Why did the Berkshires have two size trailing wheels?

I guess that means N&W 611 has the wrong trailing truck ! Hah !   Both wheel sets of the same diameter......1218 too !    Mr. King, you ready to come out and defend your chooch ??? !

In doing some research in my various Locomotive Cyclopedia (Hundman and Kalmbach editions) I noticed three basic variations in four wheel trailing trucks:

1.  Lima's articulated trailing truck, used under the early 2-8-4's and 2-10-4's, such as the B&A, B&M, and IC 2-8-4's, and T&P and CGW 2-10-4's;

2.  A "short wheelbase" design, between 4'6" and 6' wheelbase (most often from 5' to 5'6" wheelbase), with both wheels 40" to 42" in diameter.  Santa Fe's 4-6-4, 4-8-4, 2-8-4, and 2-10-4, N&W 4-8-4 and 2-6-6-4, UP FEF-2 and FEF-3 4-8-4, Jabelman 4-6-6-4, and 4-8-8-4, MILW F-6 4-6-4, NYC 4-8-4, and DM&IR 2-8-8-4 are examples of locomotives using this design trailing truck;

3.  A "long wheelbase" design, usually 6'6" wheelbase, with one 36" wheel and one 44" wheel.  The various "Van Swerigan" 2-8-4's, P&LE 2-8-4, NYC 4-6-4, C&O L-2 4-6-4 (Baker valve gear), and UP FEF-1 4-8-4 and "Fetter" 4-6-6-4 are examples of locomotives using this design trailing truck.

Why were different designs used?  I don't have an answer for that.

Stuart

How do you figure that it's wrong?

A perfect example of apples and oranges.

611 is a TOTALLY different design, built by Norfolk & Western in their own shops, not by the Lima Locomotive Works.

In the trade, the fire box is not considered part of the boiler. It is a separate part, often including a combustion chamber as well. The "boiler" is the cylindrical part of the overall structure.

Larry, I completely understand and totally agree.

Larry's wife has provided the full answer to the question in just six words, "It makes the locomotive look pretty." I wish I could be that smart! 

So that's it. We now have the definitive answer. There is nothing further to discuss. I may as well close the thread now. 

An EXCELLENT idea!!!!

just want to say that if you go to Marty Knox for a boiler, i have no doubt he'll throw in the firebox for free...

they may be two separate things to some, but i defy anyone to split them apart.  remove the firebox and you wouldn't be left with a boiler.

Might as well refer to the cylinder heads of an internal combustion engine as "the engine," then.

Rusty

That may very well be the way it is in your "live steam world", but in the days of steam, many a locomotive received a "new firebox", every 10 years for oil burners, and every 15 years for coal burners, and even thought the "firebox" was not actually disconnected/removed from the boiler, the "boiler portion" was NOT renewed.

If you separate the fire box from the boiler you have...a fire box and a boiler.

They are often referred to as "the boiler" when connected together, but they are definitely two separate items as far as maintenance is concerned. Obviously they both have to work together to make steam, but they are TWO SEPARATE parts.

Some steam locomotives were redesigned for improved performance over the years. I can't cite specific examples (memory is not that good) but many steam locomotives got entirely new and larger fireboxes welded on to their original boiler barrel.

The firebox was a very high-wear portion of the overall boiler structure. The barrel portion of the boiler was not. As Hot Water pointed out, it was not uncommon for a steam locomotive to have its entire fire box totally renewed, while nothing was done to the boiler.

To a certain extent it is semantics, but when it comes to the maintenance of a steam locomotive, the firebox and boiler are definitely two separate items.

giving it a little more thought, building a locomotive boiler without a firebox would be like asking someone to dig a pit without leaving a hole.

the boiler pictured does have a firebox, but at that point in construction the firebox is essentially only the empty space delineated by the flu sheet, the crown sheet and the rear slope sheet.  to make it a firebox, you'll need to add a grate and ashpan (coal) or burners (oil), and probably an arch.  i would call those pieces the more maintainable parts of the firebox which are likely to be replaced at least a few times within a boiler's lifetime.

how would you classify siphons?  to me they would be part of the boiler, but are located inside the firebox (space).  overfire jets?  ...that's a tough call.

say, ...wasn't this a question about trailing truck wheels?

Siphons and overfire jets are appliances.

Rusty

NYC's original Niagara was built with a trailing truck having one 36" wheel set and one 44" wheel set. The production Niagaras' trailing trucks consisted of two sets of 41" dia. wheels. The reason that NYC gave for the design change was that it permitted an increase in ash pan volume from 86 to 98 cu ft, and permitted a better shape/slope for the ash pan.

If an engine was to be booster equipped, there was a certain minimum wheel diameter that had to be used. (In checking, I was not able to discover a booster application on a wheelset with a smaller diameter than 43" (from my memory)).

NKP Berkshires front truck wheel diameter was 33", not 36". (The Model Railroader/Wescott book says 30" but I do not believe that this is correct. The Hundman books do not provide wheel diameters for the NKP Berkshires......)

I recall reading that the lead/pony truck wheel diameter for the ex W&LE Berkshires was 36"?

The four wheel trailing truck first used on a passenger engine by NYC, the Hudson, was designed with trailing truck and wheel set spacing to reduce the track stress that occurred in the rail with Pacifics between the last driving wheel set and the trailing truck whee set at the axle loading that NYC used. Obviously the greatest advantage of a four wheel trailer was the ability to use a much larger furnace area, but there were other advantages as well.....

Here is the NKP Berkshire Spec Sheet...right from the Lima drawings.

You can CLEARLY see why two sizes of wheels were used on the trailing truck...plus a lot of other things.

IF that drawing is accurate, then the frame behind the rear drive axle is as much part of the small wheel reasoning as anything else.  NKP/ PM Berks are an evolutionary design based on a downsizing of the Lima AMC 2-10-4 loco built for C&O in 1930. That piece was based to a degree on an up-scaling of the Erie 2-8-4 from the final series. They were based on the original Lima 2-8-4 design...stretched out to accommodate a 70" drive wheel and greater speed potential.  Or so the story goes.  It would appear that since the original concept worked well...why reinvent the wheel ! 

IF THAT DRAWING IS ACCURATE!!  IF??

What part of "...from the Lima drawings..." did you not understand?

Good grief. 

ROTFLMAO!!!!! I must say Rich I laughed my butt off at that comment!!! 

Next time just say the drawing is from a coloring book or better yet say the word "lashups" is an actual term! 

I am starting to think I started WWIII.  Great.

No, but you did give the gift of a very entertaining, informative, and ROTFLMAO thread that brightened my day and I'm sure it did for others also!

Larry

Ditto! Another seminar of the steam era.

And if you want to see what a booster looks like (as I wanted to), even if it is not on this locomotive, see attached.

Alex

i finally got it figured out.  Everybody has the wrong answer.  yea Rich even you.

It's because it makes the locomotive "look pretty".  My wife said so and she is never wrong.  

Larry

This reminded my of what my wife told me when I retired.  She said that she is right 95% of the time and that the other 5% doesn't count.

No, no, no......it's for the same reason why we put bigger tires on the back of our muscle cars......because it looks "cool".  

MERRY CHRISTMAS

Accurate???? Maybe.   It is most likely accurate for dimensions, but who sez the art work is accurate or even needs to be.  It's NOT a blueprint or even close to it.  The part in question here is the rear portion of the frame...not the headlight bracket or tender trucks!   There are some well known instances where such drawings have been taken as gospel and caused a bunch of grief in the process. Case in point... B&O EM1 drawing used as a dimensional reference by zillions of model builders when it was never intended to be a real blueprint.  Result: only two of the scads of EM1 models have accurate boiler profiles  (Max Gray O scale, and Challenger HO scale) ...all the rest are hump backed counterfeits. So, now to check a real NKP Van Berk print and get the skinny.   No real biggie here, the Berk would probably work just fine, even with a modified freight car truck under the firebox.  As predicted, this thread is going places and doing things!   Huzzah!   

Um...no. Trailing engine trucks and freight car trucks are two completely different beasts.

Good grief. I absolutely do NOT believe this.

If you cannot tell by LOOKING AT THE PICTURE OF THE REAL THING why there are two different size wheels on the trailing truck, then you are beyond help. 

And I am all done here.

Out.