Napier Deltic engine of a British Rail Class 55 diesel locomotive.
https://diqn32j8nouaz.cloudfront.net...tic_engine.jpg
Previously:
https://www.homemadetools.net/forum/...985#post144936
https://www.homemadetools.net/forum/...548#post158900
https://www.homemadetools.net/forum/...680#post128735
