Monday, August 24, 2009

Unusual Tandem Bicycle

I saw this unusual tandem bicycle in Santa Cruz last week. I'm trying to figure out some of the weird features of this tandem.

Weird tandem

For example,
  • How does that big ring inside the timing chain stay in place?

  • What is that extra set of cranks under the stokers bars for? Russ suggests these might be hand cranks, but I think they might allow a very short rider to pedal recumbent style.

  • What about that handle that appears to stick out obliquely from the stoker's saddle? Another hint that this might be for a short rider?
Your thoughts?


  1. With enough tension, the chain can hold the big ring in place by itself. He's probably using the ring as a DIY chain tensioner. doesn't seem particularly stable, though - either an impact or a jam at either end of the chain would be enough to dislodge it.

  2. +1 for chain tensioner. Without it, the chain was probably 1/2 a link too long.

    I also think the second crankset is for the recumbent position and the handle at the rear is for the same.

  3. is that a motor in the rear hub and possibly batteries in the bag?

  4. I think the post from the stokers seat and the cranks under the bars are for a child, the child seat clips to the bar from under the stoker and the Kid gets to peddle, to.

  5. Jasper, that looks almost like a hub motor but that's an Arai drum brake.

    Cliff -- Aha! I thought of that bar as a handle for the child but your idea makes better sense.

  6. Bet that free-floating tensioner pops out all the time when you hit an inconvenient bump. Either that, or he's just messing with us.

  7. Apparently it's called a "ghost" or "phantom" chainring.

  8. That's really interesting and I've nver seen that before!