Barn Door Tracker

As a matter of curiositt more then anything, I hope to put together a barn door tracker in the next couple of weeks.
I have seen this: www.garyseronik.com/?q=node/52
I can get a 1rpm motor, plywood and bolts etc easily enough.

Question I have though is: how does the motor drive the bolt?

The motor I can get has a 7mm shaft.
So, as I understand it, I will need two gears: one positioned on the motor and one centered on the bolt.
I presume one gear needs to have have an internal dia of 7mm and fit over the motor.
However, in terms of the other gear on the bolt, is it possible to get one to fit directly onto a threaded rod?

Also, when the bolt has reached it's maximum length and the arm is fully open, is there any easy way to reset it quickly?


Michael.

Howerya Mike.
It's a handy little project for cloudy nights
(and boy do we have some these days!)

Couple of things.
Motors are grand, but you really don't need one!
You can attach a cog and a large circle with a red line on it
to donate one second of revolution and if you use the correct
size threaded bar and nut you can wind it along by hand.
Now, this is fine of course for like a 2 min exposure but anything longer
ya, motorize it (and get thee to a dark place)

I see his design has a bent bar.
Again, no need if you don't want to.
As in the pic of the one I made there a few years back
you can just pop a dome nut on top of the bar and rest the top (door)
of the tracker on it - using a long spring to keep it from flopping off.
Works a treat.

The one I built I made extra large so I could level it
(see the 4 threaded bars through the base)
on top of a table.
Polar sight was just a piece of copper tube with a copper wire cross hair
soilderd on.

It's funny, someting so crude looking actually gave brilliant results.

Keep us posted on the build!

Frank,
My concerns with using a hand instead of a motor are vibration and poor timing.
At least the motor is consistent and doesn't need human intervention to mess it up! .
However, I take your point that it is more trouble to install.
Michael.

There are motor/gear kits in maplin, one of them might suit your needs.

Id say its easy to do it though.
You could look at a motor that you can adjust the rpm on.

sky&telescope have a 2 page spread this months on the specs on doing a manual one up, motorising it would be trivial.