I have been coal
firing my UPS BIG BOY 4002 (first series manufactured in 1981). However,
to anyone who is desirous of following in my footsteps I offer the
(1) Modify the
blower jets. For gas firing the arrangement is fine, but the jets are too
large for coal firing. Furthermore, the twin blower jet fitting in the
smoke box is attached to the steam line exiting from the boiler front end
by a rather flimsy arrangement using an M2 screw (I believe). All that has
been changed on mine.
(2) Still in the
smoke box. There will be need to seal the space between the copper boiler
itself and the boiler casing. When I did my conversion, I could not for
the love of Mike understand why I was not getting adequate vacuum
(drafting), only to realize that that space was the problem.
(3) The two ash
pans have damper openings front and back. I blanked off the front openings
on both. The ash pan to the front of the firebox has the front damper
opening located very close to the eccentric sheave and cam for the axle
driven water pump. No need to tell you why that opening should be blanked
(4) The fire grate
provided in the Aster Big Boy kit (4002 series) was a ‘folding’ type.
After one steam up session, the grate became badly distorted and I had to
condemn it and have one made (in one piece) and placed permanently in the
firebox. A couple of years ago Hans Huwyler (Aster Hobby USA) had some
made (a 2 piece arrangement) which has so far held up beautifully. That
would be the way to go.
(5) Don’t let the
apparent ‘shallow’ grate put anyone off coal firing Big Boy.
therefore, one can successfully coal fire Big Boy. I usually get a ten to
fifteen minute run at the very least before re-stoking.