shpalman wrote: Wed Aug 26, 2020 3:12 pm
You just need something which runs on the rails ahead of the train by a bit more than the safe stopping distance.
I think "just" is doing quite a lot of work there
Thanks for the extra explanations, EPD. Interesting stuff.
We have the right to a clean, healthy, sustainable environment.
plodder wrote: Wed Aug 26, 2020 3:27 pm
It's pretty simple. It's just a long pole with a little trolley in front.
Safe stopping distances for trains can be quite long, though, especially when they're going fast.
I'm not sure it's feasible to put poles hundreds or thousands of metres long on the front of every train, or to slow them all down to more pole-appropriate speeds.
There are loads of trains all the time. I was trying to think of a network-level surveillance mechanism because that seems more practical. There must at least be ways to remotely detect sudden subsidence that could be retrofitted in vulnerable places?
We have the right to a clean, healthy, sustainable environment.
plodder wrote: Wed Aug 26, 2020 3:27 pm
It's pretty simple. It's just a long pole with a little trolley in front.
This is actually what's done for Arctic/Antarctic traverses to avoid crevasses. 10m boom on the front of a tractor, with ground/snow penetrating radar. Usually supported on a "sled" which is actually a truck inner tube.
But that's for going at 10mph in a caterpillar tracked vehicle. You still only get a second to hit the brakes if a crevasse is detected.
How about we tow the UK to the equator, get the Brexit dividend to pay for it, and lob a geostationary radar satellite up to monitor the identified trouble spots every few seconds? Or we can add radar modules as well to all of the the Galileo replacement internet sats, and leave the UK where it is.
shpalman wrote: Wed Aug 26, 2020 3:12 pm
You just need something which runs on the rails ahead of the train by a bit more than the safe stopping distance.
This was actually done in the Victorian era for the royal train, generally an express engine running light. There's a preserved Caledonian 4-2-2 that was built for an exhibition that got some use for this, as it was fast, but with only one drive axle, it couldn't actually pull very much without comical amounts of wheelslip.
plodder wrote: Wed Aug 26, 2020 3:27 pm
It's pretty simple. It's just a long pole with a little trolley in front.
Safe stopping distances for trains can be quite long, though, especially when they're going fast.
I'm not sure it's feasible to put poles hundreds or thousands of metres long on the front of every train, or to slow them all down to more pole-appropriate speeds.
There are loads of trains all the time. I was trying to think of a network-level surveillance mechanism because that seems more practical. There must at least be ways to remotely detect sudden subsidence that could be retrofitted in vulnerable places?
There's already ways of detecting earth movements, yeah. Check out the kind of thing used to check if volcanos are starting to get ideas.
I did think of seismometers, but they'll also pick up trains from quite a distance away so you'd have to do something clever with the signal processing. My university had to move its seismology equipment when they built a new car park nearby. A very very small earth movement could still be very very problematic if it happens to coincide with a track.
They also wouldn't tell you if the problem was actually on the track or merely nearby.
That's why I was wondering about using something reflecting track integrity, such as conductivity, but EPD' response suggests that that wouldn't be straightforward either.
We have the right to a clean, healthy, sustainable environment.
Bird on a Fire wrote: Wed Aug 26, 2020 5:43 pm
I did think of seismometers, but they'll also pick up trains from quite a distance away so you'd have to do something clever with the signal processing. My university had to move its seismology equipment when they built a new car park nearby. A very very small earth movement could still be very very problematic if it happens to coincide with a track.
They also wouldn't tell you if the problem was actually on the track or merely nearby.
That's why I was wondering about using something reflecting track integrity, such as conductivity, but EPD' response suggests that that wouldn't be straightforward either.
Wasn't meaning seismometers, sorry. Was thinking the measurement of bulging caused by magma movements, which can by tilt sensors, or by satellite.
Maybe it's not the track that needs monitoring, but the hill next to the track. Model at risk areas and jut put poles with prisms up that get regular laser surveys?
They do this with buildings when they tunnel underneath.
having that swing is a necessary but not sufficient condition for it meaning a thing
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plodder wrote: Thu Aug 27, 2020 4:08 am
Maybe it's not the track that needs monitoring, but the hill next to the track. Model at risk areas and jut put poles with prisms up that get regular laser surveys?
They do this with buildings when they tunnel underneath.
Yeah, there's all sorts, both at the immediate lineside and on the slope itself. I'm certain that they'll definitely try to spend money on lasers if someone gives them that chance.
