Okay, just got this one. On the upper two rings of the track make a trail to the dynamite from the track, also make a trail from the upper right ring to the barrel in the lower right. Set up a barrel and trail across the track to near the safe. Now here's the part that took me forever. Set off the plunger and wait. All the coal carts will eventually light up. Then and only then put your second barrel on the tracks where it can destroy your final pig and propel the cart to the safe. The 4 coal carts in the lower right ring will relight the cart on its way to the safe.
Now I just need to figure out 3-25 and I can go on to the dlc.