I recently travelled from Embankment to Tower Hill on a Circle Line
train.

When it was moving, every ten or twenty seconds, the acceleration cut
out with a violent jerk and there was that loud popping noise. I am
not exaggerating; it happened constantly the whole way, and the same
thing was still happening as the train left Tower Hill.

So three questions spring to mind

1) Is this something to do with conditions on that part of the line?

2) I've often been in an LU train where there is occasionally a
similar jerk and popping noise. It may be something to do with having
to ease off for a speed restriction or something, or maybe when the
power is cut due to wheelspin, but I don't understand why it's
possible to simply slow down and stop normally at stations without all
the jerking and popping, but not between stations.

3) Does the driver have any control over this, ie is the power being
cut by some automatic process or could they drive more smoothly if
they wanted to?

MIG wrote:
I recently travelled from Embankment to Tower Hill on a Circle Line
train.

When it was moving, every ten or twenty seconds, the acceleration cut
out with a violent jerk and there was that loud popping noise. I am
not exaggerating; it happened constantly the whole way, and the same
thing was still happening as the train left Tower Hill.

So three questions spring to mind

1) Is this something to do with conditions on that part of the line?

2) I've often been in an LU train where there is occasionally a
similar jerk and popping noise. It may be something to do with having
to ease off for a speed restriction or something, or maybe when the
power is cut due to wheelspin, but I don't understand why it's
possible to simply slow down and stop normally at stations without all
the jerking and popping, but not between stations.

3) Does the driver have any control over this, ie is the power being
cut by some automatic process or could they drive more smoothly if
they wanted to?


The trains Motors are dropping out, this is a defect and presuming you
weren't in the drivers cab the driver may not have known much about it,
there are also gaps in the power rails which is the most normal
explanation for the jerks (metronet).

The driver has no control over the jerkiness of the motors.

www.waspies.net wrote:


The trains Motors are dropping out, this is a defect and presuming you
weren't in the drivers cab the driver may not have known much about it,
there are also gaps in the power rails which is the most normal
explanation for the jerks (metronet).

The other possibility being someone leaning against one (or more) doors,
breaking the traction interlock circuit in the process, which causes the
motors to cut out.

Cheers,

Barry

On Jul 16, 11:51 am, Barry Salter wrote:
www.waspies.netwrote:

The trains Motors are dropping out, this is a defect and presuming you
weren't in the drivers cab the driver may not have known much about it,
there are also gaps in the power rails which is the most normal
explanation for the jerks (metronet).

The other possibility being someone leaning against one (or more) doors,
breaking the traction interlock circuit in the process, which causes the
motors to cut out.



This certainly wasn't the reason in this case. It was busy, but not
overloaded.

Does the driver have do to anything? I mean, do they leave their
controller in the "go normally" position and just wait for the motors
to kick in again, or do that have to respond in some way? If the
latter, it must have been extremely tedious.

If the fault was in this train, or it was oversensitive to the faults
on the route, I also wonder how long it would have stayed in service.
There was no indication of the driver giving up or the train
terminating anywhere.

This certainly wasn't the reason in this case. It was busy, but not
overloaded.

Does the driver have do to anything? I mean, do they leave their
controller in the "go normally" position and just wait for the motors
to kick in again, or do that have to respond in some way? If the
latter, it must have been extremely tedious.

If the fault was in this train, or it was oversensitive to the faults
on the route, I also wonder how long it would have stayed in service.
There was no indication of the driver giving up or the train
terminating anywhere.


Taking a train out of service can be serious, particularly if you're
going home....!

Knowing the level of service that C Stock trains receive at Hammerstuff
depot, it'll probably be out there in exactly the same conditions for
months, even if you write it down on the trouble card the response would
probably be NDF, No Defect Found, or Not Done F***.

www.waspies.net wrote:


This certainly wasn't the reason in this case. It was busy, but not
overloaded.

Does the driver have do to anything? I mean, do they leave their
controller in the "go normally" position and just wait for the motors
to kick in again, or do that have to respond in some way? If the
latter, it must have been extremely tedious.

If the fault was in this train, or it was oversensitive to the faults
on the route, I also wonder how long it would have stayed in service.
There was no indication of the driver giving up or the train
terminating anywhere.


Taking a train out of service can be serious, particularly if you're
going home....!

Knowing the level of service that C Stock trains receive at Hammerstuff
depot, it'll probably be out there in exactly the same conditions for
months, even if you write it down on the trouble card the response would
probably be NDF, No Defect Found, or Not Done F***.

I did the same journey on the same line with a train that did that about
six months ago, so you might be right!

I always thought that it was because the driver had the controller in the
shunt position, which put a lot of energy through the resistor grids. When
the driver puts his controller back to coast after being in the
above-mentioned position, it is then that you hear the popping sound.

I could be wrong, of course, but I notice that this happens only when the
train's controller is apparently in shunt position. At least it feels like
that.

"MIG" wrote in message
oups.com...
I recently travelled from Embankment to Tower Hill on a Circle Line
train.

When it was moving, every ten or twenty seconds, the acceleration cut
out with a violent jerk and there was that loud popping noise. I am
not exaggerating; it happened constantly the whole way, and the same
thing was still happening as the train left Tower Hill.

So three questions spring to mind

1) Is this something to do with conditions on that part of the line?

2) I've often been in an LU train where there is occasionally a
similar jerk and popping noise. It may be something to do with having
to ease off for a speed restriction or something, or maybe when the
power is cut due to wheelspin, but I don't understand why it's
possible to simply slow down and stop normally at stations without all
the jerking and popping, but not between stations.

3) Does the driver have any control over this, ie is the power being
cut by some automatic process or could they drive more smoothly if
they wanted to?

wrote:
I always thought that it was because the driver had the controller in the
shunt position, which put a lot of energy through the resistor grids. When
the driver puts his controller back to coast after being in the
above-mentioned position, it is then that you hear the popping sound.

I could be wrong, of course, but I notice that this happens only when the
train's controller is apparently in shunt position. At least it feels like
that.
The popping noise is where the motors haven't had time to fully wind up
in ANY motoring position and are then taken off, the fact that the
Traction Brake Controller is in parallel makes no difference, the motors
accelerate through Series then into Parallel, I think that they don't
touch Shunt though due to the excessive heat generated in the resistors
(people who are better acquainted with C Stock will know this better
than me).

On Jul 17, 10:49 am, "www.waspies.net" wrote:
wrote:
I always thought that it was because the driver had the controller in the
shunt position, which put a lot of energy through the resistor grids. When
the driver puts his controller back to coast after being in the
above-mentioned position, it is then that you hear the popping sound.

I could be wrong, of course, but I notice that this happens only when the
train's controller is apparently in shunt position. At least it feels like
that.

The popping noise is where the motors haven't had time to fully wind up
in ANY motoring position and are then taken off, the fact that the
Traction Brake Controller is in parallel makes no difference, the motors
accelerate through Series then into Parallel, I think that they don't
touch Shunt though due to the excessive heat generated in the resistors
(people who are better acquainted with C Stock will know this better
than me).


This fits with what I have noticed over the years, but without knowing
what to call it.

That is, trains approaching stations simply ease off and brake with no
popping, but trains accelerating a bit and then easing off for a speed
restriction or something do seem to pop.

But if, say, there is a 15 mph speed restriction for some distance, is
it really necessary to accelerate - pop - accelerate - pop, or can the
train simply be driven in series or whatever? It seems to vary in
practice, but I don't know how much is down to driving style and how
much is down to faults.

This fits with what I have noticed over the years, but without knowing
what to call it.

That is, trains approaching stations simply ease off and brake with no
popping, but trains accelerating a bit and then easing off for a speed
restriction or something do seem to pop.

But if, say, there is a 15 mph speed restriction for some distance, is
it really necessary to accelerate - pop - accelerate - pop, or can the
train simply be driven in series or whatever? It seems to vary in
practice, but I don't know how much is down to driving style and how
much is down to faults.


It all depends on the topography of the section of track that the speed
restriction is over, if it's up hill you'll have to accelerate then
coast, down hill get it up to the correct then use the brakes to
regulate, and it does also come down to the driving style of the driver,
I tend to be quite relaxed, brake nice and early smooth if possible,
although if you are holding the doors open and I'm going home thats
another matter, other drivers wait later before braking and it's a bit
more of a squeaky bum time.