EQ6 belt drive modification

[George]

Well my main reason was to rid the mount of backlash which the conversion has done admirably, anything else was a bonus.

So to recap so far:

1. Backlash non existent.

2. GOTOS far superior.

3. Guiding has vastly improved.

4. Mount is much quieter on fast slew.

5. I'm much happier & confident with my mount.

Point 5 is perhaps the most important, I've never been happy with my mounts performance and I was constantly fiddling/dismantling and even contemplating a replacement.

[fwm891]

Sounds great - I need to completely re-read this thread and order some parts, polish the lathe and get started. Great contributions all round...

Edited October 29, 2011 by fwm891

[chrisshillito]

The biggest culprit still appears to be the worm which I checked for runout while everything was dismantled, runout was 0.001mm which in engineering terms is as perfect as you will get.

Ive attached my unguided log perhaps Chris can comment

Hi George,

Strictly speaking it is actually rather hard to pin down the biggest culprit on the worm alone - all we can say is that those components moving at the worm speed combine to give the biggest error. In your mount this means the worm and the worm pulley.

The overall level of PE is around half that which is typical for an EQ6Pro and the PE now almost entirely consists of elements that are harmonic with the worm. PEC should be quite effective should you ever feel the need for it.

Attached is my interpretation of the data.

I'm not sure why you should have experienced an improvement in goto accuracy unless you had a bad backlash problem before. It is true that the reduced PE amplitude will allow for greater accuracy when synching on alignment points but wouldn't have thought that would have had a significant effect unless you're observing at a long focal length, high mag.

Anyhow, all in all it looks a very successful mod and I must admit to being tempted to give this a go myself (with a bit of luck I'll find a happy EQMOD user with a lathe willing to do me a favour ).

Chris.

george_pecprep.pdf

[fwm891]

Oh Dear*** - just ordered the belts and pulleys and they are out of stock on some items...mumble mumble...

Chris if you have your gears and are willing to wait a while I'll be modifying my gears (when they arrive) - happy to do yours at the same time. Or I can practice on your gears first!!

[ncjunk]

Looks good then, no pressure but now you have to apply a PE correction George and redo the graph!

I´m in no hurry so I´ll give you until tomorrow to sort it out and post back here

It´s looking good! as soon as my Allen keys turn up I can put mine back together and test it

fwm891 be carefull with the smaller pully as we are boring it out to within 0.5 - 1.0 mm of its life, my machinist wasn´t too impressed as he thought there wouldn´t be anything left but it is just ok.

[fwm891]

Hi Neil, I'll collet the small pulley to make sure its running true before boring it out, same with the large pulley even though there's enough metal there to work with...

[chrisshillito]

Oh Dear*** - just ordered the belts and pulleys and they are out of stock on some items...mumble mumble...

Chris if you have your gears and are willing to wait a while I'll be modifying my gears (when they arrive) - happy to do yours at the same time. Or I can practice on your gears first!!

Hi Francis,

That's very kind of you, thank you. At the moment I'm in exactly the same boat as you having only just ordered and waiting for stock (seem popular these gears!) so I suspect we'll get our gears around the same time. I'll PM you when they turn up.

Chris.

[George]

Hi George,

Strictly speaking it is actually rather hard to pin down the biggest culprit on the worm alone - all we can say is that those components moving at the worm speed combine to give the biggest error. In your mount this means the worm and the worm pulley.

The overall level of PE is around half that which is typical for an EQ6Pro and the PE now almost entirely consists of elements that are harmonic with the worm. PEC should be quite effective should you ever feel the need for it.

Attached is my interpretation of the data.

I'm not sure why you should have experienced an improvement in goto accuracy unless you had a bad backlash problem before. It is true that the reduced PE amplitude will allow for greater accuracy when synching on alignment points but wouldn't have thought that would have had a significant effect unless you're observing at a long focal length, high mag.

Anyhow, all in all it looks a very successful mod and I must admit to being tempted to give this a go myself (with a bit of luck I'll find a happy EQMOD user with a lathe willing to do me a favour ).

Chris.

Thanks for taking the time to peruse my data and write a report its much appreciated

My mount certainly feels & tracks 50% better than pre-converstion, as Ive said in other posts above my main reason for changing to belts was to try rid the mount of backlash particularly in the DEC axis, as you have said this was probably affecting my gotos and certainly affected tracking with wild swings in the the form of bounce.

I also took the trouble of polar aligning to the best of the mounts mechanical ability (ie pitchs on adjustment bolts are far too coarse for minute adjustments) and spent many hours getting that last arc second adjustment.....it certainly paid off and is probably responsible for some of the goto's extra accuracy Also lapping the worm & gear must have helped smooth things to some degree.

In hindsight to pinpoint any gains it would have been better to get data after every step but with limited clear skies in the UK that would have taken months

I hope this thread and documentation helps others to go ahead with a worthwhile modification particularly to imagers who are always after that last bit of accuracy from their kit.

Regards to everyone who has helped.

George ( a happy bunny)

[Gina]

I hope this thread and documentation helps others to go ahead with a worthwhile modification particularly to imagers who are always after that last bit of accuracy from their kit.

It is a very interesting thread and I have little doubt will be very helpful to me later with my imaging. So thank you very much for posting it

[fwm891]

Hi Francis,

That's very kind of you, thank you.... I'll PM you when they turn up...

Chris.

No problem - other than the wait

[ncjunk]

One of my large pullies is slightly out so wobbles when turning. Whats the worst that could happen if i stick it on the Dec?

I'll see if there is anything i can do but it looks like i may just have to suck it and see...as they say.

Shims arrived today so everything will be put back together tomorrow.

[malc-c]

Nick, could cause the belt to wear a bit I guess, could there be a clearance issue ?

[ncjunk]

The clearance is fine but i am putting it on the Dec hopefully it won't be as critical in there. I am thinking it may cause wear as well.

Neil C

[George]

I put mine with the slight wobble on the DEC, don't think a wobble is a crucial with belts as it is gears.....think my graphs speak for that

Finally got 6 hours of imaging in last night.

[ncjunk]

How was it with the guiding George? Did it look good?

[ncjunk]

When rebuilding the mount remember to add the belt onto the worm.....i'm just saying....not that i forgot on the RA.

I'm not that silly...noooooo

[ncjunk]

The DEC is working but needs a bit of adjustment....not bad seeing as the coller for the compression bearing isnt tight enough, I couldn't wait to play!

Just need to file out the slots in the RA motor a bit first then screw that into place.

The belt can slip before the motors bind when doing adjustments, it caused me to panic a little bit.

Should all be up and running by tomorrow.

I haven't added any photos as Georges display everything you need to know. I slipped the first belt on using an Allen key, small one. Use the allen key to pull the belt down then rotate the allen key so it lets go.

That wont work for the second motor as not enough room so back to the elastic band method for that.

Saludos

Neil C

[George]

When rebuilding the mount remember to add the belt onto the worm.....i'm just saying....not that i forgot on the RA.

I'm not that silly...noooooo

Neither am I , I did it 3 times

[ncjunk]

Ok, i found using an Allen key to hook around the belt easier.

If you do the DEC first you can hook the belt with the key then put the motor in place and remove the Allen key.

For the RA you can insert the Allen key through the polar scope hole using one hand, and hook the belt. Then lower the RA motor on top.

When inserting the screws, to hold the motor in place, put a bit of grease on the washers to hold them onto the screw.

I lost one of the washers down the RA slot and had to take the RA apart to remove it.

RA is sounding wonderful but with a slight rubbing sound from the belt....i may try to adjust it a bit but it should be ok as it is.

I can't stop popping into the garage and running the motors just to see the belt go round and hear the noise it makes ;-D very sad i know!

Press....wwwwwhhhiiiiirrrrrrr....Press....whhhirrrrrr..

Press.....

[yesyes]

I can't stop popping into the garage and running the motors just to see the belt go round and hear the noise it makes ;-D very sad i know!

Press....wwwwwhhhiiiiirrrrrrr....Press....whhhirrrrrr..

Press.....

I know EXACTLY what you mean. I have lost track of how many hours I have done THAT just to watch and listen:

https://picasaweb.google.com/117034922665750406576/201109MotorFocuser#5651923656761129298

[malc-c]

Press....wwwwwhhhiiiiirrrrrrr....Press....whhhirrrrrr..

Press.....

Unlike the Press.... graunchhhh......wwwwhhhhhiiiiirrrrr.....graunchhhhhh we all get !

[ncjunk]

.....wwwhhhiiiirrrrr.....

And now for the RA

.....wwwhhhiiirrr...

I'll post a video later so people can see and because i want to play again.

Not sure if the iphone will pick out the belt but i'll give it a go.

I feel like a kid at christmas with this.

[George]

RA is sounding wonderful but with a slight rubbing sound from the belt....i may try to adjust it a bit but it should be ok as it is.

I can't stop popping into the garage and running the motors just to see the belt go round and hear the noise it makes ;-D very sad i know!

Press....wwwwwhhhiiiiirrrrrrr....Press....whhhirrrrrr..

Press.....

Have you tried adjusting the stepper pulley up or down the shaft as this will give you a little adjustment, think I moved one of mine further up the shaft by a couple of mm's or if you have a dremmel you could open the slot a little.

Nice to hear your having fun with your "NEW" mount

[ncjunk]

Thanks for sorting all the info, suppliers and references out George. You're a shining ball of burning elements!

I can adjust it down the shaft a little so that should do.

[fwm891]

You might find if you can run the worm end free with the belt engaged and at tension that the gear will align itself and you then only need to tighten the gear to the worm shaft once its settled in position...