One of the nice things about talking to the Forge World designers, whether it be at GamesDay or the Forge World Open Days is seeing how they move models from ideas and drawings to concepts to finished product.
This Ork concept vehicle based on the Ork Trukk eventually became the Big Trakk.
The other side was more of a half-trakk opposed to the full tracked side here.
If you compare it to the Big Trakk model you can see how the model evolved.
Ork Battlewagon with Supa Kannon from the Forge World displays at their Open Day in 2009.
I got this model as a Christmas present, it combines the plastic Battlewagon kit with a resin Supa Kannon. See the full workbench feature on this model.