The EMD#BlombergB is a 2 power axle locomotive bogie truck, introduced with the 1939 EMD#FT series, and were standard through their 1985~1994 GP60 series. Unofficially it is named after designer Martin Blomberg, who joined EMD in 1935. The truck evolved from an earlier 3 axle (A1A) design also by Blomberg (described in U.S. Patent 2,189,125, filed January 29, 1938, then granted February 6, 1940).
Blomberg trucks can be identified by their prominent outside swing hangers, which afford a better ride during side-to-side movement. The outside placement has the advantage of widening its spring base from 56 to 96 inches (1,422 to 2,438 mm).
Due to the swinging hanger suspension system these trucks are commonly referred to in the railroad business as "swing hanger trucks". The term "Blomberg" truck isn't used even in some railroad training literature that specifically describes truck types.
A popular modification by railroads in later years was reducing the number of brake shoes from 8 to 4 by reconfiguring the double-clasp brake rigging, removing one brake shoe per wheel. This can give the Blomberg B a similar appearance of later Blomberg M trucks.
Although possibly a few exceptions exist, where a customer specifically requested plain bearings, almost all Blomberg B and M trucks (freight), and all Blomberg A1A trucks (passenger) which preceded these, were fitted with roller bearings.
Blomberg B trucks are occasionally seen on competitors' locomotives, the General Electric Universal Series in particular, where the railroad has requested re-use of traded-in EMD trucks and possibly also EMD traction motors on new GE locomotives.
The Blomberg "M"odified version was introduced in 1972 with the EMD Dash2 locomotive series. This version typically has 2 brake cylinders with threaded adjusters and 4 composite brake shoes, instead of 4 brake cyclinders and 8 cast iron shoes on the older "B" version. Hydraulic snubbers (shocks) are mounted diagonally opposite (front right and rear left) journals. Older Hyatt roller bearings have been replaced by newer APcGG conical bearings. This version is typical on GP60 and F59PH locomotives, and on 2003 or later MotivePowerIndustries#MPX MP32 and MP36 series locomotives.
This version is directly evolved from the BlombergM, but is a new larger casting (not a rebuilt Blomberg); it is typical on 2007 or later MotivePowerIndustries#MPX MP40 and MP54 series locomotives. These have a longer 9ft 4in wheel base, steel leaf springs replaced by hybrid rubber steel laminate damper springs, and sway damper shocks between the truck and carbody; each a new feature required for more powerful trac motors, higher speeds and heavier locomotives.