3 ms·

> There's enough difference between 1435mm and 1520mm to use a 3-rail system. Can you provide an example? I've only seen 4-rail dual-gauge systems for those ga

by Gare 4y ago

> There's enough difference between 1435mm and 1520mm to use a 3-rail system. Can you provide an example? I've only seen 4-rail dual-gauge systems for those gauges.

SoftTalker 4y ago
Why would you need 4 rails? | | | | | | Left wheel uses left rail. If narrow gauuge, the right wheel uses the innner rail. If wide gauge, the right wheel uses the outer rail.
- innocenat 4y ago
  Because rails are 3 dimensional and has width. Between 1435mm and 1520mm there's only 85mm space. I am not even sure if you could mount two rail that close.
  - justsomehnguy 4y ago
    https://upload.wikimedia.org/wikipedia/commons/f/ff/NYCS_DUDLEY_127_LBS.png https://upload.wikimedia.org/wikipedia/commons/f/ff/NYCS_DUD... 3" equals to 76.2mm, which leaves only 8.8mm. No way.
    - SoftTalker 4y ago
      True, I didn't think about how close these gauges were, and was assuming adequate space for the inner and outer rail.
- justsomehnguy 4y ago
  These gauges cannot make 3-rail dual gauge with Russian gauge. 1,676 mm (5 ft 6 in) Indian gauge 1,668 mm (5 ft 5+21⁄32 in) Iberian gauge 1,600 mm (5 ft 3 in) Irish gauge 1,435 mm (4 ft 8+1⁄2 in) standard gauge https://en.wikipedia.org/wiki/5_ft_and_1520_mm_gauge_railways#Similar_gauges https://en.wikipedia.org/wiki/5_ft_and_1520_mm_gauge_railway...
  - Animats 4y ago
    I got that info reading about a dual-gauge solution for China's Belt and Road. But it was a political piece on the "Akhaura-Sylhet dual gauge project" in Bangladesh. Turns out that India, Pakistan, western Bangladesh, and Sri Lanka (also, SF's BART) use 1,676 mm gauge. There's enough space between that and 1,435 mm standard gauge for 3-rail. Not sure about 4-rail.
    - justsomehnguy 4y ago
      See my other comment[0] on this. 4-rail is a viable solution, but, unsurprisingly, it costs more than a 3-rail or sometimes a two separate 2-rail lines. [0] https://news.ycombinator.com/item?id=31880979 https://news.ycombinator.com/item?id=31880979

by Gare 4y ago

> There's enough difference between 1435mm and 1520mm to use a 3-rail system. Can you provide an example? I've only seen 4-rail dual-gauge systems for those gauges.

SoftTalker 4y ago

Why would you need 4 rails? | | | | | | Left wheel uses left rail. If narrow gauuge, the right wheel uses the innner rail. If wide gauge, the right wheel uses the outer rail.

innocenat 4y ago
Because rails are 3 dimensional and has width. Between 1435mm and 1520mm there's only 85mm space. I am not even sure if you could mount two rail that close.
- justsomehnguy 4y ago
  https://upload.wikimedia.org/wikipedia/commons/f/ff/NYCS_DUDLEY_127_LBS.png https://upload.wikimedia.org/wikipedia/commons/f/ff/NYCS_DUD... 3" equals to 76.2mm, which leaves only 8.8mm. No way.
  - SoftTalker 4y ago
    True, I didn't think about how close these gauges were, and was assuming adequate space for the inner and outer rail.
justsomehnguy 4y ago
These gauges cannot make 3-rail dual gauge with Russian gauge. 1,676 mm (5 ft 6 in) Indian gauge 1,668 mm (5 ft 5+21⁄32 in) Iberian gauge 1,600 mm (5 ft 3 in) Irish gauge 1,435 mm (4 ft 8+1⁄2 in) standard gauge https://en.wikipedia.org/wiki/5_ft_and_1520_mm_gauge_railways#Similar_gauges https://en.wikipedia.org/wiki/5_ft_and_1520_mm_gauge_railway...
- Animats 4y ago
  I got that info reading about a dual-gauge solution for China's Belt and Road. But it was a political piece on the "Akhaura-Sylhet dual gauge project" in Bangladesh. Turns out that India, Pakistan, western Bangladesh, and Sri Lanka (also, SF's BART) use 1,676 mm gauge. There's enough space between that and 1,435 mm standard gauge for 3-rail. Not sure about 4-rail.
  - justsomehnguy 4y ago
    See my other comment[0] on this. 4-rail is a viable solution, but, unsurprisingly, it costs more than a 3-rail or sometimes a two separate 2-rail lines. [0] https://news.ycombinator.com/item?id=31880979 https://news.ycombinator.com/item?id=31880979