Mounts and gears

[Oakbeard]

It had never occurred to me how complicated mounts can be. When a mount is holding a telescope in place I guess it holds it there via one of two things: friction or gear lock. I made up the name gear lock, I actually don't know what to call this. If I make 2 gear wheels how would they not simply backtrack to achieve equilibrium? Do motors create constant tension? Im puzzled how to lock them but also have them being able of reverse motion.

[Dr_Ju_ju]

Very simply, and you don't say what type of mount you're asking about (Alt/AZ, Equatorial, manual, motorised etc.), but in general, If everything is properly balanced, then friction of the gears meshing together, due to the weight pushing down. will 'hold' the mount in the same position, but slewing the mount around will obviously move the balance point, and so 'push' the mount to a different position.

Note there are additional friction locks on each axis, if you wish to stay in one place, but the target will move out of field of view due to the Earth's rotation etc. 

[Oakbeard]

I did not venture too far on my idea. I have a largish reflector to mount and thought of building something myself. Started by deciding that the simplest would be a dob mount but I wanted gears to motorize it and realised I did not know how powered mounts hold the scope in place. I think in my mind I had crossover between dob mount and those motorized forks meade uses in the LX series.

[Dr_Ju_ju]

There are motorised DOB mounts, but for DOB's, and Fork mounts, both axes motors must be driven, to counteract earth rotation, but for EQ mounts only the Azimuth motor needs to be driven to keep focused on the target....

[michael8554]

Most mounts are driven by a small Worm meshing a large Worm Wheel.

With that design it's almost impossible to make the small Worm rotate by unbalancing the scope, but easy to drive the Worm to make the Worm Wheel. move

The only movement you'll see will be small, due to Backlash between those two "gears".

"I made up the name gear lock"

An apt description.

Michael

 

 

[Rusted]

A Dobsonian reflector can be mounted on top of a "driven equatorial platform."

There are several commercial versions, different varieties & different sizes.
A number of Dob users have made their own.

Search here and online for <equatorial platform> for far more information.