more teeth, it should always appear to be 'easier' to turn?)

[Sabalias]

1 hour ago, Seelive said:

I assume that when you are moving the axes by hand you are also moving the stepper motor via the preceeding gears.  Depending upon the gearing ratios, where you try to turn the axis can make a big difference to the apparently required torque.  Ideally, you need to 'feel' the torque needed to turn only the worm and wheel when the axis is balanced (and as the RA axis wheel will have more teeth, it should always appear to be 'easier' to turn?)

So, under the side panel of the mount there are two pairs of gears. The test is to see if is possible to rotate both of the larger brass gears - the Dec gear turns easily while the RA gear requires a bit more force. Both of the axis gears rotatate 360 degrees and move the corresponding axis of the mount.

Stu

[Sabalias]

2 hours ago, Padraic M said:

Hi Stu, I'm not sure that you have a problem. I would imagine that any resistance you feel when turning the cogs by hand will come from the motor through the reduction gearing rather than from the worm. That step is to check if you have binding caused by tightening the worm too far. If the motor can rotate the axis through 360 degrees then you don't have binding - it will be pretty obvious if you've overtightened as the motor will be forced to a halt at some point in the rotation (or at least you will hear it struggling).

The trick with backlash is to tighten just enough so that there is no binding. For my mount, there is still a small amount of backlash left in the worm but you do the best you can.

Thanks Padraic. I think you might be right. As far as tuning out the backlash is concerned - I was extremely careful to make only very small adjustments until the loose movement of the RA vanished.

Stu