Humps on tube lines
 

On Tue, 3 Jan 2006, Brimstone wrote:

Tom Anderson wrote:
On Mon, 2 Jan 2006, Bob wrote:

Does anybody know if humps are still built into station tracks on new
tube lines.

The CTRL seems to do it:

http://www.ctrl.co.uk/route/tile1.asp?L=8

Although i don't know if that's really about playing tricks with
energy, or wanting to keep the tunnel nice and deep where possible.

When done by the CRL I don't think it was about "playing tricks with
energy". Electricity was still a very new form of energy and such
considerations hadn't arisen, it was simply a way of using a natural
phenomenon (gravity) to improve the performance of the trains. However
good the braking and acceleration of a vehicle on the level it will be
enhanced by going up/down hill at the appropriate moment.

Er, that *is* playing tricks with energy - the uphill slope of the hump is
a machine which converts the train's kinetic energy into gravitational
potential energy, thereby assisting the brakes, and the downhill slope is
a machine which does the inverse, delivering energy into the acceleration
process, and so assisting the motor.

It's exactly like using regenerative braking to turn a train's kinetic
energy into electrical energy during braking, which can then be
reconverted into kinetic energy during acceleration - only the hump does
it rather more reliably and efficiently!

A third equivalent would be a colossal spring lining the tunnel, which the
train would compress during braking, and whose expansion would assist
departure. Far less efficient (ISTR that you lose at least half the energy
to heat when you do that), and probably not the most reliable or safe
approach, either.

tom

--
Plus, you gotta understand I can now type far, far faster than I can
think. This is not boasting - its admitting a personal tragedy. -- D

Humps on tube lines
 

On Tue, 3 Jan 2006 20:51:55 +0000, Tom Anderson
wrote:

On Tue, 3 Jan 2006, Sir Benjamin Nunn wrote:

"Tom Anderson" wrote in message
h.li...
On Mon, 2 Jan 2006 wrote:

Is there anything approximating to a "200ft - Low - Club" on the
London Underground?

Given that the only bit of the tube that's 200 feet down is the run
between Golders Green and Hampstead [1],

If you get out at the unfinished North End Station, you can stay there
all night long.

I believe North End's official name would have been Bull & Bush.

Not clear which name offers the greatest innuendo potential, though.

actually, it's the other way around. The station was to be called
"North End," but over the years the abandonned works aquired the
erroneous name of "Bull and Bush" amongst LU workers.

--
Nick Cooper

[Carefully remove the detonators from my e-mail address to reply!]

The London Underground at War, and in Films & TV:
http://www.nickcooper.org.uk/

Humps on tube lines
 

Tom Anderson wrote:
On Tue, 3 Jan 2006, Brimstone wrote:

Tom Anderson wrote:
On Mon, 2 Jan 2006, Bob wrote:

Does anybody know if humps are still built into station tracks on
new tube lines.

The CTRL seems to do it:

http://www.ctrl.co.uk/route/tile1.asp?L=8

Although i don't know if that's really about playing tricks with
energy, or wanting to keep the tunnel nice and deep where possible.

When done by the CRL I don't think it was about "playing tricks with
energy". Electricity was still a very new form of energy and such
considerations hadn't arisen, it was simply a way of using a natural
phenomenon (gravity) to improve the performance of the trains.
However good the braking and acceleration of a vehicle on the level
it will be enhanced by going up/down hill at the appropriate moment.

Er, that *is* playing tricks with energy - the uphill slope of the
hump is a machine which converts the train's kinetic energy into
gravitational potential energy, thereby assisting the brakes, and the
downhill slope is a machine which does the inverse, delivering energy
into the acceleration process, and so assisting the motor.

It's exactly like using regenerative braking to turn a train's kinetic
energy into electrical energy during braking, which can then be
reconverted into kinetic energy during acceleration - only the hump
does it rather more reliably and efficiently!

A third equivalent would be a colossal spring lining the tunnel,
which the train would compress during braking, and whose expansion
would assist departure. Far less efficient (ISTR that you lose at
least half the energy to heat when you do that), and probably not the
most reliable or safe approach, either.

If you want to take "energy" in the widest sense, rather than the limited
term meaning that which powers the train OK.

Humps on tube lines
 

www.waspies.net wrote:
Bob wrote:
The Central London Railway began with Camel Backed Electric locomotives
hauling unpowered carriages. In order to improve efficiency distinct
humps (mini summits) were built into the track profile at stations from
Notting Hill to Liverpool Street - incoming trains were slowed by the
rising gradient whilst outbound trains were hastened on their way by
the falling out bound gradient. The heavy unsprung locomotives were
soon replaced by multiple units with intermediate powered bogies. Does
anybody know if humps are still built into station tracks on new tube
lines.

No but the effect of Metromess and TubeCrimes track replacements means
that it feels as if you are going over speed humps at 50 mph, worst bit
of track used it be Pic Acton to Hammersmith.


Er, I actually think the track replacement programme is having an
effect. Travelling around the network there are sections on many of the
lines where there is a notably smoother and quieter ride, which I
presume can only be the result of track repacement. It's still quite
patchy - i.e. it may just be between certain stations, but at least the
large scale programme has started.

What comes to mind in particular is parts of the Northern line City
branch, and parts of the Circle / District line (the southern shared
section). Unsurprisingly they've both had weekend closures so track
replacement work could be carried out on them.

BTW I'm not cheerleading for MetroNet / Tube Lines here, as I
understand they're behind schedule, and I suspect that despite the
supposed private investment that the PPP's were supposed to bring to
the table it's probably still public money that's paying for the bulk
of this. It does appear to be happening though.

Humps on tube lines
 

When done by the [CLR] I don't think it was about "playing tricks with
energy". Electricity was still a very new form of energy and such
considerations hadn't arisen, it was simply a way of using a natural
phenomenon (gravity) to improve the performance of the trains. ...

As already pointed out, that amounts to the same thing.

I'd just like to note that when the C&SLR decided to do it, they
were expecting their trains to be cable-hauled, not electric.

The energy and performance issues are of course essentially the same
either way. But with cable haulage, a hump gives a special benefit.
The train is accelerated from rest up to cable speed by tightening the
grip until it clamps firmly onto the cable; and while that's going
on, the cable is rubbing against the grip as it slides through it.
So a gravity-assisted start could significantly reduce wear and tear
on the cable.
--
Mark Brader, Toronto | "If gravity stops working, a power cut is
| the least of your problems." -- David Bell

My text in this article is in the public domain.