EQ6 Belt Mod (Belting Online)

[MarkS]

I carried out the mod today.  Just waiting for clear skies so I can record a PE chart and check the guiding performance.

Here's the kit of parts:


The kit preserves the 12:47 gear ratio so the handset will continue to work as normal.

The pulley grub screws are 1.5mm hex which is different from the existing EQ6 grubs (2mm).

The only tricky part was that the toothed pulley on the Dec worm axis just touched the bottom of the housing as it rotated, so I had to grind down the height of the flange by 0.5mm by mounting on a drill and rubbing it on P60 wet'n'dry paper as it spun:


When putting the motor in place, a bent piece of wire holds the belt in the right place so it goes over the new motor pinion:


Forget all those scary online discussions where folk have to drill out the pulleys to a bigger diameter, make modifcations to the worm housings to give clearance and cut longer lengths on the motor mounting plate slots - none of that is required for the kit I used:
http://www.beltingonline.com/heq6-belt-mod-drive-kit-12220

Since I have two EQ6 mounts with almost identical guiding performance, it will be easy to test the effect of this kit in terms of guiding. once we get some clear sky.

To be continued ...

[Rocket Pooch]

This will be interesting to see, I would expect some of the gearbox harmonics to drop off.

[MarkS]

I forgot to mention how quiet the mount is now, when it slews 

[Rocket Pooch]

Ha!  we compaired EQ6 noises in France and mine was quite quiet, wonder how yours compairs.

[JohnP]

Mark really look forward to seeing results. May go for it myself if positive.

How long did it take to install...

John.

[MarkS]

How long did it take to install...

Around 5 hours in total, I reckon. That doesn't include the 45 minutes I spent hunting round the house and garage for a 1.5mm hex key.  I eventually found one on a set of bicycle hexes. And it doesn't include the 30 minutes spent working out the best way to reduce the height of the flange

The fiddly bit is getting the belt around the motor pulley - if hooking it with a piece of wire failed I would have drilled a 10mm hole in the side of casing next to the pulley so I could manipulate the belt directly through hole.  Luckily I didn't need to resort to that!

[Mac]

Hmmm,

Looks interesting, as mine is in bits on the work bench at the moment (long story, Rusty bearings!!)
I might just wait and see before i rebuild it.

Mac.

[MarkS]

It might be clear tonight.  I can feel a test run coming up!
If it fails to impress, it might be time to order the EQ6 transfer gear set from Aeroquest. 

Maybe, in any case, I should mod one EQ6 with a belt kit and the other with the Aeroquest kit.

[The Thing]

Or cut your losses and start saving for a Mesu...

[MarkS]

Or cut your losses and start saving for a Mesu...

or two ...

[RobertM]

I've read that the aeroquest parts need lapping and lack the precision to make them worthwhile.

Make sure you do your homework first !

Robert

[Mike]

Check out Gierlinger.

[Rocket Pooch]

I think before you replace anything else get it looked at again, I'm not sure after replacing the bets the gears will be an issue because they won't be there, it should only be the RA Bearings and meshing now.

[MarkS]

I now have the results of the BeltingOnline EQ6 belt mod and it's quite a mixed set of results.

Firstly here are the graphs of PE before and after the mod:




The above graphs cover a few worm cycles of 478.69 sec

There is a slight overall improvement in peak to peak PE but it is not dramatic.  The main difference is in the amplitude of the superimposed 122.2 sec cycle (the time of one rotation of the motor).

This is a lot clearer in the graphs below which show the PE due to components running at motor rotation frequency:




Note that both graphs show the 12 peaks which is caused either by the 12 teeth on the motor pinion gear (or is 12 tooth belt replacement) or of something else running at this frequency (maybe gears within the motor body, teeth on the drivebelt?)

Following the steep peaks and troughs of these 12 peaks is difficult for the guiding - far more difficult than following the PE of the worm gear.  They have the infamous 10.2 second period. Since the guiding finds the second graph much easier to follow, I have seen a factor of 2 improvement in guiding accuracy.  The unmodified EQ6 was guiding at around 1.1 arcsec RMS error and the modified EQ6 sitting next to it was simultaneously guding on the same star at 0.5 arcsec RMS error.  This was on a night of pretty bad seeing.

This is the best guiding I've ever seen on my EQ6!  Note that it was carrying a payload consisting of a Celestron C11 plus guidescope/guidecam plus DSLR camera which is around 17-18kg in total.  Plus 4 x 5kg counterweights.


Regards,

Mark

[Rocket Pooch]

Mark,

The belts will not improve the PE much but the frequency issues, your half way there.  The next step is get the correct end bearings, measuring the centres of the worm and case and shim if needed then mesh the gears correctly under load not on the bench.

Just for reference at 1.4 meters OAG I was getting .3 pixel for good seeing and .79 for bad seeing with jumps to 1.4 pixel.  Whats the Pixel guiding accuracy of you setup post mod with focal length of the guide scope?

Also what are you trying to achive, I was imaging at 1x1 with my QSI at 1.4 meters with an OAG at .79 and getting bang on round stars, well within a nats balls anyways.  The reason for asking is our skies are rarely better than 2 arc seconds seeing anyway, so if your trying to get less than that you will be lucky to get it.

I can help you with setting up the mount properly if you like, but you will have to come to the dark side, i.e. West Sussex.

Chris