Two bolts, and you can make a simple pump

[mklrobo]

  Hello!
I ran across this idea, when I tried to make a small hydraulic
pump for my robot. Consider this;
Acquire 2 bolts; One is larger than the other, at least 1/8 inch (diameter)
larger than the small one.
Drill a hole in the center of the larger one; the hole should be
the diameter of the smaller bolt, so that the bolt can be put inside
the larger bolt. Now, put the smaller bolt through the hole in the
larger one. If you put the end of this into oil, and turn the smaller
bolt inside the larger one, the thread inside the smaller bolt will
act like a gear pump, and the oil will rise to the top of the bolts.
What do you think?

[bdeuell]

What is the use of the larger bolt or just to provide a piece of material to drill a hole in?

If i'm understanding your design right you are creating an auger or Archimedes' screw. This is fundamentally different from a gear pump as it is not a positive displacement pump. it will not be able to achieve as high of pressures as a gear pump or other positive displacement pump.

...perhaps i am missing something.

[mklrobo]

  Hello!
What is the use of the larger bolt or just to provide a piece of material to drill a hole in?
Yes, it provides a housing for the smaller bolt; but you can secure the larger bolt to a piece of metal, since it
has threads on the outside anyway. 

If i'm understanding your design right you are creating an auger or Archimedes' screw. This is fundamentally different from a gear pump as it is not a positive displacement pump. it will not be able to achieve as high of pressures as a gear pump or other positive displacement pump.
Correct! The pressure will be considerable lower, but the unit is not sealed. I got the idea from Archimedes, the story where the king wanted him to find a way to get water out of the bottom of ships.
This mechanisim is not uniquie; industral compressors, sand displacement screws, and irrigation pumps use
the same process. I was trying to add more power to my robot, with smaller parts, and tried to use this
to give him a "hydraulic heart", so to speak. I thought I would pass this along, to see if anyone else could
use it. Thanks for the feedback! 

[mklrobo]

  The "Hydraulic Heart" of the robot may be less power
than expected. The cyclone piston is a great example of
unconventional engineering!