1 a 12 volt motor does NOT run on 36 volts,, no way…what you may be seeing is 3 12 volt batterys in series…making 12 v but adding more amps..
2 get a 12v rheostat [[sort of a variable control to dial speed up/down]
3 try any Electric parts house…golf cart shop no gear reduction needed
4 get 12v timer at same place…also try a RV place…campers have 12v systems.