Diesel "A-1-A" truck sideframes

No, these are not named after the highway in southeastern Florida! The term "A-1-A" refers to a three axle truck where the outer axles are powered and the middle axle is not. Letters are assigned based on numbers of contiguous powered axles, while numbers represent sets of unpowered axles. Typically these were found under passenger and light duty units.

The models and variants

GSC Single Equalized A-1-A trucks

This truck was used under a multitude of units from Alco, Baldwin, and Fairbanks-Morse. It is a single, drop-equalized design, and a 15 foot 6 inch wheelbase. Pennsy units equipped with it include the Baldwin DR-6-4-2000 sharks, F-M Erie-Builts, and Alco PA-1 and PB-1. It came in multiple versions. That used on the Alco and Baldwin units had equalizers flat on the top and sloped on the bottom; The F-M version was the opposite. The F-M version also had a smaller third brake cylinder for the middle axle, and the same spring sets and bases later used on the C-Liner truck.
Athearn has a version of this truck for their PAs, as does Proto 2000.

F-M Erie-Built fabricated trucks

The fabricated truck used on some Erie-builts was apparently an attempt by GE to try and bring down construction costs by not having to pay for the GSC trucks.

EMD A-1-A trucks

This truck was also designed by Blomberg, but was not commonly called by his name. It has a 14 foot, 1 inch wheelbase. EMD passenger units, including the E7s and E8s of the Pennsy, used this truck. The Rivarossi, Con-Cor (ex-Roco), and Proto 2000 E units all have renderings of this truck.
Here's the one from the Proto 2000 E7B

Commonwealth cast trucks

Also a GSC cast design, this truck was found under Baldwin AS416s. It had a wheelbase of 11 feet, 6 inches, and the middle axle was slightly off-center. It was equipped with plain bearings. No known models.

Alco RSC-2 truck

This truck was only found under the Alco RSC-2. It featured single-drop-equalized trucks with even axle spacing. Wheelbase was 10 feet, 5 inches. A model was made by Kato.

Alco RSC-3 truck

Apparently the RSC-2 design didn't pan out, because the Alco RSC-3 came with a new design, double-equalized but again with evenly spaced axles. This greatly resembled the truck found on the RSD-4 and RSD-5, with the single large brake cylinder.


Thanks are due many people; They can be found on the credits page, now separate.
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These pages created by Derrick J. Brashear, shadow@dementia.org