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Old December 18th 04, 12:43 PM posted to uk.transport.london
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Default Eurostars quieter than Mark IVs + Class 91s?

This may not be the right forum for this question, but what the hell!

Standing at Hitchin station and wistfully watching the fast trains
going through, the wheel-on-rail noise of class 91 + Mark IV coaches seemed
much louder than the Eurostars. (Comparisons with HSTs are difficult because
of their noisy diesel engines - at full chat as they pick up speed going
North). This was just a casual observation. Is this generally accepted? Are
the reasons known?


Michael Bell

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Old December 18th 04, 05:48 PM posted to uk.transport.london
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Default Eurostars quieter than Mark IVs + Class 91s?

Michael Bell wrote:
This may not be the right forum for this question, but what the
hell!

Standing at Hitchin station and wistfully watching the fast trains
going through, the wheel-on-rail noise of class 91 + Mark IV
coaches seemed much louder than the Eurostars. (Comparisons with
HSTs are difficult because of their noisy diesel engines - at full
chat as they pick up speed going North). This was just a casual
observation. Is this generally accepted? Are the reasons known?


It may be because Eurostars (Class 373) are articulated, with one bogie
shared between two carriages except at the ends of each unit. Thus at
any instant while one is passing you, there are fewer bogies in contact
with the rails within x metres of your position than with a rake of Mark
IVs.
--
Richard J.
(to e-mail me, swap uk and yon in address)

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Old December 25th 04, 11:01 AM posted to uk.transport.london
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Default Eurostars quieter than Mark IVs + Class 91s?

"Richard J." wrote in message
k
Michael Bell wrote:
This may not be the right forum for this question, but what the
hell!

Standing at Hitchin station and wistfully watching the fast trains
going through, the wheel-on-rail noise of class 91 + Mark IV
coaches seemed much louder than the Eurostars. (Comparisons with
HSTs are difficult because of their noisy diesel engines - at full
chat as they pick up speed going North). This was just a casual
observation. Is this generally accepted? Are the reasons known?


It may be because Eurostars (Class 373) are articulated, with one
bogie shared between two carriages except at the ends of each unit.
Thus at any instant while one is passing you, there are fewer bogies
in contact with the rails within x metres of your position than with
a rake of Mark IVs.


I also notice a lot of dampers connecting the articulated carriages and
the shared bogies, which may have the effect of reducing vibration in
the whole train. Thus, not only do you hear fewer bogies, but they may
also be better damped.


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Old December 25th 04, 10:12 PM posted to uk.transport.london
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Default Eurostars quieter than Mark IVs + Class 91s?

In article , Richard J.
wrote:
Michael Bell wrote:
This may not be the right forum for this question, but what the
hell!

Standing at Hitchin station and wistfully watching the fast trains
going through, the wheel-on-rail noise of class 91 + Mark IV
coaches seemed much louder than the Eurostars. (Comparisons with
HSTs are difficult because of their noisy diesel engines - at full
chat as they pick up speed going North). This was just a casual
observation. Is this generally accepted? Are the reasons known?


It may be because Eurostars (Class 373) are articulated, with one bogie
shared between two carriages except at the ends of each unit. Thus at
any instant while one is passing you, there are fewer bogies in contact
with the rails within x metres of your position than with a rake of Mark
IVs.


I got the feeling that the difference was greater than could be accounted for
by that factor - and is it true anyway that there are significantly fewer
bogies per length of train? The body sections of TGVs are noticeably shorter
than British Mark IV coaches.

Being analytical, what might the reasons be?

* Steadier running by TGV wheels.

* TGV wheels less resonant. The resonance of solid metal objects such as
wheels can be damped by coating part or all of them with a viscous
material such as bitumen or polyurethane, and then fitting another rigid
sheet on top of that, it can be as thin as foil or even paper. The damping
force is then the non-elastic distortion of the viscous layer, and it is VERY
effective, it is called "constrained layer damping" and it used in sheet
metal structres such as cars and fridges, but it can also be used for
thicker metal objects.

* Greater enclosure of TGV wheels? I suggest that only to dismiss it. I
can't think it is significant.

I can't think of any other reasons.

Michael Bell

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Old December 26th 04, 06:32 PM posted to uk.transport.london
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Default Eurostars quieter than Mark IVs + Class 91s?

"Michael Bell" wrote in message
...
In article , Richard J.
wrote:
Michael Bell wrote:

Standing at Hitchin station and wistfully watching the fast trains
going through, the wheel-on-rail noise of class 91 + Mark IV
coaches seemed much louder than the Eurostars. (Comparisons with
HSTs are difficult because of their noisy diesel engines - at full
chat as they pick up speed going North). This was just a casual
observation. Is this generally accepted? Are the reasons known?


It may be because Eurostars (Class 373) are articulated, with one bogie
shared between two carriages except at the ends of each unit. Thus at
any instant while one is passing you, there are fewer bogies in contact
with the rails within x metres of your position than with a rake of Mark
IVs.


I got the feeling that the difference was greater than could be accounted

for
by that factor - and is it true anyway that there are significantly fewer
bogies per length of train? The body sections of TGVs are noticeably

shorter
than British Mark IV coaches.

Being analytical, what might the reasons be?


You might like to read one of the articles in January's Modern Railways,
which comments on the differences between forces on the track from different
wheel profiles, etc. "Seeking Excellence" on page 57.
--
Terry Harper, Web Co-ordinator, The Omnibus Society
75th Anniversary 2004, see http://www.omnibussoc.org/75th.htm
E-mail:
URL:
http://www.terry.harper.btinternet.co.uk/




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Old December 26th 04, 07:56 PM posted to uk.transport.london
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Default Eurostars quieter than Mark IVs + Class 91s?

In article , Terry Harper
wrote:
"Michael Bell" wrote in message
...
In article , Richard J.
wrote:
Michael Bell wrote:

Standing at Hitchin station and wistfully watching the fast trains
going through, the wheel-on-rail noise of class 91 + Mark IV
coaches seemed much louder than the Eurostars. (Comparisons with
HSTs are difficult because of their noisy diesel engines - at full
chat as they pick up speed going North). This was just a casual
observation. Is this generally accepted? Are the reasons known?

It may be because Eurostars (Class 373) are articulated, with one bogie
shared between two carriages except at the ends of each unit. Thus at
any instant while one is passing you, there are fewer bogies in contact
with the rails within x metres of your position than with a rake of Mark
IVs.


I got the feeling that the difference was greater than could be accounted

for
by that factor - and is it true anyway that there are significantly fewer
bogies per length of train? The body sections of TGVs are noticeably

shorter
than British Mark IV coaches.

Being analytical, what might the reasons be?


You might like to read one of the articles in January's Modern Railways,
which comments on the differences between forces on the track from different
wheel profiles, etc. "Seeking Excellence" on page 57.


Yes, I got that copy for the articles about the CTRL and St Pancras
rebuilding, but I haven't the local knowledge to make much sense of it. The
article you refer to doesn't mention noise. Or is it implied by the
discussion on conicity? And anyway, what does conicity measure?


Michael

--



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