Steam & Excursion > A few articulated questions

With all the excitement with the 4014, (and none over 3985) it might be a good time to ask a question about some mechanical parts no one ever sees. At the point of articulation, where the rear of the front engine connects to the front of the rear engine, what is the design of this connection, what type bearing is used, and how is it lubricated? Also, how does the weight of boiler and smoke box bear on the front engine? Does it rest at a single point, is it a sliding, friction type bearing, or something more complicated, and how is it lubed? These moving parts are almost never seen or noticed unless the engine is separated in the shop. Will these connections need to be taken apart or serviced before 4014 moves to Cheyenne, and is it something the steam team can service in the field ?

It cannot be serviced in the field.
It requires lifting the boiler and rear engine, then rolling
the front engine out, after disconnecting all sorts of pins
and sliding joints. This is a backshop job.

The joint itself is a tongue and groove affair, using hardened
bushings in all parts and a large steel pin. It's lubricated
by an oil line from one of the mechanical lubricators.

See Kratville's book "Big Boy" for photos that will show what
I mean more clearly than I can explain it.

ddg Wrote:
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> With all the excitement with the 4014, (and none
> over 3985) it might be a good time to ask a
> question about some mechanical parts no one ever
> sees. At the point of articulation, where the rear
> of the front engine connects to the front of the
> rear engine, what is the design of this
> connection, what type bearing is used, and how is
> it lubricated?

#1, below, shows the basic original design of American articulated locomotives. The rear engine and frame was attached to the boiler in exactly the same manner as any other locomotive of the day, except the boiler was extended further forward. The front engine was connected to the rear engine within the saddle of the rear engines cylinders. The vertical alignment of the hinge was slightly forward of the midpoint between the front an rear wheelsets, in order to allow the front engine to help guide the rear engine into curves.

Weight of the overhanging boiler was somewhat supported by the front engine by a simple radially curved, but vertically flat, bearing plate.

Remember, these were designed by experience and slide rules, not computer simulations! It was good only for VERY low speeds.

#2 illustrates this as applied to Old Maude, the first American articulated.

#3 shows the hinge arrangement used on GN's 2-6-6-2's, the first American articulated road engines. Here, the hinge was set up such that the pin was very long, and actually rigidized the from and rear engine frames such that they performed somewhat as a single unit. This was the standard de4sign for quite awhile afterwards, but the locomotives were still hard riding, unstable, and only suitable for low speeds.

Also, how does the weight of boiler
> and smoke box bear on the front engine? Does it
> rest at a single point, is it a sliding, friction
> type bearing, or something more complicated, and
> how is it lubed? These moving parts are almost
> never seen or noticed unless the engine is
> separated in the shop. Will these connections need
> to be taken apart or serviced before 4014 moves to
> Cheyenne, and is it something the steam team can
> service in the field ?

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#4 Baldwin tried to alleviate, with minimal success, with this dual hinged articulation joint. The front of the boiler was still not attached to the front engine frame, except by the siding pad.

#5 By 1940, this hinge, together with a more secure bearing pad with a centering device as shown in #6, allowed the development of successful high speed simple articulated locomotives.

-John Stein aka Larry Doyle

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Without reading all of the above, and thus I may be re-stating or otherwise messing up a point already made (let me apologize in advance), the 4-8-8-4's and later Challengers utilized a design which I believe Alco may have first used on some other power (without looking it up, I'm thinking possibly the D&H engines) in which the frame casting for the front engine utilized and extension, or tongue, which fit into a correspondingly designed "slot" (for lack of an immediately better or more correct term) in the frame for the main engine. A large pin retained the two.

Alco's Jerry Blunt, one of their best mechanical engineers, patented a centering-device arrangement in which the lead or forward engine was caused to maintain alignment. The front portion of the boiler, at least on the Union Pacific power, was borne via a large horizontal mating surface, affixed both to boiler and front engine frame.

This is a horribly simplified and probably somewhat inaccurate set of statements, but I hope it helps a little.

John Bush

Omaha

Good read, looks like parts too big to fail. Never realized they had the spring loaded centering device.

When 4014 is restored, will it be necessary to separate the engines at the hinge point for any reason? Has 3985 ever been separated since it's initial restoration? It looks like the hinge mechanism might get about as much wear and tear as the drawbars between the engine and tender.

ddg Wrote:
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> When 4014 is restored, will it be necessary to
> separate the engines at the hinge point for any
> reason? Has 3985 ever been separated since it's
> initial restoration? It looks like the hinge
> mechanism might get about as much wear and tear as
> the drawbars between the engine and tender.

That was scheduled for 3985 during the winter
of 2010-2011. AFAIK, it never happened.

Dennis, if you can, find a copy of David P. Morgan's "The Mohawk That Refused to Abdicate". I love the book, as much for how Morgan writes, as for its content.

In a Chapter entitled "Happy land of the plumber's nightmares", Morgan describes his and Phil Hastings' visit, to the DM&IR backshops, in Two Harbors, MN.

Hastings took some great pictures of the shop forces working on one of the Missabe's Baldwin built 2-8-8-4's (Pages 48 & 49). Perhaps, some of the answers you seek, might lie in Hasting's photograph's.

Bob Callahan
Monticello, IN



Edited 1 time(s). Last edit at 11/24/13 12:38 by rcall31060.

I don't have that book, but have located my old copy of "Big Boy" by Kratville. Some good photos in that book.

The photos in the DPM book show a Yellowstone with the front engine unit rolled out completely from under it. The boiler had been lifted slightly by crane to allow the front unit to be rolled out and then it was lowered back with its weight carried by cribbing of heavy timbers.

"The foreman at Two Harbors told us it was no trick at all, provided the massive pin in the hinge holding the lead engine in place did not stick. 'Sometimes they drop out at the tap of a hammer,' he mused. Then he nodded at the big Baldwin with her chin up on blocks. 'We've been working on this one since seven o'clock yesterday morning.'"