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FRC 3D printed Wheel Design and Testing
Increased traction and suspension for FRC Wheels
Increased traction and suspension for FRC Wheels
FRC robots are designed to run on carpet, which allows them to achieve coefficients of friction greater than 1. The coefficient of friction is important because robots get into pushing battles and try to accelerate quickly across the field.
While there are many COTS options available for wheels, I wanted to create a wheel with even more grip by leveraging the geometries that 3D printers can create. The goal was to increase the grip surface area through compliance while also finding a better tread geometry.
Wheel Structure
Wheel Structure
The wheels are designed for the high-impact environment of FRC matches. To ensure strength and reliability, they are constructed from flexible TPU with carbon fiber-nylon (CF-Nylon) hubs. To prevent delamination of the 3D-printed layers, the assembly is reinforced by steel pins that pass through both hubs, clamping the TPU wheel between them in a radial 'flower' pattern.
CAD LINK: Onshape
Wheel Testing Rig
Wheel Testing Rig
In order to understand the performance of our new wheels, I designed a coefficient of friction tester for FRC wheels.
In order to understand the performance of our new wheels, I designed a coefficient of friction tester for FRC wheels.
It works like a nutcracker, multiplying the force from a weight to simulate the 35 lbs that a robot would exert on its wheels. Torque is applied to the wheel through a chain, and the driving sprocket is coaxial with the clamping pivot to ensure that only torque is transferred to the carpet carriage. The coefficient of friction is extrapolated by measuring the normal force on the carriage.
It works like a nutcracker, multiplying the force from a weight to simulate the 35 lbs that a robot would exert on its wheels. Torque is applied to the wheel through a chain, and the driving sprocket is coaxial with the clamping pivot to ensure that only torque is transferred to the carpet carriage. The coefficient of friction is extrapolated by measuring the normal force on the carriage.
With this tester we found that the wheels we designed were about 20% higher coefficient of friction than over the shelf options.
Many Different Tread Types Tested
Many Different Tread Types Tested
Many different types of Tread were tested, including:
SDS (COTS) tread geometry as a control
1.19 coef, This is the number to beat
SDS tread geometry in printed TPU
1.41 coef
Spike tread, with sacrificial bridging to allow it to be printed
1.42 coef
Spike tread with no sacrificial bridging
Same coef as with bridging
Wedgetop
1.16 coef, but wears much slower
Sparse Spikes
1.32 coef
(Full data table below)
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