Still in the test stage this spring drive is now running well. The drive is taken to the inner chainwheel. Power is initially achieved by winding up the three springs with the key. The springs are rewound when going downhill so almost 100% power recovery. Tests have shown this wind up to work quite well. The cam seen in the centre gives 12 stages of power. Very quiet in operation with only a soft tick which you can barely hear when talking. Bit more time needed to tidy things up. With a carbon fibre case and the key gold plated it should look quite striking. Any comments please feel free to chime in.