Tamiya 70121 Pulley Unit Set is similar in function to a gear box and contains parts compatible with other Tamiya products. The pulleys can be mounted using the base and pulley mounts included with the set and driven with the included motor. The pulleys can also be mounted directly to parts such as the Tamiya 70098 Universal Plate Set, or they can be mounted using shafts such as those included in the Tamiya 70105 3mm Diameter Shaft Set.

The set includes seven pulleys of various sizes along with an assortment of single and double bushings that make the pulleys compatible with round and hexagonal shafts of both 3 mm and 2 mm diameters. Depending on the bushing, the pulleys can either idle on a shaft or rotate with it. The double bushings allow for pulleys to be connected and sit next to each other on the same shaft or screw. Other parts in the set include a motor, a belt guide for use with the motor’s shaft, power bands, rivets, and a screw and nut set.

• Operating voltage: 1.5-3 V
• No-load speed at 3 V: about 12,300 RPM
• Stall current at 3 V: about 2.10 A
• Stall torque at 3 V: about 36 g-cm

• One 50 mm-diameter pulley
• One 30 mm-diameter pulley
• One 25 mm-diameter pulley
• One 20 mm-diameter pulley
• Three 11 mm-diameter pulleys
• Two single and two double 2 mm hexagonal bushings
• Two single and two double 3 mm hexagonal bushings
• Two single and two double 3.1 mm round bushings (allow pulleys to idle on 3 mm hexagonal and round shafts)
• Two single and two double 2.9 mm round bushings (allow pulleys to rotate with 3 mm round shafts)
• Two single and four double 2.1 mm round bushings (allow pulleys to idle on 2 mm round shafts)
• Four single and two double 1.9 mm round bushings (allow pulleys to rotate with 2 mm round shafts)
• Power bands
• One motor
• One belt guide
• One base
• Two pulley mounts
• One motor mount box
• Five 3 x 18 mm screws
• Three 3 x 18 mm tapping screws
• Six 3 x 8 mm screws
• Six 3 x 8 mm tapping screws
• Eight 3 mm nuts
• Four 3 mm plastic nuts
• Two metal rivets