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A 15 meter turning radius is tight, but not revolutionary. San Francisco's MUNI system's tightest turns are 45 feet, or 13.7 meters. The newer vehicles are desi

A 15 meter turning radius is tight, but not revolutionary. San Francisco's MUNI system's tightest turns are 45 feet, or 13.7 meters. The newer vehicles are designed for that, and the old PCC cars had to be modified to allow the trucks some extra rotation. The turning loop on Embarcadero near Market is that tight. There is much wheel screeching when a PCC car goes through that loop, because wheels have to slip to turn that tight. But it works.[1] Battery powered trams have real potential, now that batteries with 5 to 7 minute charging and large numbers of charging cycles are a thing. That's compatible with typical end of line holding times. Steel wheel on steel rail is low friction, and you get most of the energy used to go uphill back when you go downhill. This could work out. [1] https://youtu.be/XKN0MTCUSV0?t=265 https://youtu.be/XKN0MTCUSV0?t=265

seanmcdirmid 1y ago
> 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.
- brnt 1y ago
  Problem with rubber wheels in metros is absolutely atrocious air quality. I avoid them like the plague.
  - throwaway2037 1y ago
    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"?
    - brnt 1y ago
      Lyon. Its not hard to find out where they are, Michelin is quite proud of them.
    - PaulHoule 1y ago
      Montreal uses rubber tires in the underground. Never bothered me.
      - brnt 1y ago
        Fine particulates don't 'bother' you until you have that lung cancer diagnosis.
        motorest 1y ago
        > 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?
        gsf_emergency 1y ago
        Hypothetical you ask for? https://pmc.ncbi.nlm.nih.gov/articles/PMC1757501/ 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
        shakna 1y ago
        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/ https://pmc.ncbi.nlm.nih.gov/articles/PMC6947500/
  - ahartmetz 1y ago
    What's the problem? Rubber dust? Rubber smell? Maybe even burning rubber smell?
  - stephen_g 1y ago
    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.
- masklinn 1y ago
  > 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.
- fotta 1y ago
  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.
  - seanmcdirmid 1y ago
    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 https://en.wikipedia.org/wiki/J_Church
    - fotta 1y ago
      > 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-church-climb-a-closer-look/ https://www.opensfhistory.org/osfhcrucible/2019/08/10/the-j-...
- andbberger 1y ago
  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
- jcrawfordor 1y ago
  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.
- speleding 1y ago
  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)
  - Moomoomoo309 1y ago
    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.
vidarh 1y ago
Maintaining a quiet operation is listed as one of the advantages of the turning system for this system.
closewith 1y ago
> A 15 meter turning radius is tight, but not revolutionary. San Francisco's MUNI system's tightest turns are 45 feet, or 13.7 meters. Revolutionary as the turning circle will be used at speed with passengers to traverse roundabouts in-lane. CVLR doesn't need turning loops, as the vehicles can be driven from either end.
wkat4242 1y ago
Overhead power is more efficient and sustainable though. No batteries to chug along, no batteries to replace or manufacture. And I wonder if the cost over time really makes up for hanging a few overhead lines.
torton 1y ago
Several North American older systems go down to 10-11 meters, although perhaps the tightest curves are getting upgraded over time: LRT systems on which the existing minimum curve radius falls below 15 meters include: • Boston—10 m (33 ft) and 13 m (43 ft) for the Green and Mattapan lines, respectively; • Newark—10 m (33 ft); • San Francisco—13 m (43 ft); and • Toronto—11 m (36 ft). https://onlinepubs.trb.org/Onlinepubs/tcrp/tcrp_rpt_02.pdf https://onlinepubs.trb.org/Onlinepubs/tcrp/tcrp_rpt_02.pdf (1995)

seanmcdirmid 1y ago

> 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.

brnt 1y ago
Problem with rubber wheels in metros is absolutely atrocious air quality. I avoid them like the plague.
- throwaway2037 1y ago
  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"?
  - brnt 1y ago
    Lyon. Its not hard to find out where they are, Michelin is quite proud of them.
  - PaulHoule 1y ago
    Montreal uses rubber tires in the underground. Never bothered me.
    - brnt 1y ago
      Fine particulates don't 'bother' you until you have that lung cancer diagnosis.
      - motorest 1y ago
        > 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?
        gsf_emergency 1y ago
        Hypothetical you ask for? https://pmc.ncbi.nlm.nih.gov/articles/PMC1757501/ 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
        shakna 1y ago
        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/ https://pmc.ncbi.nlm.nih.gov/articles/PMC6947500/
- ahartmetz 1y ago
  What's the problem? Rubber dust? Rubber smell? Maybe even burning rubber smell?
- stephen_g 1y ago
  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.
masklinn 1y ago
> 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.
fotta 1y ago
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.
- seanmcdirmid 1y ago
  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 https://en.wikipedia.org/wiki/J_Church
  - fotta 1y ago
    > 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-church-climb-a-closer-look/ https://www.opensfhistory.org/osfhcrucible/2019/08/10/the-j-...
andbberger 1y ago
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
jcrawfordor 1y ago
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.
speleding 1y ago
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)
- Moomoomoo309 1y ago
  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.

vidarh 1y ago

Maintaining a quiet operation is listed as one of the advantages of the turning system for this system.

closewith 1y ago

> A 15 meter turning radius is tight, but not revolutionary. San Francisco's MUNI system's tightest turns are 45 feet, or 13.7 meters. Revolutionary as the turning circle will be used at speed with passengers to traverse roundabouts in-lane. CVLR doesn't need turning loops, as the vehicles can be driven from either end.

wkat4242 1y ago

Overhead power is more efficient and sustainable though. No batteries to chug along, no batteries to replace or manufacture. And I wonder if the cost over time really makes up for hanging a few overhead lines.

torton 1y ago

Several North American older systems go down to 10-11 meters, although perhaps the tightest curves are getting upgraded over time: LRT systems on which the existing minimum curve radius falls below 15 meters include: • Boston—10 m (33 ft) and 13 m (43 ft) for the Green and Mattapan lines, respectively; • Newark—10 m (33 ft); • San Francisco—13 m (43 ft); and • Toronto—11 m (36 ft). https://onlinepubs.trb.org/Onlinepubs/tcrp/tcrp_rpt_02.pdf https://onlinepubs.trb.org/Onlinepubs/tcrp/tcrp_rpt_02.pdf (1995)