1:10 RC Car
1:10 RC Car
After starting college, I wanted to challenge myself with a hands-on mechanical project that combined software, electrical, and mechanical design. I decided to design and build my own 1/10-scale RC car entirely from scratch. Since this was my first time working with RC systems, I wanted to keep the design achievable without compromising learning opportunities. The car was intended primarily for on-road performance rather than off-road use, so I prioritized precision, control, and modularity over high-impact durability. To minimize costs, nearly all structural and mechanical components were 3D printed, with only the bearings, fasteners, shock absorbers, wheels, and electronics being off-the-shelf.
After analyzing open source models from the RC car community and more intricate designs from online, I decided on several key features to implement on my own personal car:
4 Wheel Drive: for improved traction and balanced torque distribution.
4 Wheel Steering: to enhance maneuverability at low speeds and improve high-speed stability.
Front/Rear Open Differentials: to allow independent wheel speeds and smoother cornering.
Ackerman Steering Geometry: to reduce tire slip and maintain efficient cornering paths.
Double Wishbone Suspensions: for better camber control, ride stability, and handling precision.
Custom Universal Joints: to transmit torque efficiently while accommodating suspension travel.
Custom Ball Joints: to ensure steering consistency across different suspension angles.
The differential enables independent wheel speeds during turning, improving handling and reducing tire slip. A 3:1 reduction was achieved using a 12-tooth pinion and 36-tooth ring gear, selected to meet wheel torque requirements while maintaining compact packaging. To minimize mechanical complexity and improve reliability with 3D printed components, an open differential was decided upon for its simpler design compared to other models.
The suspensions are important for ensuring consistent ground contact with the tires across variations in terrain. A double wishbone suspension design was decided upon over a MacPherson strut suspension design due to its greater stability/control, durability, and simplicity, which are critical characteristics given that all components would be 3D printed. Instead of using rubber bands, which would be unreliable and short term, 100 mm shock absorbers were used for maximizing ground contact. Extra mounting holes for the shock absorbers are distributed along the control arm, providing opportunity to modify the damping forces.
The steering system employs a four-wheel steering configuration to improve low-speed maneuverability and enhance high-speed stability. Positive Ackermann geometry was incorporated to reduce tire slip and ensure efficient cornering by allowing the inner wheel to turn at a greater angle than the outer wheel. Independent servos were used on the front and rear axles. The resulting system provided predictable handling and smooth steering response across the full range of suspension travel.
The transmission provides a 2:1 speed reduction between the motor and the differential, converting the high-speed output of the brushless motor into usable torque for acceleration. The total gear reduction was intentionally split between the transmission and differential to reduce gear size and tooth loading. A double helical gear design was selected to cancel axial thrust forces, reduce vibration, and improve durability in 3D-printed components. The transmission operated consistently under load with stable gear mesh and minimal noise during testing.
The chassis plate serves as the structural foundation of the RC Car, providing support to all subsystems. Rather than printing all of the subsystems with the chassis, the chassis plate was designed to be isolated from all subsystems, increasing flexibility with iterations for different subsystems and improving maintenance. Extra mounting holes were applied throughout the plate to accommodate any modifications or additional components that would be needed later on.
All electronics are organized on a single dedicated platform to centralize components and simplify assembly. The platform securely holds the battery (attached with Velcro), the ESC and receiver (taped in place), and the power switch, which is mounted on the side of the car for easy access. This design prevents components from shifting or “floating” during operation and keeps the layout clean and serviceable, making maintenance, replacement, or upgrades straightforward.
0 → 35 mph in 2.0 sec
a = (delta v)/(delta t) = (15.646 m/s) / (2.0 s) = 7.823 m/s²
Tractive forces at the wheels
This is the force the wheels need to push against the ground to hit the target acceleration
F = ma = (2 kg)(7.823 m/s² m/s^2) = 15.646 N
Wheel Torque
This is the torque the drivetrain needs to deliver at the wheels to hit the target acceleration
Wheel radius r = (65mm)/2 = 0.0325 m
Torque = F * r = (15.646 N)(0.0325 m) = 0.509 N·m
Angular Velocity
This is the required angular velocity of the wheels to reach the top speed
ω = v / r = (15.646 m/s) / (0.0325 m) = 481 rad/s
RPM = ω * 60 / 2π = (120.354 rad/s) * (60 / 2π) = 4597 RPM
Based off of past experience, I thought that a 3S LiPo battery would be excessive for the project at hand, so I decided on using a 2S LiPo battery. Regarding the selection of the battery, I simply chose the cheapest battery available on Amazon.
Since I chose a 2S (7.4 V) LiPo battery, the motor would need to produce an RPM range that, after gear reduction, spins the wheels fast enough to reach the target max speed and supply enough torque to reach the target acceleration. From online, I saw that most 1/10 scale RC cars used brushless motors that ranged from 3300-4200 KV. I then found an Amazon product featuring a 3900 KV brushless motor with a 60A brushless ESC for a very affordable price. I also chose this motor/ESC combo because I knew that ESC would be capable of handling the current from the motor.
Given the motor and the battery, I was then able to calculate an appropriate gear ratio.
Max Motor RPM = (Motor KV) * (Battery Voltage) = (3900 KV) * (7.4 V) = 28860 rpm
GR = (Max Motor RPM) / (Wheel RPM) = (28860 rpm) / (4597 rpm) = 6.278 ~ 6.3:1 Reduction
Motor Torque = (Wheel Torque) / (Gear Ratio) = (0.509 N·m) / (6.278) = 0.081 N·m
Torque Constant = (60 / 2π) / (KV) = 0.00245 N*m/A
Motor Current = (Motor Torque) / (Torque Constant) = (0.096 N*m) / (0.00245 N*m/A) = 33.082 A
The motor will draw about 33 A during peak acceleration. Since the ESC is rated for 60 A continuous or 320 A burst, this 3 A peak draw is well within the safe zone.
Prior to this project, I was unfamiliar with how to connect all of the electronics such that they would be able to communicate and control the mechanical aspects of the RC car. I learned how to design different types of gears through the transmission and differentials, and I also learned how to calculate necessary gear ratios given the requirements stated at the beginning of the project.
Instead of being given a set selection of electronics to use for the project, I learned how to choose which components would be both compatible with other components and suitable for working reliably, all under a limited budget.
In addition to electronics, I also tested the limits of 3D printing. Instead of using nuts for all connections, I designed for holes to be slightly smaller than the screw diameter such that the fasteners would create threads inside the prints. This proved to be much more space efficient, less prone to unscrewing from vibrations, and easier for assembly due to the reduction in components. For the custom universal and ball joints, I tested different tolerances which could balance both ease in assembly and consistency for moving at high speeds.
Almost all of the 3D printed components are created from ABS filament; however, I did experiment with using other materials. The shafts in the power train were printed in Formlabs Nylon 12 through Selective Laser Sintering (SLS). I tested this material with some components for the gear box and the steering, and I realized that the material is less ductile than typical FDM materials, meaning that it will snap under bending and self-thread holes are not possible. I ultimately decided not to proceed with SLS for components other than the shafts because the prints needed to withstand impacts/loads consistently.
In addition to Nylon 12, I wanted to take advantage of the high heat deflection temperature and flexural strength of the Markforged Onyx filament for the chassis plate, differential gears, drive shafts, and universal joints. Despite the high thermal resistance and strength of Onyx, printing the differential gears in this material proved challenging. The fine gear teeth became slightly oversized due to layer resolution and extrusion width, which caused imperfect meshing and increased friction between the gears. Additionally, the chassis plate continued to flex despite the carbon fiber reinforced material, so ABS would have been a cheaper option for printing.
Despite being printed in Onyx, the single-plate chassis is still prone to flexing and bending under load, which can affect drivetrain alignment and handling consistency. Rather than relying solely on material selection, the next design will increase stiffness through structural reinforcement. Potential solutions include embedding aluminum or carbon fiber rods within the chassis plate, adding a secondary upper plate connected via standoffs to create a box structure, or integrating vertical channels along the length of the car to resist bending moments.
For prolonged durations, very high speeds caused the 3D printed universal joints to melt and fuse into the drive shafts, stalling the entire powertrain. To remedy this, I want to investigate commercial metal universal or constant-velocity (CV) joints. These components are inexpensive, readily available, and better suited to withstand the thermal and mechanical loads present at high rotational speeds.
In confined environments, operating the motor at high speeds makes the vehicle difficult to control, requiring the ESC to limit motor output significantly. Since this approach reduces available torque rather than increasing mechanical reduction, the drivetrain stalls easily at low speeds. This suggests that the effective gear ratio is possibly too low for controlled operation. I plan to increase the overall reduction ratio to approximately 12:1–20:1, which would allow the motor to operate closer to its optimal range while improving low-speed torque and drivability.
After extended testing, the ABS gears showed noticeable wear and required replacement. In the current design, accessing the gears requires removing a control arm and both shock absorbers, making frequent iteration time-consuming. To improve serviceability, the gearbox will be redesigned to allow direct access to the gears without disturbing the suspension, significantly reducing disassembly time during testing and iteration.
With the shock absorbers mounted externally, they’re vulnerable to damage during minor collisions or impacts. To improve durability, I plan on relocating the shocks to the inner side of the gearbox, where they’re better protected and capable of maintaining suspension performance.
Since the 3D-printed differential gears directly transmit torque to the wheels, any drivetrain lock-up can concentrate stress in the gear teeth, leading to shearing or failure. To mitigate this, I want to explore pulley-based transmission systems for future designs. Unlike gears, pulleys distribute load across multiple teeth and can tolerate brief stalls or misalignment more gracefully, reducing the likelihood of catastrophic failure during drivetrain lock-ups.