I want to recommend US Patent 2030759 by Bob Neal "Compression Unit".

It is a unique way of compressing air using resonance in the compressor discharge pipe (like water hammer but in air) to do the compressing in the pipe and in the tank instead of in the compressor.  Water hammer or I should say resonance is the only method I know of that has been shown to work for getting over-unity, like the steam generators invented by Joe Griggs and Carl Schaefer and the air heater invented by Eugene Frenette.  Except other compressed air tricks which I'll discuss another time.  Air is the most natural source of free energy because it's heated by the sun 24/7.

This has been worked on by a machinist who was in communication with me for three years.  His results were very good but his machine was not built strongly enough so he moved on to work on a simpler device of his own.  Bob Neal's patent is in the public domain.

The Neal compressor has 7 pistons for each engine piston.  The 7 compressor cylinders are evenly spaced around the crank cycle so the "problem" of vibration in the discharge air is made "worse" by having so many cylinders.  In this case worse is better.

The engine piston is in phase so that while a standing wave in the compressor discharge pipe is pulsing air into an equalizer space in the pipe defined by 2 check valves, simultaneously in the tank the pulse of air leaving for the engine is communicated to the equalizer tail pipe which is an open-ended pipe that blasts squirts of air from the equalizer into the tank.  The tail pipe amplifies pulsations in the tank to produce a strong rarefaction wave that pulls at the air coming into the tank while the pressure wave at the intake to the equalizer hammers at the door.

The compressor has to be as strong as any compressor in order to compress air to 100 psi normally like any compressor.  By that time it has to reach the right rpm to trigger resonance in the discharge pipe.  When that happens a standing wave is set up in the pipe between compressor and tank so the compressor stops running hot and compression takes place in the equalizer instead, in the middle of the tank.  The compressor resists only atmospheric pressure, it is just an air mover and pulsation generator.

So not only is all compression heat conserved, but the only work the compressor has to do is to generate a wave of the right frequency and keep the air moving.  Neal's patent calls for putting air into a 200 psi tank with a single stage compressor running cool..."impossible" but my machinist friend proved it.

There is much more to say but I'll let it go at that for now.

Luther
Pneumatic Options Research Library