I thought I had seen a similar thread a while back, but I went back 25 pages (into October 22) and didn't see it. Feel free to add odd stuff you come across. If someone does find an older thread on the same general topic, I'll ask the mods to merge them.

I know we've all come across some curious things either while riding bicycles, or working on them. Recently, I was trying to tighten a saddle onto a seat pin so that it wouldn't swivel so easily. None of my wrenches could get a good purchase on the nut though.

Pentagon Whitworth?

I believe the nut is on the wrong side of the clamp.

Theft-deterrent "security" bolt to prevent your seat from being stolen!

On that style of seat clamp it is easier to just wack the nose of the seat to get it loose to steal the seat. I learned the hard way. I had a seat stolen. While I wasn't there to witness it, I had some friends tell me that that is how it is done.

What the hell? Nuts are made from hexagonal bar stock. Did someone have a sale on barstock that was defective? Fire hydrants (fire plugs) have pentagon nuts to turn on the water valve, so that the common folks can't do it themselves. This one makes no sense at all.



Of course, someone tightened that nut. Whether at the factory or the place it was assembled to be sold. Is the nut proprietary so that you have to go back to the dealer to make adjustments. Did they use a 5 point wrench? A 10 point wrench? I never heard of such a thing.

We now live with all manufacturers coming up with ways to make sure that we cannot service the stuff they make.

Is that on one of those bikeshare bikes?

I'd call that a "flutney" nut or bolt, based on what I remember from Mad Magazine's famous team sport, 43 Man Squamish.
https://43-mansquamish.weebly.com/equipment-needed.html

Gas and water utilities use pentagon bolts (13/16") for access boxes and certain automotive applications as well.

https://www.amazon.com/CTA-Tools-275...A%3D%3D&sr=8-9

Are you sure I didn't send that one to you? That's a bike share seatpost clamp, most commonly seen on first and second generation Spin bikes. You can replace the nut if you wish, but you'll be surprised how they'll tighten just fine with an adjustable wrench on one of the flats.

Gen 1 (incomplete, wrong front wheel):



Gen 2:



Gen 3 used the same saddle, but a conventional sandwich clamp seatpost (though they're non-remote dropper posts, so not so conventional).






The Gen 1 + 2 Spin clamps use a carriage bolt on one side and the pentagon nut on the other, similar to some of the Persons and Troxel saddles from the 1960's and '70s.



Need any more of those clamps? Spin closed down for good in South Florida (only responsible operator here, so quite a loss), so wound up with a few more spares from the warehouse.

-Kurt

Kurt,

I'm good thanks. Now that you mention it, the clamp looked quite a bit newer than what I'm used to, so I suspect your care package was the source. Mystery solved.

I am still hoping that this is only the first of many curiosities that forum members explore in the thread.

Curiosities? That I can provide in heaps
















And my personal favorite, "Proprietary Parts" - the name of this partsbuilt machine wearing components shared between three different operators - two of which insisted at the time that their bikes couldn't be reused or repaired because of...ahem...proprietary parts. Rubbish.



-Kurt

^ You need a few more colors on that bike.

Perfect nut for a pipe wrench.

I wanted to fit a few more parts, but we only had Spin, LimeBike, and Ofo locally. Would be fun to throw some MoBike parts at it.

-Kurt

All those dudes riding around with Vise Grips clamped to their seatposts back in the '80s were prepared for this.