Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

The 3 volt bulb would be the one. Sometimes I use a higher voltage bulb like the 6 volt. It won’t burn as bright but you really can’t burn it out by running the generator at high speeds.

E10 Base Bulbs

BULB   VOLTAGE   AMPS     WATTS

#14    2.47V     .30A     .741W    Standard for Jensen #15

#131   1.30V     .10A     .130W    Low HP motor & Jensen #15

#502   5.10V     .15A     .765W    Stepper-motor Generator

#359   1.35V     .06A     .081W    Low HP motor & Jensen #15

#222   2.25V     .25A     .563W    Focused-beam for Jensen #15

#352x  3.00V     .07A     .210W    Standard for Jensen #15E

Obviously, the faster you spin a generator the higher the voltage.  Most engines have a sweet spot of throttle position and belt shiv setting.