Quote:
Originally Posted by danstar10
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I've never pulled apart an EQ1 or 2, so I do not know from personal experience what the gear ratio of the EQ2 is but I think you are likely to find it much more difficult than has been suggested.
The calculations posted further down in this thread don't add up. Even if the EQ2 has, as stated, a 144 tooth worm, the worm drive shaft has to rotate once every 10 minutes or 1/10th RPM. If the final reduction gear is 5:1 then the drive must rotate at 1/2 rpm not 2rpm.
However I found this URL :
http://tinyurl.com/cn7lbzn states that
The EQ1 has 96 teeth.
The EQ2 has 100 teeth.
The EQ3-2 & NEQ3 have 130 teeth.
The HEQ5 & HEQ5 Pro have 135.
The CG-2 or CG-3 mount (used by Celestron AstroMaster / Powerseeker range) have 136 teeth..
The old EQ3 & EQ4, EQ5 & EQ5 PRO & Orion Skyview have 144 teeth.
The Meade LX and the Celestron CGE range have 180 teeth.
If this web site is correct, then the output shaft of an EQ2 will turn at 1 rev per 861.6 seconds x final reduction gear ratio. ie if it is a 5:1 reduction gear then you are looking at a rotation of 1 rev per 172.32 seconds. A little faster than 1/3 rpm. The EQ1 is a little easier at 900s per rev divided by the reduction ratio. These drives use quartz crystals so it is not that easy to change frequency to change speeds and you won't find gears of the appropriate ratio to solve the problem.
A barndoor drive is easy to make, but not easy to make to high precision. It's much easier to have a variable speed drive so that you can make a final speed adjustment to after it is made. These are effectively fixed speed drives unless you swap crystals.
I have used the Jaycar kits you identified but they are being phased out of production. I've swapped the timing capacitor for one that has good temperature stability and replace the timing potentiometer with two precision trimpots in series, one for course and one for fine adjustment and some push buttons to switch in different resistors for fast and slow.
The trimpots must be set with a screwdriver and once set can't be bumped out of calibration. However it is not a simple matter to attach a precision gearbox to the supplied motor. They come with a spur gear pressed onto the end of the shaft but I haven't found a suitable supply of gears. In my application, I took the spur gear off and purchased a separate high precision gearbox that was supplied with it's own spur gear. But I needed to use a lathe to make the parts to adapt it.
Joe