GP40X - MagnumMacKivler/RLCPT2 GitHub Wiki
A builders photo of Southern Pacific GP40X #7200. Note the HTB trucks and elephant ears. Photo credit to EMD, to which this photo is a part of the Rob Sarberenyi collection.
The GP40X was a General Purpose 40 series (turbocharged 16 cyl 645 cu.in. engine equipped) e_X_perimental locomotive produced by Electro Motive division between 1977 to 1978. The GP40X was the test bed for the new 16-645F engine, which increased horsepower from the existing GP40-2, and was also the testing ground for other experimental EMD tech, like the HTB 4 axle high adhesion truck and Locotrol (An early version of radio controllers for unmanned distributed power units). Upon testing finishing with the experimental locomotive, the GP50
Upon ordering of these units for testing, only 23 were made: 10 for the Santa Fe, 4 for Southern Pacific, 3 for Southern Railway, and 6 for Union Pacific. UP and SPs' order featured the experimental HTB truck, while SOU and ATSFs' units had the standard Blomberg M that was popular at the time (and ended up being the standard truck for units to come after them). Southern ended up being the only purchaser of the high hood variant.
One notable feature on Southern Pacific's units was the featuring of "elephant ears"; these fins (pictured above) were to test for heat issues in the long tunnels of California by drafting colder air from the bottom of the locomotive instead of hot, exhaust filled air. These GP40Xs later removed their fins, and the SD40T-2 (a variant of the SD40-2) and SD45T-2 (a variant of the SD45-2) fixed these heat issues with a large intake on the bottom.
PT-Specific Information
| General Info | - |
|---|---|
| Prime Mover | 16-645F3B |
| Horsepower | 3500 HP |
| Truck Type | EMD "Blomberg" M, HTB |
| Axles | 4 |
| Traction Motors | 4 |
| Minimum Weight | 274,000 lbs |
| Maximum Weight | 280,000 lbs ⚠ (1) |
| Model Base Speed | 70 MPH |
| Top Speed | 70, 76, 82 or 88 MPH |
| Electrical System | - |
|---|---|
| Generator Max Current | 6600 amps |
| Max Traction Motor (TM) Current | 1650 amps |
| Max Continuous TM Current | 1170 amps |
| Traction Motor Type | DC |
| Factor of Adhesion | 25% |
| Transition Mode | Automatic |
| Transition Groups | 1 |
| Transition Shunts | 1 |
| Generator Transition | Yes |
| Traction Control | APR with sanding |
| Dynamic Braking (DB) Mode (if used) | Mechanical Blowers |
| DB Max Current | 700 |
| DB Max Continuous Current | 700 |
| Blended Braking | No |
| Miscellaneous | - |
|---|---|
| Head-End Power (HEP) | No |
| HEP Power Consumption | N/A |
| HEP Standby/Run Mode | N/A |
| Load Ramp Speed | 2 Amps/Tick |
| TM Overload Protection | No |
| Starter Mode | Manual Primer, Manual Start |
| Air Brake Schedule | 26L |
| Compressor CFM | 269.2 (WBO @ 954 RPM) |
| Main Reservoir Volume | 35 Cubic Feet |
###Notes:
(1): This is the heaviest a GP50 could have been ordered; the heaviest a GP40x was built to was 274K, however no technical documents support any max weight capacity.
⚠: Not verified or educated guess