3D printing has made product development feasible for not just professional engineers, but anyone with passion and enough money for a 3D printer. This includes people like unicyclist and street performer Kate Reed and fencing enthusiast and entrepreneur Nathaniel Tong.

Together these two invented a wheelchair attachment that allows users to convert any regular wheelchair into a lever powered wheelchair. Best of all, they’re giving their design away for free and making it open source so anyone can improve upon it.

Lever powered wheelchairs can sell for anywhere from two to ten thousand dollars. But Kate and Nate’s attachment can be printed at home and installed for only $40 worth of supplies. A lever is attached to each wheel, and the user moves the wheelchair by pumping them back and forth.

The attachment works via a ratchet design which moves the wheelchair forward when the levers are pumped. If users wish to move backward, they can squeeze the “brakes” on the levers which disengage the main rachet and engage the other, making the wheelchair now move backward when the levers are pumped.

Kate and Nate said they were inspired to invent the attachment after hearing statistics that wheelchair users are more likely to live in poverty as they often have a more difficult time finding jobs. Currently, the amatuer inventors are working to make their design faster and more efficient.

Their hand drive is a finalist for Best Product in the 2015 Hackaday competition.