This is my variation on a fairly common theme: Generation 2 Yellow liveried Devastator with added articulation.
The individual Constructicons are (sadly) not original figures. They transform normally, and have been modified discreetly to allow for combination.
Devastator is articulated at the wrist, elbows, shoulders, neck, hips, and knees. He gains mobility at the waist courtesy of the hip section from Beast Wars Megatron. Star Wars Crossover Darth Vader contributed the forearms. The hands are therefore retractable which allows for unhindered drilling action. Wrist mobility is rotation only. All of the other joints are ball joints. The feet have been supported by additional pieces, but the classic tractor scoop/truck cab feet are still prominent. Mounted on the right shoulder is a cannon in place of the original head-mounted missile--it seems more sensible to me. The head is courtesy of Armada Starscream.