Building the World's First Computer: Babbage's Analytical Engine

 I've expanded the prototype to have 4 digits plus a sign wheel in the Store, and gotten it to be somewhat more reliable. Here's a video of four cycles in quick succession: write from Mill register to Store location restore the rack read from Store location to Mill register restore the rack This is running at the "Babbage speed" of 157 milliseconds per digit, which is the fastest he thought the engine should ever be run. Tim Robinson points out that an alternative Babbage design for restoring the racks is to use two vertical bars that come in from either side and "trap" the racks in the center regardless of what position they are currently in.  I'm looking into doing that, in part because it makes initial setup a lot easier.  As it is there are dozens of mechanisms that have to be adjusted exactly right for initial conditions, including the rack-restoring wheels. Half the time when things go wrong during a test, it's because one of them was slightly ...