EQ6 belt drive mod

[Luke Bellani]

Hi All,
I thought that I would post some results of my efforts to improve the performance of my EQ6 GEM.

I have an older model (black) that I have been using for around three or four years.

I didn't have a permenant installation for my gear (observatory) and so I was observing in fits and starts and not in any serious way prior to this.

In January this year I decided to build my observatory. I had been threatening to do it for years but like most projects astronomical it always got put back unitl I bit the bullet this year.

Now having a permenant pier for my mount meant that the time had come to try to iron out some of the performance issues I ahd identified in the past. Notably, a rather nasty worm PE.

I had read that a company called Aerquest produced higher quality gears and worms for the EQ6 and so I ordered a set of replacement transfer gears and a new worm.

To cut a long boring story short, the transfer gears did not cut it but the worm was a signifant improvrment on the one made by Synta.

At the time, I was following a discussion on the EQMOD tech group regarding modding the EQ6 to a belt drive system.

One of the members had had some success in doing it and so I decided to give it a go as well.

Now I haven't yet completed moding my mount but scrapping the transfer gears for a belt drive has been the best thing ever.

The difference in mechanical smoothness is to be seen and not heard to be believed.
Also, I went for a 4:1 pulley ratio to remove the PE synch problem caused by the 3.92... ratio of the normal 12/47 tooth gears.

The following photos should be enough to show what I did and how I did it.

In conclusion can say that for me it was quite an easy mod to do and I think it has real potential to significantly lift the performance of my EQ6.

Regards,
Luke

P.S. I have also included a photo of my observatory (probably the reason for the recent spate of bad weather).

[Visionoz (Bill)]

Luke

That looks the goods - great to hear you have success in using the belt drive system
BTW where did you obtain the belt, sprocket gear and gear drive from? Or did you machine these yourself (except the belt of course!)?

Cheers
Bill

[Luke Bellani]

Hi Bill,
The pulleys and belt came from a local (Victoria) company P.I.E.S.
They have them in stock.
I used 2.5mm pitch 15 tooth for the motor and 60 tooth for the worm.
The belt was 200mm long.
The pulleys need to be drilled to fit. 5mm for the motor and 12mm for the worm. It's better to do these in a lathe and use a reamer to make an exact hole. You want the holes as exact as possible because they will add to the final PE.

Cheers,
Luke

[bmitchell82 (Brendan)]

wow... if they make a big improvement that sounds good to me, how much did you pay for these parts if you dont mind me asking. As i do have a lathe i bore holes to within .001mm accuracy, and i have a bridgeport machine for milling of the end plates.

[gbeal]

Luke,
do you have a website for the gear and belt supplier. I tried PIES in Google, but all I got was the food derivative.
I am after a set and belt, or two gears that mesh, to make a connection between the focuser shaft and motor.
Gary

[bmitchell82 (Brendan)]

had a look earlier gaz

http://www.piesau.com.au/

im pretty sure its it

[bojan]

That looks fantastic, Luke.. clean job
Do you have PE diagrams, before and after?

BTW, those guys have belts and pulleys too (I ordered from them in the past)
http://www.smallparts.com.au/
https://sdp-si.com/eStore/

[Luke Bellani]

Hi Guys,
Sorry for late reply.
Yes that is the right P.I.E.S.
The pulleys are not very expensive and they have a web shop.
In fact it's better to buy from via the web as they give a better price as I found out the more expensive way by going to their office.
The prices are on the web. Typically $17.00 fot the 60 tooth and $11.00 for the 15 tooth.

I have got some PE traces but they show some runnout in the 60 tooth.
I just machined another one to try to get it more accurate.

As soon as the rain stops and I can see the stars again I'll get some more data.

I captured 8 worm cycles and the data showed the benefit ofg the 4:1 ratio pulley ratio.

I had a peak to peak PE of around 15 arc seconds but all cycles are perfectly in phase and EQASCOM's REC works a treat.

I think that I can do better with the second try at the 60 tooth pulley.
Also I need to lapp the worm/worm gear combo a bit more.
I got a replacement worm from Aeroquest and it needs some more work.
Not very impressed really. It is a bit better than the Synta one but that's all.

I really very happy with the mount now. It is very quiet compared to what it was. No rattling of gears. Just the musical tomes of the stepper accellerating and decellerating.

Since the EA axis turned out so well I decided to do the DEC axis as well and I did that today.
Now I have a totally belt driven EQ6.

I highly recommend it to all EQ6 owners.

It is a vey easy mod to do. and for those who don't have the machinery, you can achieve the same thing with the smaller 2.0 mm pitch pulleys and 4mm belts.
Apparently there is no machining required and they will fit in the housing.
So I have been told.

I wanted something a bit more substancial and so I went for the 2.5 mm pitch and 8mm belts.
200mm long belts fit nicely without and need to modify the motor mounts.

I'll be very interested to hear if anyone else does the same as me.

Cheers,
Luke

[Luke Bellani]

Hi Guys,
I should also have added that I use EQMOD exclusively with my EQ6.
Now the it is belt driven with a 4:1 ratio, the Synscan hand controller would no nlong track and goto correctly.

That doesn't bother me at all as I haven't used the have controller since I started using EQMOD.

The only thing I use the hand controller for now is to test the mods I make before testing on the PC.

Chris, the main delevoper of EQASCOM has provided a facility for those who modify to belt drives so that tracking and gotos are spot on and I can verify that.

For those that have not yet tried EQMOD, give it a go. I promise you will never go back to the hand controller other than for portable apps without a PC.

Cheers,
Luke

[bmitchell82 (Brendan)]

well that just killed that mod , I sometimes utilize my hand controller when i just want to go out and show people things. ahh well. not only that im getting 10.5 arc sec peak to peak measured with PEMpro and a 10" dobsonian sitting ontop and i have done nothing but adjust all the meshings and worm gears so they sit nicely!

[Luke Bellani]

Hi Brendan,
Using 12 tooth and 47 tooth pulleys instead of 15/60 tooth will maintain the normal drive ratio so that the Hand controller will still work.

The only issue is that they need to be got from the U.K
http://www.hpcgears.com/ because P.I.E.S does not stock 47 tooth pulleys.

Cheers,
Luke

[bmitchell82 (Brendan)]

interesting, but would it actually give me a better PE? currently mine is smooth and a nice sine wave shape. if it would reduce PE down to say 9 or 8 arc per second Pk-Pk then that would be worth while.

[bojan]

I think if it is smooth, leave it as is..
I am also just about to put belts into my mount but I am doing it because it is not smooth at all (gears..).
However, new worm may help to reduce PE.
Curves before and after would be very helpful :-)

[Luke Bellani]

Getting rid of the gears definately reduces some of the error sources and also some of the higher frequencies associated with the teeth meshing. However if the holes in the pulleys are not made accurately enough then that will add to the PE problems.

The first 60 tooth pulley I drilled was not good enough and that was the source of around -+7 arc seconds of my PE. The worm is contributing about 3 or 4 arc seconds PtoP.

I made a second 60 tooth pulley and that should be better (I hope).

I bought a new 12mm reamer to make the hole as close to the 12mm worm shaft as I could. I aslo have 3 grub screws 120 degrees apart in case I need to adjust a very small amount. Hopefully not.

It seems to rotate smoothly when I use the hand controller to slew at "high" speed.

One of the benefits of machining the housing is that I have a clear view of the pulleys and can see any wobbles.

As soon as I get a clear night I'll run some tests and post the results warts and all.

Cheers,
Luke

[Luke Bellani]

Brendan,
If you're getting a PE of around -+5 arc seconds then you have one of the exceptional EQ6 mounts and I wouldn't touch it.

Mine was terrible and not a nice sine wave shape.

My worm had a flat spot that was causing some significant trouble and that is what led me to get the new gears and worm from Aeroquest.

I had read that the components from Aeroquest were very good but I can't agree with that I'm afraid.

The Aeroquest worm is OK and significantly better than the Synta one but the fine tooth gears did not turn out to be very good at all and I ended up with a PE of around 40 arc seconds.

When I reported this to Aeroquest I was told that I would have to lap the gears to get good results.

I spent some considerable time lapping the gears but the best I could do was get the PE down to around 20 arc seconds.

That's why I decided to scrap the gears and go for the belts.

I could have just reinstalled the Synta gears but then I would be back where I started. Although with a better worm.

If my mount was as good as yours seems to be I never would have gone this path. A PE of 10.5 arc seconds is about 5 arc seconds better than the average PE for the EQ6 Pro.

Cheers,
Luke

[bmitchell82 (Brendan)]

yeah i see where your going on that one. Im just one of those people that know that if theres something that i can do thats cheap and the benifits are great, then im in like flynn.

Just for you to have a look at is a PE run with PEMpro run in early march this year, the blue curve is raw from the recording, the second one red, is using the PE modified curve. Of course polar alignment was very accurate.

[Luke Bellani]

Hi Brendan,
That looks quite nice.

That sinusoidal signal looks like the meshing of the 47 tooth worm gear.

To me it looks like it is contributing about 2 arc seconds p-to-p to the PE.
Maybe the meshing is too tight? Perhaps a slight adjustment of the motor mounting plate may reduce that signal.

From what I can see, it appears that you only have one 8 minute worm cycle and that would makes it difficult to get any reliable idea of the true PE.

I believe that you need about 5 or 6 cycles to get a real representation of PE for your mount.

Well that is what I have been told from others that have a much better understanding of measuring PE than I do.

I think that a belt drive would not exhibit the sinusoidal signal.
Mine certainly doesn't, however there are other noise components that I am working to remove.

I have attached the a screen dump showing the first capture of PE data from my belt drive as analysed by PECPrep.

The data shown is from a PERecorder run capturing seven worm cycles.

The largest signal component is from the 60 tooth pulley on the worm shaft.

I'm hoping that the new pulley will do better.

Cheers,
Luke
P.S. Notice how all the cycles are in phase.
PPS. Sorry, I just noticed that there are two cycles in you graph.

[bmitchell82 (Brendan)]

hehehe PEMpro takes a snippit out to show you whats happening, I did 2 PE runs, the first one was 2.5hrs worth hence why i mentioned the polar alignment i held for that long and the second one was the same.

Im very happy with it, but i do have to pull it down and give it a service, the grease is all clagged up. but i wont do that untill the winter kicks in and i have a few weeks of shiiiet weather. but its all good.

hopefully you get that nasty blip.

[bojan]

Hi Luke, how did it go?
I am starting the machining work on my EQ6...

[coldknights (Cathy)]

Originally Posted by bojan

Hi Luke, how did it go?
I am starting the machining work on my EQ6...

Hi Bojan did you finish this mod ?
If so how did it go ?