best pressure medium (homemade expresso)

[sexualjesus]

hey guys, with the price of energy drinks ive decided i want to drink expresso's, without $800 ive been wondering some ideas for a homemade one.
looking at engadets idea on using a caulk gun to apply pressure to the water ive been curious on how to apply a more powerful ammount of pressure to a homemade expresso machine.
http://www.engadget.com/2005/02/15/how-to-make-a-cheap-portable-espresso-machine/
my first idea was a car turbo, but i cant honestly see how that would work apart from having a spare engine and exhaust system lying around in your kitchen, and an electric fan just doesnt give out enough pressure.

second hand expresso machines are still so expensive so buying one and tearing out the compression aparatus is out of the question, a car tyre has 30 psi of pressure in it if its on a car, if you take a spare tyre and stand it up so the air is being pressurised inside, then sit on it while holding something heavy, it may just push out enough to punch the water through the coffee grounds.

spare a thought for your time? any ideas welcome no matter how elaborate they are

[Alamo]

You could use clamps which is basically the caulking gun just stringer and you can wind those extremely tight that should get your pressure. Seems like their idea is pretty easy though and works fine.

[Sentinel owl]

You could spring-load the plunger in the PVC idea instead. That will give you more consistancy.

Be aware, though, that PVC can really only safely take ~100psi or so. 12 bar is 174 psi, so don't expect that kind of pressure. The hot water may weaken the PVC too.

Spring loading is definitely the way to go. You could even fit a manometer to the end to test the pressure of it.