So this is a followup to my failed platen movement design
. For the axle, I used a 1-1/2 inch PVC pipe and a 1-inch PVC pipe glued inside it for strength. I used a 3/4-inch diameter metal closet rod to connect the axle to the platen.
To connect the closet rod to the platen, I glued small prism-shaped pieces of wood to either side of my platen so that I had a surface perpendicular to the ground. I drilled holes in these surfaces with a 0.202-inch drill, which is the correct size for tapping for a 1/4-20 screw, although I didn't tap the hole because this is soft wood. I drilled the holes slowly and carefully, because the hole does eventually hit the glass in the platen.
I cut off two pieces of about 1-1/2 inches of 1/4-20 threaded rod. These screw into the above mentioned holes, and can then fit into holes drilled into the closet rods, secured with washers and a nut.
Before drilling 3/4 inch holes in the axle for the closet rods, I measured the distance across the platen, added 3/4 inch (to account for two half-diameters of the rod), and laid that out on the axle. I first drilled one 3/4 inch hole, put a closet rod in, and rotated the axle so that the rod looked pretty much vertical. I could then be fairly certain that when drilling the second hole, it would be at the same angle as the first hole.
Then I fitted the axle into the scanner, put the rods through the axle holes, and drilled perpendicularly so that I could put bolts through to hold the rods in place. Then I drilled more holes on either side of the axle supports so that the platen wouldn't shift side to side.
Here is the result! I don't yet have the handle that I will use to rotate the axle, but I can still lift the platen up much more easily. Note that I left the closet rods long, so that I can add a counterbalance spring if necessary later, to make lifting the platen even easier.
(A cat is fine, too)