I suspect that the parallelogram fork of the Simplex isn't such a good idea as they suggest; it would work fine if the chainline remained parallel t o the chainring and the rear sprockets, but it doesn't (except, if line d up correctly on a three-speed block, on the middle rear sprocket) - it bends, and the Super Champion type fork follows the chainline. It seems to me that the chain would be more likely to rub on the fork with the Simpl ex parallelogram, since it won't follow the actual chainline.
If you refer to http://smg.photobucket.com/
I would be interested to know, Mark, whether the fork on your derailleu r actually does rub on the chain in practice, since I've never seeen one in operation.
Neil Foddering Weymouth, Dorset, England
Neil, the device was meant for 3 speed 1/8th only so no prob with chain rub if set up properly. I dont have a change fork of either type. I have a complete tension arm and 2 Standard type control quadrants. Any leads to a fork of either variety much appreciated. Mark Stevens Evanton Scotland