Follows information suggesting an alternative argument about the driver(s) for the transition from square corner to rounded corner Dreadnaught ends starting 1939. The previous round of discussion seems to have come to rest on the notion that the transition occurred because Standard Railway Equipment changed product design and so subsequent series builds had to accept the new design as if it were forced on subsequent assemblies by lack of alternative.
Consider the very rapid transition to be primarily a correlate of the availability of a superior design. Square corner Dreadnaught ends continued to be available after the W corner post introduction. In addition, a few other types offered by other manufacturers, for example, those used on the B&O M-55 and M-57 (1700 cars initiated 1940-1941) continued to be available. Choice did exist.
On the advantages of the W corner post:
"...corners have been rounded to a generous radius and W-section corner posts applied, this combination functioning to produce action to prevent the sides of the car pulling in under a heavy impact. By actual test at the University of Illinois, this end is 25 per cent stronger than the old conventional type without the round corners and the W-section corner post." Standard Railway Equipment Manufacturing Co. advertisement in 1940 Car Builders' Cyclopedia of American Practice (15th Edition).
4-1939: Recommended use of W corner post by AAR. This recommendation would indicate that discussion and data on the merits of the W corner post are available. I do not have resources to follow this certain possibility. It would be interesting to know about the development and testing prior to the recommendation by the AAR, apparently at the University of Illinois. Where did the design originate? Were the tests sponsored by the AAR? SRE?
Follows is a list of all series initiated in 1939 built with W corner posts. The all-welded and singular GABX #1940 (renum to ATSF 150600) has Dreadnaught 5-5 ends with rounded corners but there is no information on whether it had W corner posts. Paste it up as a puzzle.
The first series application developed jointly by UP and Standard Railway Equipment Co. 1939-1939 , 1200 BLT:
**1939-1939 and 1939-1939 187000-187499, Omaha, NB.
**1939-1939 187500-188199, Grand Island, NB.
Here are the early series incorporating the W corner post and initiated in 1939. This data was extracted from my box car database that like other lists, spreadsheets, etc., produced by our community is a work in progress (since 1983). Corrections and additions are more than welcome.
Marks Serial Qty Builder Date
GABX 1940 1 GAT 11-1938
O-WR&N 188300-188999 700 UP 6-1939 10-1939
UP 187000-188199 1200 UP 6-1939 11-1939
M-I 4000-4249 250 MTV 7-1939 8-1939
UP 9100-9199 100 UP 8-1939 10-1939
CTH&SE 19039 1 MILW 9-1939
D&RGW 68000-68399 400 PSC 9-1939 10-1939
MILW 19000-19082 82 MILW 9-1939
LAPX 101 1 PSCx-1939
MILW 18000-18999 1000 MILW 10-1939 3-1940
NYC 62000-62299 300 DSI 10-1939 x-1940
NYC 91000-91199 200 DSI 10-1939
D&RGW 65100-65199 100 PSC 1-1939 12-1939
LAPX 102-121 20 PSC 11-1939 12-1939
WM 27501-28000 500 PSC 11-1939 12-1939
NYC 176000-176199 200 DSI x-1939 x-1940
MILW 19083-19187 105 MILW 12-1939 1-1940
PRR 65400-66399 1000 PRR 12-1939 2-1940
Cars with square corner Dreadnaught ends continue to be built after 5-1939: 35 series totaling 8416 cars by the end of 2-1942. Soo Line, especially, seemed to be partial to them. Nine of the last 11 series with square corners, 1600 cars built 7-1940 to 2-1942, were for Soo. For perspective, 70,220 cars with W corner posts in 188 series were initiated 1-1940 to 2 1942. The transition was indeed rather fast. However, post WWII, Improved Dreadnaught ends became available and builds using the early standard Dreadnaught W corner design became less common. My data entries encompass new series to 12-1944. A few idiosyncratic 1945-1947 entries, by no means exhaustive, show builds using the standard Dreadnaught round corner as late as 12-1947-1-1948, 500 cars for M&StL by GAT. Are there any later?
I welcome any comments, thoughts or data!