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I live in an apartment that has sliding windows in it. The apartment is naturally warm because we live above a mechanical room, such that we either opened the windows or ran the air conditioning through the winter. I want to create a device than can open and close the windows in the apartment depending on temperature. The software and electronics are already figured out, I just need to figure out how to move the windows.

enter image description here

This is a sample of the window. It takes about 4 lbs of force to pull it open, and they only open 6 inches(since I'm 16 stories high).

Ultimately, I want to make this cheap enough that I could replicate it on 6 windows.

My first thought was a linear actuator, but most of the ones I have seen are designed for moving 100+lbs and cost several hundred dollars. Pneumatic actuators are cheaper, but I'd have to run a network of air lines and solenoids, and would have a compressor that would randomly kick in. A double winch system would be very complicated to set up and prone to failure. Lastly, I was thinking of a cheap metal gear servo(dealextreme has 15kg/cm servos for under $15.00), but it would be somewhat difficult to use a series of turnbuckles and arms to translate into 6 inches of linear movement.

Any help would be appreciated.

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    $\begingroup$ If speed is not crucial, there's also the screw! $\endgroup$ – Shahbaz Oct 8 '13 at 16:23
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    $\begingroup$ Yes... You can get a cheap screw in any hardware store and build a linear actuator. That's common for hobby CNC work... $\endgroup$ – Guy Sirton Oct 8 '13 at 21:43
  • $\begingroup$ you mind linking to what you mean by screw $\endgroup$ – Erik Sep 24 '15 at 0:07
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As others have said in comments, a screw is probably your best bet. It's mechanically pretty simple to set up, and could be made to look fairly tidy, which is always nice in a home.

But the main problem, as always is going to be doing this on the cheap. The cost of the parts soon adds up. Even if your motors are only $15, you still need to buy the lead screw and nuts. These can be shockingly expensive if you buy nice ones for CNC machines, but you can probably get away with a simple length of threaded rod attached to a motor mounted on the wall, and a nut attached to the window. Since this thing isn't going to be moving very often, it should last a reasonably long time. And when the components wear out, they'll be cheap to replace.

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You could try this: Using wire cable; mount pulleys at each corner of window; then get a suitable motor for your pull requirement (4lbs). wind the cable around the motor shatft then power forward/backward to Maybe use a block and tackle arrangement for increased torque. Don't forget the need for limit stop switches.

This could be cheaper than screw method but might not have same look and feel

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If you want to be cheap....you could go to a junk yard and grab a linear actuator used for opening and closing car door windows.

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