I have managed to get a cron job to run a rake task by doing the following:

cd /home/myusername/approotlocation/ && /usr/bin/rake sendnewsletter RAILS_ENV=development

i have checked with which ruby and which rake to make sure the paths are correct (from bash)

the job looks like it wants to run as i get the following email from the cron daemon when it completes

Missing these required gems:
      chronic  
      whenever  
      searchlogic  
      adzap-ar_mailer  
      twitter  
      gdata  
      bitly  
      ruby-recaptcha

You're running:
  ruby 1.8.7.22 at /usr/bin/ruby
  rubygems 1.3.5 at /home/myusername/gems, /usr/lib/ruby/gems/1.8

Run `rake gems:install` to install the missing gems.
(in /home/myusername/approotlocation)

my custom rake file within lib/tasks is as follows:

task :sendnewsletter => :environment do
 require 'rubygems'
 require 'chronic'  
 require 'whenever'  
 require 'searchlogic'  
 require 'adzap-ar_mailer'  
 require 'twitter'  
 require 'gdata'  
 require 'bitly'  
 require 'ruby-recaptcha'
   @recipients = Subscription.all(:conditions => {:active => true})
    for user in @recipients
      Email.send_later(:deliver_send_newsletter,user)
    end
end

with or without the require items, it still gives me the same error ...

can anyone shed some light on this? or alternatively advise me on how to make a custom file within the script directory that will run this function (I already have a cron job working that will run and process all my delayed_jobs.

Cheers!