[Stoves] Hand Crank Dynamo for Fanned Stove?

[Crispin Pemberton-Pigott]

Dear Paul

I think you could consider 4 or more small 1.5 volt fans in series and
stacked to boost the pressure.  Some little fans are made to be stacked,
clicking together very neatly to boost the pressure.  There is a principle
that in general allows that the higher the voltage, the higher the
efficiency of a motor, however one should always keep the salt hand when
hearing general rules.

>0.3 amps x 12 volts = 4 watts at full power.  So if the PWM can 
>regulate it to 6 volts, that is only 2 watts, 

Actually...if it is working properly it will give you 4 watts.  A watt is 1
volt-amp-second.  If you have 0.3 x 12 = 4 volt-amp-seconds then feeding it
back at 6 volts (by chopping the 12 volt supply) will extend the time power
can flow and you should still get just about 4 watts total, not only 2, at
the lower voltage.  An old fashioned resistor would indeed cut the total
power by the voltage drop.  That is the advantage of the PWM.

>So, now my task is to get better blower output from the 4 watts or less.

Have a look at http://www.bedek.de/Datenblaetter.53.0.html

Best regards
Crispin