South Park Wrote:
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> Clear as mud ...
>
> The tall locos were "generally" built to needs
> specs forcing a wider firebox over the frame and
> raising the boiler accordingly.
>
> Squatty dudes like mudhens and C&S 2-8-0's were
> built that way to "fit" the existing plant.
>
> Just as basic as that ?
Mudhens had trailing trucks, allowing the wide firebox to be behind the drivers and lower (see my post higher up). If mudhens were built as 2-10-0's, the boiler would have had to have been mounted higher.
C&S 2-8-0's had narrow fireboxes that fit between the drivers allowing the boiler to be lower. Small engines can be satasfactory with narrow fireboxes because the fireboxes can be made longer to give the required grate area, and the fireman can still throw coal to the front of the firebox (hence the deckless cabs on most narrow gage engines ending in -0). If you scale that design up to standard gage, the firebox becomes so long, it can't be fired. So, you change the long narrow firebox into a shorter wide firebox, and raise the boiler to ride over the rear drivers (or add a trailing truck).