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.
Ex-NYNH&H SS Opr