Ball bearings in equatorial mounts
Posted 31 January 2010 - 06:56 AM
Posted 31 January 2010 - 10:30 AM
Can someone help me understand how manufacturers mount ball bearings in equatorial mounts to reduce friction? I am a bit confused. Do they use them instead of plastic washers you can find in cheaper mounts (for instance under the ring nuts of the RA and DEC shafts) or there are other possibile locations inside the mounts?
I've also seen bearings at the ends of worm shafts.
Posted 31 January 2010 - 02:30 PM
The Meade LXD55 is a classic example. I have heard people say that it uses plastic bearings but nowhere in the mount are there any plastic bearings. Both the Dec and RA axis uses two bronze bearings that support each shaft assembly, one on the end where the weight shaft and polar scope goes in, and one on the worm wheel at the other end.
As I write this, I am LOOKING at the bearings. I have spare, and I quickly pulled the shafts out (takes 2 minutes) to confirm there were no plastic bearings anywhere.
I often see people reference plastic bearings in mounts, but I personally have never seen a plastic bearing in any astro mount I have ever taken apart.. They are just about always either bronze plain bearings supporting bearing rings cut into the shafts or castings, or roller bearings. Plastic lacks the compressibility and wear resistance that lubricated bronze does, and for that reason, any assembly that is expected to carry anything more than a very small amount of weight will use plain bearings or roller bearings.
Any plastic washers that are encountered are normally there for spacing purposes or to act as a clutch of some kind.
Hope this is helpful.
Posted 31 January 2010 - 02:34 PM
For the CG5 for example, the updated assembly used a sealed roller bearing at the bottom of the RA shaft, and near the worm, they used a thrust type bearing cage (where the bearings are loaded from the front and back of a ring rather than around the outside of the ring like a common roller bearing.
Posted 31 January 2010 - 02:47 PM
Maybe that's where people hear about plastic bearings: from fork mounted scopes.
Posted 31 January 2010 - 03:06 PM
You were really talking about equitorial mounts without those things. Pardon my confusion.
Posted 31 January 2010 - 04:06 PM
Posted 31 January 2010 - 04:18 PM
It is a significent design change. Beyond the capability to reverse engineer I think.
I am not sure why people feel that these mounts require ball bearings. The plain bearings are fine. If it is tight, doing the Astronomy Boy tuneup can make a very big difference in their smoothness. I basically did the same modifications to my LXD55 and the movement was much smoother. Tracking and pointing though did not improve one bit. Still, if you are using a standard Vixen or Celestron without motors and with slow motion controls, I could see wanting to improve the mount to eliminate as much friction as possible.
Posted 31 January 2010 - 07:26 PM
Posted 31 January 2010 - 11:29 PM
Posted 01 February 2010 - 03:32 AM