This Amazing RC Car Features AWD Differentials and a Two-Speed Manual Transmission
There are a lot of makers out there that love the idea of automotive engineering as a hobby, but that simply cannot afford to fabricate prototypes on that scale (few people have that kind of budget). RC cars present an opportunity to have fun with that kind of engineering work, but on a much more accessible scale. TRDB took that idea and absolutely sprinted with it, building this amazing RC car that features an all-wheel drivetrain complete with differentials, an actuated center differential lock, independent suspension all around, and even a two-speed manual transmission with functional clutch.
If your experience with RC cars is limited to those cheap electric Walmart specials, then the mechanical complexity involved here will amaze you. It is, essentially, a 100% custom design that TRDB developed specifically with 3D printing in mind. Other than motors, electronic components, and fasteners, virtually all of the parts are 3D-printable. That includes the dozens of gears that are necessary for the drivetrain.
TRDB designed this as an offroad vehicle, which is why it has a two-speed transmission and AWD. A typical electric RC car doesn’t need more than one gear, because electric motors provide good torque at all speeds. But this has two gears for the same reason that 4×4 trucks have transfer cases with high and low gears: to enable slow crawling that requires a lot of torque. Similarly, the AWD system has three differentials and two of them are open. But the center is lockable to prevent wheel slip when traction is poor.
In addition to the mechanical complexity, this also requires some sophisticated electronic control. It needs to operate the actuators that engage the differential lock and change gears, the stepper motor used for the brakes, the servo motor that moves the steering rack, and the DC motor that powers the drivetrain. The differential and transmission actuators are, essentially, DIY servos made with DC motors and potentiometers.
A standard RC car receiver can’t accommodate those, so TRDB used a pair of ESP32 development boards to get the job done. One does most of the work, but TRDB felt that it was necessary to add a second board to control the stepper motor. TRDB even developed a custom controller to communicate with the ESP32 boards when piloting the vehicle. That has the standard sticks for throttle and steering, but also additional buttons and switches for all of the extra functions.
We’ve barely scratched the surface here and there is so much more to this vehicle, so be sure to read through the tutorial to get all of the details.
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