worm adjustments and go-to vs. non go-to stability

I am wondering about how worm gear mesh in many different mounts affects overall system stability.

On my stepper version G11, I have the backlash set to about zero, because the stepper motors don't stall or burn out. With a gemini unit a "clunk" is recommended in the adjustment so the motors don't stall.

I began to wonder about servoCAT systems, which display a lot of backlash in the two units I know. There is a tendency for the object being tracked to wander 50% out of center while the worm "catches up" to do the tracking. So, lots of backlash there. Lots of backlash in an ASGT I've seen, and in many other go-to configurations.

It seems to me that with some backlash in the drive adjustment on one or both axes, the scope is more vulnerable to vibration because in windy conditions it can "move" the distance between the worm teeth in response to wind.

So it seems to me that on many worm driven systems there will be more loss of stability to wind shaking than on an equivalent system that can use a tighter backlash adjustment.

Is this true? thanks

Greg N

I see what you are saying, but I don't think
backlash plays much role in wind driven vibration.
I usually leave plenty of backlash in the worm
adjustment, and that backlash corresponds to a huge
motion of objects in the field (at high powers like
500x). I can grab the scope and move it to the other
side of the backlash, and its a huge motion.
But I'm not seeing that large motion in wind conditions.
Instead I see very small motions. What I see happening,
is that the wheel gear settles against one side of the
backlash (due to either slight off-balance or drive
direction for RA) and stays there.
The wind-driven vibration is instead caused by
everything from the ground to the scope bending and
flexing slightly.

Maybe if the wind completely changed direction every
few seconds, I guess you could get the backlash coming in.
Like if it came from the East for 1 second, then from
the West during the next second, then from the
East again during the third second, etc.
But instead what I get is wind from a nearly constant
direction, which varies in velocity (pressure).
Everything flexes in proportion to this side-ways
variable pressure on the tripod / mount / scope.

Some vibration sources I found in my G11 stepper
were:

Poor machining of the pier top / mount bottom joint.
Essentially the mount head was contacting the
pier top at only one or two places, and was rocking
back and forth on the pier top. Some simple shims
fixed the problem and gave 3-point contact.

The steppers ran at something like 1/2 arcsecond
steps, which showed up as a 1/2 arcsecond blur
on targets (depending on the mount load, pointing
direction, etc.). Gemini was better in this regard.

The RA worm gear was somewhat free to move along its
axis, adding a sort of springy motion in RA.