Is there a 'right' model of UP Centennial locomotive? (DDA40X)

EMD built 30 DD35Bs for both UP and SP, and 15 DD35As all for UP. The DD40X was built only for UP, 47 copies in all between April 1969 and September 1971. All are now scrapped.

The Athearn model was based on blueprints of the proposed DD40 model before it was actually built. But the actual DD40s built for UP were different, as you know. Because of the differences between the Athearn model and the actual locomotives, rebuilding the Athearn model would be difficult. The Athearn model has not been made in years. I have one, but I'm not parting with it, despite its inaccuracies. :-) It's in blue and white demonstrator livery and looks good to me. It also hauls like a team of elephants. Actually, it's close to the DD35A in appearance, which is not surprising, as it was planned to be an upgrade of the DD35.

The Bachmann loco is a DD35. It is no longer listed in their catalogue.

HTH

I don't think all of them were scrapped. The NRHS has a batch of locomotives at the Fairplex in Pomona, CA. I'm 90% positive that the UP engine there is a DD40X, not a DD35.

Follow up to my previous post. It seems a number of them have been preserved:

"Rick Jones" wrote

I sat in the engineer's seat of the pictured loco just this last fall, and I'm sure I would have noticed if the rest of it wasn't there.

Pete

That would be great news!

Good to know that I was wrong about then non-existence of DD40s. ;-)

And there's still one operating with UP (surprise, surprise!):

I wonder, why there's not a 'correct' mass-produced version of this impressive (and popular) beast?

After all, there are runs of less popular and very obscure models.

N.F.

"Nick Fotis" wrote in

Maybe it's because these huge locos look pretty silly on your average home layout's tight curves, thereby limiting their market appeal unless the owner plans on using it as a paperweight.

Pete

Granted, but look at how many mfgrs have done the Big Boy.

fl@liner

"fl@liner" wrote

There's a difference you're not taking into account: the Big Boy is an articulated, and even though it's boiler overhangs the outside of the track like crazy on a tight curve, the front engine itself follows the curve and thus the engine "bends" around the corner and the front coupler remains more-or-less oriented in the direction of the curve, as does the one mounted on the tender. (For engineering purposes, you could think of a Big Boy as being like three short diesel units coupled together in a lashup.)

On a DD anything, it's almost 90' long rigid frame places both front and rear couplers *way* outside the radius of the curve, and would likely derail any shorter car connected to it.

There's reason people don't usually try to operate 90' cars on 18" radius curves, and a DD class locomotive would present these same problems.

Pete

On 12/13/2007 11:45 AM P. Roehling spake thus:

Maybe that's a good argument for getting a DD40AX and replacing the body-mounted couplers with so-called "Talgos", eh?

"David Nebenzahl" wrote

You'd pretty much *have* to if you planned to run it on less than 30" radius curves. But then that goes back to the problem of it no longer being a 'correct' model of the prototype, and I've read that Talgo-style couplers have a nasty reputation for derailing cars when you try to back them through a switch.

Pete

Any mix of body mounted and bogie mounted couplers is going to cause problems when pushing. Bogie mounted couplers will cause problems on pushing heavy trains because a: sideways deflections are controlled by a spring of finite strength, and b: The sideways deflections cause the bogie to twist on the track causing flange/rail pressures. Underframe mounted couplers will cause problems pushing heavy trains on sharp curves because different underframe lengths create differing and extreme angles of pressure.

A more rigid form of coupling near to the track centre-line (bogie mounted but isolated from the bogie's anngular delection) will give the best result.

Regards, Greg.P.

Right. Often people use 'shortened' passenger cars -- that are a scale

70', rather than the proper 90 scale feet. (I know, the 70' cars are not really prototypical, but they do work better on the tighter curves, if one simply lacks the space for broad enough curves for 90' cars...)

"Robert Heller" wrote

Not my problem, fortunately. I mostly run at the SD&AE layout at the San Diego Model Railroad Museum where the minimum mainline radius is 48" and the switches are #8 or above. I use body-mounted Kadee #5s on everything and rarely have any coupler or derailing problems.

In fact, I'm just finishing up a 14 car S.P. heavyweight passenger train, and I can't *wait* to get it down there on the track and find out what sort of power it's going to take to drag it over the hill!

Pete

That certainly doesn't seem to inhibit the sales of UP Challengers and SP's Cab Forwards or 85' Passenger cars now does it ?

Bill

"William R. Mattil" wrote

Uh, Bill, maybe reading the rest of the thread would be a good idea?

Pete

I doubt it, see the Erie Triplexes for example :-)

Also, I am working with modules in a big layout, with long mainline switches and curve radius bigger than one meter (in fact, the 90-degree curve I have set-up is 1670mm radius!).

See

for an example of our first public meet. Definitely we wouldn't have a problem with these beast (after all, they were running in Feather River Canyon pulling freights, with barely one straight line longer than 50 feet :-) )

And yes, I am believing that a high-quality DDA40X will be a big seller (and let the company put a sticker 'suitable for curves with radius at least

24"', for example).

If Atlas or Kato (or even Athearn Genesis or some such company) made a well done mass-produced DDA40X, I would buy at least one.

Cheers, N.F.

"Nick Fotis" wrote

Not relevant: articulateds all bend around corners.( In fact, that's what "articulated" means.)

90 foot-long rigid-framed diesels don't bend hardly at all.

The companies that stand to profit -or not- obviously think otherwise.

When Overland marketed it's various DD models they advertised them as being suitable only for radii of over 30"; which no doubt cut into their sales significantly.

None of this means that nobody will ever produce a mass-market version of these huge locos; after all, an SD-90 is close to that size, but were I the executive in charge of deciding what new locos to market, I'd look at models that could be used on an average layout before I spent the money to produce something that has self-limiting sales built right in.

Pete