If it leaves a fire trail like the DeLorean does when it time travels, won't that be a bit problematic if your layout is made of foam(and/or wood?)
No, but it may melt plastic ties. NOTE: Due to the current scenario, I'd much rather save the money needed for this bash to make another SD&AE steamer or two. The time machine was only a concept for a novelty kitbash. I would be quite pleased if someone other than me would make it, though, and besides--SD&AE freights are limited to 35 MPH. If you tried to reach 88 MPH in Carriso Gorge, you'd fall 900 feet to your death. Unless--(of course)--you could make it fly... "Rails? Where we're going, we don't need... rails."
Or worse, since he'd have the trains, there'd be no point in buyuing or building them. Which means he wouldn't send them back in time. Then he'd wish he'd have them, so he'd build them, then send them backwards. There's your paradox Janeway.
