Large RC Car — v1 · Andrés Moreno

Controller

ESP32

WROOM on car + remote

Wireless

NOW

ESP-NOW · peer-to-peer

Motor Driver

DRV8876

Single H-bridge · IN1/IN2 mode

Steering

Ackermann

Servo-controlled front axle

At a Glance

TypePersonal project (first big build)

My roleSolo: CAD, 3D printing, wiring, remote, testing

TimelineJul – Aug 2025

SkillsAckermann steering · motor drivers · ESP-NOW · enclosure design

ToolsFusion 360 · Arduino C++ · 3D printing

StatusWorking, but slow: lessons went into the mini RC car

The idea was simple: build an RC car where I designed every part — chassis geometry, remote body, firmware. I started in Fusion 360, modelling the chassis geometry before I had even ordered the wheels. The chassis came out properly: four rubber tyres, a servo-steered Ackermann front axle, and a rear-wheel drive layout.

The remote was the part I was most proud of. Instead of using an off-the-shelf transmitter, I modelled a gamepad from scratch, 3D-printed the shell in two halves, fitted two analog joystick modules inside, and ran everything through an ESP32 WROOM using ESP-NOW. The latency was good. The control feel was actually decent.

What went wrong: I kept adding things. A 5A boost converter, an oversized 3500mAh LiPo, and a printed housing for every component. The real weight came from the motor itself, the MG996R metal-gear servo, the boost converter, and the stack of PLA casings I built around everything — not the electronics. The ESP32, buck converter, and DRV8876 barely register on a scale. At 565 g assembled, the motor had no performance headroom left. The lesson stuck — directly led to the small RC car, which came in at 101 g.

Build

Step 01

Chassis design in Fusion 360

Started with the wheel geometry — real rubber tyres with a proper tread pattern — and worked backwards to figure out the chassis dimensions. Modelled a working Ackermann steering linkage, front and rear axles, servo mount, and motor housing. Everything was parametric so I could adjust wheelbase without redrawing from scratch.

Differential gear assembly — 3D-printed components

Step 02

3D printing the chassis

Printed in black PLA on a Creality printer. The main chassis plate, servo mount bracket, rear motor housing, and wheel hubs all came out cleanly. The Ackermann arms took a couple of iterations to get the right pivot geometry — first print was too flexible at the steering knuckle.

3D printed chassis with rubber tyres and servo

Chassis — servo, rubber tyres, rear drive motor

Step 03

Electronics — ESP32 WROOM + DRV8876

The car runs an ESP32 WROOM as the receiver. It listens for ESP-NOW packets from the remote and maps joystick values to PWM signals — Y-axis for throttle/reverse via 20 kHz 10-bit PWM on the DRV8876 (IN1/IN2 mode), X-axis to servo angle constrained to 60–115° to match the Ackermann geometry. Power came from a WLtoys 144001 2S 7.4V 3500mAh LiPo — a 3A buck converter stepped it down to 5V for the ESP32, while a 5A boost converter pushed 12V to the DC brushed gear motor ↗. That boost converter was the mistake — the motor and MG996R metal-gear servo were already the heavy parts; adding more power chain on top just compounded the weight. Written in Arduino C++ — full receiver and sender code available in the Remote section below.

Electronics on workbench during assembly

Electronics assembly — ESP32 WROOM, DRV8876, LiPo wiring

Step 04

Assembly and first drive

Getting everything fitted into the chassis without shorting anything was the hardest part. With a buck converter, a boost converter, the DRV8876 driver, and the oversized LiPo, the electronics stack sat on top of the frame rather than inside it — raising the centre of mass. First drive test confirmed the car worked correctly: steering responsive, throttle smooth, ESP-NOW had no noticeable lag. But it was slow — way slower than expected for the motor spec. The weight was the culprit.

Fully assembled — final build

Interactive 3D model — drag to rotate · scroll to zoom

Custom Remote

Custom 3D-printed remote with dual joysticks

Designed from scratch

Gamepad remote

Instead of using an off-the-shelf transmitter I modelled a full gamepad shell in Fusion 360. The body was split into two printable halves, designed to fit exactly around two KY-023 analog joystick modules and an ESP32 WROOM board. Printed in black PLA with hand-fit tolerances — no fasteners for the shell, just press-fit clips. The joystick thumb-caps are custom 3D-modelled covers that screw on and off, allowing the sticks to be swapped or adjusted without disassembling the remote.

Modelled in Fusion 360, printed on Creality
Dual KY-023 analog joystick modules
ESP32 WROOM transmitter
ESP-NOW protocol — no pairing, peer-to-peer MAC
3.7V 18650 3000mAh 20C Li-ion cell, fits inside grip section
Screw-on/off 3D-printed joystick thumb-cap covers

Creality Studio — remote shell slicer preview

Remote assembly on workbench with components

Remote assembly — joysticks, ESP32 WROOM, wiring

ESP-NOW Protocol

ProtocolESP-NOW (IEEE 802.11 action frames)

Pairing methodHardcoded MAC address

Packet rate~50 Hz (20 ms loop)

Typical range~50 m line-of-sight

LatencyNo noticeable lag (not timed)

Power3.7V 18650 3000mAh 20C Li-ion in grip

Firmware

Written in Arduino C++ using the ESP-NOW API. The receiver maps joystick axes to 20 kHz 10-bit PWM on the DRV8876 (IN1/IN2 mode) and servo angle constrained to 60–115° for the Ackermann geometry. The sender reads GPIO34/35 with a 7-sample median filter and auto-calibrates joystick centres on power-up. Holding the BOOT button for 2 s triggers manual recalibration without a restart.

Videos

Steering mechanism — top view

Steering linkage — underside view

Steering test

Rear gear — drivetrain close-up

Drive test — run 1

Drive test — run 2

What I Learned

Lesson 01

Choose components for the job, not the spec sheet

The boost converter felt like a logical fix — more voltage, more torque, faster car. But that reasoning was backwards. The motor wasn't the bottleneck; the weight of everything around it was. Choosing the right component means identifying the actual constraint first. I needed to strip mass, not add a power chain.

Lesson 02

Weight kills performance faster than anything else

At 565 g this car weighed more than five times the v2 at 101 g — same wheel size, same concept, dramatically different result. The MG996R alone weighs ~55 g (six times an SG90), the motor adds more, and every printed casing compounds it. Mass has to be accelerated by the same motor. Strip the weight, keep the essentials, and the performance gap is immediate.

Lesson 03

Custom remote was worth it

The most complex part of the project was also the most satisfying — building a controller that actually fits your hand, with controls where you want them, communicating the way you designed it. ESP-NOW is fast enough for RC use and far simpler to implement than a radio module with its own protocol.

Large RC Car — v1

MCUESP32 WROOM

Motor driverDRV8876

Chassis3D-printed PLA, full size

SteeringAckermann servo

BatteryWLtoys 144001 2S 7.4V 3500mAh (oversized)

Power modules3A buck + 5A boost (unnecessary)

RemoteCustom 3D-printed gamepad

Weight565 g assembled

SpeedVery slow (overweight)

Small RC Car — v2 (result)

MCUESP32-C3 XIAO

Motor driverTB6612FNG

Chassis3D-printed, compact

SteeringSimplified servo mount

Battery3.7V LiPo — direct to TB6612FNG VM

Power modulesNot needed — integrated ESP32 battery input

RemoteBreadboard C3 SuperMini

Weight101 g assembled

SpeedNoticeably faster

What came next

Version 2

ESP32 Mini RC Car

Everything learned from v1, stripped back to what actually mattered. Smaller driver chip, lighter chassis, breadboard sender instead of a custom remote — faster result.

→

Large RC Carv1 — where it started

Build

Custom Remote

Videos

What I Learned

What came next

Large RC Car
v1 — where it started