I have wanted to build a heavy duty prosthetic for awhile. So I decided to get a basic concept design in CAD.
In the Slant Rugged Prosthetic 0.8, the elbow is supported by a bike spring. I downloaded the spring part, because of that the spring is a quite a bit larger than I would use in practice.
All the pieces of the arm are machined aluminum plates. This drastically reduces production costs of the prosthetic.
This arm is intended to be used by amputees with an active lifestyle. Its won't break and certainly won't short circuit. It could be used on snowmobiles, bikes, or water skis to give the amputee greater control and balance on the vehicle. It also allows for the user to perform heavier duty lifting, such as moving 2x4's, something no other prosthetic could withstand.
The passive design is a limitation since the arm is stuck in a particular static position, until the user basically leans into it. This is fine on an ATV, but not when moving boards around. (Check out my exoskeleton to see this problem in action)
Fortunately the design can easily be changed from using a spring to using a linear actuator. A slight adjustment in the fastening locations on the arm and a person would have a super strong arm, which would only require a very basic controller to operate.
But most of all this arm would be cheap. Maximum manufacturing cost would be around 200-400 dollars.
The next step will be to layout the manipulator and its attachment.