The only problem I can see with that is if your firebox is too low to the ground, you might melt the track.
P.S. - Don't quote me on that, I do not run live steam (yet).
Two problems using plastic track for live steam;
First the live steamers are significantly heavier than the electrics. There is a lot of mass in an all metal engine loaded with water. I'm not sure the plastic track would be stiff enough to support the weight or long lived enough to stand up to the wear and tear.
Secondly and most important, you need metal track for at least a steam up area. Starting up a cold engine traps a lot of condensate in the piping and cylinders that needs to be cleared at start up. Consequently one is putting a lot of boiling water into the ballast and ties as the cylinders clear. Haven't ruined any plastic ties completely but the ties in the steam up area don't have any detail left in them. Sooner or later I'm going to have to replace the ties where I start up with wooden ones. My Shay is the worst offender. Between a low firebox and a clunky way of clearing the cylinders, it probably has done 90% of the damage.
Another word of warning. Live steam can be very addicting leading to starving children and unhappy spouses.
Age is only a state of mind, keep the mind active and enjoy life
I really think that if I'm gonna use New Bright track it would have to have a roadbed, definitely. Then I'm sure the track will be fine. About the weight and tracks; believe me they can hold all the weight they can get, I can walk and stand on them and I'm 5'9, 143 lbs.
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