Frank is a Diesel who works on the Arlesdale railway.
Frank was built at Arlesburgh Works circa 1967 out of parts from several other engines. He was a very grumpy diesel always doing maintenance around the railway, and was angry that he wasn't in the first RWS book about the Arlesdale Railway (he had not been built at the time). This made him careless and he crashed through the back of a shed.
In 2016, Bill and Ben temporary came to work on the Little Western following Duck and Douglas' accident. Oliver told the twins that the Arlesdale engines were once normal standard gauge engines who were shrunk due to them misbehaving. Bill and Ben later mistaken Frank for Dennis.
Frank is based on Perkins from the Ravenglass and Eskdale Railway.
- Toad the Lucky Brake Van (cameo)
- Oliver's Tiny Tale (does not speak, not named)
- Great Western Escape (cameo)
- EnterprisingEngine93: Episode V only
Frank made his first and only appearance in the book Jock the New Engine. Neither he or Jock have appeared in the TV series yet, thought it is possible they may in the future.