3D printing technology is constantly testing new boundaries and discovering new applications. Following is a case study from our partners at Markforged about a 3D printed fiberglass-reinforced nylon application. Visit the Markforged site for more on this case study.
Charles Guan’s fiberglass-reinforced nylon steering assembly took 24 hours to 3D print and regularly withstands 800 N of force during Power Racing Series races. The materials required for the three parts are 500 cm3 of nylon and approximately 25 cm3 of fiberglass. The assembly easily handled the forces and a total system mass around 160 kg, including driver. The top speed of the Chibi-Mikuvan is 25 mph. The approximate radial load reaches 800 N per wheel. Estimated torque on the stub axle surface is 5 N·m. The nylon flexed as forces peaked but never failed. Charles won the Power Racing Series Road Course at the Detroit Maker Faire 2015!
Charles MIT pedigree and curiosity motivated him to learn additive manufacturing. Racing the light electric vehicles gave him a problem to solve with composites.
Combining a salvaged NiMh battery from a hybrid 2010 Ford Fusion, a 9″ angle grinder’s right-angle gearbox, a water-cooled R/C boat inrunner motor, and a 1/5 scale R/C car ESC, Chibi-Mikuvan is designed to superficially resemble a cartoony version of a 1987-1990 Mitsubishi “Van/Wagon” known as the Delica in non-US markets. The bodywork uses the fiberglass-foam composite sandwich construction method, and despite being decorative only, is still highly rigid.
|Motor||Turnigy Aqua Star T20 motor (also sold under the TORO and Proteus brandnames, among others)|
|Motor Controller||Turnigy Trackstar 200A|
|Battery||Roe of Ford Fusion, 28.8V 16Ah NiMH chemistry|
|Gearbox||9″ angle grinder gearbox similar to this model (4.09:1), 5:1 external #35 chain drive (12:60)|
|Electrical||Arduino Nano on 2.007 Carrier (signal processing); Panasonic AEVS main power contactor; Hella 2843 kill switch|
|Wheel & Tire||8″ Harbor Freight Pink Wheels for America|
|Brakes||Front, generic e-scooter/e-bike disc brake calipers on dual 7″ custom rotors; rear, regenerative (electronic motor braking)|
|Top Speed||25mph (as-geared, Y-termination)|
|Acceleration||to 25mph in < 3 seconds|
|Braking distance||< 30ft from top speed|
|Drivetrain||RR layout, 1 speed, spool axle (no differential)|
|Dimensions||50″ L, 28″ W, 24″ H|
|Curb Weight||113lb with battery, without driver|
|Seats||1, though if Chibikart was any indication to go by, up to 7|
The goal is to replace the heavy, failure prone steering components with lighter, just as strong fiberglass reinforced composites. Like most mechanical engineering projects it started in CAD (or Autodesk Inventor, to be specific). According to Charles,
The Mark One printed all three of the fiberglass reinforced parts in 24 hours. About 500 cm³ of nylon and 25 cm³ of fiberglass were consumed. In addition to the three-part knuckle assembly, Charles also printed a steering arm, see below.
- a total system mass around 160 kg, including driver
- approximate radial load of 800 N per wheel
- Estimated torque on the stub axle surface is 5 N·m
- The top speed of the Chibi-Mikuvan is 25 mph