Thank you gents! I genuinely appreciate it. Today was Derailer day. Or as I will be referring to it from now on, "The Great Derailer Screwup of 2019". Let me explain. Warning: Lots of pics. I'm glad the days of dialup are over!
It all started with a Google search to find out the size and pitch of the threads for a derailer. This took me to Park Tools' website, where they have a wonderful cross reference. Here's a link:
https://www.parktool.com/blog/repair-help/basic-thread-concepts
Scroll toward the bottom to see the list. And right there is derailer: 10mmx1.0mm pitch. Sweet. And that thread is also used
on a metric wheel axle. Oh, this just got interesting. I have those. You can see where this is going:
I used a removable (but aluminum, sadly) dropout from an aluminum frame as a guide for placement:
I jigged it up with a piece of flat bar underneath the inside of the wheel mount here, the nut in place with another clamp. If you pay attention to this picture, you can visibly see the first sign of trouble. I didn't. Here it is:
I inserted the axle to protect the threads, tack welded it, and then inserted a couple of steel pieces to weld to to try to fill the gap a little bit:
Some more welds on the other side, and yes I accidentally welded the axle to the nut. Whoops. Easy fix! Have you spotted the problem yet?
I cut the nut down with a cutoff disk. Have you figured out the issue?
And now look at it, all polished up! Not perfect mind you, but way better than expected for my low experience level:
Up until this point I was blissfully unaware of the problem I'd created for myself. You see, I tried to mount the derailer, and there was a problem. It wasn't mounting where I knew the gears would be. My confusion grew as I tried to mount it in a way that looked right, but then my mind visualized it in-situ and I realized my error. And as I realized it, I also understood how it is that doctors could amputate the wrong limb or operate on the wrong patient.
Incompetence. I'd put the derailer hanger on the wrong wheel mount!
I was NOT going to go through that whole process again. Operation: Derailer/Off began!
Surgery went well, and now you can hardly tell it ever happened! In this pic you can also see the little tang at the bottom of the mount that, if I'd paid close attention, I could have just left in the original nut that I cut, rather than having to go back to add it. But clearly, attention to detail was low on my list today!
This lousy picture shows that the derailer does indeed mount:
Done! With THAT derailer. The next one goes on the drive jack shaft, and I'll be working on that one tomorrow. It should be easier, as less fabrication will be involved.