Hi
i’m developing a line follower and i will use the micro metal gearmotor @ 9v and the specifications are in @ 6v. To find the specs @9v I can use a simple rule of three? like:
Gear ratio: 50:1
Free-run speed @ 6V: 630 rpm
Free-run current @ 6V: 100 mA
Stall current @ 6V: 1600 mA
Stall torque @ 6V: 20 oz·in
Gear ratio: 50:1
Free-run speed 9@ V: 945 rpm
Free-run current @ 9V: 150 mA
Stall current @ 9V: 2400 mA
Stall torque @ 9V: 30 oz·in
I just want to add that you should make sure you use something more appropriate than a 9 volt battery, as these are not good at delivering high currents and will likely work very poorly for your application.
NiMH or Lithium-based batteries are much better suited for high-current applications like driving a motor. You might find this blog post on battery capacity helpful in better understanding why this is.