I see this photo on Facebook tonight. Apparently in Mexico in the 1880s. What am I seeing?? The loco cab and two cars have additional "roofs" on top of the cab/car roofs...?? Is this to keep the heat/temperature down in the cars?

(Also of note: Loco is a 2-6-6 wheel arrangement)

I'd say that's a very good guess.

Looks like the assessment that the "extra" roof was an attempt to keep temperatures a bit more tolerable is correct.

What stands out in the link shown below is that not only was this Mason-Fairley built by Baldwin instead of Mason, but the "sun roof" came with the engine from Philadelphia!!

https://www.steamlocomotive.com/locobas ... ad=cm#3163

Looks like the assessment that the "extra" roof was an attempt to keep temperatures a bit more tolerable is correct.

What stands out in the link shown below is that not only was this Mason-Fairlie built by Baldwin instead of Mason, but the "sun roof" came with the engine from Philadelphia!!

https://www.steamlocomotive.com/locobas ... ad=cm#3163

They are on the principle of 'safari roofs'. I had one on my Land Rover and it works surprisingly, extremely well.

The construction is a usually white-painted sheet -- thickness really only determined by structure; mine was aluminum sheet with white paint -- held off the actual car roof with small-area standoffs, usually posts. There is no attempt to seal the adges; there in no 'ridge vent' to duct 'cool' air from edge to center (as on some '30s manufactured housing).

The principle is only partly to 'reflect sunlight' to decrease solar gain. The two roofs define a relatively trapped air space, with low convective transfer, and heated air is a good insulator.

Do they really want to keep the boiler head nice and cool? I've never noticed the heat in a steam locomotive cab coming primarily from the ceiling......

You spend very much time stopped in sidings or slowly working over the road in Mexican sunshine and you'll figure out why they used those roofs right quick!

Sammy will say this much more colorfully, with much more experience.

Thank you Brother Overmod, I'll take the bait: Brother Dave, it isn't about keeping the boiler head nice and cool, it's about keeping US cool. In Mexico and Guatemala, no doubt elsewhere in Latin America, we always have a shady place outside the cab to stand whenever we have to wait for an opposing train to clear, time to apply, or the tank to fill with water, etc, and this shady place is so situated that we can watch the water glass through the cab window or gangway. If nothing else was available we'd stand under the running boards for shade and check the water level every few minutes.

You'll notice in the photo that the cars with sun roofs are outfit cars, and this practice provided a little bit of relief for the spartan existences of their occupants. While most locomotives didn't have these roof top awnings, the practice was much more common with work equipment that was usually parked in a siding. And yes, we didn't want our stash of Tequila to overheat because it not only burned going down, but the alcohol would evaporate faster if it got hot...

When I worked at Texas State RR, we also had strategically located shady spots for any places where we often had to stop and wait. Both ambient temperatures and humidity were frequently around 100, and the cab got real hot real quick unless we were moving. One of our guys rounded up some meat thermometers and stuck one in the cab of each of our locomotives. At 2 or 3 mph it was plenty comfortable for the head end crews, but within a minute of stopping, it got up to 140 degrees or thereabouts. QED.