Tamiya’s twin-motor gearbox consists of two independent motors and gearboxes in one compact housing, making it perfect for small robots. You can assemble the gearboxes to have a 58:1 or a 204:1 gear ratio.
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Supplier Link: [SparkFun MPN:ROB-00319]
The Tamiya twin-motor gearbox is a small (3-inch long) plastic gearbox. It contains two small DC motors that drive separate 3mm hexagonal output shafts. There are two ways to put the kit together: with a high-speed 58:1 gear ratio or with a slower 203:1 gear ratio. Either way, the motors provide plenty of power to drive any small robot. For a gearbox with a similar form factor and more gear ratio options, see the Tamiya double gearbox.
The output shafts included in this kit are 3 mm hexagonal axles that are 10 cm (about four inches) from tip to tip. The axles work with any of the Tamiya wheels we carry, giving you many options for your robot speed. The two low-voltage motors run on 3-6 volts and draw up to a few amps, making them perfect candidates for the Pololu low-voltage dual serial motor controller. Motor overheating can be caused by excessive stalling, even at very low voltages. We recommend that you use stall-detection sensors, or just watch your robot, to make sure that it doesn’t stall for more than a few seconds at a time. For motor specs, see the Mabuchi motor FA-130 (#18100) data sheet (58k pdf).
Note that you can replace the motor in this kit with a lower-current, higher-voltage motor if you want to use this gearbox with controllers such as the qik 2s9v1 dual serial motor controller, TB6612FNG dual motor driver carrier, or Baby Orangutan B-328 robot controller.
Tamiya 70168 Double Gearbox (left) and Tamiya 70097 Twin-Motor Gearbox (right)
The twin-motor gearbox is very similar to the Tamiya 70168 double gearbox, as shown in the picture to the right. The gear ratio options of the two products complement each other well, but the mounting holes and overall dimensions vary slightly. The double gearbox is shorter and wider than the twin-motor gearbox, and the gears are a bit smaller and wider.
|Typical operating voltage:||3 V|
|Gear ratio options:||58:1 and 204:1|
|Free-run motor shaft speed @ 3V:||12300 rpm1|
|Free-run current @ 3V:||150 mA2|
|Stall current @ 3V:||2100 mA|
|Motor shaft stall torque @ 3V:||0.5 oz·in3|
Adam, who posts under the username nexisnet on the Pololu forums, has performed a detailed series of experiments to determine how operating voltage affects the lifetime of the Mabuchi FA-130 motor, which happens to be the motors used in the Tamiya 70168 Double Gearbox, 70167 Single Gearbox (4-Speed), 70097 Twin-Motor Gearbox, 70093 3-Speed Crank-Axle Gearbox, 70110 4-Speed Crank-Axle Gearbox, and 70103 Universal Gearbox.
This gearbox is an eduational kit that you have to put together yourself. It is designed for use in small, indoor projects. The gearbox comes with plastic gears and small, low-voltage motors; if you are looking to build anything meant to work outdoors or in a rugged setting, you should be ready to replace the gearbox often or consider using a more robust, pre-assembled gearbox.
You can extrapolate a theoretical torque and RPM of the gearbox based on the gear ratio you build, the motor voltage, and the motor speed and torque. In general, this gearbox is a toy, so if you need very precise specifications, you might consider a more industrial gearbox.
In general, the higher your voltage, the sooner your motors will die. Because these are toy motors, the manufacturer does not provide any official cycle-life specifications, but a customer of ours has conducted his own series of experiments that shed light on the relationship between operating voltage and motor lifetime. You can view Adam’s results here.