My most fun one was a TA set up as a 28 tooth single. I took a tired outside ring, cut it down beyond the bolts for the small rings and bolted the 28 tooth ring directly to that. Ran a 5-speed 13-21 in back (this was 1978) and my racing Cyclone RD. Chain ran under my FD cage.

This was for the Mt. Washington hill climb. Caveat was that the day before was going to be a very hard Cat 1-2 road race so the setup had to be brain dead simple to install. It was. I pulled off the racing cranks, installed the TAs, took off the chain, put a shorter one on and swapped the rear wheel. Took off the WB cages. Done. No stand required. (I did this at the Appalachian Mountain Club "hut" at Tuckerman's Ravine in a quiet spot of floor space. After a 5 hour race into a hard cross-headwind we could not echelon, I was indeed, brain dead.)

For Mt Washington - perfect gearing - except the first, flat 1/2 mile was a joke. My fellow starter horizoned me getting to the mountain. Once onto the climb, I had much, much better gearing than everyone else's 42x28. With my lower gearing and 2 tooth gaps, I had choices, could shift and did.

Those cranks went on to be mounted on my yet to be built Peter Mooney that was ordered several weeks later.