RTT-21's are a three section wheeled transporters used to transport dangerous liquids through rough terrain. They are named as a 'Caterpillar', beacuse they are usually painted green and articulated chassis makes that its move is similar to catterpillar's.
The cabin is taked from one of the 4 Juniors sets, 4653
It has an awful pattern on front, so I rotated it on the back. It looked better, but there was no room for whole minifig. But his half fits perfectly ;)
The tanks for transportnig those dangerous liquids are made from white Airtanks:
With and without load:
Each section have a pendular suspension, that provides great stability when vehicle is moving through obstacles.
Edited by Rufus, 30 July 2011 - 06:52 PM.