EQ6 belt mod

[ncjunk]

Great write up Jack, the pictures are excellent. I don´t think the out of true bore would have bothered me

too much as still improved the guiding when compared to the gears. My problem was the belt and adjustments so your cut-outs are an

excellent idea and the paint jobs fantastic!

[philming]

Hi all !

I recently purchased a Lacerta OAG at Teleskop Austria. Since I'm a new client, I went around and watched the mount accessories they had.

And hey, what did I find ?

http://www.teleskop-austria.at/shop/index.php?lng=eng&m=2&kod=sbau-bor-das-6p&skod=%2017&om=Mounts

I wrote them an email to find out if this mod did change the way the Synscan HC was acting.

And apparently not. With this kit you can keep on using the HC just like before, without having to go through the EQmod routine...

[Fred_76]

Hi

We did that mod in our club for two EQ6 and one HEQ5 (mine). It works pretty well. My periodic error felt down from the usual +/-30 arcsec to less than +/-9 arcsec.

You can see more here (in French, use Google Translate) :

http://www.webastro.net/forum/showthread.php?t=105519

[Fred_76]

Forgot to say that the ratios are the same as before the mod, so the Synscan hand controller can be used as before.

[perfrej]

I have worked with belted solutions before and have been thinking of doing this to my NEQ6 for a long time. It will complement the quality SKF bearings that I put into it year before last. I figured I'll buy the parts from a local supplier, but then comes the problem: you have to drill out the axis hole yourself. The wheels come unbored. So, at €159, ready to bolt on and tension, this seems like a very good alternative. Thanks for the link!

/per

[Fred_76]

This is cheaper here :

http://www.tavcso.hu/?o=termek&te=EQ6bord&n=en

We purchased our belt mod from them. They were very responsive and also revised they design for the heq5 after my feedback.

[jackrussell0232]

Hi

We did that mod in our club for two EQ6 and one HEQ5 (mine). It works pretty well. My periodic error felt down from the usual +/-30 arcsec to less than +/-9 arcsec.

You can see more here (in French, use Google Translate) :

http://www.webastro....ad.php?t=105519

Guys, can I just add a pinch of realism here. The belt conversion alone cannot significantly reduce the magnitude of the PE, as this is driven by the worm/ring gear (which aren't replaced) and also the worm bearings (which should be, but it isn't really an essential part of a 'belt mod'). What it does do, is remove any elements of the PE curve which come from the transfer gear (which is eliminated altogether) and also the high frequency gear mesh elements. The removal of the transfer gear also reduces backlash. These 2 factors makes the mount easier to autoguide.

I'm not saying you can't go from +-30 to +-9, after the belt mod, but you would probably have found that you could have got the magnitude down to this just by carefully resetting the worm/ring engagement. Anyone who has stripped and rebuilt eq5 and 6's knows how critical setting this mesh can be.

In terms of the ratio change, I suppose some people do still want to use the hand controller, but if you're imaging (which is the only reason you'd need to belt mod) then surely you're going to be driving the mount with EQMod, or another ASCOM driver, and therefore changing to a 4:1 ratio is not a disadvantage. This is why I went for a 15/60 pulley set up. Using a smaller stepper motor pulley increases the risk of it being bored off-centre, which can add a significant 4th harmonic to the PE (although you can have one from the worm anyway).

Much more info on my website.

[Fred_76]

Jack.

The PE is a combination of the out of tolerances of all mechanical parts of the mount driving system. It is not only the worm but also the axis of the stepper, the spur gears, their axis, the worn gear, the bearings, and so on.

The main contributors of the PE of the original mount are :

- the gears mesh

- the gears

- the worm gear

- the worm gear bearings

Replacing the 3 gears by a set if 2 pulleys and a belt reduced the PE of my mount from 30 arcsec to 9 arcsec. I did not changed anything else such as worm gear pressure, bearings...

I can still improve the PE by fine tuning the worm gear and changing its bearing (I just received the 689 2RS bearings). But I believe I will hardly go under 6 arcsec. At least the speed of PE variation will be much slower, and this is better for auto guiding.

For sure, a 15 teeth pulley will be machines with better control on its tolerances, compared to a 9 teeth pulley. It indeed tried to find some 18 and 94 teeth for T1 belt but could not find any. This size exists but is not available for public customers... too bad.

[jackrussell0232]

Fred,

I agree with almost everything you say, but I think that in most people's experience, although all the drivetrain components contribute to the PE curve, the most significant element comes from the worm.

For your mount to improve so much, the gear on the end of the worm in your mount originally must have been horrible.

All the other components add harmonics to the curve, but these typically do not have a huge impact on the pk-pk size of the PE, they just make it more lumpy.

I've helped many people belt mod their mounts, but few have seen a significant reduction in PE pk-pk amplitude. What they have got rid of is all the gear mesh noise (both audible and tracking noise) - so no more 0.2Hz ripple on the PE which is impossible to guide out. It also cuts the backlash significantly, which also helps with guiding.

And while you may not realise it, you will have changed the worm gear pressure. You must have, because there is always some radial play in the worm bearings and you are now pulling on it with a belt! Before it was being pushed around by a gear.

None of this matters if it's working well, but if I had a PE of +_9 arc secs, I probably wouldn't change the bearings! I changed mine for some which were supposedly ABEC9 and immediately changed them back.

Jack

[perfrej]

Jack,

If you change the bearings to better ones, like SKF, there is abolutely no play radially in the worm gear. The original ones that I took out did have some play after less than a year of use. That may be one of the most important simple mods to do on an NEQ6!

I will send my two 10Micron mounts off to remote sites over the summer, one of them in southern France, one in the STockholm Archipelago. The NEQ6 thus becomes my only mount at home and I will do the belt mod immediately along with a altitude bolt mod that is badly needed at my latitude. I already did main bearings and worm bearings. It is a very good mount when some of the parts are changed...

/per

[Fred_76]

You will find below all periods related to the HEQ5 and EQ6 mounts, unmodified.

HEQ5

Spur Gears module 0.8

- gears mesh : 13.6 s

- stepper gear (9 teeth) : 122.2 s

- transfer gear (28 teeth) : 382.2 s

- worm gear (47 teeth) : 638.3 s

- worm crown : 23 hours 56 min and some secondes (135 teeth)

Bearings

#689 (worm bearings)

• Defect on internal band : 108 s
  
• Defect on external band : 156 s
  
• Defect on one ball : 121 s
  

#6006 (axis bearing)

• Defect on internal band : 3 h 43 min
  
• Defect on external band : 5 h 14 min
  
• Defect on one ball : 4 h 08 min
  

#30205 (axis stop)

• Defect on internal band : 2 h 25 min
  
• Defect on external band : 3 h 21 min
  
• Defect on one cone : 4 h 05 min
  

EQ6

Spur Gears module 0.8

- gears mesh : 10.2 s

- stepper gear (12 teeth) : 122.2 s

- transfer gear (36 teeth) : 366.6 s

- worm gear (47 teeth) : 478.7 s

- worm crown : 23 hours 56 min and some secondes (180 teeth)

Bearings

#608 (worm bearings)

• Defect on internal band : 108 s
  
• Defect on external band : 187 s
  
• Defect on one ball : 139 s
  

#6008 (axis bearing)

• Defect on internal band : 3 h 29 min
  
• Defect on external band : 4 h 40 min
  
• Defect on one ball : 3 h 35 min
  

#32208 (axis stop)

• Defect on internal band : 2 h 25 min
  
• Defect on external band : 3 h 21 min
  
• Defect on one cone : 4 h 05 min
  

As a conclusion for the bearings, you'll see that only the worm bearing is critical (short periods of a few minutes) and shall be of good quality. the other bearings have very long periods and a carefull clean up and regreasing should be enough.

[jackrussell0232]

Fred, did you type all that from memory? Impressive!

However, back in the real world, anything with a period which is an order of magnitude larger than the worm period is pretty irrelevant in terms of PEC and autoguiding. Yes, a dodgy RA shaft bearing may cause a dropped sub once a night, but a speck of dirt could do that, and it will probably have transferred onto a different part of the bearing for the next rotation, so most of these numbers are pretty meaningless, sorry. This is especially the case when you consider that all of these will be going on at the same time. But having said that, I certainly won't take you on at mount error period 'top trumps'.

And Per, you make me laugh. I wish I was you. 'I need to make sure my EQ6 is sorted, because I've sent my GM2000 and GM1000 to sites with better seeing'. Are you trying to make us all green with envy? I know what you mean about the worm bearings though. I did change mine from the synta ones to SKF and saw a slight improvement. I then changed them to ones which were supposedly ABEC9, and my PE suddenly jumped from +_15 to _+35 ish - so I swapped back. Can't wait to see you images from this autumn/winter. Hope all the remote shooting goes ok.

Jack

[malc-c]

I think we can all get wrapped up in the numbers etc, but the reality is that the HEQ5 and EQ6 mounts are mass produced to a commercial tolerance to fit a set budget. If you really want high accuracy with virtually no PE then you would need to look at mid to top range mounts, costing twice, three or ten times as much.

Changing them from gear drive to belt drive improved the PE on my HEQ5 for the reasons Jack explained, leaving the worm as the biggest culprit in the graph. I've yet to replace the bearings in my mount, but as I'm getting reasonably satisfactory traces when guiding with PHD and the resulting subs are workable I can't see the point of stripping the mount just to gain a slight improvement in arcseconds. For me one of the reasons I developed the HEQ5 belt conversion for my mount was to make it quiet with out the "graunching" during the ramping stages of the steppers at the start and end of the slew.

It's interesting to note that the Avalon mount takes this belt drive a stage further. These Italian mounts in essence use the EQ6 electrics (inc the synscan handset and steppers) but with a direct drive belt system. The PE and tracking accuracy quoted is extremely good, but then the mount cost around £4000 !

[jackrussell0232]

Malc, I couldn't agree more mate, the noise mine used to make when the slews started and stopped, were truly awful. It would make anyone with any level of mechanical experience wince. I'd have done the belt conversion for that reason alone!

Jack

[JamesF]

It's interesting to note that the Avalon mount takes this belt drive a stage further. These Italian mounts in essence use the EQ6 electrics (inc the synscan handset and steppers) but with a direct drive belt system. The PE and tracking accuracy quoted is extremely good, but then the mount cost around £4000 !

I'd seen the mount, but not seen that cut-away diagram before, Malc. Looks like there are two belts in the DEC drive there. Or is that just me?

James

[JamesF]

Malc, I couldn't agree more mate, the noise mine used to make when the slews started and stopped, were truly awful. It would make anyone with any level of mechanical experience wince.

Certainly causes me to have a sharp intake of breath the first time I use it of an evening. If it were any worse I'd probably get corpses stopping by to complain.

James

[Fred_76]

Jack, I copy/paste the data I posted last year on Webastro, a French forum.

I agree with you that the long periods are useless. I have the same conclusion as you have : only the small bearings need replacement if they are not satisfactory. They have periods of about 2-3 minutes. The large ones have periods too long to be significant (several hours).

These figures are there to make people save money : it is useless to change the big (and costly) bearings - a careful cleaning and regreasing will be enough.

Fred

[Fred_76]

By the way, periods are coming from SKF :

http://www.skf.com/skf/productcatalogue/calculationsFilter?lang=en&newlink=&prodid=&action=Calc6

[malc-c]

James, one of my friends has a 11" HD Edge on one of the Avilon mounts, but wasn't willing to remove the covers so I could take a peak under the hood But yes you are right, it does have a multi belt type gearbox system, presumably to keep the pulley on the RA and DEC reasonably small in diameter without risking stalling the steppers

[Corpze]

Hi all, i am thinking really strongly about doing this mod, i have thought of using the kit from telescope-austria, that kit is working with the original ratio so the SW GoTo works right?

And why not change the worm-bearings at the same time? so what SKF-bearings should i use?

[perfrej]

Corpze!

Here is my list of bearings that I got for mine two years ago. I bought from Spekuma and I believe they substituted one of them. SKF numbers are as follows:

4st SKF 608-2RSH

6st SKF 6008-2RS1

1st SKF 30206-J2/Q

1st SKF 32208-J2/Q

At that time I had had my EQ6 for less than a year and not used it much. Still, two of the main bearings were corroded. I suggest you replace them all.

/p

[tonedeaf]

Hi all, i am thinking really strongly about doing this mod, i have thought of using the kit from telescope-austria, that kit is working with the original ratio so the SW GoTo works right?

And why not change the worm-bearings at the same time? so what SKF-bearings should i use?

i had a talk lately with tommy from telescope austria, regarding the moding kit...

problem is with the kit that you will need a "workshop" as there are some "parts" that need to be ?milled? or anything else.

he couldn´t tell it for sure, cause his hungarian colleague who makes this mods, hasn´t made a "instruction" for it

i´ve asked for photos if there are any so that i can make a picture on what has to be done...

so therefore with this moding kit it would be wise to send the eq-6 in

[Corpze]

i Believe the "millig" he is refferring to is the mods ou have to do with the worm-caseing, making room for the bigger pulleys. ( or it is the center hole in the pulleys?)

[tonedeaf]

i asked about it, that it may be, due to the fact that after the mod you can still use the synscan handcontoller -> so it must be the same gear ratio...

that maybe one of the pulleys will need some more place than the gear normaly has.

he said that there weren´t any photos

only the fact that his hungarian colleague needed around 3-4 hours for the work -> ~ € 240,-

[Corpze]

Isnt that kit "bolt on" besides the mods necessary to the housings?