Metal extender and retractor?

[littlepigboy5]

I really only have an idea of what i'm looking for but think of this, http://www.horizonplatforms.co.uk/images/D/50ES.JPG , but very small.  It doesn't have to work the same as that mechanically, but i need something that can open and close a sliding glass door.  I am going to be using an arduino to detect a gesture, and once detected open the glass door.  my idea was to have something similair to the img above, but small enough to fit in the rails of the sliding door, and has enough length to push it open.  Ideas?

[MatthewEnderle]

you're probably better off with an server with a pully on it. like this and have another one on the closed side of the door. then put another one on the door.

 

otherwise rack and pinion would be best.v

http://gate_opener.china-direct-buy.com/v/4/product_detail/7159627/Sliding_Door_Motor.html

[multifrag]

This won't work efficiently. Better use a belt and a pulley. Cheaper, takes less space and less chance of breaking. You can use servo or stepper motor with that. Stepper will be more precise 

[Patrick3D]

It's been done before:

http://hackaday.com/2011/11/27/star-trek-style-pneumatic-doors-that-dont-require-a-stagehand/