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Comment by seanmcdirmid | Hacker News Reader

> Steel wheel on steel rail is low friction, and you get most of the energy used to go uphill back when you go downhill.

If you were going up and down hills, would you still use steel wheel in steel rail unless you had some sort of cable to work with? I always thought the Muni did relatively level routes for that reason? The Lausanne m2 for example uses rubber (well, ideally you’d be able to just balance the train going up with the train going down, but that only works for simple inclines with limited stops). Actually, a battery powered rubber wheeled tram service on some sort of steep incline like SF’s cable car routes could get some wicked regen going down.

Even if level, they could still get some regen from making stops.

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Modern speed control technology has expanded the incline range for steel-wheeled trains quite a bit. Inclines that would have historically pointed towards rubber-tired or non-traction systems are usually within the range of steel wheels with solid-state motor control. Basically the control of torque is much finer than in old resistance-box parallel/series speed controllers, so you can avoid slippage much more easily.

> would you still use steel wheel in steel rail unless you had some sort of cable to work with?

A rack rail is also an option, though tends towards the noisy and slow.

But yeah usually light rail keeps under 5%, and can’t really go above 10 on pure adhesion.

muni has "relatively level routes" because the routes that were preserved were ones with tunnels that buses couldn't fit through (or narrow ROW in the case of the J), and given sf geography those tunnels invariably go through hills. muni, and especially the J, is one of the steeper adhesion railways in the world

The J Church line on Muni is still a train in part because back when they were converting lines to buses, the hill on Church St was too steep for buses.

Wiki says it was more because of the private right away used, not necessarily its steepness:

> While many streetcar lines were converted to bus lines after World War II, the J Church avoided this due to the private right-of-way it uses to climb the steepest grades on Church Street, between 18th Street and 22nd Street.[9]

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

> Ironically, this steep grade saved the J-Church line from being replaced by buses. After World War II, San Francisco began replacing the streetcar lines with buses, but the Church Street hill proved too steep.

Little bit of columns A and B

https://www.opensfhistory.org/osfhcrucible/2019/08/10/the-j-...

If the vehicle is battery operated there is no longer a need to use metal wheels. Something like ABS, nylon or rubber probably results in less wear and noise. (Perhaps at the cost of a bit more dust from braking though)

Metal wheels have significantly reduced friction, switching to something like a car tire would require much more frequent tire replacements and would have a lot more issues. Steel on steel is the way to go for fixed-route vehicles if possible.

Problem with rubber wheels in metros is absolutely atrocious air quality. I avoid them like the plague.

How many rubber wheel metros exist? I only know of a few -- Paris is one, but not all lines. Where do you live such you need to "avoid them like the plague"?

Lyon.

Its not hard to find out where they are, Michelin is quite proud of them.

Montreal uses rubber tires in the underground. Never bothered me.

Fine particulates don't 'bother' you until you have that lung cancer diagnosis.

> Fine particulates don't 'bother' you until you have that lung cancer diagnosis.

Care to point out a source that supports a hypothetical link between rubber wheels and lung cancer?

Hypothetical you ask for?

https://pmc.ncbi.nlm.nih.gov/articles/PMC1757501/

To preempt accusations that the automotive endproduct isn't represented by this study, I'll concede it's next to impossible to have conclusive studies on specific forms of road pollution, that is, the best one can do is find a link between (rail)cars and cancer but nothing more specific than that :)

--Until they replace rubber in wheels with something else, I guess. Meanwhile, feel free to accept the reindustrialization

Tires contain carcinogens. That's not purely hypothetical, it has been known for a while.

The extent of impact is still being investigated, but we've known there is a carcinogenic link since before 2000.

[0] https://pmc.ncbi.nlm.nih.gov/articles/PMC6947500/

About OP: I swear, there is a HN "rule": When there is any opportunity to discuss health scare conspiracy theories, someone will pop into the convo (wearing a tin foil hat, naturally) to add their two cents. It is the perfect embodiment of Brandolini's law.

    > The amount of energy needed to refute bullshit is an order of magnitude bigger than that needed to produce it.

As a counterpoint to "avoiding rubber tyred metro lines like the plague": Does this person also avoid all road tunnels or expressways underground? Since there are frequently multiple lanes in each direction, that would mean much more fine rubber particulates from car & truck tyres compared to a metro with much less frequent trains and only one track in each direction.

I wonder if there's every been a study if the air quality in the montreal metro vs comparable cities. Or even within Montreal... does the blue line use tires? (Edit, yes, for some reason I thought one line didn't have them, apparently they all do)

I was told the tires are to reduce noise but I wonder if part of it is to handle some of the steeper sections like Vendome up to Villa Maria.

https://en.wikipedia.org/wiki/Rubber-tyred_metro#List_of_sys...

What's the problem? Rubber dust? Rubber smell? Maybe even burning rubber smell?

Also you have to replace tyres all the time, steel wheels last longer between services and are reconditioned on a lathe periodically instead of having to be continually replaced. It's one of several reasons why the longer term operating cost is way lower for trams than buses.

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