The 3 seater- propeller driven- 1913 Thor pacer bicycle mated to a Henderson motorcycle engine with a propeller

Strange arrangement of controls... why the rider in the back gets to adjust the speed, but can't see if the bike and riders are likely to run into anything... that doesn't seem like the best idea.

Click on the above for a big full screen version

Look close at the chain, it's the only one I've seen like it. I wonder why they thought this double roller type would be better than a single link and roller