Frames?

[YellowHillsCentral]

Okay real stupid question, but what is the difference between the outside frame and the inside frame of a steam locomotive?

Thanks,
CSLM

[vic]

Inside frame is a typical locomotive setup, where the mani frame of the engine is "inside" the drive wheels.

an Outside frame locomotive , the frame is outside the drivers, the drivers are nestled in betwen the main frames, the axles stick farther out for the counterweights and drive rods.

Good examples:

Inside: Bachmann Annie 4-6-0, 0-4-0 Porter

Outside: Bachmann Connie 2-8-0, K-28 2-8-2

The move to outside frames happened only in narrow guage as locomotives needed to be more powerfull they naturally got larger, their boilers and their fireboxes got larger and  larger and the frames supporting those boilers needed to be wider to accomodate them, the first outside frames were poplularized on the 2' gauge Maine RRs, they could place a larger boiler on the engine by shifting the frame to the outside of the drivers, a big deal when your only looking at 24" between your drivers, later D&RGW became a major user with the K27 K36 and K37  being the most well known.

[Steve Stockham]

Ooooh...you forgot the K-28! The D&RG also had 2-8-0's that were outside frame. They acquired them from the Crystal River Railroad. Their designations were C-21 and C-25. (The C-21's were affectionately known as the "little mudhens," a reference to the K-27 class being known as "mudhen.")
  On of the more interesting examples of an outside frame engine is the Hawaiian plantation engine in a 2-6-2 arrangement! Now there would be a neat engine to model!!