EQ6 belt drive modification

[George]

This modification was pre-discussed here http://stargazerslounge.com/discussions-mounts/139411-eq6-belt-mod.html

****Please note****

This modification is for NEQ6/EQ6 mounts running EQmod ONLY, the Synscan/Syntrek handsets only support Skywatchers/Syntas proprietary 3.92:1 gear ratio.

You will need access to a lathe to re-bore the gears to fit the worm and stepper motor shaft.

48 tooth gear needs re-boring to 12mm

12 tooth gear needs re-boring to 5mm

48 tooth gear needs 3mm taking off the overall width of the gear.

No modification to the mount itself is needed.

Parts List

I eventually settled on the 2.03mm pitch gears 48 & 12 tooth gears for a ratio of 4:1 because it involved no modification of the mount and minimal modification of the gears themselves.

motionco_Pulleys & Belts_Aluminium MXL Timing Pulleys_Buy Online

motionco_Pulleys & Belts_Neoprene MXL Timing Belts_Buy Online

2 x Aluminium MXL Pulley, 48T, 5mm Bore (Part PL048AL) = £13.22

2 x Aluminium MXL Pulley, 12T, 3mm Bore (PL012AL) = £6.92

2 x MXL Rubber Timing Belt, 80 T (BMXL080) = £5.52

Sub-Total: £25.66

Shipping: £0.00

VAT 20.0%: £5.13

Total: £30.79

If you don't have access to a lathe you can buy and have the gears modified here HPC Gears, modifications page

The following images were taken when modifying the DEC axis on my EQ6.

DEC worm housing and stepper before modification

All the parts used from the above parts list, gears have been re-bored and width reduced on the 48 tooth gear.

A before and after shot after removing the original gears, 12 tooth gear fitted on the left.

A close up of the modified DEC stepper

48 tooth gear and belt fitted to the worm prior to fitting, make sure the belt is kept free of oil & grease

No modification is needed to the mount, the gear slot comfortably takes the new 48 tooth gear and 6.35mm belt

Elastic band used for looping the belt over the stepper pulley prior to fitting

Worm housing now fitted to mount and belt is pushed thru mount slot, in a dry run before I greased everything up the elastic band worked well for looping the belt over the stepper pulley but in final fitting I had problems, eventually I used strong cotton thread which was easily snapped off when the motor was fitted.

After slackening off the steppers screws slightly it was easy to gently lever the stepper to apply tension to the belt, I ran the mount for 2 or 3 full revolutions both ways to settle everything in before checking the belt tension. With a flashlight you can see when running if the belt is tight or slack.

Finally you have to set EQmod up to use the new gear ratio's, originally you had to edit the ini file but Chris Shillito added a drop down box in EQmod setup with a number of the most popular ratio's 4:1 5:1 6:1 etc.

Make sure the Custom Mount Enabled is checked (I just noticed its not in the image)

Phew that's it

As soon as we get a clear spell I'll be testing the mount out and hopefully show improved PHD graphs. I had really bad backlash on the DEC axis which could not be adjusted out.....that has now disappeared completely with this modification oh and did I mention how quite the mount is now?

All you can hear on full slew is the steady hum of the steppers....no more transfer gear rattle and squeal

Edited October 9, 2011 by George

[ncjunk]

Excellent! Ordering the bits now...I hope I can get my Machinest to actually do the mods quickly rather than in six months!

You are a Star George. (Well what else would you be on an Astro Forum )

[George]

Excellent! Ordering the bits now...I hope I can get my Machinest to actually do the mods quickly rather than in six months!

You are a Star George. (Well what else would you be on an Astro Forum )

Make sure he/she centres the gears correctly in the lathe before boring, I had a slight run out on my 12 tooth gear but hopefully the belt will take this up and it shouldn't have any impact unlike on a tooth to tooth gear.

[ncjunk]

He´s an Artist when it comes to lathe work, but I will make sure he understands it is vital that it is centered....it´s just a shame that my Astro stuff is normally bottom of his todo list. Still, he only has to drill and take off 3mm so I think he should be able to do it quickly (he doesn´t have to buy anything in)

All ordered now so hopefully I´ll have them by the end of the week.

[malc-c]

I wonder why Synta never thought of using belt drives in their HEQ5 / EQ6 mounts as standard. Given the volume they must make, the parts couldn't be any more expensive that the current gearing system.

[ncjunk]

Some of the original gears were plastic, I believe. But I am sure the new mount (EQ7/8) out...er...who knows when...I am sure will have a much better mechanical setup than the EQ6 has now. Plus they have improved things the current EQ6 comes with a duel puc that has a Losmondy connector.

[George]

I completed the RA axis belt conversion tonight and it was as straightforward as the DEC axis. Might have to elongate the RA stepper mounting plate screw holes a little with a file to get a little more belt tension, I'll see how this goes with a full mount load tomorrow.

Might have a chance of clear skies towards the end of the week

[malc-c]

George, any chance of uploading a video to youtube or somewhere so we can all hear the sound of the mount slewing after the conversion.

[yesyes]

What is the advantage of the belt drive conversion compared to the original gears? Is it noise reduction (as Malcom hinted at) or less backlash? or something totally different? ;-)

[yesyes]

Sorry, just read the answer in the other thread linked in the first post here...

One question though... How do you overcome the fact that with a belt it will end up rotating the other way around? Is it possible to reverse the direction of the motor?

[r3i]

What is the advantage of the belt drive conversion compared to the original gears? Is it noise reduction (as Malcom hinted at) or less backlash? or something totally different? ;-)

This was answered here in the original discussion thread.

[ncjunk]

Sorry, just read the answer in the other thread linked in the first post here...

One question though... How do you overcome the fact that with a belt it will end up rotating the other way around? Is it possible to reverse the direction of the motor?

Er...quickly visualising the gears in my knackered brain..there are three gears one on the motor, one on the worm and one connecting the two. Therefore it is the middle one that is going in reverse with respect to the other two i.e. Motor and worm gears rotate in same direction. With the belt there is a pully on the motor and one on the worm and the belt will cause them to move in the same direction i.e. No difference between belt and gears.

[yesyes]

Ah, I see... thanks... I wasn't aware that there is a 3rd gear in between...

[ncjunk]

There is a ratio difference between gears and belt but eqmod has a custom setting for the ratio to cover belt mods.

[Earl]

Very interesting thread, and not to difficult to do, which is a nice plus.

However ill go by if its not broken on mine atm...

[kookoo_gr]

very interesting. when you finish can you please post a pec curve and an image?

[George]

very interesting. when you finish can you please post a pec curve and an image?

That's the plan, with the weather here expect it sometime next spring

[malc-c]

Guys, been thinking about trying out a similar modification to the HEQ5. I've scoured the net and found an image (one of Ants funny enough) showing the gear train.

Obviously the middle idler gear would be removed, and then the large gear on the worm spindle and the small gear on the motor will need replacing with suitable pulleys, but wondered how you go about working out the belt length and pitch of the pulleys to give the 4:1 ratio. I would like to do this mod without any (or much) re-working of the covers etc (be nice to get a drop in replacement).

[Psychobilly]

Worst case I think you could get away with a "gasket" style spacer to give you the extra space for the pulleys

[JamesF]

I find myself idly wondering this evening if the knowledge of the gear ratio is built into the hardware or the firmware. If it's the latter (which would seem logical to me) then it might be possible to "hack" the firmware so it accounts for the changed gear ratio. Could be something of a slog to identify which bits need changing though.

James

[George]

Obviously the middle idler gear would be removed, and then the large gear on the worm spindle and the small gear on the motor will need replacing with suitable pulleys, but wondered how you go about working out the belt length and pitch of the pulleys to give the 4:1 ratio. I would like to do this mod without any (or much) re-working of the covers etc (be nice to get a drop in replacement).

Centre distance calculator

Measure from the centre of the worm wheel to the centre of the stepper shaft, put your pulley combination in the boxes , select the belt length until it matches your measured centres. Thats what I did and it was spot on.

James it will be in the firmware, using EQmod does away with the handset thereby doing away with the firmware.

Edited October 13, 2011 by George

[JamesF]

James it will be in the firmware, using EQmod does away with the handset thereby doing away with the firmware.

Yes. But my thinking was that if the firmware could be suitably modified then the 4:1 change could be made *and* the handset would still function correctly.

James

[George]

Yes. But my thinking was that if the firmware could be suitably modified then the 4:1 change could be made *and* the handset would still function correctly.

James

Im sure some selected source code was released a while back but Im certain it was forASCOM plugins, anyway if the firmware was hackable Im sure it would have been done by now

Check the EQ6 Yahoo group.

Edited October 13, 2011 by George

[JamesF]

Hmmm, well, it could just be too awkward to do without some information from Skywatcher. The firmware image is 1MB, and even taking out, say, eight bytes per item in the catalogue that still leaves a lot of code.

I can find the irritating solar viewing for dummies message though. I could be tempted to change that text to something along the lines of "This mount belongs to..." just to see if it would work.

James

[dark knight]

I really like the idea of this mod, I may try it on my synscan eq5 mount, will follow how others cope with it. nice one George.