It has been awhile since I have posted anything related to this. However, This does not mean progress has stopped on it!
Allen's last post got me thinking and I decided to change a few things.
I have redesigned how the gears mount to the upper bearings. Instead of being cut with the axis hub, they will be separate gears, loc-tight'ed to the bearing. The hub will also be loc-tight'ed to the bearing. This allows anybody with a large enough gear to bore to 160mm (6.299") can fit them to the mount.
In the past few months, I have been sourcing parts to build the mount. I happened to get the chance to get a set of 9" Byers gears and worms directly from Ed Byers. I talked to him on the phone a few times and he said he retired 2 years ago and was just selling off his left over inventory. He does not have much left now and what is left is on his Ebay page.
Anyways, I was able to get 2 sets of 9" gears with worms mounted on 2 bearing blocks with custom bore for $650. While this is more then I wanted to spend on gears, I could not pass up the opportunity of using Byers gears in my mount.
I have mostly made refinements to the design I posted a few months ago. Shafts the main shafts of each axis is a standard diameter for linear bearing rails. These are very accurate in roundness and also are usually chrome plated. This is perfect for needle roller bearings. The RA clutch shaft is 40mm OD with a 22mm ID. This allows some amount of cables to pass through the RA. Its better then nothing I guess.
The azimuth adjustment is done with 2 precision set screws. These are 2" long and have 80 threads per inch. The push against a block in the base to twist the mount. When your in position, there is 6 locking levers that clamp the base plate with the azimuth plate. These levers are re-position-able so once locked, you can release them and rotate them out of the way. There is +/- 7.5 degrees of azimuth adjustment.
The altitude has been modified a good bit from the original design. The adjustment screw is also a 80 thread setscrew allowing for super accurate adjustments. The block that mounts the set screw is adjustable to 4 positions. The altitude ranges are 10-25, 25 - 40, 40-55, 55-70. I'm in the middle at 42 degrees. The main pivot of the RA axis is on 2 - 3/8" shoulder bolts, and is locked in place with 2.25" 5 lobe knobs.
The biggest changes are the gear box's / gear covers. The lower half of the gear cover is actually the structural mount of the worm gear and servo mount. These are probably some of the most expensive pieces of aluminum. Its about $360 for all the material for both of the gear box's. The lower part of the gear box is 1.5" thick milled to a shell with a 1/2" bottom. Its alot of material to remove, but no real better way to accomplish a tight cover that looks good. The lower cover is bored to fit nicely around the main tube of the axis and is secured to a mounting ring with 5 - 5/16 stainless steel bolts in a circle pattern. The mounting ring is also machined to fit the main tube snugly and is secured to the tube with 5 more 5/16 bolts. Both axes are set up this way.
The upper gear cover is also milled from solid aluminum with a whole bored to fit the hub of the axis. The hub rids on the main bearing. The worm wheel is loc-tighted to the bearing and secured to the hub with 5 screws.
Half of the upper cover is removable to allow easy access to the worm gear and servo components.
The worm gear and servo are mounted on a common pivot point and are held down with shoulder screws. This allows the whole worm/servo block to pivot to maintain constant pressure of engagement between the worm gear and wheel. This pressure is applied with 2 set screws with springs. These are accessible from outside of the gear casing.
The counter weight shaft is an off the shelf piece from Astro Phsyics. It is a 1.875" shaft. I liked the look of the shaft and counter weights and wanted to use these. The shaft can be re sized easily as long as it can thread into the DEC tube.
The mount can be taken apart at the intersection of the RA and DEC for easier transport. If wanted, the RA tube can be removed from the support arms by removing the 2 hand knobs and the 2 shoulder bolts. This would break it into 3 sections roughly about 30lbs each.
Here is a few older renders of the mount with a model of my Meade LX200 12" EMC on it as well as 2 - 18lb counter weights.
I have begun building this now and will post what I have done.
Mount minus counter weight shaft:
Base of mount:
Meade 12" Tracking:
Meade 12" almost home: