Linear Actuator

I was looking for a way to lift a 3 pound robot head about 5 inches up. So I found Linear Actuators, they seemed like they would work. For the price though it doesn't seem to be worth it. Is there any cheaper alternatives or a cheaper linear Actuator.

Presumably the ones you've seen are these ones at Firgelli?

They are the only ones I've seen.

Maybe you could make a screw type actuator with a threaded rod and a nut that runs up and down?

EDIT.... how about making one from Meccano?

You could get a second hand car window lifter assembly relatively cheaply.

PeterH: You could get a second hand car window lifter assembly relatively cheaply.

Hmmm, my brother is in the motor insurance business and is "well in" with the scrap yards.... that's definitely a thing I'll look into.

The one I had in mind was this http://www.pololu.com/catalog/product/2337
90 dollars is a bit much though. I will try and look into the window motor idea.
still though I would prefer something more reliable.

arduinopi: The one I had in mind was this http://www.pololu.com/catalog/product/2337 90 dollars is a bit much though. I will try and look into the window motor idea. still though I would prefer something more reliable.

That's actually pretty cheap for a new 8" stroke linear actuator...

For your needs, I would also second building your own using a piece of threaded rod (also called "all-thread") and a nut. Basically, you attach a motor (a small gearmotor, most likely) to the rod (depending on your motor and rod, you could use anything from a drilled out piece of wood dowel, to a piece of rubber tubing, to a drilled/tapped nylon standoff, etc), and spin the rod with the motor. A proper sized nut threaded on to the rod acts as your "travelling nut" or "follower". When it is held still, it will move up/down the rod depending on the direction of rotation. Of course, you need to come up with a method to keep the nut still while still permitting linear motion along the rod.

Do some research on google; there are plenty of people who have made instructables, videos, etc - on how to build such a device; here are a couple to get you started:

http://blog.davidjbarnes.com/2009/03/making-linear-actuator-for-robots.html http://www.instructables.com/id/Making-a-Powerful-Linear-Actuator/

Here's an article showing how a linear actuator similar to the one you linked is constructed, which might help you too:

http://www.cozypad.com/linear-actuators/16000.html

Of course, you'll need to scale your implementation to fit your needs.

Good luck!

if noise and accuracy is not a problem you could use a simple air pump and pneumatic cylinder (or a large medical syringe )

arduinopi: I would prefer something more reliable.

More reliable than what? Or in other words, how reliable does it need to be?