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.
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.
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.
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.
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.
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
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.
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 |
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