Coupling two mechanical pieces for a telescope mount

[Deven Patel]

Hello PF community!

Quick introduction: I'm a fresh-out-university mechanical engineer working on a telescope altitude-azimuth mount hobby project. The mount will be designed using rotary platforms (powered by internal motors) to move the mount structure in the altitude and azimuth directions (1 for each direction).

The base of the mount structure has two purposes: 1. to support the weight of the upper mount (for the telescope) and 2. to rotate the entire structure in the azimuth direction (which will be done by 1 rotary platform that will be fixed underneath the base). The upper mount (that is holding the telescope) needs to have freedom in the altitude direction, it will be rotated by the second rotary platform that will be fixed on one side of the entire structure and needs to couple the two mounts together. Refer the picture below for a visual layout of the current design. The rotary mount underneath the structure is not shown, the rotary mount that needs to couple the two mounts is on the right. It is currently interface to the telescope mount by a custom mechanical interface piece that I designed. The large, black cylinder near the top of the picture is the telescope, the 5 small, black cylinders are the counterweights, to balance the CG of the upper mount structure.

Being an amateur mechanical engineer and never having worked with dynamic parts, I'm lost on how to design the coupling between these two mounts. The rotary platform underneath the base should be ok, but the one that's coupling the two mounts together is a problem because it's being used in an application that it's not really meant for. Generally speaking, a motor transmits torque to a mechanical piece through shaft-key or gear-pulley assemblies; but, in this case, I need to transmit torque from a rotary platform to a mechanical piece. Does anyone have any thoughts about how this can be accomplished? With the rotary platform fixed to the base mount, is a direct mechanical piece to interface the rotary platform to the upper mount the best approach?

FYI, the rotary platforms I'm using are the RM-8 (underneath base mount) and RM-5 (coupling the two mounts) rotary stages by Newmark Systems. Side note: I'm using these rotary platforms because they're what was available to me so I'm trying to make do with them so I don't have to invest more money into the project!

Thanks for the help in advance, I'll reply to messages in a timely manner!

Deven Patel

 

[Nidum]

I'm a fresh-out-university mechanical engineer

This is ridiculous - do you really have no idea how to design a simple and commonplace mechanism ?

Have you made any attempt ? Sketched out any possible solutions ? Looked in any references for standard mechanical design elements ? Found out how this problem is solved for existing telescope mounts ?

 

[russ_watters]

Refer the picture below...

Image isn't visible.

 

[berkeman]

FYI, the rotary platforms I'm using are the RM-8 (underneath base mount) and RM-5 (coupling the two mounts) rotary stages by Newmark Systems.

http://www.newmarksystems.com/rotary-positioners/

 

[Deven Patel]

This is ridiculous - do you really have no idea how to design a simple and commonplace mechanism ?

Have you made any attempt ? Sketched out any possible solutions ? Looked in any references for standard mechanical design elements ? Found out how this problem is solved for existing telescope mounts ?

I've made 3 attempts, 2 using keys to transmit the torque, but they weren't feasible designs because of the layout of our components. The last attempt is the layout and interface piece that you see in the picture in my original post. It's a direct interface from the rotary platform to the arm. I know that it's not the conventional way of transmitting torque, but it's not a conventional problem, so I turned to the PF community for their input. This isn't something you'd find in a standard mechanical design element manual or textbook (but yes, I've checked numerous engineering textbooks and online resources) and existing telescope mounts do not have this problem because they do not use this design (but yes, I've checked this as well).

Also, I've already admitted to have zero work experience in my post, so please refrain from ridiculing me.

Thank you,

Deven Patel

 

[berkeman]

The last attempt is the layout and interface piece that you see in the picture in my original post.

Picture didn't post. Did you try the UPLOAD button in the lower right of the Reply window?

 

[Deven Patel]

Picture didn't post. Did you try the UPLOAD button in the lower right of the Reply window?

Image isn't visible.

Very odd, it's showing for me. I'll try making another post when I get back to my office tomorrow! Thank for the heads up.

 

[etudiant]

There must be a good reason for your arrangement, but it seems unreasonable to set up a rotating platform for the entire telescope assembly and its pier.
Maintaining proper tracking while observers are moving around on the rotating platform will be more difficult.
What is the advantage you expect to gain by making the entire structure move rather than just the telescope?
If it is merely operator convenience, you could use a cheap rotor motor to turn the platform as the telescope turns, but rotating the platform to arc second accuracy seems expensive overkill to me.