Unit D3+ D33: CaseIH STX420 Articulated Narrow Track Tractor + Unverferth 1110 Tracked Grain Buggy Posted on January 12, 2019 (January 12, 2022) by Alex Barrie in Compaction Test Results Datasheets Plot Comments This buggy is heavy, higher stress in the lower depths when compared to light equipment.The variation in the green curve on both plots may be due to lug spacing and roller contact.