What part in LEGO digital designer can be used for a tank track? I'm using LEGO digital designer to model a LEGO tank. I don't seem to find parts that can be used to make the tank track and the inside wheels; I found a "caterpillar belt" but no wheels that can fit inside the track. 

There is a part called "caterpillar track", and unlike the belt the track requires wheels of different diameter to fit inside it. Again, I can see the wheel for the wider end of the track but not the narrower end.

Are there any parts that can be used for tank tracks at all? Or should I look for an alternative solution?
The caterpillar track and belt are both fixed length pieces.

I would recommend the more versatile #57518 'Technic, Link Tread Wide with Two Pin Holes'. The part can be used to make a track as long as long as you like.



The tread is compatible with:


#57519 - Technic Tread Sprocket Wheel Large
#57520 -  Technic Tread Sprocket Wheel Small