Rowan Belt Mod - help!

[1parsec]

I think Michael is referring to the NEQ6 and Louise the HEQ5.

On the HEQ5 the long side of the belt should stay perfectly straight as the drive is slewed backwards & forwards and the amount of deflection under light finger pressure should stay the same too.

If you can see the belt 'droop' when the motor is pulling the roller side, then the belt is loose and needs to be a bit tighter.

Finger pressure pushing against the motor block should be enough to put sufficient tension on the belt.

(For the NEQ6 you can't see the belt and it's done by feel alone.)

Dave.

[m.tweedy]

Ha well done Dave.

[Thalestris24]

I think Michael is referring to the NEQ6 and Louise the HEQ5.

On the HEQ5 the long side of the belt should stay perfectly straight as the drive is slewed backwards & forwards and the amount of deflection under light finger pressure should stay the same too.

If you can see the belt 'droop' when the motor is pulling the roller side, then the belt is loose and needs to be a bit tighter.

Finger pressure pushing against the motor block should be enough to put sufficient tension on the belt.

(For the NEQ6 you can't see the belt and it's done by feel alone.)

Dave.

Hi Dave

Thanks! I just had another look and both belts seemed a bit on the loose side... So have tightened them a bit. A quick test was ok and the mount returned precisely to the home position which seems a good sign Looking at the Met forecast map there's only a very small chance of a gap in the clouds tonight. Still, will be keeping a weather eye out! I'm just going over Astrobaby's reassembly/adjustment guide in case there's anything I need to consider.

Louise

[Thalestris24]

Just wondering how critical the 'end float adjustment' is and how it affects tracking and guiding?

Thanks

Louise

[Owmuchonomy]

Thanks for the input guys! The noise I got was when I slewed to the West and I got a brief metallic grinding noise. This was unlikely to have been anything to do with the belt mod. Could have been linked to the lower (RA) worm gear... I did do a strip down last year and maybe something isn't quite right. I normally only point East so haven't noticed it before. The noise happened when initial testing of the belt mod with the mount unloaded... So it looks like I need to adjust something with the RA worm gear? When I did the stripdown I took out the worm gears and gave them a clean but didn't touch the end float adjustment - is that a likely source of the noise?

I don't think any of the belt pulleys are slipping. GoTos have been ok and AT re-centred ok but the amount of testing I was able to do was limited cos of the clouds I have to wait patiently before I can do any further testing.

Louise

Hi Louise the grinding noise is most likely to be the motor clutch. Something is too tight, most likely the belt or the worm drive adjustment. Go through the steps on Astrobaby's website for the worm gear adjustment. I've just purchased the belt kit for my HEQ5 and am about to fit it! I've had requests from elsewhere to report back on my experiences so I will do so. Mine is the older mount so the idler shafts were cut by Rowan before they sent them.

[1parsec]

Hi Louise,

If the nut is too loose the worm will slide end-to end so the axis will have 'backlash' similar to when the worm-wheel mesh is too wide.

Too tight is probably worse because the bearing will be under a high axial load and not rotate freely and will feel sort of gritty when the worm is turned by hand. 

When tightening the nut, start with it backed out and loose. Turn it in towards the bearing just until you'll feel the resistance increase at the point it touches the bearing. Turn the nut in another 1 or 2 degrees tighter from there will probably be more than enough.

Dave.

[Thalestris24]

Hi Louise,

If the nut is too loose the worm will slide end-to end so the axis will have 'backlash' similar to when the worm-wheel mesh is too wide.

Too tight is probably worse because the bearing will be under a high axial load and not rotate freely and will feel sort of gritty when the worm is turned by hand. 

When tightening the nut, start with it backed out and loose. Turn it in towards the bearing just until you'll feel the resistance increase at the point it touches the bearing. Turn the nut in another 1 or 2 degrees tighter from there will probably be more than enough.

Dave.

Hi Dave

I've never touched the end float adjusters before and have always been a bit hesitant to. I'll see how it performs with the tightened belts  - when I get the opportunity!

Thanks

Louise

[Thalestris24]

Hi Louise the grinding noise is most likely to be the motor clutch. Something is too tight, most likely the belt or the worm drive adjustment. Go through the steps on Astrobaby's website for the worm gear adjustment. I've just purchased the belt kit for my HEQ5 and am about to fit it! I've had requests from elsewhere to report back on my experiences so I will do so. Mine is the older mount so the idler shafts were cut by Rowan before they sent them.

Hi Chris

You may be right though it was only momentary and didn't repeat when I tested today. There wasn't any problem in normal use before I did the belt mod. I'll try Astrobaby's adjustment guide if the tracking/guiding hasn't improved. Previously my RA and Dec traces have varied between +/- 4 arc secs with the finder guider + 150pds on the heq5. After the belt mod it was worse! I'm hoping the belt tightening will have improved the guiding. I may also have a problem with the finder guider... I got slightly better guiding with a 60mm guide scope recently. I'm sure it should be able to do a lot better than it has been!

Good luck with your belt mod - it's very easy to install on the heq5! Look forward to your report

Louise

[Carina Lass]

The end float is such an obvious backlash experience that you'd be shocked if you felt that sloppy a fit.

I think it is simple to adjust on the 5 - it is certainly easy on the six and sensitive female hands easily find the point at which it becomes 'zero' play.

[Thalestris24]

The end float is such an obvious backlash experience that you'd be shocked if you felt that sloppy a fit.

I think it is simple to adjust on the 5 - it is certainly easy on the six and sensitive female hands easily find the point at which it becomes 'zero' play.

Hi

I'll have a look at the end floats tomorrow I was able to do a few (shortish) guiding tests between the clouds earlier but it was still erratic compared to pre-mod. I can't believe I've managed to make it worse than it was before the mod ! Perhaps I should have left it alone...

Louise

[Thalestris24]

Looked out of the window at 01:45 and it was clear! Not forecast clear, of course... So had another quick go. Was able to get a slightly better graph (mostly +/-2 arc secs) with a not too bad RMS error but still occasional jumps. I only got the better guiding at lower alt though, and my mount does seem to have an ongoing problem with tracking/guiding when pointing at altitudes above 30 deg. Oh well, more testing and fiddling needed. I'm so envious of people who can get nice flat graphs! I know it's the stars that count, but still - I want both!

Louise

[wxsatuser]

Just wondering how critical the 'end float adjustment' is and how it affects tracking and guiding?

Thanks

Louise

It is critical.

To tight and you will pinch the bearings, to slack and the worm will float about.

Wind the adjuster in so it just touches the bearing and you can't feel any endfloat.

You can tell if it's pinched as the shaft will feel stiff, it should rotate freely with no float.

[Carina Lass]

Mines not flat, theres a slight sine wave on the dec. Periodic error I think.

But the max deviation from baseline is less than .3 pixel. I haven't done more than twiddle. Haven't even done a lube job.

I always bias my weight to the East and try to be consistent with everything I do.

Seems to work.

[Thalestris24]

Mines not flat, theres a slight sine wave on the dec. Periodic error I think.

But the max deviation from baseline is less than .3 pixel. I haven't done more than twiddle. Haven't even done a lube job.

I always bias my weight to the East and try to be consistent with everything I do.

Seems to work.

Hiya

Yeah, PE is to be expected! 0.3 pixel - what's that in arcsecs for you? Do you have the belt mod? I've kindof assumed that with the belt mod, balancing should be closer to true?

Louise

[Thalestris24]

It is critical.

To tight and you will pinch the bearings, to slack and the worm will float about.

Wind the adjuster in so it just touches the bearing and you can't feel any endfloat.

You can tell if it's pinched as the shaft will feel stiff, it should rotate freely with no float.

Thanks Mike

Um, I'm not sure what I'm looking for?? I've not been able to loosen the RA float adjuster - will try again. I've loosened the DEC float adjuster. I'm presuming it's the spindle that should then have some play? I'm not really understanding... I can rotate both spindles with some pliers (even the RA one that isn't loosened) but is there supposed to be like side-to-side play?

Louise

[Thalestris24]

Thanks Mike

Um, I'm not sure what I'm looking for?? I've not been able to loosen the RA float adjuster - will try again. I've loosened the DEC float adjuster. I'm presuming it's the spindle that should then have some play? I'm not really understanding... I can rotate both spindles with some pliers (even the RA one that isn't loosened) but is there supposed to be like side-to-side play?

Louise

Ahhh!!! I see! It's play in the actual axes that I'm looking for!! It doesn't actually say that explicitly... I don't think there was any play in either axis before. I hope I've not messed thinks up even more by loosening the adjusters... I've tightened them up as much as I can and about to give it a 360 deg test.

Louise

[Carina Lass]

What happens inside is the worm even though engaged perfectly with the gear wheel with minimal play is able to slide axially in its bearings. This allows a huge clonky movement as the spindle moves back and forth with the bearings when force is applied to the portion attached to the gearwheel (Dec or Alt).

One side of the bearing (on the neq6) is retianed by the cover (which is metal andremovable springclip pliers) It is tightened up to the mount casing before adjusting the other side.

The other side, when the cover is removed houses a retaining ring inside which abutts the outer bearing case and has two slots for tightening - this forces the bearing and thus the worm and the other bearing onto the cover on the other side. Too much force and the bearings are nipped  too little and they move about axially causing the clonky free play.

[Thalestris24]

Hiya

End float adjustment seems to be much simpler with the heq5 but hard to judge whether it's just right or maybe a bit too tight... I'm patiently waiting for some clear skies to re-test it properly again. Maybe in a couple of days if I'm lucky.

Thanks

Louise

[Tinker1947]

You should beable to judge the end float if you remove the non adjusting black cap and wobble the mount back and forth in DEC or RA which ever cao you have removed, and end play will be shown as the worm end moving back and forth, adjust until the end movement stops....you can do this in day light,,,,

[Thalestris24]

You should beable to judge the end float if you remove the non adjusting black cap and wobble the mount back and forth in DEC or RA which ever cao you have removed, and end play will be shown as the worm end moving back and forth, adjust until the end movement stops....you can do this in day light,,,,

Yeah, I did that I'm waiting for clear skies so I can test it...

[Thalestris24]

I re-balanced yesterday so that the 150pds is in perfect balance (as per Dion's video). I figure that with the belt mod I don't need the usual imbalances. Got up at 04:30 this morning (it was clear!). Calibrated ok but guide graph was still rubbish and still more erratic and bigger errors than I had before the mod There seemed to be sudden jerks sometimes up to 6 arcsecs and occasionally more. Getting fed up now and contemplating going back to the cogs

Louise

[wuthton]

Have you definitely tuned out all the backlash from the worm and the float so there's no "jiggle" in either axis when you give the scope a wiggle?

Hmmm, that nearly rhymed.

[Thalestris24]

Hi

Well I just tightened the end float a bit more... I find it hard to tell whether there may be play rather than the whole mount moving/flexing - if I put enough force on it. I've not looked at the worm adjustment since I last did a stripdown - a while ago! However, there doesn't seem to be any play in either axis now. I don't really understand why it could be worse than before I did the belt mod. I might possibly get another chance to do another quick test early evening. If not, it might not be clear until at least next week

Cheers

Louise

[1parsec]

I re-balanced yesterday so that the 150pds is in perfect balance (as per Dion's video). I figure that with the belt mod I don't need the usual imbalances. Got up at 04:30 this morning (it was clear!). Calibrated ok but guide graph was still rubbish and still more erratic and bigger errors than I had before the mod There seemed to be sudden jerks sometimes up to 6 arcsecs and occasionally more. Getting fed up now and contemplating going back to the cogs

Louise

Hi Louise,

I think from your description the guider is over correcting as it's highly unlikely the belts are causing a 6 arc sec jump.

The over corrections may have previously been 'hidden' in the gears backlash, but now showing up with the lower backlash belt mod.

Have you taken a Periodic Error log ? That is recording the star position with the guider but with the guider set so that it doesn't issue corrections ?

If the PE graph doesn't show the jumps - it's the guider causing the issue.  If the jumps are still there then it's some where in the drive.

The PE graph will tell you what is happening and when.

Thanks, Dave. 

[Thalestris24]

Hi Louise,

I think from your description the guider is over correcting as it's highly unlikely the belts are causing a 6 arc sec jump.

The over corrections may have previously been 'hidden' in the gears backlash, but now showing up with the lower backlash belt mod.

Have you taken a Periodic Error log ? That is recording the star position with the guider but with the guider set so that it doesn't issue corrections ?

If the PE graph doesn't show the jumps - it's the guider causing the issue.  If the jumps are still there then it's some where in the drive.

The PE graph will tell you what is happening and when.

Thanks, Dave. 

Hi

No - not yet though it's been at the back of my mind I need a decent clear spell to test it properly and, if necessary, make a log without guiding on. I should mention, it was giving mostly a +/- 4arcsec error. and it was doing that before the mod as well. It does tend to zig-zag... I've tried varying the guiding settings but they've not made much difference so far. Fingers crossed the extra end float tightening I did earlier might have helped. A whole evening/night of clear skies would be good. Not very likely though

Cheers

Louise