I understand Steve Boylan, Harry Wade and Jeff Williams etc. have been asking about info on coal fired G1 engine firebox sizes etc. I suggest the prime question is "in what G1 scale are you discussing?".
Please see attached an earlier e mail I sent out to a local steamer following a discussion we had, regarding the three coal burners I have. e.g.
Duchess - 4-6-2 PacificSits inside a .375" wide per side water jacket, and .375" wide water back head.
Scale 10mm:-
Firegrate pivots open for cleaning.
Firegrate is 2.5" Long x 2"wide
Firegrate is pivotted at .312" from boiler end to allow ashes to drop out. And tilts down approx 35 deg. for cleaning.For coal firing, this burner is removed to allow a stainless steel rectangular shroud approx 3.4"long x 2.250" wide and a tapered ash pan to be bolted in place. (as supplied in the kit)
Grate is made up of 12 plates spaced equi-distance across the 2" width.
When held in closed position (for firing and running) Grate has a 20degr tilt down towards the boiler, and is held in place by a removable .125" dia pin set across width of firegrate.
Grate bars are .062" thick x .250" SS plates.
When in running position, height from grate to boiler crown is approx 2.5" at rear of boiler and 2" at back of firebox.(coal loading area).
Firebox width is 2.25".
Firebox door opening is 1.25" wide x 1.05" high. Door overlaps opening by approx .093" all round to seal.
Firegrate is 1" below bottom of door , when in firing position .i.e. giving 1" coal depth.
The bottom (o/d) boiler tube is in line with the bottom of the firebox door.
Boiler has 6 small tubes at .312" dia set in a circle, surrounding single large tube at .5" dia.
Boiler is 12" long x 2.25" dia.
Britannia - 4-6-2 Pacific - 10mm Scale:- Firegrate is fixed in a recessed frame area, and needs raking through for cleaning.
Firegrate is 2.250" Long x 2.125 wide.
12 SS Plates equispaced across width @ .062" thick and .250" deep.
Firegrate is tilted approx .375" down towards boiler.
Firebox to arch is 2.375" deep at boiler end and and 1.875" at boiler.
Firebox door is 1.250" wide x .875 high. Door has approx .062" overlap for sealing.
Firegrate is 1" from bottom of door. (As Duchess)
Bottom Tube outside dia is level with bottom of firebox door. (As Duchess).
Firebox is approx .125" larger than grate are all round.
Boiler has 5 tubes at .250" dia, set in semi circle around large tube at .437" dia.
Boiler is 11.5" long x 2" dia.
Firegrate is approx 1" below bottom of firebox door opening. (As Duchess)
For cleaning, the underside of the firegrate is set in a shroud with two open vents approx .6" by .5" wide each side and to the front of the grate. This seems to work really well with > 90% of the coals/ash being vented through these. To remove the remainder or larger clinker, I turn the engine 180degr on end, and allow coals to drop out of firebox door.
Aster U1 232 - 4-6-4 Hudson 1/32 Scale Can be fired on both Alcohol and coal.
The rear truck which supports the alcohol burner bolted in situ, is held in place by 4 x3/16" screws. The alcohol burner is held to the truck by two additional screws.
This ash collection pan is approx .6'"deep at the boiler end and end and .3" deep at the cab or loading end. The ash pan sides taper down to rectangular opening 2.87" long x 1" wide to allow dispersal of ash.
On the upper side, this ash pan has a raised lip approx .25" high in which a loose firegrate sits.
Firegrate is 3.3" long x 2.125" wide.
It has 11 stainless steel bars .187" deep and .062 wide.
Firegrate has an approx 15degr tilt down towards the boiler when sitting in the ash pan shroud.
Actual firebox is 3.5" long x 2" wide.
Firegrate to crown is 1.875" high at the cab area and approx 2.200" at the boiler.
Firebox door opening is 1" dia, with door overlapping approx .062" all round
Bottom tube o/d is level with bottom of firebox door. ( as Duchess and Britannia),
Firegrate is approx 1" below bottom of firebox door. (as Duchess and Britannia).
Boiler has two .00" dia tubes set side by side and three .350" dia tubes set in line below
the two large tubes.
Boiler length is approx. 13" long and 1.875" dia.
Note;- All the firegrates on engines described are surrounded by water jackets at the sides and rear backhead. These water jackets are all at least .250" outside wide minimum, up to .375" wide on the Duchess design. Therefore overall width /length of firebox area is at least .500" to .750" wider and .250" to .375" longer than the actual grate.
On all these designs, the firebox is located outside the frames.
Inside Frames:-
For reference, the inside width of the frames on the Duchess and Britannia at 10mm scale are only 1.375" wide. For designs with an inside frame firebox and a water jacket at .250" per side, as above, this would reduce the firegrate width to .875".
Whereas a .125" wide per side water jacket could increase the available grate width to 1/125". Typical firegrate length would be approx. 2".
Scales:-
I doubt that even the larger scale G1 engines running on 45mm tracks will have an inside frame width wider than 1.5" max?. Whereas the Accucraft K27 has "outside frames", in theory and more width?. The position of the rear wheels in relation to the firebox may impede the potential wider firebox also. (Has anyone asked Larry Bangham the firegrate width on his K27?).
FYI:- I know one well known engine builder in the UK who will not build a coal fired engine with an inherent "narrow firebox" inside frame design, unless the potential owner has
considerable coal firing experience. i.e. the wider/longer/deeper firegrates are easier to fire, maintain, control and feed etc. and are more forgiving than long thin narrow grates. (Unlike alcohol poker burners!). It is a sad fact that many of the attractive 1/1 prototypes have inside frame fireboxes, but unfortuneately this make them impractical for easy scaling down to G1
for reliable consistant running.
Also, the room and method required to collect and dump or rake out the deaf ash, coals etc is also a major design/usage consideration.
Aplogies for the long winded details.
Hope all is clear to you, and you have all the dimensions you need. If not, let me know.
Have a nice day.
Best Regards,
Tony D.
