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Equipment Discussions >> Mounts

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schwimmair
super member
*****

Reged: 09/13/10

Barn Door Tracker Help Please
      #6135938 - 10/13/13 10:10 PM

A nice member in my club just gifted me a manual single arm barn door tracker. Does anyone sell a complete motor/circuit board kit preferably battery operated? I searched and only found ones you had to build and was completely overwhelmed by the wiring schematics.

I am going to donate it to my son's school so even if it's unfeasible to retrofit to electrically track I am sure manually turning by hand would be just as effective as a teaching tool.

Do you thinking posting this in the ATM section would be helpful as well.



Thanks,
Schwimm


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Phil Sherman
Pooh-Bah


Reged: 12/07/10

Loc: Cleveland, Ohio
Re: Barn Door Tracker Help Please new [Re: schwimmair]
      #6136155 - 10/14/13 12:39 AM

That's a really nice implementation of the barn door mount. The curved threaded rod will allow long tracking sessions without introducing rate errors as the door "opens".

It should be easy to motorize because all that's needed is to set a small motor against the edge of the CD that will rotate it at 1rpm. Anything using a DC motor will require a regulated power supply to give a constant rotation rate for the CD. A stepper motor kit, once adjusted for the correct step rate, might be easier to use.

Check around and see if there's an amateur radio club or a "ham" in your area where you can get some assistance with the electronics.

Phil


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schwimmair
super member
*****

Reged: 09/13/10

Re: Barn Door Tracker Help Please new [Re: Phil Sherman]
      #6136479 - 10/14/13 09:11 AM

Thanks Phil good ideas!

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wormstar
Pooh-Bah


Reged: 11/23/09

Loc: Central Ct
Re: Barn Door Tracker Help Please new [Re: schwimmair]
      #6136987 - 10/14/13 01:17 PM

How does the curved threaded rod work? Is the cd turning a nut?

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schwimmair
super member
*****

Reged: 09/13/10

Re: Barn Door Tracker Help Please new [Re: wormstar]
      #6137707 - 10/14/13 07:29 PM

Hi Wormstar, yes the cd is attached to a nut and is the manual turning wheel. You turn the cd at a constant rate for 360*. The cd has 4 lines on it to guide you where the wheel needs to be in 15 sec intervals. Please don't hold me to this as I just got it and am still figuring it out but I believe the rod is curved to help the mount track better. It would still work with a straight rod but the motor would need to be programmed to speed up and slow down during the one revolution where the curved rod is constant. I hope I explained this right, please anyone add to this if you can help explain.

Schwimm

Edited by schwimmair (10/14/13 07:33 PM)


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wormstar
Pooh-Bah


Reged: 11/23/09

Loc: Central Ct
Re: Barn Door Tracker Help Please new [Re: schwimmair]
      #6138592 - 10/15/13 09:10 AM

That's close enough, when I first looked I thought the bent rod rotated, which would be pretty awful mechanically.
Thanks


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Phil Sherman
Pooh-Bah


Reged: 12/07/10

Loc: Cleveland, Ohio
Re: Barn Door Tracker Help Please new [Re: wormstar]
      #6138835 - 10/15/13 11:28 AM

The barn door "drive" relies on the rate at which the threaded rod separates the two hinged pieces of wood. As the pieces separate, a straight rod will contact the bottom plate in different places, changing the rate at which the upper plate moves because the length of one side of the triangle formed by the hinge, boards, and rod changes as the hinge opens.

The curved rod keeps this distance constant, allowing for a long period of tracking without changing the dimensions that make this device work. An alternative to the curved rod is to use a straight rod and add a curved wedge to the bottom board that keeps the hinge to rod contact point distance constant as the hinge opens. The wedge approach will severely limit the tracking time when compared to the curved rod design but it allows the rod to be turned instead of rotating a captured nut to open the hinge, a simpler design.

Phil


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