This is a bicycle saddle:
It’s supported, though you can’t see it very well, by a single circular post, called (what else?) a seat post. The seat post either has an integrated clamp or has a clamp attached to the top that connects to two rails that run fore-and-aft under the saddle. The rails flex a little to give the rider some bum suspension.
This is a banana seat:
It has the same seat post in front, but it’s pretty obvious that it wouldn’t be adequately supported if that was all there was. Ergo, the sissy bar. It runs between the axle (usually) and the saddle, where it loops over and goes down to the axle on the other side. Sissy bars were adapted to bicycles from motorcycles, where they generally don’t support the seat, but rather, being somewhat taller, gave the rider (or more likely a passenger) a backrest, or the solo rider a lashing point for packs and bags. Wikipedia indicates that the term “sissy” derived from “sister”—since the person in back would generally be female.
Motorcycle sissy bars are generally fairly high, rising above the saddle to provide that backrest. Young male bicyclists have a history of wanting to ride motorcycles, so it should come as no surprise that in addition to various noisemakers and ridiculously-extended forks, “high” sissy bars were available. I think (but am not sure) that the one I installed rose about 18”-24” above the rear of the saddle. Coooooool!
The day after I installed my sissy bar (along with a bright orange metallic saddle) I took my bike for a spin, north along West Owasso Blvd.
I was about a block from my parents’ yard when it happened. I pressed my back against the sissy bar, stretching out like I imagined motorcyclists did, when I found myself lying on the road, a car stopping just feet from my idiot skull.
What had happened was this. I’d done a fine job of installing the sissy bar. Two bolts passed through the sissy bar, through the ears provided for them on the saddle, and into washer-and-nut combinations. Perfect. But I had also installed a new banana seat. In my hurry to complete my creation, I had forgotten to tighten the clamp on the seat post. As I leaned back, the sissy bar leaned with me and the saddle came free of the seat post. The whole meshuggah folded back and the tip of the sissy bar landed on the road, the bar itself forming a very nice slide for my posterior.
I literally slid down the bar and onto the road. The bike proceeded without me for a few yards, sparks rising in the dusk from the contact between road and sissy bar, and finally heeled over onto its side.
I think I thanked the driver for not hitting me, and slightly scraped up, retrieved my disobedient steed, and went to my folks’ garage where I nearly stripped that saddle clamp bolt, I tightened it so much. Never again did I have that particular problem, and the chrome on the top of the sissy bar served to remind me of my folly.
That was the first time I can remember that a bike tried to kill me. There have been a few further attempts, but (so far) so good. We seem to have reached a modus vivendi of sorts. My banana seat days are happily behind me, as are the family-jewels-wrecking designs like stick shifts and suicide levers. But never forget, something you think is safe can one day reach out and bite you.
Children, this is why it’s important to check your work.