Rixe Single Cotter Crank?
 

I'm working on a Rixe folding bike. The Sachs Torpedo Duomatic hub is a '69 model, and I presume it's original to the bike. It has a new-on-me crank -- this crankset has a cotter on the NDS and...nothing on the DS. The DS arm and ring seem to be swaged together and I can see what I presume is the end of the spindle protruding through, and ending flush with, the crank arm. There is nothing obvious that fastens the crank arm to the spindle. The NDS arm has a conventional cotter. But the end of the spindle has a strange triangular "hole" in the end. There's a large hex nut just inboard of the NDS crank arm.

I'm guessing that the NDS arm is fastened to the spindle with a conventional cotter. Once the NDS arm is removed, I'm guessing this nut is removed, and the DS arm and spindle assembly slide out from the DS? Sort of like a strange combination of an Ashtabula crank and a 3-piece crank?

I like to get the cranks off this bike frame, as I'd like to give it a deep clean and fresh paint. But I also don't want to fix something that's not broken, and I'm wondering If I shouldn't just leave this whole contraption in place. The bearings sound dry, but they're also smooth and seem to be adjusted well.

Thoughts? Ideas? Dark tales portending very bad things if I try to remove this crank?

This is the DS:

https://cimg1.ibsrv.net/gimg/bikefor...daa720cebf.jpg

And the NDS:

https://cimg4.ibsrv.net/gimg/bikefor...93853cdb85.jpg

A bike that can't be serviced isn't worth riding for long so go for it. I'd measure the width of the cotter to make sure it's a standard available size, maybe 9.5 mm. Remove it carefully in case you do have to use it for some reason. The triangle is probably for a tool to help break it apart if needed

This old thread has pictures of this type crank. You should be able to figure out how to disassemble it.

https://www.bikeforums.net/classic-v...tage-bike.html

Thanks to you both. The cotter is a 9.5mm cotter, so I should be able to get this back together, even if all I can do is remove the parts and grease the bearings. It does seem like this has to be similar to the example in that linked thread where the cups are pressed in or set in to the bottom bracket (the shell may not even be threaded) and the cones are on the outside of the cup, trapping the bearings between. (Backwards from a "conventional" crank spindle, where the "cone" is part of the spindle and the cup threads in from the outside and traps the bearings between.)

I put some penetrating oil in the cotter last night. I'll give it a try with a vice-and-socket today and see if I find success.

With the name of the bottom bracket identified (a Thompson-Simplex design), I found a YouTube video of my exact bike and bottom bracket, so I should be good to go from here. I appreciate clubman, Jeff Wills, and @juvela from the other thread, for the info.