Tamiya’s double gearbox packs two independent gear trains into a compact and affordable package that is great for small mobile robots. Each side can be assembled to have one of four gear ratios: 12.7:1, 38:1, 115:1, or 344:1.
Documentation and other information
Tamiya Gearbox Gear Ratio Comparison
Table comparing the gear ratios available in the many different Tamiya gearboxes we carry.
Tamiya “Toy” Motor Testing by Adam Borrell (a.k.a nexisnet) (Printable PDF: tamiya_toy_testing.pdf)
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.