building the locomotive roster

The Cape Ann has chosen three models as "standard" road power. This takes into account cost (this is a low-budget operation, and we need quite a few - all locos have been purchased used on eBay for $15 or less), availability of used units from eBay, and ease of service. The back story is that CAX management likes to buy older, used power and rebuild them as needed in their own shops.

Bachmann F7A is the power for all passenger service . This 4 wheel pickup / 4 wheel drive pancake motor model is plentiful and cheap. Most modelers detest the pancake motor but I find them easy to use and reliable as long as you can get power into them uninterrupted, and they leave plenty of room for other mods. The notch in the skirt over the fuel tank (under the A in the CA logo here) is usually an indicator it is a pancake motor model.

F7A 350
Bachmann F7A with pancake motor

AHM GP-18 is the power for most freight service. This 4 wheel pickup / 8 wheel drive GP18 can be operated either-end forward, so we don't need to turn the loco.

GP18 628
AHM GP-18

AHM BL-2 is the power for light branch line service and switching the industrial park. This 4 wheel pickup / 4 wheel drive model has a vertical shaft 5-pole motor with makes a healthy growl - no sound effects needed here. Prototype BL-2's were not provided with MU capability, so these run solo. Same drive train as used in the AHM FM C-liners.

BL2 402
AHM BL-2

Modifications include adding weight, cleaning electrical pickups, lubrication as needed. The entrance exam is if a loco can pull 11 NMRA-weighted freight cars up the 3% ruling grade. If so, then directional constant-intesity LED lighting is added, paint and decals, and numbering.

Road numbers: Numbers are assigned as follows. Powered locomotives have even numbers. Dummy (no electrical pickup, no motor) or Slug (electrical pickup only, no motor) units have odd numbers. This makes it easy to tell at a glance which units are powered.

MU (Multiple Unit) wiring Let's face it, these locos are trainset quality and typically some have unreliable electrical pickup, or are underpowered. The layout is essentially point-to-point with runaround tracks at each end. There is no ability to turn locos. The strategy is to permanently couple and jumper-wire pairs of units back-to-back so they do not need to be turned. With the units wired together, the number of electrical pickup axles doubles, which solves the electrical issues and provides smooth running over block gaps and switches, as the 'hot' axles are spaced quite a bit apart. Wiring two powered units provides a two-motor unit, easily capable of running up the 3% grade to the northern end of the layout.

F7A 466 470
Two powered (note the even road numbers) F7A's easily haul a full length streamliner up the 3% ruling grade.

Multiple unit wiring
Grey 2-conductor speaker wire runs between the units for MU operation.

Wiring one powered and one dummy unit together provides a 8-wheel pickup loco suitable for flatland use. These dummies are called "slugs" - they work like prototype slugs but in reverse - their only job is to pick up more power from the rail and send it to the connected power unit.

GP18 687 678
One powered (678) and one unpowered slug (687) GP-18 work local freight service. For freights heading up the 3% grade, two powered units are used.


home • Revised Aug 1 2014