Question

[SeriousSam]

QUOTE: Originally posted by egmurphy

Close enough. To quote a little more from McDonnell's book:

Outwardly, the most dramatic change was a 3-foot increase in length of the locomotive's frame. Necessary to accomodate the longer HT-C trucks, the added length gave the SD40-2 one of its most distinguishing features, a spacious platform behind the rear hood - the famous "back porch."



Regards

Ed

ah, thanks. That proves that i'm not crazy. I wi***hey would release an SD38-2 in N Scale. The HO models look beautiful

[egmurphy]

Close enough. To quote a little more from McDonnell's book:

Outwardly, the most dramatic change was a 3-foot increase in length of the locomotive's frame. Necessary to accomodate the longer HT-C trucks, the added length gave the SD40-2 one of its most distinguishing features, a spacious platform behind the rear hood - the famous "back porch."



Regards

Ed

[SeriousSam]

Thanks for the help. The main "physical" change that I have noted, and I dont know if its like that in all models, is the length of the front and rear walkways of the locomotive. On the SD40, the very last rear wheel is not as far back, as in the SD40-2, where the last wheel is way back there, to where the actual body of the locomotive is not over it. I dont know if I am explaining myself. But yeah

[tstage]

Thanks for the edumacation, fellas! [:)] I always wondered what the difference was. Thanks, Sam, for asking the question! [tup]

Tom

[egmurphy]

Just to elaborate a bit on what Eric has already said. The Kalmbach published book, "Field Guide to Modern Diesel Locomotives", by Greg McDonnell has a good short description of the major changes. I'll just quote a few parts of the description as follows:

"...Re-engineered from the rails up, the Dash 2 line incorporated some 40 component changes and improvements, most of which focused on increasing reliability, ease of maintenance and operating efficiency.

...newly developed high-adhesion HT-C truck ... WS10 wheelslip controls, ... The 645E3 engine was fortified with toughened pistons... but the defining Dash 2 difference was the introduction of the solid-state, modular electrical control system.

The Dash 2's revolutionary electrical control system heralded a major advance in locomotive technology.... a radically redesigned electrical control system made up of transistors and printed circuit boards managed by solid-state modular components governing everything from voltage regulation, battery charging and excitation, to throttle response, wheel-slip control, dynamic braking and even sanders."


It's an invaluable book. I recommend getting a copy at your LHS.

Regards

Ed

[ericsp]

They made significant upgrades to the design in 1972(?). So a SD40 built prior to the changes is called an SD40. The same basic locomotive built after the changes is called an SD40-2. Some railroads will call an SD40 rebuilt to the -2 standards an SD40-2. This is why there are no SD60-2s. However, there has been a significant redesign of the SD70M (I think mainly to meet new emissions standards), so there is a SD70M-2.

[SeriousSam]

What does tha "-2" stand for in SD and GP diesel locos? I see "SD40" and "SD40-2".