Belt Mod Tuning

[Dec]

Hi,

I recently fitted the rowan belt mod to my NEQ6 but the guiding (with PHD2) is worse than pre-modification. The PHD2 graph is all over the place.

I've checked my polar alignment and balanced everything.

I'm pretty happy with the mod as the mount now moves silently on both axis and there is virtually no backlash in either axis.

I think the guiding is down my poor tuning of the RA & DEC axis grub screws but am not sure.

Do I need to alter the PHD2 settings?

Could the worm gear be too tight on the main cogs?

Do I need to tighten/loosen the belt motors?

Any tips/advice would be greatly appreciated

[vlaiv]

Can't really tell what might be going on without further information of how is guiding affected.

What I do know about belt mod (on HEQ5 that is), is that I had trouble with poor guiding due to it because of improper belt/gear meshing. I had infamous 13.7s oscillation due to it (period of single tooth on RA drive). This was easily fixed just by tightening RA belt (by moving motor away from RA worm) - on HEQ5 there is a bit of room to adjust tension in belt.

This problem manifests itself depending on load on mount. By increasing tension I first stopped having it with small (light) scope, but heavier scope still experienced it. After further increase of tension it stopped showing with heavier scope as well.

HTH

[Peter Drew]

I agree with Vlaiv, belt drives can be affected by belt tension and/or alignment of the belt pulleys, successful running adjustments can be fiddly and need imaging sessions to prove any improvement. Certainly tight is better than loose.  

[Dec]

28 minutes ago, vlaiv said:

Can't really tell what might be going on without further information of how is guiding affected.

What I do know about belt mod (on HEQ5 that is), is that I had trouble with poor guiding due to it because of improper belt/gear meshing. I had infamous 13.7s oscillation due to it (period of single tooth on RA drive). This was easily fixed just by tightening RA belt (by moving motor away from RA worm) - on HEQ5 there is a bit of room to adjust tension in belt.

This problem manifests itself depending on load on mount. By increasing tension I first stopped having it with small (light) scope, but heavier scope still experienced it. After further increase of tension it stopped showing with heavier scope as well.

HTH

Thanks Vlaiv, I'll tighten up the belts and see if that helps.

I thought I had it cracked as the scope pointed perfectly at the target after the plate solve but when I started guiding the Dec and Ra lines were moving wildly on the graph.

 

[vlaiv]

Another thing that might be the issue, again related to tightness of belts - was it windy? Belts unlike regular gears put a bit of "elasticity" in mount, especially if a bit loose - and oscillations caused by wind can then have greater impact on guiding then usual.

[Dec]

31 minutes ago, Peter Drew said:

I agree with Vlaiv, belt drives can be affected by belt tension and/or alignment of the belt pulleys, successful running adjustments can be fiddly and need imaging sessions to prove any improvement. Certainly tight is better than loose.  

Thanks Peter. I'll check the pulley alignment too.

You're partly to blame for this as it was a trip to your Astronomy Centre last year that inspired me to take up this wonderful (sometimes frustrating) hobby ?

To be honest I love every minute of it.

Really appreciate your help. 

[Dec]

17 minutes ago, vlaiv said:

Another thing that might be the issue, again related to tightness of belts - was it windy? Belts unlike regular gears put a bit of "elasticity" in mount, especially if a bit loose - and oscillations caused by wind can then have greater impact on guiding then usual.

No vlaiv, it wasn't particulary windy when I tested it. Although a good point and one I hadn't considered.

I have the scope in an enclosed area and pretty well protected from the wind. Its a 10" Newtonian so a bit susceptible to getting blown about.

Thanks again for your help.

[r3i]

I did the Rowan Belt mod a couple of years ago and it took me 2 or three attempts to get it right (my fault, not the Rowan the kit).  I found had to increase the tension on the belts to get it sorted but once I had got it right, the mount has performed really well, my PE was almost halved.

[Dec]

11 minutes ago, r3i said:

I did the Rowan Belt mod a couple of years ago and it took me 2 or three attempts to get it right (my fault, not the Rowan the kit).  I found had to increase the tension on the belts to get it sorted but once I had got it right, the mount has performed really well, my PE was almost halved.

Thanks r3i that's really good to know. My first reaction when I saw the guiding performance was that I'd done something wrong or maybe hadn't lubricated the components properly. If tightening the belts and checking pulley alignment doesn't work, I will probably strip the parts and start again.

[kens]

Other things to look at are the worm end float and make sure you have not over tightened the collar on the counterweight shaft. Check out Astrobabys guide:

http://www.astro-baby.com/EQ6 rebuild guide/EQ6 Strip Down Home.htm

[Dec]

7 minutes ago, kens said:

Other things to look at are the worm end float and make sure you have not over tightened the collar on the counterweight shaft. Check out Astrobabys guide:

http://www.astro-baby.com/EQ6 rebuild guide/EQ6 Strip Down Home.htm

Thanks kens I'll have a look at that. The Astro baby guide will be a great help.

[LightBucket]

There are other threads on here about this exact issue, i recently posted abou this, and found that the locking ring on the worm gear does not need to be very tight at all, in fact just tight enough to take out slack of worm and then maybe another 1/8th of a turn, the same with the counterweight bar locking collar, people tend to tighten as far as they will go, but again just tight enough to remove the bearing slack and another 1/8th of a turn..these two things are NOT covered in the astrobaby guide, in fact the former regarding the worm gear locking ring in the Astro baby is actually incorrect, as it states to “tighten the locking ring until the worm binds then loosen a bit”, well if you do that when you tighten till it binds you may well damage the bearing at that point, and its then too late and no point in loosening a bit....so ignore that section..

William