Organizing rails model files into subdirectories

I'm organizing my models into subdirectories as listed below. I've tried every solution listed in StackOverflow as well as a few others keep getting errors. Seems like a simple task and am in need of help.

Makandra - Organizing Large Rails apps

Rails 4: organize rails models in sub path without namespacing models?

How to organize Rails models that are too fat?

Rails models in subfolders and relationships

However, I keep getting this error:

ActiveRecord::StatementInvalid: Could not find table 'blog_posts'

config/application.rb:

  1 require File.expand_path('../boot', __FILE__)
  2 
  3 require 'rails/all'
  4 
  5 # Require the gems listed in Gemfile, including any gems
  6 # you've limited to :test, :development, or :production.
  7 Bundler.require(*Rails.groups)
  8 
  9 module Multifile
 10   class Application < Rails::Application
 11     # Settings in config/environments/* take precedence over those specified here.
 12     # Application configuration should go into files in config/initializers
 13     # -- all .rb files in that directory are automatically loaded.
 14 
 15     # Set Time.zone default to the specified zone and make Active Record auto-convert to this zone.
 16     # Run "rake -D time" for a list of tasks for finding time zone names. Default is UTC.
 17     # config.time_zone = 'Central Time (US & Canada)'
 18 
 19     # The default locale is :en and all translations from config/locales/*.rb,yml are auto loaded.
 20     # config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}').to_s]
 21     # config.i18n.default_locale = :de
 22 
 23     # Do not swallow errors in after_commit/after_rollback callbacks.
 24     config.active_record.raise_in_transactional_callbacks = true
 25   end
 26 end

Files:

app/models
├── blog
│   └── post.rb
├── blog.rb
└── concerns

Routes:

 3   resources :blogs do
 4     resources :posts
 5   end

models/blog/post.rb

 13 class Blog::Post < ActiveRecord::Base 
 14   belongs_to :blog
 15 end

models/blog.rb

 11 class Blog < ActiveRecord::Base
 12   has_many :posts
 13 end