Attached a 9vdc motor to an LED to simulate a simple "generator" and I can get it to illuminate by swiftly spinning the motor in quick bursts, but if I connect a drill to the motor so there's a constant spin, the LED doesn't illuminate at all. Why is that?
A DC generator's output voltage maximum is proportional to the speed at which it is cranked; possibly you need to get a faster drill, or drive the motor shaft indirectly. You can gear up with a rubber wheel in the drill, such as some sanding drum attachments, or from a large-radius pulley with a rubber-band belt.
It takes two or three volts to make a simple LED shine brightly; some LED lamps are actually multiples in series, can take more than that. If you can get a voltmeter, look at the generator output, with the LED connected, for the spin-by-hand and the spin-with-drill setups. A series limit resistor (1k ohms) is a good precaution against overdriving the LED while you experiment.