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Rowan Belt Mod - help!

Thalestris24

By Thalestris24
in Discussions - Mounts

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Thalestris24

Thalestris24

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Hi

I'm trying to fit the belt mod to my Heq5. I'm following the instructions and doing the DEC motor first. I've got to step 9 but have a problem with fitting the 5mm pin on to the motor plate. Even with the two grub screws removed I can't get the pin fully in to the hole - it needs to go in about another 7mm. It doesn't mention having to bash it in! Any suggestions?

Thanks

Louise

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sbooder

sbooder

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It's ok - I think! I'm having to kind of screw it in with the aid of a pair of pliers... Fingers crossed!

How old is you HEQ5?  I watched a video on youtube that said the older ones need to have the pin hole drilled out before fitting the pins.  Here is the video.

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Thalestris24

Thalestris24

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How old is you HEQ5?  I watched a video on youtube that said the older ones need to have the pin hole drilled out before fitting the pins.  Here is the video.

Hi Simon

It's only just over a year old. It was ok in the end - the pin just needed some persuasion! But thanks for the link :)

It seems to be running ok. I'm a little unsure about how well the belt will stay on. I've made it tight-ish but not excessively but did notice it moved towards the front of the pulley with slewing. Hopefully both will stay on!

The mount did make a horrid noise once when I pointed it west (unloaded) and it was nothing to do with the mod. Maybe something else needs an adjustment...?? Worm gear??

I also noticed that in certain positions the RA motor/belt would sort of 'tick' (visually and audibly) once every 4 secs. Not sure if that's normal?

Anyway, there may be some clear spells tonight which might be long enough to give it a tracking and a guiding test. Fingers crossed all goes well!

Louise

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Thalestris24

Thalestris24

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I've not been able to confirm anything yet. Tried calibrating with PHD2 but it was a bit squiffy. It still wanted to do backlash steps... Decided I should probably check and adjust PA. Clouds have come in and raining a bit now :(

Hanging on for a clear spell.

Louise

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Thalestris24

Thalestris24

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Louise. The belt does need to be reasonably tight, if too loose it will make a horrible rattling noise with no drive or it will tick if nearly tight enough.  We had similar problems with one recently.  :smiley:

Hi Peter

Thanks - I might go back and tighten a little if I have any problems. The 'horrid noise' I got was not from the belt mod - it was metallic/gear sort of sound and came from elsewhere on the mount...

Louise

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Thalestris24

Thalestris24

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Well I managed to get a short break in the clouds. Calibrated ok but guiding was rubbish! Worse than before the mod! Not happy :(. I thought it would be a lot smoother without any backlash but it was more zig-zaggy than before :( I'll obviously have to investigate...

Louise

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1parsec

1parsec

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Hi Louise,

By your description it appears the guider is causing mount oscillation. Is the zig-zag in RA or Dec?

You've mentioned earlier in the thread PHD wanted to calibrate the backlash and perhaps these settings are still too high following the belt mod.

The belt mod will reduce the amount of backlash in the system and hence more responsive to guide corrections.

You'll need to re-set the guider settings accordingly. Did PHD successfully calibrate the backlash?

Try reducing the backlash setting - or set it to zero to start with. If the guider has to make several corrections before the guide star is re-centred, then increase the backlash setting.

Reducing the 'aggressiveness' of the guide corrections, will also help dampen any possibility of oscillation.

Also try increasing your guide exposures so the guider is not chasing the seeing.

Thanks, Dave.

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Thalestris24

Thalestris24

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Hi Louise,

By your description it appears the guider is causing mount oscillation. Is the zig-zag in RA or Dec?

You've mentioned earlier in the thread PHD wanted to calibrate the backlash and perhaps these settings are still too high following the belt mod.

The belt mod will reduce the amount of backlash in the system and hence more responsive to guide corrections.

You'll need to re-set the guider settings accordingly. Did PHD successfully calibrate the backlash?

Try reducing the backlash setting - or set it to zero to start with. If the guider has to make several corrections before the guide star is re-centred, then increase the backlash setting.

Reducing the 'aggressiveness' of the guide corrections, will also help dampen any possibility of oscillation.

Also try increasing your guide exposures so the guider is not chasing the seeing.

Thanks, Dave.

Hi Dave

Yeah, it was oscillating in both RA and DEC... I was doing longish exposures - 3s. I wasn't able to fiddle with settings because of cloud. I was expecting the belt mod to eliminate backlash so was surprised to see a 'clear backlash' step. Backlash compensation was set to 0 in eqmod. Also, had guide speed set to 0.3. There didn't seem to be any improvement over the original gears and might have been performing worse so that was a disappointment. I obviously expected too much for £100+ !.

Do you have some recommended settings? That would be useful!

On the plus side, Astrotortilla seemed to still work ok :) I'll try again when I get the opportunity - looks like remaining cloudy until at least Tuesday :(.

Thanks

Louise

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1parsec

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Hi Louise,

If the guider is oscillating in both RA and Dec, the guider is over compensating and needs the settings adjusting/ calibrating.

Backlash in itself doesn't cause the oscillation you're seeing.

Usually I have the East side on my mount slightly heavy so the drive is always 'lifting' taking up any backlash.

The belt mod removes the backlash from the brass gears in the drive and also more importantly the reduces the high frequency PE ripple from the tooth-tooth meshing which cycles every 10 sec or so. This ripple is difficult to guide out. The belt mod usually reduces the guide corrections due to the teeth meshing by around 50%.

The backlash from the worm-wheel is unaffected by the belt mod, and should be tuned as normal.

Also check the locking that holds the worm bearings in position are snug and are not allowing the worm the float axially.

I don't use PHD so can't give advise on typical settings, hopefully some one who does could chip in.

Thanks, Dave.

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Skipper Billy

Skipper Billy

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@Louise    Did the noise sound like a belt slipping over the teeth - almost a low frequency vibration ????

The reason I ask is that I once adjusted the worm drive on my HEQ5 to tight and that the sort of noise it made.

It wasnt the belt slipping but it did sound remarkably like it!!!

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r3i

r3i

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Louise. The belt does need to be reasonably tight, if too loose it will make a horrible rattling noise with no drive or it will tick if nearly tight enough.  We had similar problems with one recently.  :smiley:

I found that was also the case when I fitted the corresponding kit to my NEQ6.  I was getting a kind of grinding sound when tracking.  I increased the tension on the belt and it has been fine ever since.

Another problem I had was that I didn't sufficiently tighten the grub screw that holds the worm pulley in place on the 'flat part' of the worm shaft.  That introduced quite an alarming amount of 'backlash'!

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Thalestris24

Thalestris24

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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

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m.tweedy

m.tweedy

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I had what felt like a tick evey turn of the worm. My NEQ6 has has a number of niggles since new hence the belt mod. I had to have a washer made for the end of the worm as it was snagging (nothing to do with the mod) and had to get the belts lined up and tensioned properly as they were initially rubbing on the wall. all minor but cumulatively made the mount initially seem worse. NOT NOW :-) 

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m.tweedy

m.tweedy

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19. Temporarily place the 47 tooth pulley on the worm shaft and check the shaft shoulder is above the pulley face by 1.0mm. Loop a belt around a 47 tooth pulley and slide the worm back into position. Gently tighten the 2 grub screws with longer grub screw against the shaft flat. Check the pulley does not rub on the casting. There must be a small gap between the pulley and side wall of the casting.

mine did at first.

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Thalestris24

Thalestris24

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Mine just says:

Loop the toothed belt around the pulleys and roller

as shown. Gently slide the motor plate to tension the

belt and ‘nip’ the screws to hold in position. The belt

should deflect about 2mm with very light finger

pressure only. Do not over tension the belt.

Louise

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