Astrophotography forum > Mounts Questions & Expirience

Friction drives. Potential problems?

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unoritvie:
Hi,

I am putting serious thought into purchasing a Mesu Mount 200.  It utilizes friction disk technologies, which I guess from the amount of users that have Mesu's, Fornax's and Gemini's G53F is still not fully understood concerning performance and behaviors with differing geographical locations (climate).

I work remotely (5hrs away) and while Friction Drives seem great on paper, the 1 thing that's preventing me from pulling the trigger is how the mount slides when off balance.  Not so much that I've troubles balancing, however, the idea of slipping.

My observatory is located in a cold, dry and windy climate.  Very cold in the winter (as I write this, it is currently -27*c and also feels just like -36*c down there).  I currently use my CGEM remotely there.  It and all of my other equipment have handled the cold quite well.  On these sharp ultra chilly nights, when seeing is spectacular, the mount has yet to let me down (brief of slewing electricity issues from a 120 cca Deep Cycle Marine battery that's hooked up to a trickle charger).

What happens when it is -30*c and the metal interior contracts?  Is it possible that the coldness can cause a slip and all of my gear smash into my dock, even when the telescope isn't in use?  Or I suppose that could require it to be away balanced?

obenanus:
<p>
--- Quote ---Hi,
</p>
I'm putting serious thought into purchasing a Mesu Mount 200.  It utilizes friction drive technology, which I guess by the number of users who have Mesu's, Fornax's and Gemini's G53F remains not fully understood in terms of functionality and behaviours with differing geographical locations (climate).

I operate remotely (5hrs off) and while Friction Drives appear great on paper, the one thing that's keeping me from pulling the trigger is the way the bracket slides when off balance.  Not too much that I've troubles balancing, however, the idea of slipping.

My observatory is located at a cold, dry and windy climate.  Very cold in the winter (as I write this, it's now -27*c and also feels just like -36*c down).  I currently use my CGEM remotely there.  It and all my other equipment have managed the cold quite well.  On these sharp ultra cold nights, when viewing is magnificent, the bracket has yet to let me down (short of slewing power issues from a 120 cca Deep Cycle Marine battery that's hooked up to a trickle charger).

What happens when it's -30*c and the alloy interior contracts?  Is it feasible that the coldness could make a slip and all my gear smash in my pier, even when the telescope is not in use?  Or I suppose that could need it to be off balanced?


--- End quote ---
The friction required to turn a balanced head should in theory, be quite low.  Thus even contraction shouldn't necessarily affect its functionality.

That said, the bearing substance is likely to really make a difference.  Over time, there'll be wear resulting from the compression.  I suspect that certain sorts of aluminum could work out prematurely, whereas distinct sorts of steel would not.

Thus I would say a significant feature of any friction drive would be the capability to re-tension the joint as required (which ought to be quite in-frequent).  If the mount does not let you adjust this strain, or utilizes soft bearings, then the bracket will have a shelf life to it.

Kyle Styles:
I've had the same musings -- anyone remember the days of cassette tapes and the dreaded flat spot on the capstan roller? The folks who sell these mounts claim there are no issues with slippage or wear.

unexaric:

--- Quote ---I've had the same musings -- anyone remember the days of cassette tapes and the dreaded flat spot on the capstan roller? The folks who sell these mounts claim there are no issues with slippage or wear.


--- End quote ---

Yea, and Celestron claims their mounts go thru QC 3 times.

Mark Patterson:
I'm pretty certain Lucas has carefully considered operating environment. One of the benefits of a friction roller drive is that lubrication isn't used (well, at the drive interface) and it will be "stiff" over a greater range of temperatures than a lubricated worm drive. Position and tracking accuracy should be more consistent. Perhaps it would be wise to ask about bearing lubrication and for a customer referral in a similar climate.

How about using a pair of solenoids to stop the axes in the event of loss of power to the motors? It would be easy enough to integrate a separate current-monitoring watchdog system if that worry keeps you up at night.

I wouldn't be too concerned with wear or at least any more than I would with a belt or gear driven transmission system. Mechanical items wear. That and manufacturing tolerances are why adjustments are provided.

Clear skies,
Bill

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