Steam engine question

[Lester Perry]

I wish I could find the story, it was in C&O historical society magazine. I should have it here somewhere but no time to look for it.

[Beamish]

Is this combustion air reglulated by any sort of damper? Or is it smiply a gap above the ashpan?

I am speaking in regards to steam traction engines here. That is where I have a lot of experience in the 1:1 scale. There is most certainly dampers over these air intakes. This allows the fireman to control how much air is getting in. If the engine is working hard there will most likely be a big fire going to keep the pressure up. When the engine comes to a stop suddenly the fire is much too large for the amount of steam that is needed. This causes the pressure to build up. Eventually it reaches the point where the pressure relief values must lift, this is a waste of water. By closing the dampers when stopped it essentially blankets the fire and causes it to smolder away. Thus not burning as hot. Then once the engine is back underway it is possible to open the dampers and the fire that has been smoldering away will roar to life as it suddenly has lots of access to oxygen.

Hope this helps.

Mike

[Sumpter250]

The boilers, and fireboxes are significantly smaller in a traction engine, and dampers would most probably be very useful. In a locomotive, dampers would most likely be marginal at best, which is why the draft is aided/controlled by way of the stack, and exhaust nozzle. Using the exhaust steam, "automatically" adjusts the draft, and as a result, the heat of the fire. It's also rare that a locomotive will experience an unexpected sudden stop, so the fireman can anticipate the reduced need for "heat" and not feed fuel at the same fast rate.
The "teamwork" between the fireman and the engineer is one of the most essential components in an efficiently operated steam locomotive. What one does, greatly effects what the other has to do.