Comments on: Six units (SW1200RS 1293, 1262, 1287, and 1265, GP9 45xx, and an RS18) start up the Halton sub with an eastbound freight. Yes, that order of units is correct–due to control issues, SW1200RS (and GMD1) units were supposed to lead bigger units in such lash-ups! (Perhaps another member can explain the exact reason.)

By: RonaldB

RonaldB — Sat, 27 Jan 2024 16:55:26 +0000

ignore last 9 words above, I meant to delete them in composing the message. Senior moment perhaps?

By: RonaldB

RonaldB — Sat, 27 Jan 2024 16:52:50 +0000

Also, with regard to shoving with power consists, CP has (had?) a rule that limited powered axles when shoving. If it was necessary under that rule to cut out some units, those closet to the cars being shoved were to be powered, and the rest cut out, excepting the leader, account need to watch loadmeter. required that units in the rear of the consist

By: RonaldB

RonaldB — Sat, 27 Jan 2024 16:49:21 +0000

At one time, we had a rule on CP that an SW1200RS must not be placed behind 6 axle power. It was supposed to be cut in the middle of the consist. That meant for example, if we lifted one of the “pups” enroute, the big power had to be split to place the small unit in the middle. I believe this was due to lack of coupler alignment feature. This rule was sometimes not known or ignored, & in later years the units may have been modified. I’ll bet there are photos on here or out there, that depict both examples of placement.

By: ngineered4u

ngineered4u — Thu, 28 Mar 2019 16:29:19 +0000

LOL@mercer. Thanks for the post. Conversation is a good thing.

By: mercer

mercer — Thu, 28 Mar 2019 16:06:07 +0000

Boy, I’m glad I found this photo when I did, or the Comments would be into a 2nd edition by now.
This is the Niagara Falls turn, exToronto as 461 and back home as 462. The date is Dec 23/67 and the trailing 2 roadswitchers are IDLING !
(likely if for no other reason than not required).
Plus, all 4 of these GR-12′s were assigned to Montreal Yard at this date, so they are captured out of their usual territory. ( I had just recorded 1293 freshly repainted at CN Walkley Yard 2 weeks prior).

By: MrDan

MrDan — Thu, 28 Mar 2019 08:26:26 +0000

From what I’ve seen on CN’s own locomotive datasheets, the SW1200RS units (and GMD1′s) are listed as having automatic forward transition but manual backwards transition. All the standard road stuff like GP9′s and RS18′s had fully automatic transition. Rebuilts like the 7300′s also got fully automatic transition.

Running SW1200RS units together or leading wouldn’t be a problem, from what I’ve read it’s if one was trailing a unit like a GP9 with fully automatic transition. The trailing SW1200RS wouldn’t make the manual backwards transition without briefly reducing the lead unit’s throttle to idle. If the SW1200RS was leading, it would be run as a unit with backwards-transition and operate fine, and the trailing GP9 would make transition automatically as it normally would. This was an issue with some earlier CP units as well, notably the E8A’s when they were used as trailing units on the Atlantic Ltd (a crew out west was running a freshly overhauled one in a freight consist once and fried a brand new MG because they didn’t know about the manual backwards transition).

That selector would be the “Road Service Switch”, allowing faster loading depending on what use it was working in.

By: Larry Parks

Larry Parks — Thu, 28 Mar 2019 01:21:09 +0000

Zing.

By: ngineered4u

ngineered4u — Thu, 28 Mar 2019 01:17:18 +0000

@MrDan..not sure about the SW1200RS’s as all the ones i drove tended to make transition together and they did have a switch that you could move between road and yard.

By: MrDan

MrDan — Thu, 28 Mar 2019 01:12:39 +0000

I think the reason may have been that some early smaller EMD units like these SW’s didn’t have automatic backwards transition – they had manual backwards transition.

When one of those was trailing in a consist with a leader with fully automatic transition, the engineer needed to do something like briefly returning the throttle to idle to trip the backwards transition for any manual transition units trailing (or else you’d overload the main generator). Perhaps making those units lead helped avoid that situation.

By: ngineered4u

ngineered4u — Thu, 28 Mar 2019 00:59:59 +0000

@5248. When i say draft gear i am talking about the entire assembly not specifically the housing. Auto racks and parts cars couplers can slide quite a distance and this sometimes causes crossed couplers. Some older power have non aligned couplers and that is why they have certain restrictions.