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It’s Called An Equatorial Motor Drive!

It’s been 3 weeks since the idea came to me. This super secret mini-installation piece I’ve been working on has not all been fun and games I tell you. I can’t reveal too much until it’s all finished and “working” but I have been working on a fairly complicated kinetic installation that will be documented on film. I’m going to reveal one part of the piece and that is the main kinetic part. It’s called an equatorial motor drive!

For this project I needed a small electric motor that would rotate once every 24 hours. Let me reword that. It needs to take 24 hours to complete a rotation. Very slow. Like the hour hand on a 24 hour analog clock. But also be able to pull about 2 lbs of weight. The mechanism from a 24 hour analog clock generally can’t pull this much and they are too expensive. I had been on hobby forums, physics forums, read parts of my “How to Make things Move” e-book on the kindle. I’ve racked brain with newtonian physics and calculations. I tried using a wall timer. You know, those timers for lights to go on and off while you are on vacation. I modified one of this for my project and it worked for about 4 hours before it would stall and I assumed their just wasn’t enough torque for what I was trying to rotate. Also, this approach would only provide once every 12 hour rotation not 24. I was looking into modifying a disco ball motor but couldn’t figure out how to slow it down to 1/1440 revolutions per minute (one revolution per day). I looked into PWM (Pulse Width Modulation) to control the speed of a DC motor, but again, I was worried about torque and there was some debate on whether a DC motor controlled by PWM could be slowed down that much. It’s been a rough road for my wee little brain but last night while plugging in “one revolution per day motor” into google, I came across an astrophotography site and found the name of what I needed, the equatorial motor drive. These motors are for tracking the sky with a telescope or camera to compensate for the rotation of the earth. Exactly what I’m looking for, although I’m not doing anything with the night sky.  I promptly ordered one for about $30 which was in my budget. It should get here on Wednesday and I’ll start my second round of tests with it. More to come!

 

Modified Wall Timer is not going to cut the mustard for this project!:

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