Replacing the rear derailleur

Yesterday I removed the rear derailleur. Since I only use a single chain disc in front, there's no real need for a derailleur. It's only been there for the purpose of tensionning the chain. I replaced it with a single pully chain tensioner, the same I have on my mountain bike (it also has a Shimano Nexus hub). Took me about 15 minutes to install and shorten the chain and another 10 minutes to get my hands clean ;-).
Took a ride afterwards for about 2 hours near the canal, on the tow path. Though most of my rides are near the canal, I never seem to get bored riding there. Since no motorvehicles are allowed on the tow path, it's so nice to ride your bike without the noise and needed attention of motorised traffic and just enjoy the scenery.

When I returned home, I crossed a bike I've never seen on the road before : the PINO from Hase. Although I've seen some in bike shops, I recongnized the bike immediately. In front a woman was sitting very relaxed, her arms crossed on her chest and a big smile on her face, while her boyfriend (husband ?) was riding in the back. Since we were riding opposite directions I have no idea about there speed, but it must about the same as other tandems.

The single pully chain tensioner