Re: [PSUBS-MAILIST] Pressure air drive.

[MerlinSub@t-online.de (Carsten Standfuss)]

Pierre Poulin schrieb:
> 
> Hi,
> 
> I've check some air grinders that could be transformed into motor.
> 
> Free speed: 25000 rpm
> - Operation pressure: 90 psi
> - 0.6 HP
> - Air consumption: 3 cfm
> - Weight: 1.5 lb
> 
> What do you think about that?
> 
> Pierre
> 

Hmm.. 3 cfm means cubif -foot- minute ? 
than it is 
are equal (sorry I think in metric..)
to 3 x 0,3048 x 0,3048 x 0,3048 m = 3 x 0,028 m3 or 84 Liter

if we estimate that the boat need two engines of 0,6 hp we need
2 x 84 liter = 168 Liter a minute.

A normal scuba bottle has 10 Liters at 225 bars = 2250 Liters
air and run the drive just 2250/168 = 13 Minutes

A yard size bootle for weld gas has 50 liter and is 1,5 m (4,9 feet)
high with a diameter of 280 mm (11 inch) runs about 
5 times longer = 65 minutes.. 

Two tanks of 50 Liters gives you 2 hours and 10 minutes..
Not so bad - Batterys has to be replace after some years - 
pressure bottles not - and a 50 Liter industrial one is about
300 Dollar new and maybe cost the half if you purchase a used one. 

Problems: 
- to get an engine made from seawater resistant material
- the noise ?  -> no fish around the boat
- the air bubbles all the time ? -> no fish around the boat
 
Most problem is maybe that high pressure scuba compressor 
is mcuh more expensive than a battery charger.. :-(
But for peoples which are allready scuba divers - and have allready
a compressor - a solution. 

Carsten