Diesel Locomotive Wheel Arrangements

Diesel locomotive wheels are typically described by the number of powered and unpowered axles per truck. For example, a GP9 has 2 trucks, each having 2 axles and 2 traction motors. Thus, a GP9 is designated Bo-Bo, where the 'o' means no unpowered axles. Usually the o's are left off, leaving the more common designation B-B.

Powered Axles Unpowered Axles
A=1, B=2, C=3, D=4 o = 0, 1 = 1

EMD A1A
A1A-A1A
As used on EMD E-unit or ALCO PA.
3 axles per truck, the center axle without a motor.
EMD Blomberg
B-B
The Blomberg, basically unchanged since 1939.
EMD HT-C
C-C (HT-C)
EMD truck has three powered axles.		 EMD Radial
C-C (HTCR)
EMD low-friction radial truck.
EMD DD
D-D
EMD DDA40X truck has 4 axles and traction motors.		 GE HTTC
C-C (HTTC)
GE high-traction truck.


  Page by Randy Houk
Updated 12-16-2010