Barry, to answer your questions:

The axis of rotation for your second screw is determined by the Frame input of your Rotate node.
The Frame input is fed by the point x,y,z node, which needs to have its y input set by a Basic/Constant of y-value of the second screw's axis.

The direction of rotation can be reversed by running the x-axis input of the rotate factory through a negative Math node.
I used Math node of a-b, with input a = constant 0, and input b coming from the quarts clock. (I have not seen a straight minus node.)
(This is a going upstream explanation, so the flow is sort of backwards.)

(I am a rank amateur at the nodes:-)

- Brian

A picture would be very nice, but I am about out of upload bytes...
I'm working off of the motor2 node, for modification experiments.
The crankshaft represents the RH screw, and moved up by Y, would represent the LH screw
The red piston represents the bottle.
Obviously there must be some modifications in the nodes, and swap in screws and the bottle, and adjust orientations, but the basics are there.
The quartz node is nice to use.