Steam & Excursion > An exercise in the absurd

This idea came to me one evening as an exercise in the absurd, and a bit of fun to come up with.

What follows is a theoretical oddball of a locomotive… a twelve-cylinder cross between a Mallet compound, a triplex, a four-cylinder compound locomotive, and the duplex drive concept.  Functioning properly, it would be a well-balanced locomotive; capable of producing high torque and smooth power at higher speeds.

The locomotive?  An articulated 4-4-4-4-4 with 80-inch drivers!

To start with the locomotive would be designed with a large boiler the somewhere between the size of a large Northern and an N&W Class A.  Steam would pass through a superheater, and on to four small cylinders of 12-inch diameter on the third set of drivers.  The cylinders would drive the second axle, with two outer cylinders in the conventional fashion and two inner cylinders driving a cranked axle.  Steam admission would be controlled by rotary cam poppet valves.  Inner and outer cylinders would be quartered to each other as normal, with eight exhausts per driver revolution at 45-degree intervals.

Ahead of the third driver pair would be the articulation hinge, with the articulated frame housing the forward two sets of drivers.  This would aid adhesion, placing more weight on the forward frame than would be possible with just the lead set of two drivers.

Exhaust steam from the rear driver set would exhaust into a common receiver on the front frame, feeding two sets of four cylinders of identical configuration to the rear set.  Additionally, a reducing valve would feed high pressure steam into the receiver to charge it for starting the locomotive.  Exhaust piping of generous proportions from the low-pressure cylinders would minimize back pressure.

The exhaust from the lead cylinder set would pass through an exhaust nozzle in the smokebox in the standard way, drafting the fire.  Exhaust steam from the middle set would pass into a feedwater heater and condenser, with condensate being returned to the tender for reuse.  This arrangement would not only draft the fire, but also recycle nearly half of the locomotive’s boiler water.

With the combination of small cylinders driving sets of two drivers and lightweight reciprocating parts, speed would not be restricted as with the standard Mallet compound.  Additionally, the combination of cross-balancing and the rodding from four cylinders would make for a smooth-riding locomotive at speed.  It would also be a locomotive that would be unusually efficient in is consumption of fuel and water.

An absurd idea?  Yup.

A pain in the ass to maintain?  Yup.

But it would be an interesting machine, to say the least.

This conceptual locomotive is a hodge-podge of different ideas taken from actual locomotives, thrown into a blender, and spit back out in a single over-the-top amalgamation.  Some of these are as follows:

Four cylinders per driver set were not uncommon in Europe, and four-cylinder passenger Pacifics in the U.K. come to mind.  In this case, the four-cylinder concept is combined with the small cylinders powering a pair of drivers from the P.R.R. T-1.

The single high-pressure cylinder exhausting into a pair of low-pressure cylinders of the same size has also worked.  Two examples are the Erie and Virginian triplexes and the Baldwin 60,000.  One could argue that the triplexes were unsuccessful but their downfall was in boilers that lacked capacity, rather than running gear issues.  The Baldwin locomotive ran high-pressure steam in its center cylinder, and low-pressure steam in the outer pair.  This concept does the same basic thing, except four cylinders proved steam to eight rather than one to two.

Condensing locomotives ran successfully in Europe and South Africa.  Also, the triplex designs used exhaust from only one set of low-pressure cylinders to draft the fire.

Now we have some ideas that to my knowledge are untested:

The uneven articulation with two sets of drivers on the hinged portion… how would this impact the overall stability of the locomotive at speed?  Would the hinge point be better located between the first and second pair?

Would the exhaust nozzle setting to get a proper draft from the lead four cylinders result in excessive cylinder back-pressure, given that only half of the steam being used by the locomotive is being exhausted into the atmosphere?  With less steam passing through the nozzle, the nozzle must be constricted to give a stronger blast.  How constricted would the exhaust flow have to be?  Also, would this have an effect on the other set of low-pressure cylinders?

Would a rotary cam poppet valve assembly be viable with one side of the locomotive driving the valves for both the inner and outer cylinders?  Some poppet valve designs that were tried late in the steam era turned out not to be rugged enough.  This application would be even more demanding.

So, what do you think?

Besides the fact that it is a ridiculous idea that would never be built……

Mary McPherson
Dongola, IL
Diverging Clear Productions

I think the U S Patent Office is going to require a working model on this one!

My head is swimming.  Does it have a booster?



Edited 1 time(s). Last edit at 07/17/19 09:45 by Frisco1522.

Mary...you are back!   Are you Ok?

Keystone1 Wrote:
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> Mary...you are back!   Are you Ok?

I didn't know Mary was "gone". Maybe you are thinking of SPFan, Margret?



Edited 1 time(s). Last edit at 07/17/19 12:34 by HotWater.

Where does the JP-57 engine fit in? Or is that for the stoker feed?

Wes or Jack: Can it be built?

Some years back (like, maybe in the 70s??) didn't TRAINS have an article about Hitler's proposed SUPER railroad? As I kinda-sorta recall the fuhrer promised that everything, including steam locomotion would be the most "Tremendous", biggest, bestest, fastest, most technologically advanced, "like the world has never seen before". Of course, it goes without saying that any new steam engines would have blue eyes & blonde hair... ;^)

Lance/199

Of course it can be built...

Would be best if burned waste fryer-oils, or solid fuels prepared from combustible trash ( that ordinarily would be headed for a landfill).

I would advocate for a multi-port exhaust scheme similar to the UP’s 3900’s and 4000’s.
The multi-port designs work because of the (vast surface-area increase) in multiple-columns of steam having greater exposed surface ( impingement ) area compared to a single-column exhaust jet..

And as we have seen, the multi-jet readily ‘drafts’  a solid-fuel firebed as well as oil burners....UP did not need to modify the front end designs, with the changes of fuel types.

The frame casting and machining would probably be re-worked from the original concept...
but, that’s a product of the compromises necessary in the final manufacturing, engineering concepts.

Biggest challenge is Constant Utilization....reducing as much as possible all “ utilization cripplers” related to crew scheduling, 
freight shipping schedules, and normal daily schedule interruptions.
 Sitting around and waiting, while maintaining a fire,  is the true enemy of the return of the steamers.
Diesels do a better job of sitting around, unused...waiting for hours on-end..sometimes days...
Manning a fleet of steamers in such conditions is extremely expensive...

You’d have to build multiple copies ( probably 6 to start with) in order to make a credible test bed for the next generation of recip steamers....

Welcome back, Mary!
Let me know when you hit the Big One...we could have a prototype on the rails in 36 months... !!!!

Wes.



Edited 2 time(s). Last edit at 07/17/19 13:04 by wcamp1472.

Needs the accordian boiler like the ATSF 2-10-10-2

Keystone1 Wrote:
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> Mary...you are back!   Are you Ok?

Not at all.  I'm suffering from the residual effects of contracting a severe case of "Charger Power" back in 1979.  It's horrible.

Seriously, I've been working on a video retrospective on the "Air Coryell" era San Diego Chargers.  Tired of waiting for NFL Films to get around to it.

Mary McPherson
Dongola, IL
Diverging Clear Productions



Edited 1 time(s). Last edit at 07/18/19 07:04 by MaryMcPherson.

SD45X Wrote:
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> Needs the accordian boiler like the ATSF 2-10-10-2

Can we have Weird Al play it?

Mary McPherson
Dongola, IL
Diverging Clear Productions

SD45X Wrote:
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> Needs the accordian boiler like the ATSF 2-10-10-2

The ATSF 2-10-10-2 had rigid boilers.  Several of the 2-6-6-2's had hinged boilers, some with ball-and-socket joints, others with accordian joints,

Stuart

Interesting, I was always under the impression that the 2-10-10-2s indeed had hinged boilers though the hinge on the
2-6-6-2 is really apparent.

Out



Edited 1 time(s). Last edit at 07/18/19 16:31 by callum_out.