Very very small electric motor, extremely fast – 100.000+ Rpm.
Hi. You can buy this micro electric motor 66000 Rpm at 3,7volt. When the volts is higher the rpm rises until the motor burn. 6 volt gives you about 99000 rpm. See this Link http://www.ebay.com/itm/DC-3-7V-66000RPM-4-x-12mm-Wired-Micro-Coreless-Motor-for-Helicopter-Model-Toy-/291157828040?pt=LH_DefaultDomain_3&hash=item43ca5be1c8
This electric motor run at 6 volts 100000 Rpm.
My Rmp. meters can`t go higher.
At 7 volts the electric motor are running over 100,000 Rpm.
I have now destroyed 2 dc. motors.