Add custom rake task in rails project

1. Create a rake file as your_tasks.rake and put it in project_path\lib\tasks\

2. Here is a sample rake task

namespace :cron do

  desc "Starts cron job"

  task(:start => :environment)do

    #do some tasks

  end

  desc "Stops cron job"

  task(:stop => :environment)do

    #do some tasks

  end

end

Test 
namespace :cron do
  desc "Starts cron job"
  task(:start => :environment)do
    #do some tasks
  end

  desc "Stops cron job"
  task(:stop => :environment)do
    #do some tasks
  end
end
3. Now run in command prompt from the project folder as 
rake cron:start