Efaz Bhuiyn's 3D-Printable Portable Workout Machine Turns Effort Into Electricity

Mechanical engineering student Efaz Bhuiyn has built a device to help busy people workout just about anywhere — and charge a phone while doing it: a 3D-printed workout machine that doubles as a generator.

"I'm passionate about energy generation and renewable energy sources," Bhuiyn explains of the project's inspiration. "My Portable Workout Energy Generator […] turns the energy we humans put in to workout into electricity that we can use! This version is an attempt to make the project more lightweight, use less and cheaper material, generate more consistent output, and finally, allow interchangeable resistance gears so the user can swap out 'weights' for more resistance. The key point of this version is to try implementing this interchangeable system to be multi-compatible with whatever resistance gear the user designs by adding an idler tensioner."

Currently on its sixth revision, Bhuiyn's design is a compact cable-based exercise machine that turns a motor into a generator — turning it as the user pulls and releases the cable, causing it to convert that motion into electricity rather than converting electricity into motion. A capacitor and buck converter combine to stabilize the output of the motor, making it suitable for charging devices like mobile phones and USB power banks — albeit slowly, and with considerable effort on the user's part.

"This was designed mainly for students who have hectic schedules that are so harsh on them that whenever they do end up being free, it would end up being really late or be a inconvenience to go [to a gym]," Bhuiyn explains. "The goal of this project is to make a portable, lightweight workout machine that is compact enough to fit in a backpack for travel, and mountable in any room. This allows any student to get a workout in anywhere, anytime, while generating energy to charge electronics later."

The project is documented in full, with links to earlier versions, on Instructables, including a parts list and 3D print files for building your own.