I knew I'd stir up a hornets' nest. But I know they're friendly hornets.
I've actually been following this discussion pretty closely. I know pretty
well what most of you are talking about. But I've stayed out of the
discussion mainly because I didn't really have any good real world data to add
and didn't want to present myself as having good engineering knowledge that I
talk to without sounding like some foggy old engineering professor (old &
foggy-yes. Engineering prof-NO). I haven't even tried to analyze the cooling
system in Doug King's modified roadster. Why? Cause it has a good vent and
works very nicely. As long as everybody tells whoever is driving to turn on
the water pump when we fire the engine at the starting line.
I think the heat exchanger concept is a good one. It lets the engine run at a
higher coolant temperature and pressure which reduces hot spots and allows
more BTU's to transfer for each gallon pumped. As long as the "bathtub"
venting is completely reliable and the primary engine cooling loop has very
reliable pressure cap with maybe a high quality relief valve as a backup,
you're probab;y OK. In a road car the rubber hoses will blow safely in the
engine compartment if the radiator cap fails and thermal expansion of the
water causes a rapid pressure buildup. In a race car we like to use high
pressure fittings which can end up putting the primary system's weakest point
somewhere else. Like the radiator in the "bathtub" . So the idea of copper
tube coils for the heat exchanger is a better idea. My advice to anyone
experimenting in this area is just be sure you have thought through where and
how this thing might fail under every possible set of circumstances.
I'm not trying to talk here to the experienced hands like Joe, Dave and Kieth.
But there are lots of other creative types who read this list and I just want
them to go into any such experiments with this stuff with their eyes wide
open.
With respect to code adherence pressure testing and all that--we really don't
need that. The live steam model train builders, the big guys that run 3-3/4"
and 7-1/2" gauge, have to have all their locomotive boilers hydrotested and
certified. We likely will never have to go there; unless someone gets hurt in
a freak accident.
Ed Weldon
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