Pictured is a Great Western Railway "Dukedog" 4-4-0, operable in the UK. Given the outside frame configuration of the chassis, were these locomotives built for easy conversion to or from the GWR broad gauge to standard?

http://abpr.railfan.net/abprphoto.cgi?d ... 103_16.jpg

Negative. These things do not go that far back.

The "Dukedog" is a GWR combination of a "Bulldog" 4-4-0 chassis with a "Duke" class boiler. Think a PRR E3s retrofitted with a K4s boiler for more power. An experimental was produced in 1930 after a brainstorm in the Swindon shops, and after satisfactory results 29 of the class were constructed anew from 1936 to 1939, intended for the steep grades but light track of the former Cambrian Railways.

Outside frames (actually, in this case, double frames) were just a throwback to conservative locomotive design on the GWR.

Incidentally, 3217/9017 was the first GWR loco to be purchased for preservation, by T.R. Gomm of Birmingham in 1960, and has spent its life on the Bluebell Railway.

http://www.bluebell-railway.co.uk/bluebell/pic2/gwr/dukedog.html