This was an early Pacific that can nicely illustrate the difference between an Atlantic and a Pacific. Locobase 4096 shows the 1901 E-1 4-4-2s. Compared to that set of Atlantics, the I-1 had a nearly identical firebox, cylinders only 2" greater in diameter (and supplied through similar 12" piston valves), but tubes lengthened by 4 ft (and their number increased by about 2 dozen), and an extra axle of adhesion. Firebox heating surface included 28 sq ft of arch tubes.
This same locomotive would be superheated; see Locobase 9046.
In superheating the Harriman Pacifics (Locobase 5313), the Alton installed its standard 28-element superheater assembly that included a reduction in tube count as well as individual tube diameter. Because the Harriman's had smaller boilers to begin with, the result was a high degree of superheat that undoubtedly increased their power.
The two sub-variants of the I-5 class went into service as saturated steam locomotives; see Locobases 9051-9052.
When the Alton's 4-6-2s were superheated, the I-5s remained divided into two subgroups based on driver diameter. They were otherwise identical except for a 5,500-lb difference in adhesion weight in favor of the 77"-driver engines shown here.
This class had some free-steaming qualities inherent in a relatively large boiler and 14" piston valves, but the Harriman Standard grate area may have prevented a full exploitation of a decent amount of superheat.
See Locobase 9053 for comments on the superheating of this HCS design.
These Harriman Pacifics were the equivalent of the Southern Pacific's P-6 class. Drury (1993) notes the tapered boiler course that joined the extended firebox to the front course. Although they were delivered as long ago as 1913, this decade of locomotives was the last new passenger power the Alton would buy. Drury notes that a 1943-1944 upgrade included a new superheater, Nicholson thermic syphons, and Worthington feedwater heaters.
Both early Pacifics underwent a superheating makeover that confined itself to redoing the boiler; this entry refers to the 73" diameter variant. The usual subtraction from the total tube number in favor of flues occurred, but was accompanied by an unusual reduction in tube diameter at the same time. The firebox now showed 29.7 sq ft of arch tubes as contributing to firebox heating surface. The engine still had its 12" piston valves.
The makeover kept the locomotive in service for more than a decade and a half before it was retired in September 1938.
In the same month that Baldwin built the 73"-drivered I-1 (Locobase 9045), it also produced this express passenger version. The grate remained the same size, as did the cylinders (with their 12" piston valves), but the boiler contained 50 fewer tubes.
The I-2 was superheated; see Locobase 9048.
Although the saturated version of this design was quite different from the I-1 (Locobase 9045), the superheated conversion resulted in a locomotive whose only differences were the taller drivers and a greater adhesion weight.
Like the 600, the 601 was withdrawn in September 1938.
The grate seems much too small for the boiler, although the relatively small cylinders kept the grate demand factor reasonable. An article in the October 1908 American Engineer & Railroad Journal comments that "has the largest ratio ...of heating surface to grate area in our records."
It's odd that the adoption of the Pacific layout didn't lead to a wider grate. (Drury - 1993 - comments on the narrow firebox, but ascribes 22"cylinders to this batch, which the RAG clearly shows had 23" pistons.)
RAG's equivocal prediction was"...these are high-powered machines for passenger service, and as the design has been worked out in light of experience with locomotives built some time ago, the performance should be satisfactory."
Locobase 9050 shows the results of superheating this quintet.
The superheated I-4 Pacifics retained the narrow firebox they had when originally delivered as saturated-steam engines. A later update would remove the boiler with the small grate and replace it with the one used by the I-5 engines. Even in 1930, however, 2 of the 5 -- 605 & 609 -- would still be using the narrow grate.
Except for the 5270 (ex-605), which for some reason was retired in August 1933, the I-4s carried on through World War II before being scrapped in October 1946 (5271), January 1947 (5272-5273), and March 1947 (5274).
These were the first five locomotives of a 15-engine order from Brooks. They had the tallest drivers of any Alton class, 14" piston valves, and the Harriman-Pacific size grate. See Locobase 9051 for the 77"-drivered variant.
These were the first five locomotives of a 15-engine order from Brooks. They had the tallest drivers of any Alton class, 14" piston valves, and the Harriman-Pacific size grate. See Locobase 9054 for the superheated variant.
Baldwin appears to have taken the firebox of the E-1 Atlantic that immediately preceded it and attached to it a longer boiler less densely packed with tubes. At the same time, cylinder diameter grew by 2 inches. The result was a design that put 30,000 more lb on the drivers.
Drury (1993) says these were Harriman Pacifics and they do have the standard grate. They entered service with Stephenson gear and inside-bearing trailing trucks, but were later fitted with outside Walschaerts valve gear and outside-bearing trucks. They were also superheated
| Specifications | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Class | I-1 | I-3 - superheated / P-12 | I-5A - 77"" / P-15 | I-5A - 80"" / P-14 | I-6 / P-16 | I1 - superheated / P-10 | I2 | I2 - superheated / P-11 | I4 | I4A - small grate / P-13 | I5 - 77"" drivers | I5 - 80"" drivers | P (Harriman)/I3 |
| Locobase ID | 9045 | 9049 | 9053 | 9054 | 7584 | 9046 | 9047 | 9048 | 4199 | 9050 | 9051 | 9052 | 5313 |
| Railroad | Chicago & Alton (C & A) | Chicago & Alton | Chicago & Alton | Chicago & Alton | Chicago & Alton | Chicago & Alton (C & A) | Chicago & Alton (C & A) | Chicago & Alton (C & A) | Chicago & Alton (C & A) | Chicago & Alton (C & A) | Chicago & Alton (C & A) | Chicago & Alton (C & A) | Chicago & Alton (C & A) |
| 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 | 4-6-2 | 4-6-2 | 4-6-2 | 4-6-2 | 4-6-2 |
| Road Numbers | 600 | 602-604 | 625-634 | 620-624 | 650-659 / 5290-5299 | 600 | 601 | 601 | 605-609 /5270-5274 | 605-609 | 625-634 | 620-624 | 602-604 / 5267-5269 |
| Gauge | Std | Std | Std | Std | Std | Std | Std | Std | Std | Std | Std | Std | Std |
| Builder | Burnham, Williams & Co | C & A | C & A | C & A | Alco-Brooks | C & A | Burnham, Williams & Co | C & A | Burnham, Williams & Co | C & A | Alco-Brooks | Alco-Brooks | Burnham, Williams & Co |
| Year | 1903 | 1920 | 1922 | 1922 | 1913 | 1922 | 1903 | 1922 | 1908 | 1920 | 1910 | 1909 | 1904 |
| Valve Gear | Stephenson | Walschaert | Walschaert | Walschaert | Walschaert | Stephenson | Stephenson | Stephenson | Walschaert | Walschaert | Walschaert | Baker | Stephenson |
| Locomotive Length and Weight | |||||||||||||
| Driver Wheelbase | 13.75' | 13.33' | 13.75' | 13.95' | 13.33' | 13.75' | 13.75' | 13.75' | 13.75' | 13.25' | 13.75' | 13.75' | 13.33' |
| Engine Wheelbase | 32.67' | 33.33' | 34.71' | 33.75' | 35.67' | 32.67' | 32.67' | 32.67' | 32.67' | 34.71' | 34.71' | 24.71' | 33.33' |
| Ratio of driving wheelbase to overall engine wheebase | 0.42 | 0.40 | 0.40 | 0.41 | 0.37 | 0.42 | 0.42 | 0.42 | 0.42 | 0.38 | 0.40 | 0.56 | 0.40 |
| Overall Wheelbase (engine & tender) | 65.46' | 63.83' | 66.29' | 65.46' | 65.62' | 65.46' | 63.92' | 65.46' | 65.70' | 65.94' | 66.29' | 66.29' | 62.73' |
| Axle Loading (Maximum Weight per Axle) | 48100 lbs | 52800 lbs | 51000 lbs | 49800 lbs | |||||||||
| Weight on Drivers | 138900 lbs | 138000 lbs | 154000 lbs | 149500 lbs | 163500 lbs | 138900 lbs | 145000 lbs | 145000 lbs | 146500 lbs | 146500 lbs | 154100 lbs | 149500 lbs | 135119 lbs |
| Engine Weight | 219500 lbs | 219000 lbs | 248000 lbs | 248000 lbs | 278000 lbs | 219500 lbs | 221300 lbs | 221300 lbs | 243200 lbs | 243200 lbs | 249100 lbs | 248000 lbs | 221509 lbs |
| Tender Light Weight | 174350 lbs | 173520 lbs | 167600 lbs | 167600 lbs | 175100 lbs | 174350 lbs | 171250 lbs | 171250 lbs | 161800 lbs | 166000 lbs | 167600 lbs | 167600 lbs | 156000 lbs |
| Total Engine and Tender Weight | 393850 lbs | 392520 lbs | 415600 lbs | 415600 lbs | 453100 lbs | 393850 lbs | 392550 lbs | 392550 lbs | 405000 lbs | 409200 lbs | 416700 lbs | 415600 lbs | 377509 lbs |
| Tender Water Capacity | 8500 gals | 9000 gals | 8500 gals | 8500 gals | 9000 gals | 8500 gals | 9000 gals | 8500 gals | 8250 gals | 8250 gals | 8500 gals | 8500 gals | |
| Tender Fuel Capacity (oil/coal) | 14 tons | 15 tons | 14 tons | 14 tons | 15 tons | 14 tons | 14 tons | 14 tons | 12.5 tons | 14 tons | 14 tons | 14 tons | tons |
| Minimum weight per yard of rail on which locomotive could run | 77 lb rail | 76.67 lb rail | 85.56 lb rail | 83.06 lb rail | 90.83 lb rail | 77 lb rail | 81 lb rail | 81 lb rail | 81 lb rail | 81 lb rail | 86 lb rail | 83 lb rail | 75 lb rail |
| Geometry Relating to Tractive Effort | |||||||||||||
| Driver Diameter | 73" | 77" | 77" | 77" | 77" | 73" | 80" | 80" | 73" | 73" | 77" | 80" | 77" |
| Boiler Pressure | 200 psi | 200 psi | 200 psi | 200 psi | 200 psi | 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" | 23" x 28" | 23" x 28" | 25" x 28" | 22" x 28" | 22" x 28" | 22" x 28" | 23" x 28" | 23" x 28" | 23" x 28" | 23" x 28" | 22" x 28" |
| Tractive Effort | 31559 lbs | 29920 lbs | 32702 lbs | 32702 lbs | 38636 lbs | 31559 lbs | 28798 lbs | 28798 lbs | 34494 lbs | 34494 lbs | 32702 lbs | 31476 lbs | 29920 lbs |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 4.40 | 4.61 | 4.71 | 4.57 | 4.23 | 4.40 | 5.04 | 5.04 | 4.25 | 4.25 | 4.71 | 4.75 | 4.52 |
| Heating Ability | |||||||||||||
| Firebox Area | 230 sq. ft | 208.70 sq. ft | 232 sq. ft | 232 sq. ft | 240 sq. ft | 231.70 sq. ft | 202 sq. ft | 231.70 sq. ft | 206 sq. ft | 236 sq. ft | 202 sq. ft | 202 sq. ft | 180 sq. ft |
| Grate Area | 54 sq. ft | 49.50 sq. ft | 49.50 sq. ft | 49.50 sq. ft | 70.40 sq. ft | 54 sq. ft | 54 sq. ft | 54 sq. ft | 33 sq. ft | 49.50 sq. ft | 49.50 sq. ft | 49.50 sq. ft | 49.50 sq. ft |
| Evaporative Heating Surface | 4078 | 2847 | 3345 | 3345 | 3951 | 3099 | 3438 | 3099 | 3927 | 3349 | 4071 | 4071 | 3054 |
| Superheating Surface | 651 | 745 | 745 | 784 | 651 | 651 | 745 | ||||||
| Combined Heating Surface | 4078 | 3498 | 4090 | 4090 | 4735 | 3750 | 3438 | 3750 | 3927 | 4094 | 4071 | 4071 | 3054 |
| Evaporative Heating Surface/Cylinder Volume | 331.03 | 231.10 | 248.43 | 248.43 | 248.37 | 251.56 | 279.08 | 251.56 | 291.66 | 248.73 | 302.35 | 302.35 | 247.91 |
| Computations Relating to Power Output (More Information) | |||||||||||||
| Robert LeMassena's Power Computation | 10800 | 9900 | 9900 | 9900 | 14080 | 10800 | 10800 | 10800 | 6600 | 9900 | 9900 | 9900 | 9900 |
| Same as above plus superheater percentage | 10800 | 11742.45 | 11703.30 | 11703.30 | 16411.30 | 12636 | 10800 | 12636 | 6600 | 11682 | 9900 | 9900 | 9900 |
| Same as above but substitute firebox area for grate area | 46000 | 49508.08 | 54851.83 | 54851.83 | 55947.62 | 54218 | 40400 | 54218 | 41200 | 55696 | 40400 | 40400 | 36000 |
| Power L1 | 10327 | 20312.92 | 21369.05 | 21369.05 | 19695.37 | 19983 | 9628 | 21899 | 8958 | 20302 | 9686 | 10063 | 8238 |
| Power MT | 491.73 | 973.53 | 917.74 | 945.36 | 796.71 | 951.51 | 439.16 | 998.88 | 404.42 | 916.55 | 415.72 | 445.19 | 403.24 |
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