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.
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
VAT 20.0%: £5.13
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 by George, 09 October 2011 - 08:21 PM.