Roland Perry <roland@perry.co.uk> wrote:
> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>
>>>>
>>>> Just curious: which laws of physics were violated?
>>>
>>> Force acting on a body, causing motion.
>>
>> Downward force against a slope produces a lateral component.
>
> Even when most of the slope has eroded away, so as not to be touching
> the bottom of the sleepers any more?

That was later in the cycle. As you have been repeatedly told, the sideways
movement happened when the embankment first started slipping to the right
and dragged the track with it.

Anna posted a tweeted photo in this thread that clearly illustrated this.
As you still appear unable to find it, here it is again:
<https://pbs.twimg.com/media/FKW719VX0AAUoku?format=jpg&name=large>

>
> In any event, given the tension in the rails, to "twang" them sideways
> would take, in my opinion, more than the horizontal component of that
> gravitational pull downwards.
>

Please share your calculations.

And please explain how these supposedly rigid, high tension rails sag into
the gap when all the support has gone? Surely, by your logic, they should
remain arrow straight.

Tweed <usenet.tweed@gmail.com> wrote:
> Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> wrote:
>> Roland Perry <roland@perry.co.uk> wrote:
>>> In message <suj76u$r50$1@dont-email.me>, at 16:02:38 on Wed, 16 Feb
>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>> On 16/02/2022 14:31, Roland Perry wrote:
>>>>> In message <suhai3$p7q$1@dont-email.me>, at 22:47:32 on Tue, 15 Feb
>>>>> 2022, ColinR <rail@greystane.shetland.co.uk> remarked:
>>>>>> On 15/02/2022 17:00, Roland Perry wrote:
>>>>>>> In message <suebst$vsp$1@dont-email.me>, at 19:51:57 on Mon, 14 Feb
>>>>>>> 2022, Anna Noyd-Dryver <anna@noyd-dryver.com> remarked:
>>>>>>>>>>> It would also help for you to re-cite any photos/links you
>>>>>>>>>>> believe  were
>>>>>>>>>>> posted before the train arrived, so we can see if the track was
>>>>>>>>>>> kinked
>>>>>>>>>>> already.
>>>>>>>>>>
>>>>>>>>>> Why on earth would anyone have happened to be flying a drone
>>>>>>>>>> around  that
>>>>>>>>>> particular area before the train (non-)derailment? The only such
>>>>>>>>>> pictures
>>>>>>>>>> would be from the train's FFCCTV, and until the RAIB report on
>>>>>>>>>> the matter,
>>>>>>>>>> we're unlikely to see that.
>>>>>>>>>
>>>>>>>>> I agree that I don't know why such a photo would be available.
>>>>>>>>> But it's
>>>>>>>>> crucial to the assertion that the zig-zag in the track was there
>>>>>>>>> before
>>>>>>>>> the train arrived, rather than being caused *by* its arrival.
>>>>>>>>
>>>>>>>> You still haven't said where this has been asserted.
>>>>>
>>>>>>>  Recliner has been banging on about it ad nauseam, with his "slid
>>>>>>> sideways" due to track-bed erosion theories.
>>>>>>
>>>>>> I think that you will actually find that Recliner's views are the
>>>>>> views of the majority, you are the ONLY outlier.
>>>
>>>>> Only within the people commenting here, and absolutely none have
>>>>> (unless I missed it) come up with a plausible engineering reason why
>>>>> the tension in the rails didn't keep them straight, when the ground
>>>>> below had eroded away.
>>>
>>>>> To move (or stay) sideways there has to be a substantial sideways
>>>>> force. Where is it coming from?
>>>>
>>>> Gravity.
>>>
>>> Which acts downwards, not sideways.
>>>
>>> If the rails were in compression (I suspect everyone would agree this is
>>> extraordinarily unlikely) then when the ground subsides away, that
>>> compression force could cause the track to kink, now that there's no
>>> ballast holding it in place.
>>>
>>> Or even if it was neutral, the ground falling away would put the track
>>> into tension (because it's stretched due to the dip), which would tend
>>> to resist any sideways motion.
>>>
>>> But I think it's under tension.
>>
>> IIUC you have a wide-ranging engineering education, so if the rails are
>> going to stay straight in the horizontal plane, and are under tension but
>> free to move in the vertical plane, can you tell us how big would the dip
>> be, and how close would the train driver have to be before it was visible?
>>
>> Sam
>>
>
> Imagine an elastic band under tension (rails) then imagine hanging some
> weights on the elastic band at intervals (sleepers). Imagine putting all
> this on a flat surface (intact track bed). Now take a section of that flat
> surface and tilt it at 45 degrees. What do you think will happen to the
> weights on that 45 degree slope?

I know what I think might happen (with a degree of caution because I don’t
know the actual sequence of events), but Roland is apparently convinced, by
his knowledge of soil mechanics and other engineering disciplines, that the
rails would have remained straight. That being the case I’m interested to
find out what telltale allowed the driver of the train to stop it where
s/he did.

Sam

--
The entity formerly known as Sam.Wilson@ed.ac.uk
Spit the dummy to reply

Ken <ken@birchanger.com> wrote:
> On Wed, 16 Feb 2022 11:18:12 -0000 (UTC), Sam Wilson
> <ukr@dummy.wislons.fastmail.co.uk> wrote:
>
>> ColinR <rail@greystane.shetland.co.uk> wrote:
>>> On 15/02/2022 17:00, Roland Perry wrote:
>>>> In message <suebst$vsp$1@dont-email.me>, at 19:51:57 on Mon, 14 Feb
>>>> 2022, Anna Noyd-Dryver <anna@noyd-dryver.com> remarked:
>>>>>>>> It would also help for you to re-cite any photos/links you believe
>>>>>>>> were
>>>>>>>> posted before the train arrived, so we can see if the track was kinked
>>>>>>>> already.
>>>>>>>
>>>>>>> Why on earth would anyone have happened to be flying a drone around
>>>>>>> that
>>>>>>> particular area before the train (non-)derailment? The only such
>>>>>>> pictures
>>>>>>> would be from the train's FFCCTV, and until the RAIB report on the
>>>>>>> matter,
>>>>>>> we're unlikely to see that.
>>>>>>
>>>>>> I agree that I don't know why such a photo would be available. But it's
>>>>>> crucial to the assertion that the zig-zag in the track was there before
>>>>>> the train arrived, rather than being caused *by* its arrival.
>>>>>
>>>>> You still haven't said where this has been asserted.
>>>>
>>>> Recliner has been banging on about it ad nauseam, with his "slid
>>>> sideways" due to track-bed erosion theories.
>>>
>>> I think that you will actually find that Recliner's views are the views
>>> of the majority, you are the ONLY outlier.
>>
>> Cue Sir Tom Jones…
>>
>> Sam
>
> Why, why, why, Recliner ....

I was thinking of something more usual… :-)

Sam

--
The entity formerly known as Sam.Wilson@ed.ac.uk
Spit the dummy to reply

On 17/02/2022 10:51, Sam Wilson wrote:
> Ken <ken@birchanger.com> wrote:
>> On Wed, 16 Feb 2022 11:18:12 -0000 (UTC), Sam Wilson
>> <ukr@dummy.wislons.fastmail.co.uk> wrote:
>>
>>> ColinR <rail@greystane.shetland.co.uk> wrote:
>>>> On 15/02/2022 17:00, Roland Perry wrote:
>>>>> In message <suebst$vsp$1@dont-email.me>, at 19:51:57 on Mon, 14 Feb
>>>>> 2022, Anna Noyd-Dryver <anna@noyd-dryver.com> remarked:
>>>>>>>>> It would also help for you to re-cite any photos/links you believe
>>>>>>>>> were
>>>>>>>>> posted before the train arrived, so we can see if the track was kinked
>>>>>>>>> already.
>>>>>>>>
>>>>>>>> Why on earth would anyone have happened to be flying a drone around
>>>>>>>> that
>>>>>>>> particular area before the train (non-)derailment? The only such
>>>>>>>> pictures
>>>>>>>> would be from the train's FFCCTV, and until the RAIB report on the
>>>>>>>> matter,
>>>>>>>> we're unlikely to see that.
>>>>>>>
>>>>>>> I agree that I don't know why such a photo would be available. But it's
>>>>>>> crucial to the assertion that the zig-zag in the track was there before
>>>>>>> the train arrived, rather than being caused *by* its arrival.
>>>>>>
>>>>>> You still haven't said where this has been asserted.
>>>>>
>>>>> Recliner has been banging on about it ad nauseam, with his "slid
>>>>> sideways" due to track-bed erosion theories.
>>>>
>>>> I think that you will actually find that Recliner's views are the views
>>>> of the majority, you are the ONLY outlier.
>>>
>>> Cue Sir Tom Jones…
>>>
>>> Sam
>>
>> Why, why, why, Recliner ....
>
> I was thinking of something more usual… :-)
>

<groan>

--
Graeme Wall
This account not read.

In message <sujbp0$bfp$1@dont-email.me>, at 17:20:32 on Wed, 16 Feb
2022, Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> remarked:
>Roland Perry <roland@perry.co.uk> wrote:
>> In message <suj76u$r50$1@dont-email.me>, at 16:02:38 on Wed, 16 Feb
>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>> On 16/02/2022 14:31, Roland Perry wrote:
>>>> In message <suhai3$p7q$1@dont-email.me>, at 22:47:32 on Tue, 15 Feb
>>>> 2022, ColinR <rail@greystane.shetland.co.uk> remarked:
>>>>> On 15/02/2022 17:00, Roland Perry wrote:
>>>>>> In message <suebst$vsp$1@dont-email.me>, at 19:51:57 on Mon, 14 Feb
>>>>>> 2022, Anna Noyd-Dryver <anna@noyd-dryver.com> remarked:
>>>>>>>>>> It would also help for you to re-cite any photos/links you
>>>>>>>>>> believe  were
>>>>>>>>>> posted before the train arrived, so we can see if the track was
>>>>>>>>>> kinked
>>>>>>>>>> already.
>>>>>>>>>
>>>>>>>>> Why on earth would anyone have happened to be flying a drone
>>>>>>>>> around  that
>>>>>>>>> particular area before the train (non-)derailment? The only such
>>>>>>>>> pictures
>>>>>>>>> would be from the train's FFCCTV, and until the RAIB report on
>>>>>>>>> the matter,
>>>>>>>>> we're unlikely to see that.
>>>>>>>>
>>>>>>>> I agree that I don't know why such a photo would be available.
>>>>>>>> But it's
>>>>>>>> crucial to the assertion that the zig-zag in the track was there
>>>>>>>> before
>>>>>>>> the train arrived, rather than being caused *by* its arrival.
>>>>>>>
>>>>>>> You still haven't said where this has been asserted.
>>>>
>>>>>>  Recliner has been banging on about it ad nauseam, with his "slid
>>>>>> sideways" due to track-bed erosion theories.
>>>>>
>>>>> I think that you will actually find that Recliner's views are the
>>>>> views of the majority, you are the ONLY outlier.
>>
>>>> Only within the people commenting here, and absolutely none have
>>>> (unless I missed it) come up with a plausible engineering reason why
>>>> the tension in the rails didn't keep them straight, when the ground
>>>> below had eroded away.
>>
>>>> To move (or stay) sideways there has to be a substantial sideways
>>>> force. Where is it coming from?
>>>
>>> Gravity.
>>
>> Which acts downwards, not sideways.
>>
>> If the rails were in compression (I suspect everyone would agree this is
>> extraordinarily unlikely) then when the ground subsides away, that
>> compression force could cause the track to kink, now that there's no
>> ballast holding it in place.
>>
>> Or even if it was neutral, the ground falling away would put the track
>> into tension (because it's stretched due to the dip), which would tend
>> to resist any sideways motion.
>>
>> But I think it's under tension.
>
>IIUC you have a wide-ranging engineering education, so if the rails are
>going to stay straight in the horizontal plane, and are under tension but
>free to move in the vertical plane, can you tell us how big would the dip
>be, and how close would the train driver have to be before it was visible?

As I don't have figures for the mass and tension in question, I can't
give a number. But "enough for the driver too spot it and stop".

Six inches should be more than sufficient.
--
Roland Perry

In message <sujf4u$70b$1@dont-email.me>, at 18:18:06 on Wed, 16 Feb
2022, Tweed <usenet.tweed@gmail.com> remarked:
>Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> wrote:
>> Roland Perry <roland@perry.co.uk> wrote:
>>> In message <suj76u$r50$1@dont-email.me>, at 16:02:38 on Wed, 16 Feb
>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>> On 16/02/2022 14:31, Roland Perry wrote:
>>>>> In message <suhai3$p7q$1@dont-email.me>, at 22:47:32 on Tue, 15 Feb
>>>>> 2022, ColinR <rail@greystane.shetland.co.uk> remarked:
>>>>>> On 15/02/2022 17:00, Roland Perry wrote:
>>>>>>> In message <suebst$vsp$1@dont-email.me>, at 19:51:57 on Mon, 14 Feb
>>>>>>> 2022, Anna Noyd-Dryver <anna@noyd-dryver.com> remarked:
>>>>>>>>>>> It would also help for you to re-cite any photos/links you
>>>>>>>>>>>believe  were posted before the train arrived, so we can see
>>>>>>>>>>>if the track was kinked already.
>>>>>>>>>>
>>>>>>>>>> Why on earth would anyone have happened to be flying a drone
>>>>>>>>>>around  that particular area before the train (non-
>>>>>>>>>>)derailment? The only such pictures would be from the
>>>>>>>>>>train's FFCCTV, and until the RAIB report on the matter,
>>>>>>>>>>we're unlikely to see that.
>>>>>>>>>
>>>>>>>>> I agree that I don't know why such a photo would be available.
>>>>>>>>>But it's crucial to the assertion that the zig-zag in the
>>>>>>>>>track was there before the train arrived, rather than being
>>>>>>>>>caused *by* its arrival.
>>>>>>>>
>>>>>>>> You still haven't said where this has been asserted.
>>>>>
>>>>>>>  Recliner has been banging on about it ad nauseam, with his "slid
>>>>>>> sideways" due to track-bed erosion theories.
>>>>>>
>>>>>> I think that you will actually find that Recliner's views are the
>>>>>> views of the majority, you are the ONLY outlier.
>>>
>>>>> Only within the people commenting here, and absolutely none have
>>>>> (unless I missed it) come up with a plausible engineering reason why
>>>>> the tension in the rails didn't keep them straight, when the ground
>>>>> below had eroded away.
>>>
>>>>> To move (or stay) sideways there has to be a substantial sideways
>>>>> force. Where is it coming from?
>>>>
>>>> Gravity.
>>>
>>> Which acts downwards, not sideways.
>>>
>>> If the rails were in compression (I suspect everyone would agree this is
>>> extraordinarily unlikely) then when the ground subsides away, that
>>> compression force could cause the track to kink, now that there's no
>>> ballast holding it in place.
>>>
>>> Or even if it was neutral, the ground falling away would put the track
>>> into tension (because it's stretched due to the dip), which would tend
>>> to resist any sideways motion.
>>>
>>> But I think it's under tension.
>>
>> IIUC you have a wide-ranging engineering education, so if the rails are
>> going to stay straight in the horizontal plane, and are under tension but
>> free to move in the vertical plane, can you tell us how big would the dip
>> be, and how close would the train driver have to be before it was visible?
>
>Imagine an elastic band under tension (rails) then imagine hanging some
>weights on the elastic band at intervals (sleepers). Imagine putting all
>this on a flat surface (intact track bed). Now take a section of that flat
>surface and tilt it at 45 degrees. What do you think will happen to the
>weights on that 45 degree slope?

The track will rotate, but quite soon (way before 45 degrees, more like
10 degrees) the ground on the lower side will no longer be in contact
with the sleepers. Any sideways motion of the track can therefore only
be a result of the component of gravity acting on the remaining contact,
not because the ground on the lower side is "pulled" the track with it
(that's where the soil mechanics aspect comes in) and it failed to twang
back.

The tweeted photo <https://twitter.com/ianhardie9018/status/148778339566
0869633?s=21> however shows a void under that side too. Which is why the
sequence of events is important.

I remain of the view that the kink shown there wasn't caused by the
track sliding sideways "downhill", because tension in the rails would
prevent that. Rather it's caused by the deceleration and subsequent
static weight of the train.
--
Roland Perry

On Thu, 17 Feb 2022 13:57:37 +0000, Roland Perry <roland@perry.co.uk> wrote:

>In message <sujf4u$70b$1@dont-email.me>, at 18:18:06 on Wed, 16 Feb
>2022, Tweed <usenet.tweed@gmail.com> remarked:
>>Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> wrote:
>>> Roland Perry <roland@perry.co.uk> wrote:
>>>> In message <suj76u$r50$1@dont-email.me>, at 16:02:38 on Wed, 16 Feb
>>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>>> On 16/02/2022 14:31, Roland Perry wrote:
>>>>>> In message <suhai3$p7q$1@dont-email.me>, at 22:47:32 on Tue, 15 Feb
>>>>>> 2022, ColinR <rail@greystane.shetland.co.uk> remarked:
>>>>>>> On 15/02/2022 17:00, Roland Perry wrote:
>>>>>>>> In message <suebst$vsp$1@dont-email.me>, at 19:51:57 on Mon, 14 Feb
>>>>>>>> 2022, Anna Noyd-Dryver <anna@noyd-dryver.com> remarked:
>>>>>>>>>>>> It would also help for you to re-cite any photos/links you
>>>>>>>>>>>>believe  were posted before the train arrived, so we can see
>>>>>>>>>>>>if the track was kinked already.
>>>>>>>>>>>
>>>>>>>>>>> Why on earth would anyone have happened to be flying a drone
>>>>>>>>>>>around  that particular area before the train (non-
>>>>>>>>>>>)derailment? The only such pictures would be from the
>>>>>>>>>>>train's FFCCTV, and until the RAIB report on the matter,
>>>>>>>>>>>we're unlikely to see that.
>>>>>>>>>>
>>>>>>>>>> I agree that I don't know why such a photo would be available.
>>>>>>>>>>But it's crucial to the assertion that the zig-zag in the
>>>>>>>>>>track was there before the train arrived, rather than being
>>>>>>>>>>caused *by* its arrival.
>>>>>>>>>
>>>>>>>>> You still haven't said where this has been asserted.
>>>>>>
>>>>>>>>  Recliner has been banging on about it ad nauseam, with his "slid
>>>>>>>> sideways" due to track-bed erosion theories.
>>>>>>>
>>>>>>> I think that you will actually find that Recliner's views are the
>>>>>>> views of the majority, you are the ONLY outlier.
>>>>
>>>>>> Only within the people commenting here, and absolutely none have
>>>>>> (unless I missed it) come up with a plausible engineering reason why
>>>>>> the tension in the rails didn't keep them straight, when the ground
>>>>>> below had eroded away.
>>>>
>>>>>> To move (or stay) sideways there has to be a substantial sideways
>>>>>> force. Where is it coming from?
>>>>>
>>>>> Gravity.
>>>>
>>>> Which acts downwards, not sideways.
>>>>
>>>> If the rails were in compression (I suspect everyone would agree this is
>>>> extraordinarily unlikely) then when the ground subsides away, that
>>>> compression force could cause the track to kink, now that there's no
>>>> ballast holding it in place.
>>>>
>>>> Or even if it was neutral, the ground falling away would put the track
>>>> into tension (because it's stretched due to the dip), which would tend
>>>> to resist any sideways motion.
>>>>
>>>> But I think it's under tension.
>>>
>>> IIUC you have a wide-ranging engineering education, so if the rails are
>>> going to stay straight in the horizontal plane, and are under tension but
>>> free to move in the vertical plane, can you tell us how big would the dip
>>> be, and how close would the train driver have to be before it was visible?
>>
>>Imagine an elastic band under tension (rails) then imagine hanging some
>>weights on the elastic band at intervals (sleepers). Imagine putting all
>>this on a flat surface (intact track bed). Now take a section of that flat
>>surface and tilt it at 45 degrees. What do you think will happen to the
>>weights on that 45 degree slope?
>
>The track will rotate, but quite soon (way before 45 degrees, more like
>10 degrees) the ground on the lower side will no longer be in contact
>with the sleepers.

Of course it will! The track and sleepers sag with the ground. You seem to think that the rail tension is far higher
than it is.

> Any sideways motion of the track can therefore only
>be a result of the component of gravity acting on the remaining contact,
>not because the ground on the lower side is "pulled" the track with it
>(that's where the soil mechanics aspect comes in) and it failed to twang
>back.

Wrong. The sideways motion of the track was caused by the sideways motion of the slipping ground, which the track
followed as it sagged down with the ground.

>
>The tweeted photo <https://twitter.com/ianhardie9018/status/148778339566
>0869633?s=21> however shows a void under that side too. Which is why the
>sequence of events is important.

Yes, that shot was taken later. Eventually, the track was completed unsupported, and sagged down (contrary to your
theory that the track us under such high tension that it remains ramrod straight).

>
>I remain of the view that the kink shown there wasn't caused by the
>track sliding sideways "downhill", because tension in the rails would
>prevent that. Rather it's caused by the deceleration and subsequent
>static weight of the train.

The driver must have seen the slewed track long before the train got close enough to affect it, so your theories of the
train causing the slewing make no sense.

Roland Perry <roland@perry.co.uk> wrote:
> In message <sujbp0$bfp$1@dont-email.me>, at 17:20:32 on Wed, 16 Feb
> 2022, Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> remarked:
>> Roland Perry <roland@perry.co.uk> wrote:
>>> In message <suj76u$r50$1@dont-email.me>, at 16:02:38 on Wed, 16 Feb
>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>> On 16/02/2022 14:31, Roland Perry wrote:
>>>>> In message <suhai3$p7q$1@dont-email.me>, at 22:47:32 on Tue, 15 Feb
>>>>> 2022, ColinR <rail@greystane.shetland.co.uk> remarked:
>>>>>> On 15/02/2022 17:00, Roland Perry wrote:
>>>>>>> In message <suebst$vsp$1@dont-email.me>, at 19:51:57 on Mon, 14 Feb
>>>>>>> 2022, Anna Noyd-Dryver <anna@noyd-dryver.com> remarked:
>>>>>>>>>>> It would also help for you to re-cite any photos/links you
>>>>>>>>>>> believe  were
>>>>>>>>>>> posted before the train arrived, so we can see if the track was
>>>>>>>>>>> kinked
>>>>>>>>>>> already.
>>>>>>>>>>
>>>>>>>>>> Why on earth would anyone have happened to be flying a drone
>>>>>>>>>> around  that
>>>>>>>>>> particular area before the train (non-)derailment? The only such
>>>>>>>>>> pictures
>>>>>>>>>> would be from the train's FFCCTV, and until the RAIB report on
>>>>>>>>>> the matter,
>>>>>>>>>> we're unlikely to see that.
>>>>>>>>>
>>>>>>>>> I agree that I don't know why such a photo would be available.
>>>>>>>>> But it's
>>>>>>>>> crucial to the assertion that the zig-zag in the track was there
>>>>>>>>> before
>>>>>>>>> the train arrived, rather than being caused *by* its arrival.
>>>>>>>>
>>>>>>>> You still haven't said where this has been asserted.
>>>>>
>>>>>>>  Recliner has been banging on about it ad nauseam, with his "slid
>>>>>>> sideways" due to track-bed erosion theories.
>>>>>>
>>>>>> I think that you will actually find that Recliner's views are the
>>>>>> views of the majority, you are the ONLY outlier.
>>>
>>>>> Only within the people commenting here, and absolutely none have
>>>>> (unless I missed it) come up with a plausible engineering reason why
>>>>> the tension in the rails didn't keep them straight, when the ground
>>>>> below had eroded away.
>>>
>>>>> To move (or stay) sideways there has to be a substantial sideways
>>>>> force. Where is it coming from?
>>>>
>>>> Gravity.
>>>
>>> Which acts downwards, not sideways.
>>>
>>> If the rails were in compression (I suspect everyone would agree this is
>>> extraordinarily unlikely) then when the ground subsides away, that
>>> compression force could cause the track to kink, now that there's no
>>> ballast holding it in place.
>>>
>>> Or even if it was neutral, the ground falling away would put the track
>>> into tension (because it's stretched due to the dip), which would tend
>>> to resist any sideways motion.
>>>
>>> But I think it's under tension.
>>
>> IIUC you have a wide-ranging engineering education, so if the rails are
>> going to stay straight in the horizontal plane, and are under tension but
>> free to move in the vertical plane, can you tell us how big would the dip
>> be, and how close would the train driver have to be before it was visible?
>
> As I don't have figures for the mass and tension in question, I can't
> give a number. But "enough for the driver too spot it and stop".
>
> Six inches should be more than sufficient.

So you have no idea, really. Does it not occur to you that a small
sideways movement would be much more noticeable than a vertical one, and
that any deviation would have to be visible from the train’s stopping
distance for things to have turned out how they did, and that the stopping
distance of a train is really quite large?

Anna, perhaps you could tell us how visible a vertical displacement on a
stretch of straight track is?

Sam

--
The entity formerly known as Sam.Wilson@ed.ac.uk
Spit the dummy to reply

In message <sum1e9$i55$1@dont-email.me>, at 17:42:33 on Thu, 17 Feb
2022, Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> remarked:
>Roland Perry <roland@perry.co.uk> wrote:
>> In message <sujbp0$bfp$1@dont-email.me>, at 17:20:32 on Wed, 16 Feb
>> 2022, Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> remarked:
>>> Roland Perry <roland@perry.co.uk> wrote:
>>>> In message <suj76u$r50$1@dont-email.me>, at 16:02:38 on Wed, 16 Feb
>>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>>> On 16/02/2022 14:31, Roland Perry wrote:
>>>>>> In message <suhai3$p7q$1@dont-email.me>, at 22:47:32 on Tue, 15 Feb
>>>>>> 2022, ColinR <rail@greystane.shetland.co.uk> remarked:
>>>>>>> On 15/02/2022 17:00, Roland Perry wrote:
>>>>>>>> In message <suebst$vsp$1@dont-email.me>, at 19:51:57 on Mon, 14 Feb
>>>>>>>> 2022, Anna Noyd-Dryver <anna@noyd-dryver.com> remarked:

>>>>>>>>>>>> It would also help for you to re-cite any photos/links you
>>>>>>>>>>>>believe  were posted before the train arrived, so we can
>>>>>>>>>>>> kinked already.
>>>>>>>>>>>
>>>>>>>>>>> Why on earth would anyone have happened to be flying a drone
>>>>>>>>>>>around  that particular area before the train
>>>>>>>>>>>(non-)derailment? The only such pictures would be from the
>>>>>>>>>>>train's FFCCTV, and until the RAIB report on the matter,
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> I agree that I don't know why such a photo would be
>>>>>>>>>>available. But it's crucial to the assertion that the
>>>>>>>>>>zig-zag in the track was there before the train arrived,
>>>>>>>>>>rather than being caused *by* its arrival.
>>>>>>>>>
>>>>>>>>> You still haven't said where this has been asserted.
>>>>>>
>>>>>>>>  Recliner has been banging on about it ad nauseam, with his "slid
>>>>>>>> sideways" due to track-bed erosion theories.
>>>>>>>
>>>>>>> I think that you will actually find that Recliner's views are the
>>>>>>> views of the majority, you are the ONLY outlier.
>>>>
>>>>>> Only within the people commenting here, and absolutely none have
>>>>>> (unless I missed it) come up with a plausible engineering reason why
>>>>>> the tension in the rails didn't keep them straight, when the ground
>>>>>> below had eroded away.
>>>>
>>>>>> To move (or stay) sideways there has to be a substantial sideways
>>>>>> force. Where is it coming from?
>>>>>
>>>>> Gravity.
>>>>
>>>> Which acts downwards, not sideways.
>>>>
>>>> If the rails were in compression (I suspect everyone would agree this is
>>>> extraordinarily unlikely) then when the ground subsides away, that
>>>> compression force could cause the track to kink, now that there's no
>>>> ballast holding it in place.
>>>>
>>>> Or even if it was neutral, the ground falling away would put the track
>>>> into tension (because it's stretched due to the dip), which would tend
>>>> to resist any sideways motion.
>>>>
>>>> But I think it's under tension.
>>>
>>> IIUC you have a wide-ranging engineering education, so if the rails are
>>> going to stay straight in the horizontal plane, and are under tension but
>>> free to move in the vertical plane, can you tell us how big would the dip
>>> be, and how close would the train driver have to be before it was visible?
>>
>> As I don't have figures for the mass and tension in question, I can't
>> give a number. But "enough for the driver too spot it and stop".
>>
>> Six inches should be more than sufficient.
>
>So you have no idea, really.

There's lots of level crossings around here, which afford ample
opportunities to gaze up the line, and even at the slightly lower level
than a driver, it's my opinion a dip that much should be visible at the
sort of line speed that Basil will have been doing.

>Does it not occur to you that a small sideways movement would be much
>more noticeable than a vertical one,

A cow on the line would be more visible too, but that doesn't mean it's
what happened.

>and that any deviation would have to be visible from the train’s
>stopping distance for things to have turned out how they did, and that
>the stopping distance of a train is really quite large?

How fast was the train going, or do you have "no idea, really"?

It's almost exactly 800m from the next station were it would stop, and
the previous station is 4.5 miles away, transit time 9mins, so that's an
average of 30mph (yes the cruising speed will be more, but not vastly
so).

>Anna, perhaps you could tell us how visible a vertical displacement on a
>stretch of straight track is?
>
>Sam
>

--
Roland Perry

In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
remarked:
>On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>wrote:
>
>>In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>2022, Tweed <usenet.tweed@gmail.com> remarked:
>>
>>>>>
>>>>> Just curious: which laws of physics were violated?
>>>>
>>>> Force acting on a body, causing motion.
>>>
>>>Downward force against a slope produces a lateral component.
>>
>>Even when most of the slope has eroded away, so as not to be touching
>>the bottom of the sleepers any more?
>>
>If your erosion is not in a uniform manner then you will get a
>variable result from the vertical forces applied at different places.

To zig-zag requires lateral forces, not vertical ones.

>>In any event, given the tension in the rails, to "twang" them sideways
>>would take, in my opinion, more than the horizontal component of that
>>gravitational pull downwards.

--
Roland Perry

On 19/02/2022 11:27, Roland Perry wrote:
> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com> remarked:
>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>> wrote:
>>
>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>
>>>>>>
>>>>>> Just curious: which laws of physics were violated?
>>>>>
>>>>> Force acting on a body, causing motion.
>>>>
>>>> Downward force against a slope produces a lateral component.
>>>
>>> Even when most of the slope has eroded away, so as not to be touching
>>> the bottom of the sleepers any more?
>>>
>> If your erosion is not in a uniform manner then you will get a
>> variable result from the vertical forces applied at different places.
>
> To zig-zag requires lateral forces, not vertical ones.
>
>>> In any event, given the tension in the rails, to "twang" them sideways
>>> would take, in my opinion, more than the horizontal component of that
>>> gravitational pull downwards.
>

Roland, think about the various strange traditions in our country such
as cheese rolling down a hill. Why do the cheeses roll down the hill? It
is because of gravity. Why do the cheeses not just fall vertically?
Because they are on a slope. So the gravity has a downward force, the
slope engenders a sideways movement.

Same with this incident, the ground gave way due to water action on one
side of the track forming a slope and gravity pulled the right hand (as
we look at the pictures) down the slope, hence the sideways component.

You are correct that gravity is a vertical pull, but when there is a
slope the vertical pull becomes a part of the overall force and the
track slipped sideways.

--
Colin

Roland Perry <roland@perry.co.uk> wrote:
> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
> remarked:
>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>> wrote:
>>
>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>
>>>>>>
>>>>>> Just curious: which laws of physics were violated?
>>>>>
>>>>> Force acting on a body, causing motion.
>>>>
>>>> Downward force against a slope produces a lateral component.
>>>
>>> Even when most of the slope has eroded away, so as not to be touching
>>> the bottom of the sleepers any more?
>>>
>> If your erosion is not in a uniform manner then you will get a
>> variable result from the vertical forces applied at different places.
>
> To zig-zag requires lateral forces, not vertical ones.
>
>>> In any event, given the tension in the rails, to "twang" them sideways
>>> would take, in my opinion, more than the horizontal component of that
>>> gravitational pull downwards.
>

A slope is a handy means of converting vertical forces into lateral ones.

In message <suqnsd$e9p$1@dont-email.me>, at 12:30:07 on Sat, 19 Feb
2022, ColinR <rail@greystane.shetland.co.uk> remarked:
>On 19/02/2022 11:27, Roland Perry wrote:
>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29
>>on Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>>remarked:
>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>> wrote:
>>>
>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>
>>>>>>>
>>>>>>> Just curious: which laws of physics were violated?
>>>>>>
>>>>>> Force acting on a body, causing motion.
>>>>>
>>>>> Downward force against a slope produces a lateral component.
>>>>
>>>> Even when most of the slope has eroded away, so as not to be touching
>>>> the bottom of the sleepers any more?
>>>>
>>> If your erosion is not in a uniform manner then you will get a
>>> variable result from the vertical forces applied at different places.
>> To zig-zag requires lateral forces, not vertical ones.
>>
>>>> In any event, given the tension in the rails, to "twang" them
>>>>sideways
>>>> would take, in my opinion, more than the horizontal component of that
>>>> gravitational pull downwards.
>>
>
>Roland, think about the various strange traditions in our country such
>as cheese rolling down a hill. Why do the cheeses roll down the hill?
>It is because of gravity. Why do the cheeses not just fall vertically?
>Because they are on a slope. So the gravity has a downward force, the
>slope engenders a sideways movement.
>
>Same with this incident, the ground gave way due to water action on one
>side of the track forming a slope and gravity pulled the right hand (as
>we look at the pictures) down the slope, hence the sideways component.

Even if that happened initially (and I am very sceptical that the
sideways component of gravity down a perhaps ten-degree slope is enough
to overcome the tension in the rails, let alone the extent to which the
surface even is a "had slope down which things slide", rather than a
rapidly dispersing porridge) once the ground has sunk below the level of
the bottom of the sleepers, it can't exert any force at all, and the
rails will twang back.

>You are correct that gravity is a vertical pull, but when there is a
>slope the vertical pull becomes a part of the overall force and the
>track slipped sideways.

I take issue with the word "slipped". It's almost as if you think the
ground underneath the ballast is a stretch of tarmac.
--
Roland Perry

In message <suqrj1$pnd$1@dont-email.me>, at 13:33:21 on Sat, 19 Feb
2022, Tweed <usenet.tweed@gmail.com> remarked:
>Roland Perry <roland@perry.co.uk> wrote:
>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
>> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>> remarked:
>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>> wrote:
>>>
>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>
>>>>>>>
>>>>>>> Just curious: which laws of physics were violated?
>>>>>>
>>>>>> Force acting on a body, causing motion.
>>>>>
>>>>> Downward force against a slope produces a lateral component.
>>>>
>>>> Even when most of the slope has eroded away, so as not to be touching
>>>> the bottom of the sleepers any more?
>>>>
>>> If your erosion is not in a uniform manner then you will get a
>>> variable result from the vertical forces applied at different places.
>>
>> To zig-zag requires lateral forces, not vertical ones.
>>
>>>> In any event, given the tension in the rails, to "twang" them sideways
>>>> would take, in my opinion, more than the horizontal component of that
>>>> gravitational pull downwards.
>
>A slope is a handy means of converting vertical forces into lateral ones.

But it's not a slope, it's porridge. Flowing down and sideways.

Even the Daily Mail said so: "Water had washed away stones which were
supporting the track". No support, so it goes down, not sideways.
--
Roland Perry

Roland Perry <roland@perry.co.uk> wrote:
> In message <suqrj1$pnd$1@dont-email.me>, at 13:33:21 on Sat, 19 Feb
> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>> Roland Perry <roland@perry.co.uk> wrote:
>>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
>>> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>>> remarked:
>>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>>> wrote:
>>>>
>>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>>
>>>>>>>>
>>>>>>>> Just curious: which laws of physics were violated?
>>>>>>>
>>>>>>> Force acting on a body, causing motion.
>>>>>>
>>>>>> Downward force against a slope produces a lateral component.
>>>>>
>>>>> Even when most of the slope has eroded away, so as not to be touching
>>>>> the bottom of the sleepers any more?
>>>>>
>>>> If your erosion is not in a uniform manner then you will get a
>>>> variable result from the vertical forces applied at different places.
>>>
>>> To zig-zag requires lateral forces, not vertical ones.
>>>
>>>>> In any event, given the tension in the rails, to "twang" them sideways
>>>>> would take, in my opinion, more than the horizontal component of that
>>>>> gravitational pull downwards.
>>
>> A slope is a handy means of converting vertical forces into lateral ones.
>
> But it's not a slope, it's porridge. Flowing down and sideways.
>
> Even the Daily Mail said so: "Water had washed away stones which were
> supporting the track". No support, so it goes down, not sideways.

Unless it’s a pure liquid there will still be a conversion of vertical to
lateral force.

On 19/02/2022 14:47, Roland Perry wrote:
> In message <suqrj1$pnd$1@dont-email.me>, at 13:33:21 on Sat, 19 Feb
> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>> Roland Perry <roland@perry.co.uk> wrote:
>>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
>>> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>>> remarked:
>>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>>> wrote:
>>>>
>>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>>
>>>>>>>>
>>>>>>>> Just curious: which laws of physics were violated?
>>>>>>>
>>>>>>> Force acting on a body, causing motion.
>>>>>>
>>>>>> Downward force against a slope produces a lateral component.
>>>>>
>>>>> Even when most of the slope has eroded away, so as not to be touching
>>>>> the bottom of the sleepers any more?
>>>>>
>>>> If your erosion is not in a uniform manner then you will get a
>>>> variable result from the vertical forces applied at different places.
>>>
>>> To zig-zag requires lateral forces, not vertical ones.
>>>
>>>>> In any event, given the tension in the rails, to "twang" them sideways
>>>>> would take, in my opinion, more than the horizontal component of that
>>>>> gravitational pull downwards.
>>
>> A slope is a handy means of converting vertical forces into lateral ones.
>
> But it's not a slope, it's porridge. Flowing down and sideways.
>
> Even the Daily Mail said so: "Water had washed away stones which were
> supporting the track". No support, so it goes down, not sideways.

I'm sorry but I don't regard a Daily Mail reporter as an authoritative
source for railway matters. Especially when they describe ballast as
stones.

In message <sur1bq$g0q$1@dont-email.me>, at 15:11:53 on Sat, 19 Feb
2022, martin.coffee@round-midnight.org.uk remarked:
>On 19/02/2022 14:47, Roland Perry wrote:
>> In message <suqrj1$pnd$1@dont-email.me>, at 13:33:21 on Sat, 19 Feb
>>2022, Tweed <usenet.tweed@gmail.com> remarked:
>>> Roland Perry <roland@perry.co.uk> wrote:
>>>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
>>>> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>>>> remarked:
>>>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>>>> wrote:
>>>>>
>>>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>>>
>>>>>>>>>
>>>>>>>>> Just curious: which laws of physics were violated?
>>>>>>>>
>>>>>>>> Force acting on a body, causing motion.
>>>>>>>
>>>>>>> Downward force against a slope produces a lateral component.
>>>>>>
>>>>>> Even when most of the slope has eroded away, so as not to be touching
>>>>>> the bottom of the sleepers any more?
>>>>>>
>>>>> If your erosion is not in a uniform manner then you will get a
>>>>> variable result from the vertical forces applied at different places.
>>>>
>>>> To zig-zag requires lateral forces, not vertical ones.
>>>>
>>>>>> In any event, given the tension in the rails, to "twang" them sideways
>>>>>> would take, in my opinion, more than the horizontal component of that
>>>>>> gravitational pull downwards.
>>>
>>> A slope is a handy means of converting vertical forces into lateral ones.

>> But it's not a slope, it's porridge. Flowing down and sideways.
>> Even the Daily Mail said so: "Water had washed away stones which
>>were supporting the track". No support, so it goes down, not sideways.
>
>I'm sorry but I don't regard a Daily Mail reporter as an authoritative
>source for railway matters. Especially when they describe ballast as
>stones.

We've almost come full circle. I was originally criticising reports
which implied the driver had stopped because he saw the track had
zigzagged.

Anyway, whatever you call them - stones or ballast, how are they
exerting a sideways force on the rails after they've washed away?
--
Roland Perry

In message <sur0p8$3r9$1@dont-email.me>, at 15:02:00 on Sat, 19 Feb
2022, Tweed <usenet.tweed@gmail.com> remarked:
>Roland Perry <roland@perry.co.uk> wrote:
>> In message <suqrj1$pnd$1@dont-email.me>, at 13:33:21 on Sat, 19 Feb
>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>> Roland Perry <roland@perry.co.uk> wrote:
>>>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
>>>> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>>>> remarked:
>>>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>>>> wrote:
>>>>>
>>>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>>>
>>>>>>>>>
>>>>>>>>> Just curious: which laws of physics were violated?
>>>>>>>>
>>>>>>>> Force acting on a body, causing motion.
>>>>>>>
>>>>>>> Downward force against a slope produces a lateral component.
>>>>>>
>>>>>> Even when most of the slope has eroded away, so as not to be touching
>>>>>> the bottom of the sleepers any more?
>>>>>>
>>>>> If your erosion is not in a uniform manner then you will get a
>>>>> variable result from the vertical forces applied at different places.
>>>>
>>>> To zig-zag requires lateral forces, not vertical ones.
>>>>
>>>>>> In any event, given the tension in the rails, to "twang" them sideways
>>>>>> would take, in my opinion, more than the horizontal component of that
>>>>>> gravitational pull downwards.
>>>
>>> A slope is a handy means of converting vertical forces into lateral ones.
>>
>> But it's not a slope, it's porridge. Flowing down and sideways.
>>
>> Even the Daily Mail said so: "Water had washed away stones which were
>> supporting the track". No support, so it goes down, not sideways.
>
>Unless it’s a pure liquid there will still be a conversion of vertical to
>lateral force.

Only briefly, while it's still in contact with the bottom of the
sleepers. What's the coefficient of friction between (ahem) rolling
stones, and sleepers, anyway?
--
Roland Perry

On 19/02/2022 15:48, Roland Perry wrote:
> In message <sur1bq$g0q$1@dont-email.me>, at 15:11:53 on Sat, 19 Feb
> 2022, martin.coffee@round-midnight.org.uk remarked:
>> On 19/02/2022 14:47, Roland Perry wrote:
>>> In message <suqrj1$pnd$1@dont-email.me>, at 13:33:21 on Sat, 19 Feb
>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>> Roland Perry <roland@perry.co.uk> wrote:
>>>>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at
>>>>> 00:08:29 on
>>>>> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>>>>> remarked:
>>>>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>>>>> wrote:
>>>>>>
>>>>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Just curious: which laws of physics were violated?
>>>>>>>>>
>>>>>>>>> Force acting on a body, causing motion.
>>>>>>>>
>>>>>>>> Downward force against a slope produces a lateral component.
>>>>>>>
>>>>>>> Even when most of the slope has eroded away, so as not to be
>>>>>>> touching
>>>>>>> the bottom of the sleepers any more?
>>>>>>>
>>>>>> If your erosion is not in a uniform manner then you will get a
>>>>>> variable result from the vertical forces applied at different places.
>>>>>
>>>>> To zig-zag requires lateral forces, not vertical ones.
>>>>>
>>>>>>> In any event, given the tension in the rails, to "twang" them
>>>>>>> sideways
>>>>>>> would take, in my opinion, more than the horizontal component of
>>>>>>> that
>>>>>>> gravitational pull downwards.
>>>>
>>>> A slope is a handy means of converting vertical forces into lateral
>>>> ones.
>
>>>  But it's not a slope, it's porridge. Flowing down and sideways.
>>>  Even the Daily Mail said so: "Water had washed away stones which
>>> were  supporting the track". No support, so it goes down, not sideways.
>>
>> I'm sorry but I don't regard a Daily Mail reporter as an authoritative
>> source for railway matters.  Especially when they describe ballast as
>> stones.
>
> We've almost come full circle. I was originally criticising reports
> which implied the driver had stopped because he saw the track had
> zigzagged.
>
> Anyway, whatever you call them - stones or ballast, how are they
> exerting a sideways force on the rails after they've washed away?

What about before they were totally washed away?

I think we're going to have to wait for RAIB report on this one.

Roland Perry <roland@perry.co.uk> wrote:
> In message <sur1bq$g0q$1@dont-email.me>, at 15:11:53 on Sat, 19 Feb
> 2022, martin.coffee@round-midnight.org.uk remarked:
>> On 19/02/2022 14:47, Roland Perry wrote:
>>> In message <suqrj1$pnd$1@dont-email.me>, at 13:33:21 on Sat, 19 Feb
>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>> Roland Perry <roland@perry.co.uk> wrote:
>>>>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
>>>>> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>>>>> remarked:
>>>>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>>>>> wrote:
>>>>>>
>>>>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Just curious: which laws of physics were violated?
>>>>>>>>>
>>>>>>>>> Force acting on a body, causing motion.
>>>>>>>>
>>>>>>>> Downward force against a slope produces a lateral component.
>>>>>>>
>>>>>>> Even when most of the slope has eroded away, so as not to be touching
>>>>>>> the bottom of the sleepers any more?
>>>>>>>
>>>>>> If your erosion is not in a uniform manner then you will get a
>>>>>> variable result from the vertical forces applied at different places.
>>>>>
>>>>> To zig-zag requires lateral forces, not vertical ones.
>>>>>
>>>>>>> In any event, given the tension in the rails, to "twang" them sideways
>>>>>>> would take, in my opinion, more than the horizontal component of that
>>>>>>> gravitational pull downwards.
>>>>
>>>> A slope is a handy means of converting vertical forces into lateral ones.
>
>>> But it's not a slope, it's porridge. Flowing down and sideways.
>>> Even the Daily Mail said so: "Water had washed away stones which
>>> were supporting the track". No support, so it goes down, not sideways.
>>
>> I'm sorry but I don't regard a Daily Mail reporter as an authoritative
>> source for railway matters. Especially when they describe ballast as
>> stones.
>
> We've almost come full circle. I was originally criticising reports
> which implied the driver had stopped because he saw the track had
> zigzagged.
>
> Anyway, whatever you call them - stones or ballast, how are they
> exerting a sideways force on the rails after they've washed away?

They obviously aren't at that point, and nobody claimed they did.

Roland Perry <roland@perry.co.uk> wrote:
> In message <sur0p8$3r9$1@dont-email.me>, at 15:02:00 on Sat, 19 Feb
> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>> Roland Perry <roland@perry.co.uk> wrote:
>>> In message <suqrj1$pnd$1@dont-email.me>, at 13:33:21 on Sat, 19 Feb
>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>> Roland Perry <roland@perry.co.uk> wrote:
>>>>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
>>>>> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>>>>> remarked:
>>>>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>>>>> wrote:
>>>>>>
>>>>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Just curious: which laws of physics were violated?
>>>>>>>>>
>>>>>>>>> Force acting on a body, causing motion.
>>>>>>>>
>>>>>>>> Downward force against a slope produces a lateral component.
>>>>>>>
>>>>>>> Even when most of the slope has eroded away, so as not to be touching
>>>>>>> the bottom of the sleepers any more?
>>>>>>>
>>>>>> If your erosion is not in a uniform manner then you will get a
>>>>>> variable result from the vertical forces applied at different places.
>>>>>
>>>>> To zig-zag requires lateral forces, not vertical ones.
>>>>>
>>>>>>> In any event, given the tension in the rails, to "twang" them sideways
>>>>>>> would take, in my opinion, more than the horizontal component of that
>>>>>>> gravitational pull downwards.
>>>>
>>>> A slope is a handy means of converting vertical forces into lateral ones.
>>>
>>> But it's not a slope, it's porridge. Flowing down and sideways.
>>>
>>> Even the Daily Mail said so: "Water had washed away stones which were
>>> supporting the track". No support, so it goes down, not sideways.
>>
>> Unless it’s a pure liquid there will still be a conversion of vertical to
>> lateral force.
>
> Only briefly, while it's still in contact with the bottom of the
> sleepers.

It was clearly long enough to slew the track before the train got there.
Eventually, the whole lot washed away, long after the train stopped. So the
horizontal displacement probably lasted for hours, not the milliseconds you
seem to be assuming.

> What's the coefficient of friction between (ahem) rolling
> stones, and sleepers, anyway?

They weren't rolling. The whole top of the embankment, including the
ballast and track, was sliding down the slope.

Roland Perry <roland@perry.co.uk> wrote:
> In message <suqrj1$pnd$1@dont-email.me>, at 13:33:21 on Sat, 19 Feb
> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>> Roland Perry <roland@perry.co.uk> wrote:
>>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at 00:08:29 on
>>> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>>> remarked:
>>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>>> wrote:
>>>>
>>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>>
>>>>>>>>
>>>>>>>> Just curious: which laws of physics were violated?
>>>>>>>
>>>>>>> Force acting on a body, causing motion.
>>>>>>
>>>>>> Downward force against a slope produces a lateral component.
>>>>>
>>>>> Even when most of the slope has eroded away, so as not to be touching
>>>>> the bottom of the sleepers any more?
>>>>>
>>>> If your erosion is not in a uniform manner then you will get a
>>>> variable result from the vertical forces applied at different places.
>>>
>>> To zig-zag requires lateral forces, not vertical ones.
>>>
>>>>> In any event, given the tension in the rails, to "twang" them sideways
>>>>> would take, in my opinion, more than the horizontal component of that
>>>>> gravitational pull downwards.
>>
>> A slope is a handy means of converting vertical forces into lateral ones.
>
> But it's not a slope, it's porridge. Flowing down and sideways.
>
> Even the Daily Mail said so: "Water had washed away stones which were
> supporting the track". No support, so it goes down, not sideways.

Ultimately, yes, but not initially.

<martin.coffee@round-midnight.org.uk> wrote:
> On 19/02/2022 15:48, Roland Perry wrote:
>> In message <sur1bq$g0q$1@dont-email.me>, at 15:11:53 on Sat, 19 Feb
>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>> On 19/02/2022 14:47, Roland Perry wrote:
>>>> In message <suqrj1$pnd$1@dont-email.me>, at 13:33:21 on Sat, 19 Feb
>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>> Roland Perry <roland@perry.co.uk> wrote:
>>>>>> In message <f94r0hp65iijl7tac2c6m5440vjfkav864@4ax.com>, at
>>>>>> 00:08:29 on
>>>>>> Thu, 17 Feb 2022, Charles Ellson <charlesellson@btinternet.com>
>>>>>> remarked:
>>>>>>> On Wed, 16 Feb 2022 14:34:57 +0000, Roland Perry <roland@perry.co.uk>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> In message <sugq0l$cql$1@dont-email.me>, at 18:05:09 on Tue, 15 Feb
>>>>>>>> 2022, Tweed <usenet.tweed@gmail.com> remarked:
>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Just curious: which laws of physics were violated?
>>>>>>>>>>
>>>>>>>>>> Force acting on a body, causing motion.
>>>>>>>>>
>>>>>>>>> Downward force against a slope produces a lateral component.
>>>>>>>>
>>>>>>>> Even when most of the slope has eroded away, so as not to be
>>>>>>>> touching
>>>>>>>> the bottom of the sleepers any more?
>>>>>>>>
>>>>>>> If your erosion is not in a uniform manner then you will get a
>>>>>>> variable result from the vertical forces applied at different places.
>>>>>>
>>>>>> To zig-zag requires lateral forces, not vertical ones.
>>>>>>
>>>>>>>> In any event, given the tension in the rails, to "twang" them
>>>>>>>> sideways
>>>>>>>> would take, in my opinion, more than the horizontal component of
>>>>>>>> that
>>>>>>>> gravitational pull downwards.
>>>>>
>>>>> A slope is a handy means of converting vertical forces into lateral
>>>>> ones.
>>
>>>>  But it's not a slope, it's porridge. Flowing down and sideways.
>>>>  Even the Daily Mail said so: "Water had washed away stones which
>>>> were  supporting the track". No support, so it goes down, not sideways.
>>>
>>> I'm sorry but I don't regard a Daily Mail reporter as an authoritative
>>> source for railway matters.  Especially when they describe ballast as
>>> stones.
>>
>> We've almost come full circle. I was originally criticising reports
>> which implied the driver had stopped because he saw the track had
>> zigzagged.
>>
>> Anyway, whatever you call them - stones or ballast, how are they
>> exerting a sideways force on the rails after they've washed away?
>
> What about before they were totally washed away?

As in this photo, which was probably taken an hour or so after the slippage
started.

<https://pbs.twimg.com/media/FKW719VX0AAUoku?format=jpg&name=large>

>
> I think we're going to have to wait for RAIB report on this one.

I await Roland's explanation of why the RAIB misunderstood Fenland Physics.

Roland Perry <roland@perry.co.uk> wrote:

>
> How fast was the train going, or do you have "no idea, really"?
>
> It's almost exactly 800m from the next station were it would stop, and
> the previous station is 4.5 miles away, transit time 9mins, so that's an
> average of 30mph (yes the cruising speed will be more, but not vastly
> so).
>
>

From the clues available in the picture (white house, trackside hut) and
also what's not visible (two pylons behind the photographer), the location
is around halfway along the straight alongside the Haddiscoe Cut <Dropped
pin
https://goo.gl/maps/Ba6QPUDY4wF3LgpA8>

Linespeed is 20mph across Reedham swing bridge then 60 mph through the
non-derailment site and Haddiscoe station then drops to 30mph for
Somerleyton swing bridge.

It’s around 2.5 miles between the speed increase and the station, so I'd
fully expect the train to reach 60mph. Around 1.5 miles from the station, I
don't think the driver would be braking yet.

Anna Noyd-Dryver

Anna Noyd-Dryver <anna@noyd-dryver.com> wrote:
> Roland Perry <roland@perry.co.uk> wrote:
>
>>
>> How fast was the train going, or do you have "no idea, really"?
>>
>> It's almost exactly 800m from the next station were it would stop, and
>> the previous station is 4.5 miles away, transit time 9mins, so that's an
>> average of 30mph (yes the cruising speed will be more, but not vastly
>> so).
>>
>>
>
> From the clues available in the picture (white house, trackside hut) and
> also what's not visible (two pylons behind the photographer), the location
> is around halfway along the straight alongside the Haddiscoe Cut <Dropped
> pin
> https://goo.gl/maps/Ba6QPUDY4wF3LgpA8>
>
> Linespeed is 20mph across Reedham swing bridge then 60 mph through the
> non-derailment site and Haddiscoe station then drops to 30mph for
> Somerleyton swing bridge.
>
> It’s around 2.5 miles between the speed increase and the station, so I'd
> fully expect the train to reach 60mph. Around 1.5 miles from the station, I
> don't think the driver would be braking yet.
>

So the stopping distance would be several hundred metres?