More Great info.
Thank You.
I spent a few minutes checkin' for rivets and welding.
I found that Alco seems to have used pretty small rivets on the cab sides. So, if you're seeing welded, you might be seeing riveted.
I have a couple of really nice Alco builders photos of SP&S S-1 #10 and S-2's #20 and #25. All have riveted-side cabs. Which, considering the build dates, is no surprise.
Ed
From what I can tell, at least some S-1 through S-4 were built with riveted cabs, from looking at photos of MEC and PT cab end switchers. I did not look at BM alco's however they were generally ordered with MECs as joint orders (that stopped when McGinnis showed up 1954-1955), so it is a safe assumption they were built to the same specs.
MLW built more than 30 S-4s in 1949. The last S-4s were built in the summer of 1957 as part of an Alco Shop order for 40 units. The very last of this S-4 production wasn't sold until 1961. See http://www.thedieselshop.us/Alco_S4.HTML and note how all the last S-4s sold are all in the same block of serial numbers.
Here is what I found in Steinbrenner's book and around the net: https://en.wikipedia.org/wiki/Talk:ALCO_S-2_and_S-4
mandealco Another difference: S-1/2 had riveted cabs, S-3/4 had welded cabs.
Another difference: S-1/2 had riveted cabs, S-3/4 had welded cabs.
Never heard of that difference, I would like to see some documentation of that. It is possible. We will probably never know for sure.
Some posssbilities
1) all S1/2 riveted, all S3/4 welded
2) early S1/2 riveted, latter S1/2 welded, all S3/4 welded
3) all S1/2 riveted, early S2/4 riveted, latter S2/4 welded
4) riveted and welded cabs mixed throughout all production
5) all had riveted cabs
6) all had welded cabs
Alco S1 production Apr 40 - Jun 50 540
Alco S3 production Mar 50 - Nov 53 292
Alco S2 production Apr 40 - Jun 50 1502
Alco S4 production Aug 50 - Jan 61 797
I tried to sell my two cents worth, but no one would give me a plug nickel for it.
I don't have a leg to stand on.
And to further confuse life, some roads later replaced the Blunt trucks with AAR trucks released from other retired locomotives.
John
Ain't there always an exception to the rule. GN put AAR trucks under some of their Alco S-2's.
As DSchmitt has pointed out, the trucks are the only visible external differences between the S2s and S4s.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
The S-2 had ALCO's own "Blunt" trucks, and the S-4 had standard AAR Type A Switcher Trucks.
Yet another one for my forums friends: What is/are the external differences between an S-2 and an S-4?
As usual, thank you for any assistance the forums can provide.