Electric motors. These scale out about 1/4" dia so they are fairly large motors in the smaller scales .. the attached pulley drives an old school belt drive lathe - presumably converted from overhead belt drive.
- 1:160 – 40″ dia
- 1:87 – 21-3/4″ dia
- 1:64 – 16″ dia
- 1:43 – 10.75″ dia
- 1:48 – 12″ dia
- 1:25 – 6.25″ dia