ditching the lifter springs

The initial version of the prototype had all the axles fixed. Vertical motion was effected by moving sleeves surrounding the axles that the components to be lifted (digit fingers, pinions, carry levers, etc.) would be trapped between. When the lifter was lowered, a spring on the top would push the components back down.

There were two problems with this approach:

• The sleeves were long and introduced too much friction sliding against the axles.
• The spring force was often inadequate to move the components down. Besides, Tim Robinson says that Babbage never wanted to depend on either springs or gravity for positive motion.

Consequently I redesigned the lifters so that the components are fixed permanently to the axle, and the axle is driven positively to move both up and down. The components are still spaced and trapped by concentric sleeves, but they are fixed in position and don't slide on the axle.

Here's what the drive mechanism on the bottom looks like for a rotating shaft that also has components that must be moved up and down.

The axle slides up and down as much as 1" while staying within the tall keyed rotator. This works much better, and the springs on the top are gone.

The gear train on the lifter lead screw is only there because the stepper motor shafts can't be closer than 1.7", but the lifter needs to be close to the axle being lifted so that the lifter platform doesn't tilt.

Notice the vertical ridge on the keyed rotator? That's going to be for detecting the orientation of the fingers inside the digit wheels during setup.