Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Mounts

Pages: 1
Groo
member


Reged: 03/05/09

Loc: Calgary, AB Canada
Barndoor mount new
      #6139201 - 10/15/13 02:36 PM

Hello, Does anyone know what rate I would need to increase the gear rotation on a simple straight rod barn door mount to adjust for tangent errors? I would like to use the Arduino to adjust the rotation speed.

Thanks


Post Extras: Print Post   Remind Me!   Notify Moderator  
Phil Sherman
Pooh-Bah


Reged: 12/07/10

Loc: Cleveland, Ohio
Re: Barndoor mount new [Re: Groo]
      #6140517 - 10/16/13 09:38 AM

Divide the rate by the cosine of the angle of the hinge where 0 is closed. You could probably get by with a table that adjusts the speed every rotation or two.

It's easier to make a curved pillar block for the rod to push against. This will keep the distance from the hinge to the contact point a constant, eliminating the need to adjust the motor speed.

Phil


Post Extras: Print Post   Remind Me!   Notify Moderator  
Groo
member


Reged: 03/05/09

Loc: Calgary, AB Canada
Re: Barndoor mount new [Re: Phil Sherman]
      #6140713 - 10/16/13 11:32 AM

for the curved pillar block how much of a curve is needed? or is it better to try and bend the threaded rod?

Post Extras: Print Post   Remind Me!   Notify Moderator  
Groo
member


Reged: 03/05/09

Loc: Calgary, AB Canada
Re: Barndoor mount new [Re: Groo]
      #6140720 - 10/16/13 11:35 AM

Nefver mind, I see your post in the other thread

Post Extras: Print Post   Remind Me!   Notify Moderator  
Phil Sherman
Pooh-Bah


Reged: 12/07/10

Loc: Cleveland, Ohio
Re: Barndoor mount [Re: Groo]
      #6142598 - 10/17/13 10:15 AM

The big problem with a bent rod is that you can't rotate it. You need to use a captive nut (one that doesn't move as it's rotated) that rotates and forces the rod through it. The advantage of the bent rod in this case is that you can attach a larger disk to the nut and rotate it using a motor that presses against the edge of the disk. The ratio of the diameters between the disk and the motor shaft is a gear reduction mechanism that multiplies torque and, for a stepper motor, increases the step resolution.

The critical issue with the disk is to get it perfectly centered on the nut. It might be easiest to attach it then spin it and trim down the edge so it's concentric with the threaded hole in the nut.

Phil


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1


Extra information
27 registered and 49 anonymous users are browsing this forum.

Moderator:  Dave M, richard7, bilgebay, iceblaze 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 191

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics