A Blomberg "M" type truck on a BNSF GP38-2. The Blomberg "M" type truck is based off of the Blomberg "B" type truck, which has been in service since 1938. The first locomotive that used the "B" type truck was the EMD FT, starting in November 1939. The last locomotive to use this truck was the GP60, which ended production in 1994. This truck has one brake cylinder per axle, shown here above the rear wheel. A large leaf spring in the center absorbs vertical movement, while hydraulic shocks on the front axle absorb horizontal movement. The Blomberg truck is named after Martin Blomberg, who joined EMD in 1938. He was a Swedish-American engineer who designed the truck. Blomberg also help design the AAR type "A" switcher truck. Two air dryers can be seen in the middle left of the photo, right in front of the fuel tank.
Generally speaking, shots where less than a full engine is shown. But I want to feature details, not half engines or full cabs, and definitely not full nose shots. Just shots where someone has zoomed in with purpose.