Southern Pacific P-4

[SP-4-2401]

Thanks for any additional Information
I,ll be on Vacation myself.

[Gary Bonine]

Got it. 2401 had 155,000 lbs. on the drivers and 58,000 lbs. on the trailing truck.

[SP-4-2401]

Hallo
Thanks for the Infos

[Miserlou57]

A little late to the game, but here's the full print.

http://imgur.com/a/t09IN

[Gary Bonine]

Looks like that is from SP's locomotive diagram book, something I am trying to acquire for myself.

[jcbrock]

A little late to the game, but here's the full print.

Answered a question for me, now I know the right BL is a BL-3. Thanks!

[Rwilliams]

Dug around and found my copy of the Southern Pacific steam locomotive compendium by Diebert & Strapac. Published in 1987, it covers most known SP steam locomotives and their modifications from factory to scrapping or selling to another railroad.

Beginning in the Spring of 1927 the rebuilding program of some P-1 class locomotives into the P-4 class was started. Only 10 locomotives were rebuilt into the new class when the program was stopped in late 1929. Changes included new cylindercastings, outside Walschaert valve gear, Delta trailing truck, C-2 booster, the 3BL feedwater heater, and a sloped style cab front known as the Sport Cab. This allowed for easier access by the shop crews to some of the flexible staybolts of the firebox. A larger tender was the final touch on the transition. The boiler had already been modified for superheating back in 1918. The boiler pressure was also increased from 200 to 210 PSI. The 2401 was the final P-1 to be given the P-4 treatment in LA General Shops with a completion date of 12-23-29. Just in time for Christmas and the Depression.

The cylinder bore was increased with the new cylinder casting from 22 inches in diameter to the slightly larger 23 inches in diameter. The valve chamber bore was also increased to feed the bigger cylinder bores.

The total weight of the improved P-4 locomotive was 265,100 pounds. Weight on the drivers, including the trailer truck booster axle was 155,000 pounds. Just the addition of the feedwater heater was worth an increase of 3000 pounds of weight. No wonder some of the hoggers always wanted a locomotive with a feedwater heater to increase their pay.

The tractive effort was now 34,320 pounds and with the booster tractive effort of 11,520, the total tractive effort was 45,840 pounds. This improved tractive effort was equal to the average Mikado of the day.

Built in August of 1904, the 2401 served well until being wrecked at Thermal, California in June of 1950. It was scrapped in Los Angeles October of 1950. The wreck caused the 2401 to become the first of the P-4 class to be scrapped. The remainder followed in 1951 through the end of 1954.

[Doug_Edwards]

To add a little more info for those interested, it is easier to list
what was reused rather than what added new to the rebuild of this
class.

The major items reused were the boiler and attachments (domes, stack,
bell, etc.), lead truck, drive wheels, and pilot beam. That was
pretty much it. The running gear aside from the reused drivers was
totally new. The frame was of the same design as the MT class with
the frame being one piece under the cylinders. The P1 and P3 classes
that these engines were rebuilt from had a split frame that went under
and over the cylinders, and both pieces were bolted to the main
portion of the frame behind the cylinders. The one piece frame pieces
were much stronger and I suspect cheaper to build as well. All the
frame spreaders were new. The rear frame extension and trailing truck
of course were new as well.

The new cylinders were made with extended valve chambers that
shortened the steam passages from valve to cylinder, thus using less
steam per stroke, due to the lesser volume of steam wasted in the
passages. The cylinder pattern was the same as for the A6 Atlantic
class that was rebuilt at the same time (with the same rebuild
features), but with an option on the pattern to extend the saddle a
couple more inches for the Pacifics. The two classes had the same
valve events and shared the valve and valve chest bushings with the
E27 class 4-4-0, the T32 and T40 class 4-6-0. Commonality of parts,
you know!

I puzzled for a long time why more of the A6 and P4 class engines were
not built. An old timer who worked in the engineering dept. on Market
street clued me in that these locos were purpose built for special
needs. This makes sense when you consider all the Consols, Mikes,
Tenwheelers and Moguls of the same vintage, of which none except the
10 M21 class moguls (and T40 class) received a like treatment.

The term "rebuild" on these locos does not reflect how extensive the
upgrades were, since the rebuilt locos comprised of essentially a new
loco with a reused boiler. I suspect that the term "rebuild" is only
valid for accounting or tax purposes, since as a "rebuild", the costs
of rebuilding the locos would be deprecated/written off immediately
rather than over a number of years had the locos been purchased new.
This would have been especially true for the M21 moguls, as they used
even less parts from the MM1 2-6-6-2's that they were "rebuilt" from
then the P4 or A6 classes did.

The T40 class 4-6-0 (one loco), also shared a commonality of parts and
design with the P4 and A6 classes. I never heard what the reasoning
for it was. It was the heaviest 4-6-0 built, btw, and the M21 moguls
the heaviest and most powerful 2-6-0's, at around 45,000TE.

Perhaps more than anyone wanted to know, but a bit more trivia on this
and related classes.

Regards,

Doug

[SP2403]

Hello my friend, I am now also here. Charly

[SP-4-2401]

Hi Charly