Railroaders' Nostalgia > EMD General purpose class

EMD had two classes of diesels we are all familiar with, the special duty, and general purpose. It has seemed that they were both quite common amongst the rails at one time, but now it seems that EMD (under CAT) has been dragging their feet on general purpose diesels. From what I understand, there hasn't been a GP diesel since 2001, but on the SD side of things things, those are the only about. Most notably there is te sd70 ace being quite common amongst the rails along with the GEVOs and previous ACs. My question is, with the new ace t4s making their ways, what happened to the EMD GPs, is there any more plans for them or are they being put on hold, or all together forgotten. I appreciate any answers and replies, and I thank you for reading this.

Posted from iPhone

If we generalize the question to "4-axle" (GP) vs. "6-axle" (SD) locomotives, it's because horsepower per unit rose to the point where the four-axle units couldn't use all the available horsepower at low speeds without slipping. Even the GP-40 of 45 years ago (3,000 hp) had to de-rate to 2,300 HP at low speeds to keep from spinning its wheels. Except for high-speed service with light trains (passenger and some "classic" piggyback trains), the need for maximum tractive effort at low speeds makes six-axle units the better choice, even with today's improved factors of adhesion thanks to AC motors and traction control systems.

Yes, it is about tractive effort, not horsepower when it comes to tackling hills. Example 4 3000 HP SD 40's would out pull 4 3000 HP GP40's.

Yes thank you, I wasn't sure about any switching locos made. I found it quite obvious after the fact of posting this that the four axles weren't practical to compete with modern railroading equipment.

Posted from iPhone

To address your question, the GP9's are quite ancient and outdated. Class One railroads are rebuilding second and third generation power for their local and switching needs. These would be more efficient, easier to maintain, and more powerful. Models would include the GP30, GP35, GP38-2, GP40, GP50, and now even some GP60's.

Yes, thank you

Posted from iPhone

Two BIG contributing factors that ended sales/production of 4-axle units, was:

1) The development of the "steerable" HTC-R Radial truck, which then allowed 6-axle SD units to be used in sharper curve environments (Alaska RR for one).

2) Price! When 4-axle units were approaching the price of 6-axle units, with DC traction motors, only one or two U.S. railroads continued to purchase GP60 units. When AC traction hit the market, with their Radial 3-axle trucks, there really was no longer a market for 4-axle units. Price was also a major factor in why railroads stopped purchasing switchers, as it was much less expensive to re-manufacture an old 4-axle unit, than purchase a new switcher.

So they aren't dragging their feet after all, are they ?

Dragging their feet? Not quite.

GP20C-ECO was probably the closest build you will see to a current GP.

Those ECO units reused, trucks, equipment racks, fans from the GP9. When you look
back into the history of EMD orders. While it was looked at as a repower it was more
common place in the 1960's for EMD to make deal with a railroad to reuse some equipment
on locomotives that were traded in, or even use Alco trucks.

Entropy Wrote:
-------------------------------------------------------
> Dragging their feet? Not quite.
>
> GP20C-ECO was probably the closest build you will
> see to a current GP.
>
> Those ECO units reused, trucks, equipment racks,
> fans from the GP9. When you look
> back into the history of EMD orders. While it was
> looked at as a repower it was more
> common place in the 1960's for EMD to make deal
> with a railroad to reuse some equipment
> on locomotives that were traded in, or even use
> Alco trucks.

I have heard GE is also looking into a short block T4 4 axle unit, using existing 4 axle frames.

This brings the question, at least up here in the great white north... I'm curious to see what CN is going to do?? I know they've put in orders for new tier 4 high horsepower road units, but the venerable GMD-1's, GP9's, GP40-2's are all aging, what are they're long term plans for the switchers???? I've seen SD40-2W's being utilized for yard duties, but for warehouse's or industries the 6-axle units won't traverse the curves and switches very well... Maybe reason to abandon trackage???

BCR_766 Wrote:
-------------------------------------------------------
> This brings the question, at least up here in the
> great white north... I'm curious to see what CN is
> going to do?? I know they've put in orders for new
> tier 4 high horsepower road units, but the
> venerable GMD-1's, GP9's, GP40-2's are all aging,
> what are they're long term plans for the
> switchers???? I've seen SD40-2W's being utilized
> for yard duties, but for warehouse's or industries
> the 6-axle units won't traverse the curves and
> switches very well...

Actually the HTC-R "Radial truck", or "Steerable Truck" to some folks, works very well on "tight curves". Thus, when the HTC-R truck came out on the EMD 70 series units, the Alaska Railroad finally purchased six axle units

Maybe reason to abandon
> trackage???

Absolutely the case with Alaska Railroad. Many tight curves and on the south end I think there were a couple in the 18 degree range.
I worked as General Foreman of the Anchorage diesel shop and can say that if we saw any degree of flange wear on a Mac we better look at a truck issue as normally you just did not see flange wear. In fact it appeared the GP locos evidenced more flange wear than the radial truck SD's.