Custom Powered Scooter

Designers: Dave Chen, Brian Chon, Ian Gao, Bryan Lawlor

Supervising Professor: Larry Bohs


Our client is an active eleven-year-old boy.  Because he has Thrombocytopenia with Absent Radius (TAR) syndrome, his arms are short and his legs have limited strength and flexibility. He wanted a device that would assist him in traveling but not be as cumbersome and restrictive as his electric wheel chair. The Custom Powered Scooter includes a custom seat, handlebars, auxiliary wheels for stability, and foot-controlled accelerator and brakes. A custom freewheel allows him to free scoot when he doesn’t need motor power. The device gives the client more freedom in transporting himself.


The Personalized Scooter allows our client to be more independent. After several months of use, his mother commented, “The scooter … has been very useful and helpful for[him].  We take it to the library, the movies, and to church. On his new scooter, he is able to explore, learn and not worry about his legs hurting or being tired. He is also able to go around the block with our family and enjoy the outdoors!”


The Custom Powered Scooter (Figure 1) is modified from an E200 Razor electric scooter.  Custom additions include a  freewheel mechanism, adjustable seat, auxiliary wheels, extended handlebar, and foot-mounted brake and accelerator controls.

A one-way bearing (model CKS20,,) incorporated into the back wheel allows the scooter to free scoot.  Two custom adaptors, machined from aluminum, secure the bearing to the rear wheel with a press fit. One adapter connects the outer surface of the bearing to a sprocket driven by the motor, and the other adapter connects the inner surface of the bearing to the hub of the rear center wheel.

A threaded stainless steel rod 10mm in diameter serves as a rear axle to mount two auxiliary 8” pneumatic tires. A support frame, made from a ¼” thick x 1” wide x 21” long strip of steel, attaches to both sides of the axle from the scooter frame to prevent flexing of the axle. Wheel guards, made from aluminum strips ¼”x1”x16.5” long, attach to the back axle and cover each of the auxiliary wheels, preventing inadvertent catching of the wheels on low objects.

A SchwinnTM No Pressure Bike Seat is attached to an aluminum plunger .995” in diameter and 1’ long. The plunger is encased by a seat post and allows for 8” of height adjustment. The seat post is 1.25” in diameter at the base, 1” at the top, and 14” long. The seat post is secured to a plate on the scooter frame with a short, 3” long aluminum sleeve having a 2” outer diameter and a 1.25” inner diameter, which fits around and bolts to the base of the seat post.

The handbrake of the E200 was moved from the handlebars and secured to the right side of a 20” long,  7/8”diameter steel rod, attached to the front base of the scooter with a custom aluminum adapter. A plastic pedal allows the client to control the brake with his right foot. The hand throttle of the E200 was moved from the handlebars and secured to the left side of the steel rod. A plastic pedal allows the client to control the speed with his left foot.

Bicycle handlebars are bolted to a U-shaped bar attached to a handlebar stem. The handlebar stem fits into a 21.5” long shaft of 1” inner diameter bicycle tubing, which is welded to the neck of the scooter. Figure 2 shows the client using the Custom Powered Scooter. The cost of the components for the device is approximately $380, not including the cost of the Razor E200.

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