The late Don Ashton was a widely acknowledged expert on locomotive valvegear design for both full size and model locos. He summarised much of the information in a webpage, which at the request of his executors Polly is now pleased to host, ensuring that this valuable informaton will be continue to be available to model engineers and enthusiasts.

Click this link to go to Don Ashton's pages.  (This link will open in a new window)