[Steam-engine] Firebox door (rookie question #999,999)

[Andy glines]

We have talked about keeping the door closed when we
are running our engines because this lets air come
over the top of the fire instead of coming up throught
the grates where it will aid combustion.  Closing the
door along with the damper allows you to choke the
fire down.  Sarturday I visited Francis Lindauer in
Ferdinand, IN to borrow the door from his 16 HP Huber
to use as a pattern to have a new one made for my
engine.  I had noticed the hole in the door before but
never thought much of it.  Paul Pavlinovich has a good
pic here: 
http://www.steamengine.com.au/events/reports/old_threshers_2001/pics/DSC01098-huber-firebox-door.jpg
 As you can see there is a baffle behing the hole but
there is a hole in the bottom of it about the same
size.  What is the purpose of this hole?  Should it
have some type of damper to close it off?

Andy Glines
Evansville, IN

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