Atlantic Coast Line 4-6-2 "Pacific" Type Locomotives

Class P (Locobase 7673)

Data from ACL 4 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

These were the first ACL Pacifics and the last to be delivered with saturated boilers (The first 10 used Walschaert radial valve gear while the last 5 had Baker gear (by Pilliod). Later ACL 4-6-2s had shorter boiler tubes. Some were later superheated; see Locobase 7674.

Class P - superheated (Locobase 7674)

Data from ACL 4 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

When compared to the superheated P-1-S delivered a year later (Locobase 7681), the pressure vessel in the only set of Pacifics it had purchased with saturated boilers (Locobase 7673) was quite a bit larger. As a result, superheating the design actually added overall heating surface area to the boiler. Moreover, unlike many retrofits that took the opportunity of superheating to reduce boiler pressure, the ACL maintained its P-class engines at their original settings. The result was a powerful express passenger engine.

Class P-1-S (Locobase 7681)

Data from ACL 12 - 1954 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

P-1s were delivered by Baldwin with superheaters and piston valves, thus becoming the first of the line's Pacifics to have that valuable addition. They were passenger engines as opposed to the mixed-traffic 4-6-2s the ACL would soon purchase.

Class P-2 (Locobase 7669)

Data from ACL 12 - 1954 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

This was the third class of Pacifics to run on the ACL and the variant designed to work freight trains. As with most other such designs, the ACL found them less satisfactory than other arrangements. A good factor of adhesion and a relatively large boiler probably accounted for their surviving to the end of steam.

Class P-3 (Locobase 7670)

Data from ACL 12 - 1954 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

Taking the grate of the P-2 (Locobase 7669) as is, and trimming the boiler tubes and flues by two feet, then carrying it on 69" drivers, Baldwin came up with a successful mixed-traffic Pacific that served throughout the system. Like the P-2s, the P-3s had relatively generous 14"-diameter piston valves.

Class P-4 (Locobase 7672)

Data from ACL 12 - 1954 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

P-4s were essentially P-3s (Locobase 7670) with more tubes and flues. Baldwin delivered 7 in 1917 and the other 20 in 1918. Like the earlier ACL Atlantics, this class had relatively generous 14"-diameter piston valves. For some reason, a few of the class (e.g., 458, 460, 463, 473, & 480) had 18-ft

Class P-5-A (Locobase 1417)

Data from 1946 ACL locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

This was the "light" Pacific design standardized by the government-run USRA created in World War I and built by Baldwin and Alco. Alco-Brooks and Alco-Richmond delivered these to the ACL.

Slightly modified versions were built as the P-5-B, which see.

Class P-5-B (Locobase 448)

Firebox had combustion chamber contributing 44 sq ft of heating surface.. Almost identical to USRA light Pacific design except for smaller driving wheels and slightly less tube and flue area.

165 built by Baldwin in 1922-1926 as dual-service locomotives. J Parker Lamb (in Perfecting the American Steam Locomotive, 2003) says that this dual-purpose use was unique among US Pacific operators. The reason lies with the ACL's type of freight traffic -- typically lightweight agricultural products. Like the New York Central, moreover, much of the ACL consisted of water-level running.

Retired in 1950-1953.

Specifications
Class	P	P - superheated	P-1-S	P-2	P-3	P-4	P-5-A	P-5-B
Locobase ID	7673	7674	7681	7669	7670	7672	1417	448
Railroad	Atlantic Coast Line (ACL)	Atlantic Coast Line (ACL)	Atlantic Coast Line (ACL)	Atlantic Coast Line (ACL)	Atlantic Coast Line (ACL)	Atlantic Coast Line (ACL)	Atlantic Coast Line (ACL)	Atlantic Coast Line (ACL)
Whyte	4-6-2	4-6-2	4-6-2	4-6-2	4-6-2	4-6-2	4-6-2	4-6-2
Road Numbers	260-274	260-274	456-482	400-411	411-455	456-482	1500-1569	1600-1764
Gauge	Std	Std	Std	Std	Std	Std	Std	Std
Builder	Baldwin	ACL	Baldwin	Baldwin	Baldwin	Baldwin	Several	Baldwin
Year	1911		1912	1913	1914	1917	1918	1925
Valve Gear	Baker or Walschaert	Baker or Walschaert	Walschaert	Walschaert	Walschaert	Walschaert	Baker	Walschaert
	Locomotive Length and Weight
Driver Wheelbase	13'	13'	13'	13'	13'	13'	13'	13'
Engine Wheelbase	33'	33'	33'	33'	33'	33'	34.92'	34.91'
Ratio of driving wheelbase to overall engine wheebase	0.39	0.39	0.39	0.39	0.39	0.39	0.37	0.37
Overall Wheelbase (engine & tender)	67.56'	67.56'	67.52'	67.48'	67.48'	67.19'	70.79'	70.82'
Axle Loading (Maximum Weight per Axle)	48200 lbs	48200 lbs	48100 lbs		48700 lbs	52600 lbs	58200 lbs
Weight on Drivers	138950 lbs	138950 lbs	139800 lbs	145000 lbs	139400 lbs	151050 lbs	168000 lbs	177460 lbs
Engine Weight	220850 lbs	220850 lbs	225900 lbs	225900 lbs	227300 lbs	243850 lbs	278000 lbs	280610 lbs
Tender Light Weight	159800 lbs	159800 lbs	162733 lbs	159800 lbs	166220 lbs	166220 lbs	188000 lbs	188000 lbs
Total Engine and Tender Weight	380650 lbs	380650 lbs	388633 lbs	385700 lbs	393520 lbs	410070 lbs	466000 lbs	468610 lbs
Tender Water Capacity	8000 gals	8000 gals	8000 gals	8000 gals	8000 gals	8000 gals	10000 gals	10000 gals
Tender Fuel Capacity (oil/coal)	15 tons	15 tons	12 tons	12 tons	12 tons	12 tons	16 tons	16 tons
Minimum weight per yard of rail on which locomotive could run	77.19 lb rail	77.19 lb rail	77.67 lb rail	80.56 lb rail	77.44 lb rail	83.92 lb rail	93.33 lb rail	98.59 lb rail
	Geometry Relating to Tractive Effort
Driver Diameter	72"	72"	73"	64"	69"	69"	73"	69"
Boiler Pressure	200 psi	200 psi	200 psi	200 psi	200 psi	200 psi	200 psi	200 psi
Cylinders (dia x stroke)	22" x 28"	22" x 28"	22" x 28"	22" x 28"	22" x 28"	23" x 28"	25" x 28"	25" x 28"
Tractive Effort	31998 lbs	31998 lbs	31559 lbs	35998 lbs	33389 lbs	36493 lbs	40753 lbs	43116 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort)	4.34	4.34	4.43	4.03	4.18	4.14	4.12	4.12
	Heating Ability
Firebox Area	220 sq. ft	220 sq. ft	230 sq. ft	230 sq. ft	248 sq. ft	268 sq. ft	242 sq. ft	268 sq. ft
Grate Area	54 sq. ft	54 sq. ft	54 sq. ft	54.20 sq. ft	54.20 sq. ft	56.50 sq. ft	66.70 sq. ft	66.70 sq. ft
Evaporative Heating Surface	3547	3005	2933	2934	2649	3420	3333	3210
Superheating Surface		660	590	587	524	782	794	794
Combined Heating Surface	3547	3665	3523	3521	3173	4202	4127	4004
Evaporative Heating Surface/Cylinder Volume	287.93	243.93	238.09	238.17	215.03	254.00	209.52	201.79
	Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation	10800	10800	10800	10840	10840	11300	13340	13340
Same as above plus superheater percentage	10800	12744.88	12608.69	12647.18	12630.15	13402.95	15906.50	15985.34
Same as above but substitute firebox area for grate area	44000	51923.60	53703.66	53668.84	57791.11	63575.06	57711.75	64228.97
Power L1	9053.25	19569.59	18553.52	16221.08	16065.68	20153.31	17879.89	16910.29
Power MT	430.92	931.49	877.76	739.89	762.24	882.43	703.90	630.24