The Schlumpf Speed Drive is an internal overdrive gear system that can be used on the front or bottom bracket of a trike or bike. They eliminate the need for having a front derailer, shifting components on the handles, or cables coming from the main bracket.
Schlumpf makes multiple types of Drives all with unique gearing ratios. The Speed Drive is their base model, and takes whatever base gear that is installed on it and increases it when overdrive is engaged by 1.65. So for me, my 30 tooth gear instantly behaves like a 49.5 tooth gear, without changing the physical diameter.
This is important for me to get the maximum range out of my rear Rohloff Hub.
I took this video to walk thru the installation of the drive. You will need some special tools for the install, and it is recommended that a qualified shop does this for you, but I was not able to find one near me.
http://schlumpfdrive.com/ – information about the drives
http://www.cyclemonkey.com/schlumpf-innovations.shtml – a supplier of the milling tools and information about the drives
http://www.utahtrikes.com/ARTICLE-33.html – another good article about the schlumpf high-speed drive. (NOT THE SPEED DRIVE)
You can see how it performs as I ride my recumbent trike around the world. Riding thru 100 countries for the next 5 years. Subscribe to my Youtube channel or find me on my website… http://www.JaYoe.com