I did a bunch of reading on this subject today. However I’m thinking that you’re a little dimensionally challenged on this: The driver wheels are 4’-8" apart. The side rods are connected to the outter face of the drivers, at the outside radius. Height wise, the rods are a little taller off the ground than the drivers. No matter how you offset the connecting rods outward, the dimension between the drivers will remain about 4’-8".
The old steamers had the fire box between the drivers- therefore less than 4’-8" wide. The newer designs looked like the firebox was moved back, behind the drivers and no longer resrained to 4’-8" dimensional width. To carry the firebox weight, it looks like either 2 or 4 trailing wheels were added.
Well…probably the best known engine was the 4-4-0 American. The wheel arrangement and suspension were designed specifically for U.S. roads with their poor track and that particular wheel arrangement was the main type during the period when U.S. roads were being built at breakneck speed.
Murphy - Email your mailing address and I’ll send you a drawing so you know what I’m talking about. It would be relatively easy to fit a 9’ x 9’ firebox in between a set of drivers which are 9.5’ apart lengthwise and rods which are extended outward from the drivers at 9.5’ apart widthwise.
Whether the weight of a larger firebox can be suspended between the two sets of driving wheels is another question altogether.
A large problem with the concept of the ‘extended rods’ concept
would be a very serious increase in dynamic augment-the inertia
of extra mass reciprocating around the axles. It seems to me that
you would have a very rough-riding locomotive that would be almost
impossible to properly counterbalance-thereby increasing wear on
bearings and bushings. After all, counterbalancing even the locos
that existed was one of the more difficult tasks given to mechanical
departments and locomotive designers.
A notable steam loco, in my opinion is the class N3 2-8-8-0 as
rebuilt by the GN in 1940-42. An articulated loco with 63 inch
drivers, no trailing truck and only a two wheeled lead truck that
was capable of running with heavy loads at 50-60 mph. And with
an 118,000 lb tractive effort. Impressive-yet undernoticed.
On the issue of how large fireboxes fit on locomoitves. Suggest you find a photo of a 19th century locomoitve (ie. 4-4-0) and see how the firebox fits between the drivers. Then get a look at a superpower locomotive with a four or six wheel trailing truck and see how the firebox is place up over the back drivers. This is particularly noticable on the UP’s Big Boys. A picture is worth…
One very notable steamer was the SP cab forward,so designed to keep the engine crew from getting asphyxiated in the long tunnels on Donner pass.
Rick: If it is a 2-8-8-0 with no trailing truck, the firebox must be on top of the drivers? Wouldn’t construction like that negate the need to do what futuremodal is asking?
In fact, that’s true, Murphy. The N3 turned out to be the tallest locomotive
on the GN, in part due to that very thing. Actually, I wasn’t really advocating
the N3 as a response to futuremodal, I was simply submitting that loco
as a notable achievement by GN’s shop forces. The two paragraphs don’t
really dovetail that way. I was just expressing the opinion that longer-extended
rods would create a bad counterbalance problem and then a separate
opinion on the N3. It is intersting to note that GN got as much out of
the N3 as it did with that arrangement-of firebox built on top of the rear
drivers instead of a deep, truck-supported firebox as on most modern
steam locomotives of that time.
Did GN have their steam engines built with Belpaires until they started getting diesels ?
Nanaimo, That is basically true. The only classes of modern steam
power on the GN without Belpaire fireboxes were the class P2 4-8-2s
and the S2 4-8-4s. (The Z6 Challengers don’t count-they are not
representative of GN locomotives). Almost all other steam power no
the GN was Bepaire-equipped. The GN had the idea that the Belpaire
design was more efficient in heating (it was) and that design also
added more weight-which the GN liked on their freight locos-the
Belpaire design being heavier than an equivalent radial-stayed
boiler.
I assume that you are describing the “gap” between the drivers on turn of the (last) century 4-6-0 locomotives where the firebox (or possibly just the ashpan below the firebox) dropped down between the frames between the second and third axles. The later 1920s locomotives, like the Pennsylvania G5s had a gap despite the fact that they had a wide firebox above the driving wheels. The gap allowed the front of the firebox with its sloping grate to fit between the second and third axles. The G5s was as powerful as a Pacific type, but the firebox above the driving wheels limited the size of the driving wheels to 5’8" (if I remember correctly). The G5s was an excellent locomotive for commuter trains where the high adhesion from the firebox over the drivers allowed fast acceleration but the relatively small drivers were not a problem.
In the late 1930s a small number of oil burning 4-8-0s with wide fireboxes were built
Has anyone read “Dropping the Fire” by C.P. Atkins ? Feltonhill said this book has a unbiased comparison of NYC’s Niagara 4-8-4 and PRR’s T1 4-4-4-4. What did this comparison say ?
Was the PRR really the only railroad that quartered with the other side ahead? Why was this ?
Did railroads order their coal in certain sizes, or did it not matter ? Did small pieces of coal drop through the grates and burn in the ashpan ? Did this cause problems ?
The rods were quartered on opposite sides of any steam locomotive to avoid the possibility of both pistons being stopped at dead centers at the same time, which would make it impossible to start the locomotive under its own steam.
Rick: I was the one who put the subjects together-'was thinking about futuremodal’s question, and suddenly saw a mental picture when I read your post. I e-mailed futuremodal my address, so I’m looking forward to a drawing.
No problem, Murphy. I was just trying to avoid any confusion. Certainly
not trying to find fault or anything. Have a great day.
Rick: You mentioned that the N-3’s were re-built. What were they before?
The GN’s Class N locomotives were always 2-8-8-0s. When originally
built in 1912, they were compound locomotives and were equipped
with very small tenders. They were classed N1 at that time. In the years
between 1924 and 1927, the GN took the entire class in hand and rebuilt
them to simple configuration. They added large Vanderbilt tenders at
that time as well and also upgraded appliances like feedwater heaters
and more modern air pumps.This incarnation was classed N2. In 1939,
GN totally rebuilt the entire class again, this time applying new cast
frames, roller bearings, new boilers and modern appliances. This
final form of GN’s 2-8-8-0s were classed N3. In this final form, they
were capable of fast freight service and were even occasionally used
on troop trains during WWII. They exerted a tractive effort of 125,000
lbs, according to Robert LeMassena’s book, “Articulated Locomotives
of North America”. This is an excellent example of a railroad not
giving up on a design, but reworking it until it became a superlative
locomotive. They are not as well known as, for example, GN’s other
exceptional loco designs-the O8 Mikado (largest 2-8-2 ever built) and
the R2 2-8-8-2. This may be because the N fleet mostly operated on
the Mesabi Range in iron ore service. When in general freight service,
they could outwork many more-modern designs-NP’s Z6 through Z8
Challengers, for example. Hopefully, this is helpful to you.
Another class of GN locomotive with the wide firebox over the driving wheels was the 2-6-8-0 class M-1, 22 of which between 1929 and 1931 were rebuilt to class O-7 Mikados retaining the original boiler. This may be the only example where a given boiler was used both over coupled wheels and later over a trailing truck. The O-7 was of course a very large Mikado with 69" driving wheels. In fact, the O-7s were later rebuilt as O-8 locomotives.
M636C
“Why couldn’t the drivers support a wider firebox by extending outward the connecting rods between the driving axle in front of the firebox and the driving axle behind the firebox? That way you have more weight being supported by the drivers (e.g. more traction) instead of a non-driving trailing truck, while still maintaining the advantage of the larger firebox.”
Hmm… you’re proposing the rear driver would be 20 or 30 feet behind the driver ahead of it, with 20-30-ft side rods? And a firebox that’s less than 4 ft wide, and 20-30 feet long?
Or is your firebox to be above the drivers, not between them? If it’s above the drivers, why are the siderods a problem?
You should chase or ride a few steam fantrips.You will be hooked for life[:)].I used to feel the same way about steam that you do until I first saw the freedom train and chased it for two days[:p].