Here's my retro-direct drive Harry Quinn
I was inspired to build this after seeing one listed on eBay. It has two independently spinning freewheels (a 16 and an 18 tooth). Pedaling forwards is the low gear and backwards is the higher gear. The pulley is made from some tektro downhill component bolted onto an old shimano shifter pod. The first freewheel is spaced out 3 mm and a non-drive side bottom bracket cup is threaded into the remaining freewheel threads. I put another 1mm spacer on and then threaded the second freewheel on. Voila!
The french manufacturer Hirondelle first began manufacturing these two speed bikes back in the early 20th century. They started making 4 speeds in the 30's using a spring loaded pulley. A man in Australia made one that you can see here.
Here are a couple of other retro-diect links of interest: