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## Using gravity

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• An idea I ve toyed with... Assuming their is some sort of metro-rail within the city, like specified in the reference design, what if we changed the elevation
Message 1 of 7 , May 12, 2004
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An idea I've toyed with...

Assuming their is some sort of metro-rail within the city, like
specified in the reference design, what if we changed the elevation
of the rail's tracks so that the track was at the highest elevation
at the stations, and the lowest elevation between stations. I'm not
talking roller coaster proportions, but enough that gravity alone
would assist in the gentle acceleration and deceleration between
stops.

I don't have the formulas handy right now to crunch the numbers, but
simply physics would help us find the grade required to produce the
desired acceleration rate. This would cut down both on brake use,
and energy use. In fact, if done correctly, only minimal energy
would be required to overcome friction (which will be low because
rolling friction tends to be very low) and minimal brake use would be
required to exactly control the stop at each station.

Let me know what you think.
• Interesting idea... Relatedly, some ski lifts and related vertical transport devices (including elevators) rely on counterweights (e.g., the up-car tied to the
Message 2 of 7 , May 12, 2004
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Interesting idea...

Relatedly, some ski lifts and related vertical transport devices
(including elevators) rely on counterweights (e.g., the up-car tied to the
down-car). There is also a certain amount of energy capture that can
happen from braking (some of today's hybrid cars demonstrate this).

A similar idea I play with is the idea of an "Escher City" for bicycles,
wherein long gentle downhill slopes would connect various destinations,
and cyclists could take a lift or pedal/climb to get up onto the slope.
Some years ago there were plans floating around for covered bicycle
expressways with an airflow introduced (big fan at one end, or perhaps
vents which capture and direct natural windflow) with the added advantage
of shielding from rain (unless you like rain).

Then there's the idea of elevating bikeways in the densest areas to avoid
conflicts with pedestrians.

Jason

On Wed, 12 May 2004 flyboy472@... wrote:

> An idea I've toyed with...
>
> Assuming their is some sort of metro-rail within the city, like
> specified in the reference design, what if we changed the elevation
> of the rail's tracks so that the track was at the highest elevation
> at the stations, and the lowest elevation between stations. I'm not
> talking roller coaster proportions, but enough that gravity alone
> would assist in the gentle acceleration and deceleration between
> stops.
>
> I don't have the formulas handy right now to crunch the numbers, but
> simply physics would help us find the grade required to produce the
> desired acceleration rate. This would cut down both on brake use,
> and energy use. In fact, if done correctly, only minimal energy
> would be required to overcome friction (which will be low because
> rolling friction tends to be very low) and minimal brake use would be
> required to exactly control the stop at each station.
>
> Let me know what you think.
>
>
>
> To Post a message, send it to: carfree_cities@...
> To Unsubscribe, send a blank message to: carfree_cities-unsubscribe@...
> Group address: http://www.egroups.com/group/carfree_cities/
> Yahoo! Groups Links
>
>
>
>
>
• Long ago I read a position that *inter* city trains could save a huge amount of energy if one bored tunnels that went directly from station to station, rather
Message 3 of 7 , May 12, 2004
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Long ago I read a position that *inter* city trains could save a huge amount of energy if one bored tunnels that went directly from station to station, rather than following the curvature of the earth--the tunnels would then appear to dip gently into the ground and arise farther on (being in effect tangents, though inside rather than outside the circle). Graivty would then assist the train's acceleration (and deceleration). The paper also posited establishing vacuum gates so that the tunnels could maintain very low air pressure to reduce resitance further--probably not proactical.

Anyway, an interesting idea, though obviously suitable for longer distances only.

Being that this came out decades ago, there must be some references somewhere on gravity-assisted rail systems.

Richard

-----Original Message-----
From: flyboy472@...
Sent: May 12, 2004 10:22 AM
To: carfree_cities@yahoogroups.com
Subject: [carfree_cities] Using gravity

An idea I've toyed with...

Assuming their is some sort of metro-rail within the city, like
specified in the reference design, what if we changed the elevation
of the rail's tracks so that the track was at the highest elevation
at the stations, and the lowest elevation between stations. I'm not
talking roller coaster proportions, but enough that gravity alone
would assist in the gentle acceleration and deceleration between
stops.

I don't have the formulas handy right now to crunch the numbers, but
simply physics would help us find the grade required to produce the
desired acceleration rate. This would cut down both on brake use,
and energy use. In fact, if done correctly, only minimal energy
would be required to overcome friction (which will be low because
rolling friction tends to be very low) and minimal brake use would be
required to exactly control the stop at each station.
• Good idea. Jason is right about breaks being tied to generators that covert the energy back into power on hybrids. I believe some electric trains have been
Message 4 of 7 , May 12, 2004
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Good idea.

Jason is right about breaks being tied to generators that covert the
energy back into power on hybrids. I believe some electric trains
have been using this technology for sometime, but it is not used as
much as it could be, trains are connected to a power grid, making
these fairly easy to do. However, there is some energy loss going
from motion to a generator then to the power gird then to a motor and
finally back to motion energy. Your idea, in its elegance, is more
efficient and would have less maintenance costs.

One other point as riders would be pitched backward on deceleration
and forward on acceleration. Both movements would be more
comfortable, I think.

Greg

--- In carfree_cities@yahoogroups.com, Jason Meggs <jmeggs@b...>
wrote:
> Interesting idea...
>
> Relatedly, some ski lifts and related vertical transport devices
> (including elevators) rely on counterweights (e.g., the up-car tied
to the
> down-car). There is also a certain amount of energy capture that
can
> happen from braking (some of today's hybrid cars demonstrate this).
>
> A similar idea I play with is the idea of an "Escher City" for
bicycles,
> wherein long gentle downhill slopes would connect various
destinations,
> and cyclists could take a lift or pedal/climb to get up onto the
slope.
> Some years ago there were plans floating around for covered bicycle
> expressways with an airflow introduced (big fan at one end, or
perhaps
> vents which capture and direct natural windflow) with the added
> of shielding from rain (unless you like rain).
>
> Then there's the idea of elevating bikeways in the densest areas to
avoid
> conflicts with pedestrians.
>
> Jason
>
> On Wed, 12 May 2004 flyboy472@j... wrote:
>
> > An idea I've toyed with...
> >
> > Assuming their is some sort of metro-rail within the city, like
> > specified in the reference design, what if we changed the
elevation
> > of the rail's tracks so that the track was at the highest
elevation
> > at the stations, and the lowest elevation between stations. I'm
not
> > talking roller coaster proportions, but enough that gravity alone
> > would assist in the gentle acceleration and deceleration between
> > stops.
> >
> > I don't have the formulas handy right now to crunch the numbers,
but
> > simply physics would help us find the grade required to produce
the
> > desired acceleration rate. This would cut down both on brake use,
> > and energy use. In fact, if done correctly, only minimal energy
> > would be required to overcome friction (which will be low because
> > rolling friction tends to be very low) and minimal brake use
would be
> > required to exactly control the stop at each station.
> >
> > Let me know what you think.
> >
> >
> >
> > To Post a message, send it to: carfree_cities@e...
> > To Unsubscribe, send a blank message to: carfree_cities-
unsubscribe@e...
> > Group address: http://www.egroups.com/group/carfree_cities/
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
• Hi All, ... Long ago is the early 1960s, in an article in Scientific American that proposed both 600 MPH trains running long distances through partially
Message 5 of 7 , May 12, 2004
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Hi All,

Richard Risemberg replied:

>Long ago I read a position that *inter* city trains could save a huge amount
>of energy if one bored tunnels that went directly from station to station,
>rather than following the curvature of the earth--the tunnels would then
>appear to dip gently into the ground and arise farther on (being in effect
>tangents, though inside rather than outside the circle). Graivty would then
>assist the train's acceleration (and deceleration). The paper also posited
>establishing vacuum gates so that the tunnels could maintain very low air
>pressure to reduce resitance further--probably not proactical.

Long ago is the early 1960s, in an article in Scientific American
that proposed both 600 MPH trains running long distances through
partially evacuated tunnels; the trains would be propelled by
admitting a charge of air behind the train as it entered the
tunnel (through an air lock). I've never seen any reason that
this might not be possible, but it certainly has not been done
in the way the article envisioned. (Pneumatic trains go back a
long way but have never really caught on.)

The same Sci Am article also proposed shorter-haul lines (commuter
rail) that would pitch up and down, using gravity to accelerate
and retard the trains. The great advantage of this is that it's
the only way to exceed the approximate limit of 0.2 G for lateral
acceleration in vehicles that may have standing passengers.
Because the acceleration is vertical, people are not greatly
affected by it (at least not at levels up to about 0.5 G or so).

The fly in the ointment is the cost of drilling the tunnels...

Regards,

>Anyway, an interesting idea, though obviously suitable for longer distances
>only.
>
>Being that this came out decades ago, there must be some references
>somewhere on gravity-assisted rail systems.
>
>Richard
>
>-----Original Message-----
>From: flyboy472@...
>Sent: May 12, 2004 10:22 AM
>To: carfree_cities@yahoogroups.com
>Subject: [carfree_cities] Using gravity
>
>An idea I've toyed with...
>
>Assuming their is some sort of metro-rail within the city, like
>specified in the reference design, what if we changed the elevation
>of the rail's tracks so that the track was at the highest elevation
>at the stations, and the lowest elevation between stations. I'm not
>talking roller coaster proportions, but enough that gravity alone
>would assist in the gentle acceleration and deceleration between
>stops.
>
>I don't have the formulas handy right now to crunch the numbers, but
>simply physics would help us find the grade required to produce the
>desired acceleration rate. This would cut down both on brake use,
>and energy use. In fact, if done correctly, only minimal energy
>would be required to overcome friction (which will be low because
>rolling friction tends to be very low) and minimal brake use would be
>required to exactly control the stop at each station.
>
>
>
>
>To Post a message, send it to: carfree_cities@...
>To Unsubscribe, send a blank message to: carfree_cities-unsubscribe@...
>
>
>
>

-- ### --

J.H. Crawford Carfree Cities
mailbox@... http://www.carfree.com
• This was first done in London over 100 years ago on the deep-level Tube lines. Leaving a station the lines fall at 1 in 30 for 300 feet and approaching the
Message 6 of 7 , May 12, 2004
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This was first done in London over 100 years ago on the deep-level Tube
lines. Leaving a station the lines fall at 1 in 30 for 300 feet and
approaching the next they rise at 1 in 60 for 600 feet. The 10 ft drop
accelerates a train to around 17 mph. This was a big help for the
low-powered little electric locos used at that time.

Modern-day electric trains and trams can use regenerative braking, from full
speed to a standstill in many cases. However, if there is no train
accelerating fairly nearby the regenerated current is fed to on-board
resistors to prevent the line voltage going too high and is wasted as heat.

It would be better to have an on-board energy storage system, such as lots
of super-capacitors or, more realistically, an electro-mechanical flywheel.
But the most energy-efficient braking system is and always will be a hill!

Tony

> An idea I've toyed with...
>
> Assuming their is some sort of metro-rail within the city, like
> specified in the reference design, what if we changed the elevation
> of the rail's tracks so that the track was at the highest elevation
> at the stations, and the lowest elevation between stations. I'm not
> talking roller coaster proportions, but enough that gravity alone
> would assist in the gentle acceleration and deceleration between
> stops. <snip>
• This would, also, reduce noise.
Message 7 of 7 , May 13, 2004
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This would, also, reduce noise.
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