Hello Tom,

Over the last 5 years or so I have noticed that some of the rails on the railway causeway to Venice seemed
to be painted white and I have posted some images of same on this great Users Group:











This resulted in some discussion on this forum after my post which wondered if this was to counter the effects of heat :



Regards,


Philip

its hard to believe that this works.

A black object radiates and absorbs heat faster, so painting the sides of the rail white is going to slow the rate at which heat radiates from it. The sides are not perpendicular to the sun's rays, so I would expect a net increase in temperature by painting the sides white.

But surely half the problem is the rails absorbing heat, so the white will slow down the absorption, which will mean they don't reach the same temperature during the day, and hence the rail expansion will be lower.

It works well on wind turbines

25 - 30 years ago, the first wind turbines were grey, because they were galvanized.

In Scandinavia, this was not a problem; but when the first turbines were installed in Texas, the grey towers got so hot that it
was hard to work inside; even though the heat-producing parts like the generator etc. is above the tower, in the nacelle.

Painting them white reduced the average temperature in the towers with more than 10 degrees Celsius.

This is what I was told; apparently there are a few reasons more: https://interestingengin...posite%20rotor%20blades.

Per.

Loco drivers complained about the white rails, you can't see them in winter time when the tracks are covered with snow and therefore you don't know where you going

Sorry to side track. During WW2, an RAF person was sitting at an airfield when a civilian plane took off. He watched it for a while, looked down, then found it hard to see it again. He made inquiries and found out it was painted a pale green. Thats why WW2 British aircraft most often were painted pale green underneath.
Interestingly, the lightened spitfires [ no armaments etc to help them go faster ] used for spying, were painted pink, so they could not be seen coming out of the sun. They used these apparently to track coastal installations deemed dangerous to the allies, and the flew very low over the sea and coast taking pictures.

Cant remember where I read about that.



With the modern technique of welding rails together, there was now no ability to absorb expansion [ talked about in the films mentioned by ShannonN ] that I could work out.
Dereck


Couldn't resist when spitfires were mentioned. But I did get back on track.

yes, but the sides of the rails are vertical, and the solar flux comes from above, so the effectiveness of blocking the sun's rays will be limited by the angle of incidence of the rays.

In other words the sides of the rail is not where a lot of the heat gets into the rail. Black sided rails would radiate as much as possible.

It makes sense to paint surfaces that face the sun, such as a roof.

Hello Tom!

long time no hear! Glad to see you are here!

Next years Insider wagon ???

Interesting (?) facts on suncurves from the Swedish Transport Administration:

Welded rails should be laid during neutral conditions, e.g. approx. in the areas average temperature. In these conditions, rails are laid without having any tension.

Proper laid welded rails should not move at all.

On welded tracks, suncurves generally only occur

- when there are bad fastenings to the concrete sleepers or bad ballast OR
- if they are laid under non-neutral conditions OR
- in areas close to turnouts or non-welded sections.

Suncurves still occur every year even on welded tracks, mainly due to lack of funding for maintenance.

There are bigger challenges in northern Europe than in southern Europe, due to the wider span in temperatures.

MY OWN CONCLUSION: Painting the rails is a temporary solution for managing badly laid or badly maintained tracks.

In the UK you would set a solar panel at about 55 degrees and it will get roughly even illumination at the extremes of sun altitude (i.e. longest and shortest days).

I would think that Germany would be at a similar enough angle, so painting the sides of the rails would be worth while.