Oh crap
!. I can explain some of it, but not all. On this particular model the piping is hard to figure out do to poor pictures available. The thing under the cab is the water injector. Locomotives always have two of them, one on each side. So there is a piping coming from the cab with steam to power up the injector and the steam propells the water from the injector toward the front of the boiler and you can barely see the valve hidden by the deck where water is shot into the boiler. Right above that valve is a sand box and the three pipes coming down from it are sand lines to throw sand under wheels when slipping or starting a heavy train. Sand box is that huge reservior behind the chimney. The three lines coming from under the cab and running just below the walkway (right side of the locomotive), are for the brake system. The main tank on the F-1 was on the left side of the locomotive:
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That is the huge torpedo like tank just above the driving wheels. Secondary tank is located under the front of the smoke box:
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You can just barely see it under the smoke box hidden behind the set of air compressors-those vertical things sitting behind the shields right in front of the smoke box. Air compressors were of course powered by steam and that adds more piping. On a model like that i can not reproduce all piping exaxtly because the boiler is screwed to the main frame and there's a need to separate assemblies. Getting back to that left side there you see more piping just above that main tank and it loooks like it goes back and forth, that's in order to cool the compressed air a little, sort of like a radiator, otherwise hot air would cause damage. Also on left side you see sand pipes coming down from sandbox just like on right side. Under the cab is the other injector with its associated piping; steam is released into injector and it pushes the water from tender into the boiler. Normally one injector is used and the other is used as a spare in case one fails. There is more piping on top of the boiler right in front of the cab, that device is the turret (sort of like distributor) and by turning nobs in the cab the steam from the boiler is used to power the devices i described. What i can't figure out are those two very thick pipes running forward from the turret and then turning diagonally to run under the walkway. They deffinitely run forward and i wonder if they power the compressors, all pictures are very dark in that area and i'll have to do more digging to figure out how they run under the walkway. This particular model will have another very thick pipe on the right side that will come from the boiler near where the cylinders are, that was a steam pipe to power the booster truck on the tender:
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On the picture above you can see that pipe starting just behind the cylinder block, running under the power reverser, making an "S" curve to run under the grate and then under cab, i didn't get to that pipe yet on my model. I hope that explains some of it a little. There is also a bunch of small piping at the front, on the side of the smoke box, i have no clue what that piping was for and the earlier F-1s; 401 and 402 didn't have that.