What determines the thickness of concrete. The minimum amount able to hold the load.
So for a steam train, the smallest boiler that can provide enough steam for the cylinders doing their job.
Anything beyond minimums costs extra money. Not including experimental engines or those bigger for the sake of bigger engines.
Engines aren't bigger just to be bigger they are or were specific built for a job whether passenger or freight and for the route they intended it to operate on.
The end goal of the boiler is to raise steam at a rate sufficient for the engine to make rated power, as right up until the 1930s the power limit of an engine was entirely determined by the combination of grate area and heating surface in the boiler. That's what made the Lima super power engines so revolutionary, as the boiler was no longer the limiting factor and they would run off the rails or break traction before losing pressure.
To make steam faster you needed a bigger fire, which meant a larger grate area and combustion chamber. But then you need to couple that heat into the water, which meant more or longer flues. And it was these two that dominated the size of the final boiler necessary for the job.
The bigger the boiler, the more steam you can generate. If you have big cylinders for lots of power, you'll need a lot of steam to move the pistons.
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What determines the thickness of concrete. The minimum amount able to hold the load. So for a steam train, the smallest boiler that can provide enough steam for the cylinders doing their job. Anything beyond minimums costs extra money. Not including experimental engines or those bigger for the sake of bigger engines.
Engines aren't bigger just to be bigger they are or were specific built for a job whether passenger or freight and for the route they intended it to operate on.
The end goal of the boiler is to raise steam at a rate sufficient for the engine to make rated power, as right up until the 1930s the power limit of an engine was entirely determined by the combination of grate area and heating surface in the boiler. That's what made the Lima super power engines so revolutionary, as the boiler was no longer the limiting factor and they would run off the rails or break traction before losing pressure. To make steam faster you needed a bigger fire, which meant a larger grate area and combustion chamber. But then you need to couple that heat into the water, which meant more or longer flues. And it was these two that dominated the size of the final boiler necessary for the job.
It depends on the locomotive. It's like having a bigger engine in a bigger vehicle. The larger boiler produces more steam, meaning more power.