Ok so I'm planning on a new project, and one of the components needs some linear motion.
Thing is, it needs a good amount of travel and some decent force behind it.
Rough estimate about 5-6inches of travel and apply 5-10lbf.
Linear actuators can do this easily, but they are really expensive and move kind of slow. I want a quick pop for this, so I was thinking a push action solenoid would give me the kind of action I'm looking for. Problem is, the off-the-shelf solenoids I could find don't meet the travel and force specs I need, so I was planning to make my own.

Basically I'd like some feedback from some of the people here that are more electrically inclined than myself if you think this is doable and any insight in to the construction of it you have.
One of my other concerns is that it is possible but would take a ridiculous amount of power to run. I was kind of hoping to run it off an AC adapter plug at 9, 12 or 24v. The solenoid would only be energized for less than a second at a time so I'm not too worried about overheating, but I'd like to keep the current draw as low as possible anyways.

Find something that is the same inner diameter as you the solenoid should be. It will over heat and use alot of power.
It will get hot even it is only for less than a second repeatedly. As for the power source I would say build it to run off the 120. I have a large coil you plug in and never had any problems besides it getting ridiculously hot.

Definitely possible to build your own if you put forth effort and ALOT of time.

I think you will want to use a capacitor to drive the coil. Basically charge it to a specific voltage (that you will determine by experimentation) and then dump it into the coil. You will want to design it with some resistance in it as well, so as to not have the current oscillating. It is much more complicated than just designing a circuit that is critically damped, because the iron rod is going to induce a back EMF as it moves along its travel, thus it must be accounted for in the equations. But you get the basic idea. I'm not that well versed in knowing how the field moving through the solenoid is going to effect the voltage at the ends of the inductor.

Actually, now that I think of it, the inductor wants to maintain a certain field by back EMF, and will resist by setting up a voltage. However, that back EMF voltage is lowered because of how the magnetic field inside the solenoid is changing as the rod moves along its travel. Conservation of energy, you know. Thus the inducted voltage isn't simply -(L di/dt), but rather the completed form of back EMF:

ε = -dΦ/dt = - [ (L di/dt) + (i dL/dt) ]

Normally inductance doesn't change with time, and that's why you almost never see this form of EMF.

Why not use a pneumatic cylinder?

Argon is right. You might be able to use a disposable camera circuit but I doubt it will be able to move 5lb.

I was thinking of something much more powerful than 300V and a few microFarads...

That was my first thought, but air compressors are just so damn noisy.
I might go back to that though, still kicking a bunch of ideas around.

That was my first thought, but air compressors are just so damn noisy.
I might go back to that though, still kicking a bunch of ideas around.

Not really. A small rotary-vane pump would be capable of reaching high pressures and be very quiet since it doesn't have reciprocating parts.

Those seem to be pretty expensive too, just the pump would account for like 80% of the cost of this project.
It's still on the list of options, I just want to make sure I've exhausted everything before I pick what route to go down.
And if I had a decent sized air tank with a regulator then the pump wouldn't need to run continuously, just flick it on for a bit whenever the tank starts running dry. It's still not ideal but better than nothing.

The other ideas I've been thinking of are more mechanical. I was thinking of getting a DC motor with a gear box revved down for high torque and having that drive either a slider crank or a rack and pinion. A stepper motor would be nice to control the up/down motion but then I need to add controls for it.
There's a lot of things on the drawing board right now.

Could you usea cock-and-release mechanism?

Possibly, that's something I didn't consider yet. I'll give it some more in depth thought later.