Diversity in MU operation ?

On the New Haven (not the PC years), was it either physically possible or actual that one manufacturer of locomotive, say an FL-9 would train with another locomotive manufacturer, such as one of the Alcos ?

most locomotives had compatible trainlines, one noted exception whas Fairbanks Morse.

Thanks, Dutch. I wondered if they were made so that if the gearing was radically different, say a switcher compared to a road diesel, that they could not train. If they could train, would RPM be compensated on either unit to match the other engine ?

the 8 notch system lets each engine pull at 1/8 of each trottle setting of its max power.
just like a team of horses, with two donkeys lashed in.
each will do its upmost at 1/8 increments, no matter if unit is 4000 or 1200 hp.
off course the max speed is determined by slowest unit.

EMD FL9s could MU with other EMD FL9s, EMD GP9s, Alco RS-11s, FM H-16-44s (1600-series), Alco C-425s, GE U-25Bs, and rebuilt Alco FAs and RS-3s. Alco PA-1s could (and did) MU with Alco DL-109s and FM CPA-24-5s.

Much could be, and has been written, on the mixing of manufacturers and models in a particular lash-up. Ideally, for example, GP9s should only be MUed with other GP9s. MU jumper capability aside (a separate issue), one manufacturer's model provided different output at different times from another manufacturer's model, even if both are from the same manufacturer. Different oil engines, coupled with different generators (or alternators), transitioned (esentially shifted gears) from series to series-parallel to parallel at different points along the progression from Run 1 to Run 8. For example, Engine A might run all out at 65 m.p.h. while Engine B, coupled to it, might run all out at 67 m.p.h. One engine ends up pushing or dragging the other, and the constant fighting between the engines gets worse working their way up from Run 1 to Run 8.

What should be done, and what was done, regarding engine lash-ups, was generally based on necessity. Thus, FL9s occasionally did pull freight trains, and get mixed in with GP9s, and GP9s were coupled to 1600-series H-16-44s for passenger runs.

The real question is - exactly how compatible were the first 30 FL9s with the second 30 FL9s? Electromechanically, the first 30 were identical to GP9s, but the second 30 were identical to GP18s.

Thank you very much.

Here's a follow-up, putting everything into perspective:

Tonnage rating per unit varies as to wheel diameter, gear ratio, minimum continuous MPH and a few other small things.

Here's some of the specific differences between EMD GP9s, FM H-16-44s and Alco RS-11s. Data was obtained from manufacturer's manuals:


FM H-16-44: Total weight 244 to 260,000 lbs. depending on modifications and ballast.

64:19 gear ratio with 40" wheels: 80 MPH max., 43,400 lbs. continuous tractive effort at 10.7 MPH.

Under load, total amperage time limit:
1,085 amps, no limit
1,100 amps, 50 min. limit
1,200 amps, 12 min. limit
1,300 amps, 6 min. limit
1,400 amps, 4 min. limit
1,660 amps, 2 min. limit

The above-listed rating's are for Series-Parallel. In Parallel the operator should not exceed 880 amps to avoid overheating the main generator. Do not go above 1,000 amps for 20 min. after using any short time rating.


EMD GP9: Total weight 244 to 248,000 lbs. depending on modifications and ballast.

59:18 gear ratio with 40" wheels: 83 MPH

EMD units had a 4-transition control circuit, which "shifted gears" depending on amps and speed:

#1 (series-parallel): 19.5 MPH at full throttle, 18 MPH at partial throttle, then shifts to
#2 (series-parallel shunt): Approx. 28 MPH at full or partial load, then shifts to
#3 (parallel): Approx. 55 MPH, then shifts to
#4 (parallel shunt): To top speed.

Maximum amperage rating is 1,500 amps.


Alco RS-11 (DL-701): Total weight 240 to 260,000 lbs. depending on options and ballast.

64:19 gear ratio with 40" wheels: 80 MPH max.

RS-11s had automatic transmissions which shifted as follows:

1 - 2: 21 MPH
2 - 3: 33 MPH
3 - 4: 56 MPH

Minimum safe speed: 12 MPH

No amp rating is listed, but the amp gauge goes from green to yellow. Full to 50 min, 12, 6, 4, 2 and if less than the max. time in that range is met, 1/2 the time in the next higher can be used.


Dynamic brakes for all three models have different loads and speeds for the units at given speed:

RS-11: Max. braking up to 30 MPH
GP-9: Best braking is between 15 to 25 MPH and is limited to 700 amps going through the grids.
H-16-44: Designed to automatically limit the current to 800 amps at 68 MPH and 900 amps at 25 MPH. Over 68 MPH you can manually limit it to 600 amps.


Over the 3 units listed, one can see why there is bucking, shoving and the like. All 3 have different starts, stops, loads, and running qualities.

Yes, you could mix-and-match, but it wasn't the ideal way to go.

Oh, if a rebuilt Alco RS-3 was in the batch, it had to be the front locomotive since they were not rebuilt with automatic transmissions (deliberately so).



The preceding was copied from a posting on the NHRHTA discussion forum.

Thanks, Stakowski!
The (later) F-M H-16-44, like the Alco RS-11, had GE electrical gear: so it is surprising how different their descriptions are.
All these models are listed as having high-speed gearing (80mph for the GE-motored, 83 for the EMD). The most common gearing for the GE 752 motor (74:18) gave a top speed of 65 or 70 mph, and I think EMD's most popular gear ratio for GP-9 would have given something similar. So New Haven special-ordered unusual gear-ratios tallow optional use of these units on passenger trains... or at least to allow them, running light or with short freights... to do bait of scampering to get out of the way of passenger trains.

Most of the New Haven's road switchers were ordered as dual-purpose engines, well capable of working passenger or freight. Even after the steam generators were deactivated/removed from the 1600-series H-16-44s and RS-11s, the steam piping was retained so that they could serve as the second unit in a passenger consists.

I don't think the steam lines on the 1400's and 1600's were maintained in shape for pass through steam. The steam generators were a real mess with missing pipe, parts and everything else. It was the intention of the railroad (New Haven that is) to run these particular units in through and local freight service and sometimes in yard service as well. I know when the Springfield job had two GP-9's (1200's) on trains 71 and 50, these same two 1200's were coupled to a third road switcher at Springfield after they arrived on 50 for SN-1 and NS-2 which at the time was a turnaround through freight job between Slpringfield (B & M) and Cedar Hill and the 1400 or 1600 was always coupled at the end, usually the north end of the consist. When NS-2 went to the pit at Springfield the 1400 or 1600 was dropped and the two 1200's again made the round trip in passenger service on 71 and 50. This engine assignment was in effect for quite some time, maybe right up until the end of the New Haven. I think if you look at photos of various 1400's or 1600's from the early 60's on you would find that many of them did not even have steam connectors on them.
Noel Weaver

Circa 1964, took a train to Hartford. Front unit was a GP9, but the second was an H-16-44. Working steam on the train, so the steam line was good. Couldn't comment on the steam generator, though.

Statkowski wrote:Circa 1964, took a train to Hartford. Front unit was a GP9, but the second was an H-16-44. Working steam on the train, so the steam line was good. Couldn't comment on the steam generator, though.

1960 was the last year that any of the 1600's had steam generators working on them. I do not buy that they had good steam lines in 1964, maybe you rode train 50 which did not need steam except in cold weather for train heat, train 71 had steam year round for the grill car. I worked on all of the 1600's at one time or another and all of the steam equipment that was still on the locomotives was a real mess and not likely servicable even for pass through steam.
Noel Weaver

Was either 50 or 66. It wasn't cold, so maybe the steam wasn't working.

How about the SW1200s? Did they have a standard 27 pin jumper? I have heard that they had the 2 pipe #6 brakes which were incompatible with the 24RL equipment on the FL9, GP9, DL701, and H1644. Is this so?

Engineer Spike wrote:How about the SW1200s? Did they have a standard 27 pin jumper? I have heard that they had the 2 pipe #6 brakes which were incompatible with the 24RL equipment on the FL9, GP9, DL701, and H1644. Is this so?

The 640's (SW-1200's) had a 27 point jumper but they had no. 6 brake equipment and could only MU with other 640's. With these particuar engines the most common MU operation was on the hump jobs at Cedar Hill although in earlier years they also ran on the Canal Line between Cedar Hill and Holyoke in MU operation. These particular engines were good in the yard and not too bad on a local freight but they were terrible riding and as a result were not good on through freight trains. On the Canal Line at 30 to 35 MPH you had to hang on for dear life.
Noel Weaver