Go Back   IceInSpace > Equipment > ATM and DIY Projects

Reply
 
Thread Tools Rate Thread
  #1  
Old 06-05-2019, 05:00 PM
Astrofriend's Avatar
Astrofriend (Lars)
Registered User

Astrofriend is offline
 
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 222
EQ6 Mount, dismantling and maybe timing belt?

Hi,
My EQ6 mount is old now. Very stiff RA and DEC axis, it's time to dismantle it and see how bad the inside is.

I followed the Astro Baby guide and it was not any big problem to dismantle it. It looks fine inside, I suspect some earlier owner already have done this cleaning and put new grease on. But that must be years ago.

When I now have dismantled everything, shall I rebuilt it and install timing belt drives? I feel it's a little to much money to put on this old mount. I have to think about it and see what alternatives there are.

Here is my EQ6 dismantling story:
http://www.astrofriend.eu/astronomy/...ebuilding.html

Only first part, now I'm drawing plans.

/Lars
Reply With Quote
  #2  
Old 07-05-2019, 12:36 PM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,978
I highly recoomend installing belts and conversiont to ONStep.
I did it on both my mounts. it is not hard to do and it is not costly, if ytou do it yourself with components from ebay (used for 3D printers. .that is why they are so cheap).
(please note, the link is not current - in the latest version, I do not have any gears, I am using 400s/rev steppers and 1:5 timing belt pulleys. I am still trying to locate my post with curent version).
Reply With Quote
  #3  
Old 09-05-2019, 06:56 AM
Astrofriend's Avatar
Astrofriend (Lars)
Registered User

Astrofriend is offline
 
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 222
Hi Bojan,
Thanks for information and links. Looks you are not afraid to dig deep into the problems :-)

For the moment I do measurement to see what can be fittet inside the mount. With T2.5 timing belt and 6 mm wide belt there are a lot of more to chose from. But it will be tight. I also had a look at the gears if I shall keep them. But first impression is that it will be a big problem to have them run smoth and with low backslash.

Do you have any supplier of T2.5 pulleys with 4 mm belt width ?

What stepper motors with 400 step / rev have you found? Do they work with the original EQ6 driver board?

Lars
Reply With Quote
  #4  
Old 09-05-2019, 07:33 AM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,978
Hi Lars,

I purchased belts and pulleys from Sdp-Si, but it was quite some time ago and today there are cheaper options (BangGood, ebay...). GT2, 60 and 12 teeth (5:1).
It was a tight fit, some machining was necessary, it was pretty fiddly to place belt onto motor pulley, but it is perfectly doable with adequate patience.
Motor (similar) came from ebay.
There is even a set 4:1, not sure if bellt length is adequate, it mat be specified... if not you can buy belt of any length on BangGood for ~$5.


As to your existing controller, 400s/rev motors may not work, the problem will be overall mechanical reduction ratio of steps/arcsec.
You will have to find the right pulleys as well - what kind of reduction you have in your mount?

Is it 12 teeth gear on motor, 47 teeth gear on worm (idler (36 teeth) is not relevant for reduction ratio)? It that case, you will have to find timing pulleys with the same number of teeth (12 is OK, 47 teeth pulley may prove to be tricky... however you can print one with 3D printer) - if you want to keep the same controller.

Or, if it is possible to re-program controller for different mechanical reduction ratio, you can use common pulleys.

My EQ6 original controller was old-style (only tracking and fine positioning) so I went straight to Bartels system, and later to OnSTEP (Arduino platform), using 16 ustepping pulse/dir Pololu drivers.

Last edited by bojan; 09-05-2019 at 08:39 AM.
Reply With Quote
  #5  
Old 09-05-2019, 11:47 PM
Astrofriend's Avatar
Astrofriend (Lars)
Registered User

Astrofriend is offline
 
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 222
Hi Bojan,
There is so much to think and plan for. Many good alternatives goes away because of too high cost.

But now after I have clean the mount and done some measurement I get a better overview of the alternatives. I wrote them down on the second page:

http://www.astrofriend.eu/astronomy/...ebuilding.html

Maybe it's easier for me to implement a kind of semidirectdrive on the shaft of the worm gear. But still need a gearbox, a builtin planetary gearbox with low backlash.

I'm waiting for the roller bearings I ordered and still looking for shims, I think I go for steel shims if I find any. Inner diameter 40 mm and outer 56 mm, thickness 0.1 to 0.5 mm.

Many thanks for the links and tips!

/Lars
Reply With Quote
  #6  
Old 10-05-2019, 07:19 AM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,978
Lars,
Belt mod (with 4:1 or 5:1 GT2 (12 & 60) belts & pulleys) fits nicely inside EQ6 enclosure (4mm belt width is quite adequate), while for T2.5 you will have to remove the part of housing to fit the larger pulley (it will protrude out of it - some people did that, though). It is also easy(er) to adjust transmission ratio (by varying teet number on pulleys), and Banggood has large number of various timing belt lengts in stock, cost is couple of AUD. And 3D-printing of 47-teeth pulley is a viable option.

Also, OnSTEP electronics is actually very affordable/low cost solution, so it make sense to sell existing controller and maybe recover a significant part of the investment in new electronics.

As to stepper with planetary gearbox, there will be backlash (no backlash is present with timing belt transmission/reduction). This motor is 200steps/rev.. so you will have to use 32 /usteps or even 64.

Also, any gearbox will be louder compared to timing belt transmission. This motor assembly may not fit inside EQ6 either.. External placement is not so good for mount carrying around as it could be easily damaged. And if it does fit inside, you will need belt transmission to couple it to worm anyway...


Have a look at this webpage, it is similar to what I have done (I went for 5:1 belt transmission, 60 & 12 GT2, and I did not make those large holes in the aluminium enclosure)

Last edited by bojan; 10-05-2019 at 08:07 AM.
Reply With Quote
  #7  
Old 10-05-2019, 08:09 AM
Astrofriend's Avatar
Astrofriend (Lars)
Registered User

Astrofriend is offline
 
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 222
Hi Bojan,
Sorry, didn't understand earlier that GT2 was another standard for timing pulleys. Looks to be more common and then more to choose from.

When you say 4:1 is that 48t and 12t ?

And 5:1 60t and 12t ?

According to the data a 60t has a diameter of 44 mm and I can't see that I have more space then a diameter of 39 mm. Do I missing something?

But a 48t will fit.

Now I'm surfing with my mobile, tomorrow I will do a new search on the computer which is much easier.

Thanks a lot, now I'm back in the timing belt thinking again.

Your comment about planetary gears, do you mean all of them? Some say they are backlash free (special version).

Lars
Reply With Quote
  #8  
Old 10-05-2019, 08:58 AM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,978
60t must be fitting inside because I am using it (with other one being 12t, so the timing belt reduction is 5:1). (I will double check, but I am 100% sure it is 5:1)

Planetary gears with small backlash are expensive. And they will always have some introduced periodic error ("noise").
The one you are looking at is US$41..
Attached Thumbnails
Click for full-size image (c_01.jpg)
26.3 KB39 views

Last edited by bojan; 10-05-2019 at 01:41 PM.
Reply With Quote
  #9  
Old 10-05-2019, 09:11 AM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,978
Yep, it is 5:1. 60-12 teeth..
(Attached is my calculator spreadsheet).

My pulleys came from SDP-Si:
http://shop.sdp-si.com/catalog/produ...A51M012DF0603#
http://shop.sdp-si.com/catalog/produ...6A51M060DF0606

(BTW, SPI-SI catalogue says GT2 60t pulley pitch diameter is 38.2mm, with belt this is ~same as 47-teeth gear... maybe your 44mm is with flanges? You don't really need them, belt will not slip from pulley if everithing is square and because it will be guided by slot in the enclosure).
Attached Files
File Type: zip EQ6_Gear_ratio.zip (9.6 KB, 5 views)

Last edited by bojan; 10-05-2019 at 01:42 PM.
Reply With Quote
  #10  
Old 10-05-2019, 08:37 PM
Astrofriend's Avatar
Astrofriend (Lars)
Registered User

Astrofriend is offline
 
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 222
Thanks again Bojan for all information you sheer to me and all other who read this.

Yes it was with flanges, only because that was the only option I found, but the flanges looks easy to remove.

I have found some timing pulleys on Ebay and they have a 12 mm bore. Good for me because when living in a flat I no longer have any machines.

But one more problem, did you use the 60 teeth with out any machining? The link with data say it's 18 mm wide, in my EQ6 chassis there is only space for 16 mm and it looks exactly as your according to the photo you send.

Is it 6 mm wide belt you using or the 4 mm you wrote about earlier?

How many teeth or length does your belts have?

Almost ready to order now.

Sorry for all questions.

ps.
I read that they prefer the GT2 relative the T2.5 because it gives better precision in 3D printing. Good for ur too.

/Lars
Reply With Quote
  #11  
Old 11-05-2019, 01:47 AM
Astrofriend's Avatar
Astrofriend (Lars)
Registered User

Astrofriend is offline
 
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 222
With Bojan's information I have now come closer to a workning rebuilt drive system:

http://www.astrofriend.eu/astronomy/...ebuilding.html

/Lars
Reply With Quote
  #12  
Old 11-05-2019, 05:30 AM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,978
I have to find drawings, please wait a sec...
BTW. they are the same length...

Found the drawing (in dxf format - you can open it in LibreCAD, v 2.13))
There are some funny issues in the drawing - consequence of conversion from ACAD (dwg) to dxf format, but the drawing itself is reasonably accurate, you will not have any problems with dimensions.

According to my notes (from drawing), belts are:

176mm
88 teeth
B-G2-88-060-NF
A 6R51M088060


I also made new motor plates (as per drawing - there was a problem with motor height and shaft length) and some machining on pulley was necessary to fit it in.
Attached Files
File Type: zip RA_DEC_Motor_plate_5_1.zip (20.8 KB, 3 views)

Last edited by bojan; 11-05-2019 at 08:34 AM.
Reply With Quote
  #13  
Old 12-05-2019, 07:23 AM
Astrofriend's Avatar
Astrofriend (Lars)
Registered User

Astrofriend is offline
 
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 222
Hi Bojan,
Thanks for the drawing, maybe I already has a CAD software installed, otherwise I follow your link and download.

Now back to the drawing board and start thinking again.

Lars
Reply With Quote
  #14  
Old 15-05-2019, 06:57 AM
Astrofriend's Avatar
Astrofriend (Lars)
Registered User

Astrofriend is offline
 
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 222
Hi Bojan,
You helped me a lot with ideas how to proceed, many thanks!

Now I have ordered timing pulleys, I choosed a 60 teeth pulley with no flange and a 16 teeth pulley, it gives a non standard 3.75:1 ratio. Small pitch, wider belt and bigger pulleys should give a bit less elastic and smoother run compare to the normal kits, at least according to my ideas and help from forums. But I can not use the handterminal with this non standard gear ratio, but I never do that anyway.

I bought them at https://www.active-robots.com/ in Great Britian because I live in Europe Union and then I don't have to pay custom fees and taxes. They was one of few that could offer the 60 teeth pulley with a 12 mm diameter bore.

I have done some updates and put in more links with information:

http://www.astrofriend.eu/astronomy/...ebuilding.html

At page three there is a link to a belt length calculator.

/Lars
Reply With Quote
  #15  
Old 15-05-2019, 07:10 AM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,978
Hi Lars,

I am happy I was able to help :-)
As to 16-teeth pulley, it is standard (for 3D printers) and that is why it is low cost. If you intend to use 400s/r stepper and OnSTEP (or similar) with ustepping Pololu module (32 usteps), you will have 0.15 arcsec resolution (100Hz stepping rate for tracking) - more than enough (I have 0.225 arcsec, and no tracking problems with 1000mm FL AP & visual).
Reply With Quote
  #16  
Old 15-05-2019, 07:43 AM
Astrofriend's Avatar
Astrofriend (Lars)
Registered User

Astrofriend is offline
 
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 222
Hi Bojan,
Internet is fantastic, Sweden and Australia very far away from each other. 30 years ago it had been much more difficult. You must figure out yourself how to solve problems.

I got also a lot of interesting reading from 3D people.

Maybe my 20 Euro kit will perform better then the standard mod kit :-)

The OneStep driver you mention, I read about it and it sounds really interesting. My EQ6 driver do 64 microsteps, with 200 / rev it gives the same step size. But 400 step / rev with 32 microstep should give better quality.

Do you have any idea if the OneStep with 400 / rev could perform better then the standard EQ6 driver ?

Maybe next time I rebuilt a mount. But I need something better to start with then the EQ6, does a Losmandy G11 perform better if you only look at the mechanics? From what I have read you have to replace a lot of parts on the older G11 to get high performence from it.

Lars
Reply With Quote
  #17  
Old 15-05-2019, 07:57 AM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,978
Lars,

OnSTEP is low cost solution because it uses cheap h/w platform (Arduino), and firmware (actually I should use Arduino term "sketch" ) is quite capable and still evolving (I am using 3y old version and it is quite OK for what I do). I have Pololu stepper drivers inside EQ6, and I am driving it from external Ardiono MEGA board via cable (so I can also use other controllers - Bartels, SoundStepper, my own controller....)

As long as you can reprogram your controller (via ASCOM) to suit your belt transmission ratio, you should be OK regardless of 400 or 200 s/rev.
I wouldn't know about G11 - but I know that stronger and heavier the mount is, the better (in principle) it is. The size of the worm gear is also important (bigger = more precise).
Reply With Quote
  #18  
Old 22-05-2019, 07:11 AM
Astrofriend's Avatar
Astrofriend (Lars)
Registered User

Astrofriend is offline
 
Join Date: Aug 2017
Location: Stockholm, Sweden
Posts: 222
Hi Bojan,

Now I got my new timing belts and pulleys from England. Looks very good even if it was not exactly the dimension I expected. But it was as close as I could get.

Here are what I got:
http://www.astrofriend.eu/astronomy/...ebuilding.html

Not very difficult work to do, just one problem, I living in a flat and does not have a lathe.

/Lars
Reply With Quote
  #19  
Old 22-05-2019, 07:35 AM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,978
Yep.. you have to find a friend (with a lathe!) :-)

Living in a flat is not a problem - in my previous life (~30 years ago), we lived in one-bedroom flat (2nd floor), in Zagreb....
And one day I had to replace the head gasket and insert one bolt thread in the engine block of my Fiat 126.. So I removed the engine, placed on the kitchen table (to the rightfull horror of my wife) and did it....
My wife forgave me when she heard the sound of the running engine couple of hours later when I went to test drive around the flat block...
Reply With Quote
  #20  
Old 22-05-2019, 08:07 AM
The_bluester's Avatar
The_bluester (Paul)
Registered User

The_bluester is offline
 
Join Date: Feb 2011
Location: Kilmore, Australia
Posts: 2,138
You sound like my dad bojan.

It was before I was born but my mum's Fiat 500 apparently used to do a head gasket with some regularity and he had replacing it down to a fine art, doing it on the dining table. A table which we still have and that half a century later still has marks on it to prove it where oil went in to the oak and marked out the corner of where the head was sitting one time, among other things like a clear imprint of a ball bearing.
Reply With Quote
Reply

Bookmarks

Tags
dismantling, eq6, mount, timing belt

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 10:09 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Astromechanics
Advertisement
Meade Australia
Advertisement
Celestron Australia
Advertisement
Lunatico Astronomical
Advertisement
Bintel
Advertisement
OzScopes Authorised Dealer
Advertisement
SkyWatcher Australia
Advertisement
Astronomy and Electronics Centre
Advertisement