Ford Model T Gearbox Demonstration Model

Engine flywheel (white) had 3 short axes with planetary gears and long central axis connected to the main clutch.
The disk on the other (clear) end was connected to the drive shaft and hence the rear wheels.

Gear activation was done with brakes applied to the remaining two disks (purple).
By stopping one disk reverse gear was activated - slower rotation in the opposite direction.
By stopping another disk the first gear was activated - slower rotation in the same direction.
When main clutch was engaged it locked the flywheel to the driving disk giving direct gear.
In this mode everything was rotating with the flywheel, no additional friction.

Printing

Highly recommend using random seam orientation for all parts, helps with keeping them symmetrical.

Need 3 copies of planetary gears (each has two parts).

Assembling

Mark the same spot on all three planetary gears, for example where all 3 stacked gears have aligned teeth. Make sure all these marked spots touch the same location on the driving gear when rotated, result should look like the last picture. The rest of the gears will easily fall into their places.