I saw A train eng. yrs ago at Sacremento,What was it?

Question

This was huge steam locomotive,I believe it had 16 drivers Or power wheels,This giant had the crew comp.in fwd end of motor,

as opposed to others with crew compartmen behind.The info. given was,it was designed this way because of long tunnels it

went thru and crews didn"t have to be overcome by smoke.

Answer 1

contact union pacific railroad they know.

Answer 2

that was a 4-8-8-2 cab forward engine,check wikepedia under steam locomotive.The Southern Pacific was the only railroad to operate engines of this wheel arrangement. All were built by the Baldwin Locomotive Works

Answer 3

Indeed this was a 4-8-8-2, and the last one built for the Southern Pacific #4294, the only Class 1 railroad to operate these engines designed to run "cab forward".  Its class is AC-12, (Articulated Consolidated) and is the last of its kind.

There were many versions of this type over the years.  The first were an operating type called a "Mallet", so named for its inventor.  Though many called all of the articulateds "mallets", the only true mallets were the very fist generations, up and through the AC-5s.  A true mallet is what is known as a "double expansion" system or, more correctly "compound engine."  The articulateds had a set of low pressure cylinders, and a set of high pressure cylinders.  When operating, the exhaust steam from the low pressure cylinders was expanded a second time, in the high pressure cylinders before exhausted through the "smoke box".

There were also locomotives with a single engine under the boiler that employed the mallet system.  These had a low pressure cylinder on one side, and a high pressure cylinder on the opposite side.  These were referred to as "cross-compound" engines.  Now that you know what to look for, you'll be able to identify the mallets easily.

I believe beginning with class AC-6 and later, SP's cab forwards were constructed as a "single expansion", or simple expansion engines.  Another introduction with this class and up, was running on "super heated" steam.  As its name implies, able to develop more power than the old "saturated steam" engines, that were also known as "soakers."  A number of the older models were converted to single expansion engines to finish their service.

At 500 tons wet, these were the largest of the engines operated by the SP.  They were indeed designed specifically for the run from Roseville, California, over the Sierra Nevada through the "Donner Pass", althoung these engines worked all over the SP system.  There were over 40 miles of snowshed and tunnels, and conditions for the crews on conventional engines was pretty tough.  Little known is that the many conventional type engines often used in helper service when power was short, like the 2-8-0 "consolidation" were equipped with a respirator, if you can call it that.  There was a hose with a mask running from the main air reservoir.  Health wise, this was not too far removed from the exaust, but better than nothing.  It kept them alive, anyway.

This was a good question.  I'll be going into depth on this and others via my 360 blog, accessable through this site.