[ihc] Air Brake Systems

[Tom Mandera <tsm1@xxxxxxxxx>]

Mac McMuffin wrote:

> for all the air brake systems i'm familiar with, pressure in the air system
> is regulated by an in-line pressure-activated mechanical governor and
> constant-duty compressor.  when the system pressure falls below 95psi, the
> governor cuts in and the compressor feeds more pressure to the system.  the
That's pretty much what I figured.

They're "constant duty" but will "vent" the air pressure (thus making 
"no" pressure against the compressor) except when needed.

By not working against a pressurized vessel, it should make the air pump 
run cooler when not actively pressurizing things.

I bring this up, partly because I bought a used SpeedAire compressor a 
few weeks back.  2hp pump, with a 3hp 220V (15amp) electric motor.  I 
paid $75, and for the money, the electric motor was a good investment 
even if I junk the rest.

But I also have a Honda gasoline engine lying around from a generator 
someone parted out.

I have friends that bring generators and 110V air compressors to races. 
 The gas generator makes electricity that powers the air compressor 
that makes compressed air.

I was thinking I could just run the compressor pump off the gasoline 
engine directly and avoid all of the energy loss by converting gas to 
recip motion / heat energy to electricity to an electric motor to an air 
compressor.

I just wasn't sure how I would "regulate" the output of the "always 
turning" compressor pump when coupled to a gasoline engine.

One idea that might work, would be a one-way check valve into the tank, 
but between the valve and the compressor output, install a "T", with an 
electrically controlled air solenoid actuated by a typical pressure 
switch on the tank.

This would let the compressor pump vent to atmosphere except when the 
switch indicated the tank needed more air.

But where to get the electricity for the switch and solenoid?  How about 
adding a regular 12V alternator to the mix.  Bonus, it can charge the 
battery on the trailer for the trailer winch.

Heck, get a big enough power inverter and add that into the mix, too..

Meanwhile, the 3hp electric motor from the original air compressor can 
be used to run a PTO hydraulic pump feeding a tie-rod ram to operate my 
JD2 tubing bender. :D

-Tom