If you want to Travel From Howrah to Delhi but you couldn't get Confirmed Ticket so you can make reservation in 12175/77 Chambal Express upto Mughalsarai and then 12815 Nandan Kanan Express from Mughalsarai to New Delhi you will get 100% confirm ticket in both trains even one day before without tatkal and Travel Time is same as Poorva Express or Kalka Mail.