Both
B81 and B82 motors come standard with an electro-magnetic 24v parking
brake, which can easily be removed if that function is not necessary.
Built for continuous 24 volt 30 amp duty, they can be run at 36 volts
for 5 minutes, adding about 50% more speed and torque. This motor
comes in either left or right side shaft drive configurations, and
makes a great drivetrain for a large
robot. B81 is shown here.
24V-36V
Reversible, Permanent Magnet
18:1 gear ratio
20.4 pounds untrimmed
17 pounds trimmed
180 rpm / 18:1 gear ratio
Overall length of motor & gearbox = 14 5/8"
Width of gearbox = 3-3/8"
Diameter of motor = 3-3/4"
Length of output shaft 1-3/4"
Output shaft diameter = 17 mm
Keyway = 6mm
CAD Drawing (dwg format) 
NPC-B81 Left-Side Geared Motor
NPC-PH817 Hub