Originally Posted by
Jipe
I agree with you, even if it works, such a tensionner cannot provide the tension rated by Gates and will probably reduce the belt and sprocket life.
The tensioner is only there to help with the fold - the belt is kept on the rear sprocket by the snubber wheel you can see in the second pic. It's the same method Ben from Kinetics uses on his Brompton conversions and seems to work fine