Nostalgia & History > Santa Fe 3751's little sister

Probably most of the last three generations wouldn't know about 3751's little sister.  Santa Fe 3752 was built shortly after 3751 and had a long life through WWII.  But after the war, the Santa Fe mechanical department was still interested in making steam more efficient, even though diesels were already strong on the railroad during the war.  They had a lot of FT's operating from the early 40's.  It was decided to take a 3751 class northern and rebuild it with a poppet valve system built by Franklin.  To get it done, they hired an engineer from Franklin to lead the effort at the Topeka shops and selected 3752 for the honors.  I read about this engine in a book written about this engineer.  My memory is shot to h*ll so I cannot remember his name nor the book reference.  It was said that the engine had a few problems initially, but with a few adjustments here and there it turned out to be a real performer.  There was an account written by this engineer of a test trip with the engine on No. 7, the fast mail, from Kansas City to La Junta, CO, with the old Santa Fe dynamometer car.  On this trip, they determined that 3752 could get higher horsepower at higher speeds and considerably lower fuel consumption.  The highest speed recorded on the trip was 106 mph somewhere near Syracuse, KS.  Unfortunately, due to the inevitable dieselization of the Santa Fe, 3752 ended up in the scrap yard along with most of her other siblings.  About 65 years before I read the book, I was playing with a cousin in a creek near Matfield Green, KS on the main freight line between Los Angeles and Chicago.  My uncle was a signal maintainer on the CTC system on this route and my cousin and I were big time railfans, of course.  That afternoon, I heard a train coming so we climbed out of the creek to watch.  The train was all express refrigerator cars and moving at passenger train speed.  My uncle told us later that the train was all California table grapes.  The thing that I remembered about the train, however, was the sound the steam engine was making.  At that speed, one would expect to hear almost a continuous roar, with the chuffs so close together.  No.  Not this one.  It literally sounded like a machine gun flying by.  I never before or after ever heard a square exhaust like that.  3752 got to be known by its sound all up and down the line.  The operators at stations and towers knew which engine was coming by her sound.  I would love to hear that sound again.

---

Everything I've ever read about 3752, indicated that she was dead-on square.

Brian E

Posted from Android

Would make sense that the locomotive would be square, a normal spool valve is virtually analog
while a poppet valve digital, it's 1 open or zero closed. While it's totally possible (in hydraulic applications)
to both meter and modulate opening and closing rates on a locomotive a poppet valve offers zero lap, large area
and very fast reponse without the inertia issues of moving a large spool. Just of those things that got lost in the
rush to dieselization.

Out

To be a bit more accurate, the valve gear on 3752 was a Franklin rotary cam poppet valve system.  

Well, jdw3460, what you wrote matches what I read about this series of ATSF locomotives in Sunset magazine back in 1955. These were great machines, designed to use every ounce of power. What put them out of business was that diesels were cheaper to maintain. 

Yes.  Diesels brought big change to railroads.  Not only could they run all the way across the desert without water,  they could get along with only a small percentage of the manpower to keep them running.  A lot of people had to look elsewhere to make a living.  But those of us who saw the steam engines at work won't ever forget them.

My copy is in storage, but I seem to recall Vernon Smith's One Man's Locomotives talked about the 3752 at length.  Franklin rotary cam poppet valve gear, which must surely be one of the best collections of syllables ever attached to a railroad appliance, reportedly increased the engine's efficiency but incurred higher maintenance costs than the usual Walschaerts.  As I recall, it was a valve gear problem that took 3752 out of service for the last time. 

Hydraulic poppet valves are pilot actuated ie pilot pressure on an operating piston to open the valve,
essentially zero mechanical interface. The cam operated poppets used in steam used the cam to directly
open the poppets so you have several hundred psi on top of a large area poppet being lifted by the cam
action. This leads to mechanical wear and early failure, kinda why the springs and valve gear in a top fuel
car only last a few runs!

Out