Plastic shim between Mount and Tripod
Posted 02 May 2011 - 07:54 AM
If it was here, then I hope that whoever would show me the link so that I can read an account of how that shim works. Getting to be slight annoyance when doing my polar scope alignment to have to fight those knobs.
Also, out of curiosity, what about the newer CGEM DX mount. Is this still a factor? I will admit that I have not taken the time yet to read up on that mount. It seems that the only change is that it is able to handle more weight. I need to read up on that.
Thanks in advance for any help.
Posted 02 May 2011 - 08:30 AM
The Meade LXD-750 has a very large plastic bearing that fits between the head and the tripod.
It is just a circular "Gasket" made from a very thick material similar to the plastic used in milk bottles in its composition. The circle is about an inch wide around the outside edge, and the back third is completly filled in.
It is about 1/16th inch thick. It is simply glued to the bottom of the head so that when the head is lifted off, the bearing comes away with the head.
Now the LXD-750 was I think DESIGNED to be used with this bearing.
The LXD-750 has a post on the bottom of the head that is a couple of inches long. The mound will not sit flat on the floor.
The post on the bottom goes into a recess on the top of the tripod plate.
The purpose of this shaft is to keep the assymetrical weight of the mount (I can do the azimuth adjustment with the scope and counterweights in place) from pinching on the north side of the bearing because the shaft prevents this from happening.
The base of the head is also very large, being maybe 1- inches in diameter, so there is a LOT of bearing surface.
In a mount without a posts, you might find that the bearing pinches if you have counterweights on.
But it sounds like it would be cheap to try.
A better choice might be to use the material they use in Dob telescopes to cut your bearings from this material. I would think this would give you the best chance of being able to rotate the base even with pressure on the bottom knob.
Posted 02 May 2011 - 09:55 AM
I guess it all comes down to manufacturing / design / and cost. If in the design was a seriously robust ball-bearing design that the azimuth could be rotated with good pressure, then that would add to cost, etc. Now, what would really be nice is to have a separate motor driven platform that would control azimuth alone.
ps. I guess one thing that I need to think about is getting a plastic shim like you say that will have almost no tolerance for reduction of thickness when pressure is applied so that when the Scope is slewing around, the thickness of the plastic will not "give" under the pressure of the RA moving around. When the RA is moving around, it alone is going to change the dynamics of where the pressure is being applied to the different points of the shim. Then the shim can't have any friction to it.
I wonder what would happen if two shims were used.
Posted 02 May 2011 - 10:50 AM
Posted 02 May 2011 - 10:52 AM
They work very well...at least mine does.
Clear, Dark, and Steady
Posted 02 May 2011 - 11:56 AM
Posted 02 May 2011 - 12:18 PM
Posted 02 May 2011 - 12:25 PM
Some light grease on the face isn't going to hurt anything either, espically if the head is normally left in place on the tripod when not in use. This way, the grease film won't pick up dirt.
I used a thin coat of Superlube on mine. When I bring the mount in, I always put the head back on though, and this keeps dirt off.
Wiping it clean though would be simple enough.
So, plastic milk jug with superlube would work too I suspect.
Posted 02 May 2011 - 12:30 PM
The real problem here is that you don't have enough leverage on the little knobs that drive the scope in Azimuth.
Have you considered just going with bigger knobs and a little grease?
A good knob may do more for the situation than a plastic bearing.
Just though I would mention it...
Posted 02 May 2011 - 12:45 PM
Posted 02 May 2011 - 01:23 PM
National Astronomy Day THIS Saturday
Posted 02 May 2011 - 06:31 PM
Posted 03 May 2011 - 07:17 PM
Posted 05 May 2011 - 09:19 PM
Posted 06 May 2011 - 01:22 PM
Posted 19 May 2011 - 12:37 PM
It made a huge difference. I can really lock down the mount and still use the AZ knobs to make fine adjustments without the need of turning the knob below to loosen the mount.
This turns out to be a worthwhile mod.