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Comment by teruakohatu | Hacker News Reader

> dates back to the late 1890s and will be replaced with a modern, more durable, metal trough.

I think any infrastructure that has lasted over 130 years is already quite durable.

It's wood, I'm sure the MBTA has a workshop that can build replacement parts.

Odds are the replacement is going to be some custom metal machined overseas and will be basically irreplaceable due to cost and skill issues.

The MBTA has a quite capable metal shop that's been making replacement parts for the 1960s vintage subway cars for quite a while.

Right but it will be something they can't work with. Like some custom magnesium-aluminum metal that has to be cast and can't be machined with normal tools.

And being the MBTA, it will be installed in the wrong size and have to be replaced in a couple of months.

My bet is on that there will be some kind of interaction of the metal catenary in the environment and maybe causing friction in the cables and shorts, which no one thought of since 1890 when they chose wood due for its insulating properties.

Then they will have to replace the metal with some fancy plastic one, because you can’t just admit the wood was better after all, but the plastic will also be unsuitable and degrade quickly which will ultimately end up with going back to wood in another 10 years. But that wood will then only last a fraction of the original wood, because we do not have old growth wood anymore and all the pine plantation wood won’t last a similar 130+ years.

So after about $3 billion dollars in costs and another $5 billion in economic and lifestyle impact after 20 years, they’ll declare it all a wonderful success, even though the wooden catenaries will live on as art or interior decor for another 200 years.

If we’re lucky, the death toll will even be low.

I foresee a "oh we can't replace the plastic one it with wood now because that would be a new material and we don't have data to prove it conforms with some rule we made up so the only solution is to pay some engineering firm who knows people on beacon hill a ton of money to say that pine is fine" situation before they go back to wood.

And as bad as the MBTA is... Keolis is worse (arguably).

Har, har, har, Buy Murican, amirite?

I encourage anybody who gets the opportunity to ride the green line. It's cool that they managed to build it in a time before tunnel boring machines (by literally digging a huge, long pit, building the track, then covering it with a roof and dirt again). Just wear noise cancelling headphones or something cuz those trains screech

Cut and cover is still the cheapest way to build subways, but is less often used nowadays because of the surface disruption.

Long before tunnel boring machines existed we needed to develop methods to dig under rivers. Brunel invented the tunnelling shield for digging under the Thames in 1825 and later a more refined version was used to dig the first deep-level tube line which opened in 1890.

https://en.wikipedia.org/wiki/Tunnelling_shield

THIS kind of comment is what makes HN gold!

TIL...

It's probably not the same wood since 1890. Requires more repairs and replacements.

I think there's a good chance it is. Not out in the sun, not in contact with ground/moisture, pretty consistent temperature. Wood can last a very long time under those conditions.

It could be. A lot of wood has been around for longer than that. Wood is easier to damage so I expect some has been replaced over the years, but there is no reason to think it wouldn't last in that application.

Yeah, I watch mine exploration videos and it's shocking how well wood in a dry and stable environment will last.

I wouldn't exactly call the environment on the green line as dry, especially in the summers.

The city of Venice is literally built upon timbers driven into the seafloor.

That haven't ever been replaced.

Maybe the chemicals they've used to treat the wood were so hardcore

Once again, promo-driven culture rears its ugly head.

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