Mix

Nope.  They just mix and match.

What the prototype has to watch is mixing engines with high speed gearing or AC engines with older DC engines.

Back on the MP we mixed and matched GP38's and SD40's all the time.

Thanks Dave

Thanks for verifying.

On my railroad there is no real need for consisting but it looks cool and is fun to play with from time to time. It's good to know that a wide mix of locos would be legit.

I know on the SP

Mixed consists

I live about a third of a mile from the old SP Santa Cruz branch line and could listen to the various engines from my deck. For decades it was GP9 and SD7/9 power but later years brought turbo charged GPs and SD40's ,a few GE's, rarely the unmistakable sound of an SD45. In these later years it was a treat to hear an GP15-1 or GP38-2 non turbo charged....DaveB

Southern Pacific

SP was a good tip for finding lashup variety.

In 1989 Richard Sugg shot this SDP45, SD9, GP38-2 combo.

Yes!

Yes, that shows the hood height difference nicely between the SD9 and the second generation diesels. The SD9 hood is noticeably lower.

My understanding is they needed the higher hood to accommodate the newer diesels' electrical cabinet — note the GP30's distinctive higher front half, with the back half still down at first generation height. After the GP30, they just made the entire hood higher and never looked back.

Hope he knows how to stretch brake

Haha, I've never considered that the Company gave any concern about consisting turbo/no turbo. They didn't, excepting truly non compatible units, such as MU 'ing FM baby TMs with anything else account the very different deck heights, and other non compatible MU setups.

An early dynamic brake was the field loop, that required separate cables. (The plug was rectangular and just above the standard MU plug. B&O used them at one time, but had converted those units to standard MU with pins in that cable. But we saw a lot of C&O GPs that still used field loop. If you had a  unit with field loop, your dynamics were inoperable behind that unit. No concern for consisting there, pal.

My cryptic subject line above refers to my thoughts the night I took my local freight into Brunswick, Md. While passing through Point of Rocks, I went by an eastbound grain train stopped on no.2 track, waiting for a fresh crew. In this pre-wide body era, there were four or five SDs and big GPs on that train...all led by an ex RF&P GP 40.

RF&P units were not equipped with dynamic brakes; thus, you couldn't operate the trailing unit dynamics. That's when I thought...[see subject line above]

....

I miss the days of the old BN.  It wasn't uncommon to spot Kadachrome SD-40-2s lashed up with GE U-33Cs.

The U-33Cs went to South America at the beginning of the 2000s and both SF, SPSF and BN disappeared under the BNSF banner...

Pretty much anything goes

I've seen consists where AC44's were MU'ed to GP40's (yes, they were running and not cut out). There's a few things to watch out for on the prototype:

1) Top speed. If you've got an ES44AC (75 mph limited), don't be leading a GP38 (65 mph). Most rulebooks don't state that you can't lash these together, just that the lowest-top-speed has to lead. Otherwise the slower unit gets sheared gears or a bird-nested traction motor.

2) Tractive effort. Same as above, let your GP38 lead your ES44AC. Your Geep will stop gripping the rail long before the ES44 starts to lose its footing.

If you look through thedieselshop.us' data sheets, you can find some weird facts. For instance, an SW1500 is effectively a GP7, both in terms of tractive effort, horsepower, weight, and top speed (if equipped with Flexicoils). Although they look like an odd couple, they're effectively the same.

...

Here's the 90s in Northern Arizona in a nutshell...even if it is in Oklahoma...

RailPictures.Net Photo: ATSF 5049 Atchison, Topeka & Santa Fe (ATSF) EMD SD40-2 at Belva, Oklahoma by Charles Stookey