Monday, January 27, 2020

Bicycle: Propel Adaptive Cycling Pedal

Propel Adaptive Cycling Pedal

I have multiple sclerosis. The disease causes neurological fatigue. When cycling, the MS affected nerves can slow muscle engagement. A light bulb dimmer switch describes the neurological effect. When turned off, the switch allows the bulb to be bright. As the switch turns on, the bulb becomes dimmer.  In MS, the effects of exercise can cause the nerve's conduction to become dimmer. The diming condition appears as fatigue. 

In the test rides for acquiring a recumbent trike, I tried many different pedal styles. All failed designs for valid reasons. Safety was the most common. As a result of the tests, a new pedal design emerged. With the help of many people, the ideas became the Propel Adaptive Deck Pedal.

While the initial concept came from my desire to ride the trike, during my 31 years with MS, many mobility machines, exercise devices, and therapy equipment use cage-like variations of footrests. The cage can be a safety hazard. Propel's user safety model has three dimensions, mount, travel, and dismount. Within each dimension are multiple design extents. And each extent addresses one or more problems.

The drawing shows the Propel's general design concepts. When traveling, the locomotion power transfer to the trike is by the foot pushing the pedal's axle. During the pedal stroke cycle, several factors affect the efficiency of power transfer. Throughout the pedal stroke cycle, the fulcrum for the body's power transfer is the axle. As the stroke rotates, the foot's position over the axle changes leverage, therefore the leverage change affects power transfer. The two main factors affecting leverage is the position of the foot over the axle and the foot's movement on the axle. 

Traditional bicycle pedals place the forefoot (the ball) over the axle. Propel riders use centric foot placement where the foots' arch is centered over the axle. The foot's movement on the axle is similar to an airplane's pitch, yaw, and role. Airplane power is either acceleration or drift. The five factors, pitch, yaw, roll, acceleration, and drift combine as trim to indicate the efficient use of power. Propel's design assists the rider with keeping the foot and pedal in trim for the entire pedal cycle. Forefoot pedaling is like an airplane's center of gravity being in the cockpit with the pilot, whereas centric pedaling is like the plane's center of gravity near the wings. Propels centric pedaling allows the stroke trim to occur as if the axle's position is similar to an airplane's rotation around its wings.

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