Talked to one of the UP guys, the yellow tenders are just for water, the black tender is mostly water also, the angled part holds the fuel, so maybe those tanks were for fuel or lubricants. Great fun doing these shots. I think I got some of my best ones of the Challenger and I've shot it several times. It was GREAT lighting with it being early morning. Notice the weird heavyweight car with the cupola on top? Said 'lab car' on the side. The 'flatcar' looked like a cut down coach. Never seen that run with it or 844 before.