I have two builds on the go, for accidental reasons, and one small modification:
1. 1951 Holdsworth Tornado, which will use a Sturmey-Archer AM medium-ratio rear wheel. The rest of the kit will be modern-ish as I'm not faffing around with cottered cranks and brake cables that get broken if you flip the bike on its back. Frameset currently at Argos being painted and with an SA roller and cable stop added - the clamp-on ones are horrid. The idea behind this, as well as using a nice rear wheel that has been hanging up for years, is to build a fast bike that can make the most of the hub; it's much nicer than a derailleur and, although it only has three speeds, they're exactly the right three speeds (16.6% up or 14.3% down, compared to the common AW 33% up or 25% down). Will be geared at 42 x 18; I already run one of these on the clubman at 41 x 18 and it could do with a slightly higher ratio on a stripped-down bike.
2. Mystery (very light) late 1940s frame, possibly an Ellis-Briggs, which will use a 1960s Sachs Duomatic kickback-to-change hub. This will have short straight bars with just a front brake lever on them (the Duomatic has a coaster brake built in). Will gear it unconventionally at 42 x 20, so normal gear is the cruising gear and high gear is an overdrive for downhills. Most people seem to gear them so high gear is for cruising and low gear is for starting, but on a 3-speed with normal gear at 55-60", I use the low gear a lot less than I do the high gear. Also, there is less wear and more efficiency if you use direct drive as the cruising gear.
3. Refit the original crankset to the Raleigh Twenty. The chainline is problematic with the short cranks I got for Miss Z's legs and I'm sure she can cope with 165mm cranks. One problem is that the original owner (who wrote off the fork) also cross-threaded the pedal, but it didn't go in very far and the crank will probably be OK, even if it needs a 9/16" tap running through it. I have managed to find some nice "R" cotter pins. There is absolutely no front chainline adjustment possible with a Twenty as it uses an super-wide BB shell* which nothing fits apart from the original 26TPI Raleigh BB.
*probably to accommodate the twin struts between the main tube and BB shell - it's a cross frame design.