Because of the Government's restrictions on tank car size that went into effect on 1 December 1970, the era of RailWhale construction was quite brief.  The first prototype was completed in 1963, followed by a second in 1965; but all of the other 817 cars were built within a 5-year period, between January 1966 and November 1970. 

The first RailWhale was UTLX 83699, an 8-axle car completed by Union Tank Car in March 1963.  With a light weight of 176,700 pounds and 70-ton trucks (6x11-inch bearings and 33-inch wheels), its load limit was a fairly low 263,000 pounds; but its capacity of 50,105 gallons would be the second highest of any tank car.  This would be Union Tank Car's only RailWhale; but it was used in revenue service and remained in the Official Railway Equipment Register for 20 years before going to the Galveston Island Railroad Museum in 1983.  One of only three preserved RailWhales, it was scrapped after being damaged by Hurricane Ike in 2008.

The second RailWhale was another 8-axle car, GATX 96500, built by General American Transportation Co. in September 1965.  Like UTLX 83699, it too rode on 70-ton trucks.  It weighed a hefty 193,000 pounds, about eight tons more than the UTLX car, so its load limit was lower by the same amount; but it could hold 10,000 gallons more, a whopping 60,018!  Only DUPX 28050-28090 weighed more – and only by 700 pounds – but they rode on 100-ton trucks so their load limit was 85,000 pounds more.  GATX 96500 was never used in revenue service; nevertheless, General American went on to own the second largest fleet of RailWhales, as listed below.  The car was donated to the National Museum of Transport in St. Louis in 1971. 

ORIGINAL OWNERS
MARK	6 axle	8 axle	TOT	OWNER
ACFX‑SHPX	68	25	93	The Shippers Car Line Div. of ACF Industries
CELX	98	3	101	Celanese Corp.
DUPX	182	116	298	E. I. du Pont de Nemours & Co., Inc.
ESMX	0	34	34	Essem Corp.
GATX	96	20	116	General American Transportation Corp.
GCX	0	55	55	General Chemical Div., Allied Chemical Corp.
IAPX	5	0	5	Industrial Air Products Co.
MCPX‑MONX	37	0	37	Monsanto Company
NATX	57	0	57	North American Car Corp.
PRR	2	0	2	Pennsylvania Railroad
RAIX	0	20	20	United States Leasing International
UTLX	0	1	1	Union Tank Car Co.
TOTAL	545	274	819

The first two RailWhales cars were engineering exercises to try new ideas and to see who could produce the biggest tank car, but they were not really practical prototypes for future production.  Both of them cars had heavy and expensive-to-make whalebelly tanks.  With the exception of the Monsanto elemental phosphorus cars, production RailWhales had easier-to-build straight tanks. 

All of the 6-axle RailWhales were built with 150-ton trucks (6½x12-inch bearings and 36-inch wheels) and a gross rail load (GRL) of 394,500 pounds, although on many cars this was rounded down to an even 394,000!  At least four of the 396K cars were refitted with 7x12 bearings, the size used on 125-ton 2-axle trucks, raising their GRL to 472,500 pounds.  Most 8-axle cars had 100-ton trucks and a GRL of 526,000 pounds, but 77 of them (including the two prototypes) rode on 70-ton trucks and had a GRL of only 440,000 pounds. 

PRODUCTION CAR CHARACTERISTICS
AXLES	GALLONS	LIGHT WEIGHT	LOAD LIMIT	GROSS RAIL LOAD
6	22,500-43,000	93,000-139,000	255,000-295,000	394,500
8	27,000-48,000	131,000-194,000	298,000-395,000	440,000 or 526,000

As with many freight cars, a RailWhale's physical size was determined by the density of its intended load.  Eight-axle cars for very dense tetraethyl lead were about 70 feet long and held around 27,000 gallons, and a few cars built for intermediate density loads were about 80 feet long and held about 33,000 gallons; but most of the 8-axle cars were about 90 feet long with capacities of around 42,000 gallons.  The top capacity was held by ESMX 4800-4833 at 48,000 gallons, followed closely by CELX 7500-7502 at 47,000.  The table below lists the densities of liquids which were known to have been carried in RailWhales.

DENSITY OF LIQUIDS IN GRAMS/CUBIC CENTIMETER
0.641	Butadiene		1.000	Water
0.791	Methanol		1.003	Methyl Chloride (liquid)
0.820	Lube Oil-Light		1.050	Acetic Acid
0.840	Hexamethylenediamine		1.080	Acetic Anhydride
0.850	Lube Oil-Medium		1.110	Ethylene Glycol
0.640	Tetrahydrofuran		1.210	Toluene Diisocyanate
0.900	Lube Oil-Heavy		1.650	Tetraethyl Lead
0.911	Vinyl Chloride		1.820	Elemental Phosphorous

RailWhales entered service at a time when much of the railroad industry was in poor financial health, and deferred track maintenance was a fact of life on many railroads.  Derailments were a common occurrance, and images of burning tank cars were a regular feature in newspapers and on televison. 

In an effort to reduce the risks associated with large-capacity tank cars transporting hazardous materials, the Department of Transportation's Hazardous Materials Regulations Board had a proposed rule published in the 11 December 1969 Federal Register that would prohibit the construction of any tank car with a GRL exceeding 263,000 pounds or with a capacity greater than 34,500 gallons.  The proposed effective date was 1 July 1970; but when the actual rule (35 CFR 14216) was published on 9 September 1970 the effective date had been moved back four months, to 1 December.  The final RailWhale order – RAIX 4300-4319 – was completed in November. 

This regulation not only ended the constuction of RailWhales, but also of 4-axle tank cars with 125-ton trucks (7x12-inch bearings and 38-inch wheels) and a GRL of 315,000 pounds; although the weight restriction was subsequently raised to 286,000 pounds for cargoes which did not pose a toxic inhalation hazard.

---

The order in which production RailWhales appeared isn't completely clear, because I don't have construction dates for some of the cars; but we can use the Official Railway Equipment Register as a guide.  The ORER usually comes out in January, April, July and October, and comparing the cars appearing in each issue for the first time with the construction information I do have shows that cars were typically listed 3-5 months before their actual construction date.  So, while this isn't an exact method, it provides a good idea of the order in which the cars were built. 

Between the July 1963 isssue and the last issue for 1965 (October), only one RailWhale was listed, UTLX 83699.  Even though the second RailWhale, GATX 96500, had been completed in September 1965, it was not added until January 1967.  The table below lists the cars which show up in each issue of the ORER between January 1966 and the last new RailWhale entries in April 1970.

CARS ADDED TO THE OFFICIAL RAILWAY EQUIPMENT REGISTER JANUARY 1966-APRIL 1970
* Column 7 is the cumulative total of cars listed. UTLX 83699 was first listed in JUL 1963.   * Column 8 is the actual number of cars listed in each issue.
ORER	6-AXLE	NO	8-AXLE	NO	TOT	7*	8*
JAN 1966	IAPX 1001	1	none		1	2	2
APR 1966	MCPX 23000‑23036  NATX 37300 PRR 500001	37 1 1	none		39	41	41
JUL 1966	IAPX 1003, 1004 PRR 500000	2 1	none		3	44	44
OCT 1966	none		GATX 96500	1	1	45	45
JAN 1967	SHPX 17451-17475 SHPX 17481-17495	25 15	none		40	85	85
APR 1967	DUPX 79500-79574	75	none		75	160	160
JUL 1967	none		none		0	160	160
OCT 1967	IAPX 1005 NATX 37301 NATX 38000-38054 SHPX 88348‑88375	1 1 55 28	DUPX 28050‑28055	6	93	251	251
JAN 1968	none		DUPX 28056‑28060	5	5	256	256
APR 1968	CELX 6400-6458 DUPX 29600-29642 GATX 98200-98220	59 43 21	none		123	379	378 *
* One car deleted: PRR 500000
JUL 1968	GATX 98221-98231 IAPX 1008	11 1	CELX 7500-7502 GCX 731000‑731007	3 8	23	402	401
OCT 1968	GATX 98232-98238 GATX 94650-94654	9 5	DUPX 29700-29769 GCX 741600-741621	70 22	106	508	502 **
** Five cars deleted: GATX 98201, 98215, 98216; SHPX 17482, 17489
JAN 1969	GATX 94655-94677	23	DUPX 28061-28070 GCX 741622-741646	10 25	58	566	560
APR 1969	DUPX 29400-29439 GATX 94678-94706	40 29	ACFX 18948-18952 ACFX 85299-85302 ESMX 4800-4834 GATX 11571-11574	5 4 34 4	144	680	671 ***
*** Three cars deleted: 2 DUPX 29500-series, MONX 23035
JUL 1969	CELX 10400-10438	39	none		39	719	709 ****
**** One car deleted: NATX 38000-series
OCT 1969	none		DUPX 12401-12405 DUPX 28071-28090 GATX 81663-81677	5 20 15	40	759	749
JAN 1970	none		ACFX 89331-89332	2	2	761	751
APR 1970	DUPX 29643-29666	24	ACFX 17779-17790 ACFX 89351-89352 RAIX 4300-4319	12 2 20	58	819	809
TOTAL	6-AXLE	545	8-AXLE	274		819	809
The difference between the total of 819 cars built and the 809 cars listed in the April 1970 ORER is the 10 cars that had been deleted, as identified in the orange bands.