table=car
oid, something, something_else, ...
has many properties -> car_properties

table=car_properties
oid, car_id, keyname, value, ...
belongs to car

@car = Car.first
@car.something = something
@car.someprop = something

class CarProperty < ActiveRecord::Base
   set_primary_key :oid

   belongs_to :car
end

class Car < ActiveRecord::Base
   set_table_name :car
   set_primary_key :oid

   has_many :car_properties

   accepts_nested_attributes_for :car_properties
end