Air impact tools (zero audi content)

[Dave Conner <conner@cfm.ohio-state.edu>]

At a ProRally service area (STPR) I heard the sound of an air impact wrench
being used.
This seemed strange because there was no electrical supply and no sound of
a generator or air compressor to go with it.

I asked the guys how they did this.
They were using a gas cylinder with compressed nitrogen.  Turns out this is
fairly popular among the racing crowd.  
The gas is at about 2000PSI when tank is full, and they use a regulator to
control the flow and monitor the amount remaining.  
I did some checking and found you can buy a bottle with regulator for about
$200.  This is for an 80 cubic foot bottle of nitrogen, which is about 3 ft
tall and 7 inch diameter.    Tank refills cost $16.

Of course for $200 you could also buy an air compressor, but it takes up a
lot more space and isn't portable.

Dave C.