Table schema:
CREATE TABLE table_20866024_3 (model_designation VARCHAR, gvw__kg_ton_ VARCHAR, axle_ratio VARCHAR)

Question: What's the model designation of the model with GVW of 2828/2.78 kg/ton and axle ratio of 9/47?
SQL: SELECT model_designation FROM table_20866024_3 WHERE gvw__kg_ton_ = "2828/2.78" AND axle_ratio = "9/47"