I've seen photographs from what's been called the "Pioneer Era" of American railroads of locomotives with outside frames but as Overmod said by the time the 4-4-0 American type of locomotive was pretty much standardized the outside frame was obsolete. Some hung on through the Civil War period but were certainly retired by the 1870s.
Outside frames were already obsolescent by the time of standardization of the American type into inside Stephenson, outside valves and rods, and division of the frame into front and rear sections for maintenance.
By the time of cast bar frames and then cast engine beds, the necessary thrust was in excess of practical outside cross-bracing, even with Woodard's 'central machinery support' cylinder location and mains 'inside' tandem side rods. You see outside cast frames a lot with motor drive (as in the GG1 or those GE Steamotive turbines of 1938) and of course the B&O constant-torque W-1 would have had them, but the transition to driver roller bearings in cannon boxes, and effective lateral-motion bearing on hub liners really required 'inside frames' to work right.
Closest thing to an 'outside' frame might be the Timken bearings applied to the early N&W A 2-6-6-4s. You almost need a 3D model to figure out how these worked: the actual roller bearings were outboard of the frame, actually inside the rim of the driver, in an assembly cross-reinforced by a hollow tube; the drivers were joined (and kept quartered and parallel) by a heavy axle which did no supporting of the frame at all. This got around the large openings in the frame that would be needed for roller-bearing boxes in the usual place...
I can't think of any, might have been a few in the 19th century? Generally ones I've seen are in effect standard gauge designs adjusted to outside frame so they could run on narrow gauge track. In the UK inside cylinders were more common so would make sense they would have some standard gauge engines with the outside frames.
Hello everyone I've gotten into the habit of modelling some strange steam locomotive prototypes and was wondering if anyone was aware of any standard gauge north american outside-frame locomotives. So far I've only had luck with finding narrow gauge locomotives with outside frames such as the ones that served the Oahu Railway and Land Company, Deadwood Central Railroad, and the D&RGW. Although I have been able to find a few British standard gauge locomotives with outside frames and inside cylinders with several railways operating a variety of different classes of locomotives with these characteristics like the GWR, Midland Railway, and Rhymney Railway. I hoping someone here more knowledgeable than I am would be able to point me in the right direction. Thank you and all the best.
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