• Question on F2, F3, F7s on B&M

  • Discussion relating to the pre-1983 B&M and MEC railroads. For current operations, please see the Pan Am Railways Forum.
Discussion relating to the pre-1983 B&M and MEC railroads. For current operations, please see the Pan Am Railways Forum.

Moderator: MEC407

  by JayBee
 
X2200 South shows 4268A as being built seven months after the other three and it has a builder's number totally separate from the others.
  by jbvb
 
After Bangor & Aroostook passenger service ended, there wasn't a resale market for 1st generation E-7s. So the BAR had EMD re-gear their E-7s for freight service. They were repainted the solid blue scheme and lasted till 1967 before being traded in on GP-38s. The B&M had a surplus of road freight diesels in the late 1950s and 1960s, so I doubt this was ever considered for B&M E-7s.
  by BR&P
 
b&m 1566 wrote: Fri Jan 15, 2010 10:09 pm Why were the dynamic brakes removed from the F7's? Since the 4266 is still in operation, I wonder if it would be possible for the dynamics to be reinstalled; the folks at Conway Scenic could sure use it!
Well nobody answered this for 11 years, so I'll take a go at it! :P

The dynamic brake reversed the purpose of the traction motors, making them into generators and thereby making resistance. The heat thus produced had to be dissipated and that was done by means of resistor grids. Somewhat similar to the toaster in your kitchen. These resistor grids sometimes burned out and had to be replaced. When in use, they had to be cooled by means of a large fan. The controls to activate the dynamic brake included various relays, contacts and interlocks, plus extra wiring. And there was also connections to the air brake system to nullify the dynamics if the train went into emergency

So the maintenance and testing of a loco with dynamics went beyond the degree of expense and time needed for one without, leading in some cases to railroads deciding to remove them.

As for restoring the dynamic on the one in tourist service, no doubt wiring drawings exist to guide the process and it should be possible to do so. All you would need is to find the parts needed, spend the money to buy them, and have a bunch of guys re-wire everything as it used to be. Nothing to it, right? :wink: (translation - it certainly could be done, but would very likely not be worth the time, money and effort required to do so.)
  by SSW921
 
JayBee wrote: Mon Jan 25, 2021 12:22 am X2200 South shows 4268A as being built seven months after the other three and it has a builder's number totally separate from the others.
The B&M roster in Extra 2200 South shows the final rebuild date and sale date for the F7A that became B&M #4268A. The history of the former EMDX #930 is that it was built in March 1949, the same as the other three B&M F7As. The #930 was used in high altitude testing, there is a photo of it testing on the Rio Grande. After testing the unit returned to EMD and was placed on loan to the Burlington at the Chicago Railroad Fair. Then the unit returned again to EMD for refurbishment, likely some internal electrical changes and sale to the B&M in October 1949. The EMD 16-567B engine blocks originally installed in 4265A-4268A are serials #6842, 6816, 6822, and 6818 respectively.

The wiring diagrams for B&M 4265A-4267A are identical. The wiring diagram for B&M 4268A is a later diagram.

Has anyone else noticed the similarity of the pilot of B&M #4268A with Pennsylvania Railroad F7As and FP7s? The Pennsylvania also had F7s built in March 1949 with similar engine block numbers as the B&M units and EMDX #930. My working theory is that EMDX 930 was originally production scheduled as a Pennsylvania unit and taken by the EMD Engineering Department for testing.

Ed in Kentucky
  by b&m 1566
 
Can you share the photo of when it was EMDX #930?