Finger, Robotic, Modular, pull string actuated

Here are some modular finger joints that I designed that worked really well. Was trying to imitate the movement of the finger withing the space of the finger. They seem pretty tough and stay together well. They use Hillman Fasteners extension spring 540213, #71, 5/32" x 15/16", .016" wire, I got from True Value Hardware Store. The finger joints snap together in the out of joint position. I used some weed wacker twine as a pull string. The finger tip has an angled tube inside, you can push the twine right in under the finger nail, it is held in place with a 6-32 set screw deep in the finger tip. You will need to cut some threads with a 6-32 tap. There are hopefully enough sizes to make a realistic size hand if needed. I have included a knuckle maybe you can adapt to a hand. There are two different joint angles the finger tip is a 60 degree angle but you can use it with the 90 degree angle. The finger joints are 90 degree angle. I tried using these with the string pulley servo winch in my things, but it didn't have enough pull with cheap servos. I don't think you can make a device small enough but strong enough to pull 5 strings within say the confines of a forearm. My servo winch will work with 1/8" nylon air brake tubing with the weed wacker line inside for a remote operation. Hope someone can incorporate this design into a usable hand. The springs stay in well, but if the spring shaft breaks a little model glue does the trick. A paper clip wire end helps get the spring in it's hole. Probably pretty useless, but they worked pretty close to a human finger, all the joints want to move the same and with the thicker weed wacker string it had some push back also. If you change the scale, you change the spring size. I may have some smaller finger sizes already drawn if you need them for little finger. These are patterned from the size of my hand, I have attached a picture of hand bones and a trace of my hand with joint measurements. Anyway I thought these where really cool to mess with. Hopefully they will spark an idea in someone else. Enjoy!