The Azimuth Drive

(Were half way there!)

 

My idea for the Azimuth drive has its origin from the “Mad Hatters Tea Cup Ride” at Walt Disney.  In the ride you sit in a cup, and in the center is a wheel you grab and ‘spin’  Spinning the wheel actually spins the cup your sitting in.  Which also causes nausea and Vomiting J

 

I did the same thing but the ‘wheel’ is the Az Worm ring gear and housed on top/inside the Azimuth base.

 

Here’s a Pic to help visualize what I did

 

 

The Ground Board has three perimeter bearing to support the Azimuth base which look similar to this:

 

 

 

The Bearings are less than $1.00us each, and are originally intended for Roller Blade Bearings.  I’ve used these bearings exclusively on the scope so far and there great!  They are 7/8” OD and 5/16” id (ID is the only ‘problem’)

 

To Motorize the Az drive, here is what I did

 

  1. Bolted 5/16” threaded rod to ground board, pointing straight up about 6 inches
  2. enlarged the azimuth base center hole to accept a bearing, then slid the azimuth base over the bolt in the middle of the ground board.
  3. Then I bolted the Ring gear to the top of the threaded rod.
  4. Attached the stepper motor to a long piece of masonite, with a wood guide block for the other end of the threaded worm and added a fly wheel and tension spring.

 

The First try at this failed miserable!  The 5/16 threaded rod flexed like hell inducing incredible accelerations / Oscilations and slop in the system.

 

To solve this problem, where every there was exposed thread, I put a NUT and tighten the hell out if it to the one below, along with excessive amounts of ‘lock tite’ thread adhesive.  So now from the base board to the top of the ring gear there is either a Nut, or a Bearing.  This stopped the wobble and slop.  I still have a little bit of slop in the worm itself, but That will be solved soon enough.

 

The next problem I ran into were ‘rough’ spots in the threads, causing high speed slews to stall.  To solve this problem I made a paste from some Gear lube and 220 grit abrasive and worked the ‘rough’ spots out.  I now have consistent 360 degree slews nearing the 1 RPM mark J

 

The kid in me just had to hop on for a ride!  Other than increasing the Ramp up / Down parameter it actually worked J

 

Here’s a video of the azimuth base in motion,  Note the time it takes for 1 Revolution! OF course great slew speeds (Min delay is @ 400 in this video) may result in a terrible eyepiece experience, but time will tell. ;)

 

Here the link to the video Motion.avi

 

Amazingly its not very noisy, but that may be relative, and become obnoxious when out in a quit field somewhere J

 

Any Questions, Give me a shout.

 

James Lerch

Jlerch1@tampabay.rr.com