On Jul 7, 7:26 am, Paul Terry wrote:
They are branded in quite large letters front and rear:

http://www.busandcoach.com/featureStory.aspx?id=640

Interesting article. Not sure these buses will be quite as great as
hoped:

FTA:

"Acceleration from 0 to 30mph takes 18 seconds, comparable with a
diesel bus"

Not sure what diesel bus he's refering to unless its something pre
WW2. I don't have any figures but every bus I've ever been in seems to
get to road speed a damn sight quicker than that.

"The diesel engine is set to run constantly - unlike some hybrid
systems where it shuts down for periods."

So how does that help pollution or fuel economy if the bus is crawling
along in some endless jam? I thought the whole point of hybrids is
they can switch the engine off and crawl on electric power om traffic?

"TfL expects that the battery packs will have to be replaced every
three years, at a cost of around £3,000."

So thats 400 kgs of batteries down to the tip every 3 years not to
mention the new set that has to be manufactured? Oh very green.

B2003

On Jul 6, 11:26 pm, Paul Terry wrote:

They are branded in quite large letters front and rear:

http://www.busandcoach.com/featureStory.aspx?id=640


TY for that, buses do remain a mystery to me.

You are talking here to someone who probably never got into double
figures on trips by Routemaster.

True way back long ago I worked for NBC and could tell the difference
between an RE a VR a Panther a National an LH or a Leopard from an
inspection pit viewpoint but that was rather a long time ago . Oh
yeah, we had some FLF600s as well which made a lot of noise.

But London buses remain a mystery to me.

--
Nick

Boltar wrote:

On Jul 7, 7:26 am, Paul Terry wrote:

They are branded in quite large letters front and rear:

http://www.busandcoach.com/featureStory.aspx?id=640

"The diesel engine is set to run constantly - unlike some hybrid
systems where it shuts down for periods."

So how does that help pollution or fuel economy if the bus is crawling
along in some endless jam? I thought the whole point of hybrids is
they can switch the engine off and crawl on electric power om traffic?


Another point with hybrid drive is actually that the engine can run on
most fuel-efficient rpm when it runs, in this case all the time. This
does not matter practically, a small engine can be compensated with
running it constantly and using a larger battery pack, which is what I
think they have done here.

The problem with direct-driving diesel engines is that they need to be
large and are very fuel-consuming while they accelerate, such engines
are not capable of providing enough torque in any other way, while
eletrical motors are used to what they are best for, that is providing
enough torque from still standing while they would not be efficient for
keeping speed once the vehicle has accelerated. Diesel engines are on
the other hand good at providing constant amounts of energy over longer
time so they are best used for generators and for direct-driving the bus
once it has enough speed. ...and the battery pack is used to even out
the electrical power consumption over time.

In shorter words, the engine, battery pack and electrical motors are
used to what each of them are doing best.

"TfL expects that the battery packs will have to be replaced every
three years, at a cost of around £3,000."

So thats 400 kgs of batteries down to the tip every 3 years not to
mention the new set that has to be manufactured? Oh very green.


I am in most cases looking forward with great interest to inovative
experiments on making fuel-efficient transport solutions but this one
surprises me somewhat. Instead of expensive large battery packs,
wouldn't it be better to build a trolley-bus network with trolley buses
with regenerating brakes? Larger initial investment costs probably but
it would surprise me if trolley-buses would not turn out cheaper after a
few years.

It should be said though that with this kind of battery cells it is as
far as I have understood it possible to use large parts of the materials
in the process of building new ones, but still, the batteries need to be
replaced and in other aspects the buses still need at best the same
amount of maintenance as traditional diesel buses, if not even more.

--
Olof Lagerkvist
ICQ: 724451
Web: http://here.is/olof

On Jul 7, 10:20 pm, Olof Lagerkvist wrote:
Another point with hybrid drive is actually that the engine can run on
most fuel-efficient rpm when it runs, in this case all the time. This
does not matter practically, a small engine can be compensated with
running it constantly and using a larger battery pack, which is what I
think they have done here.

True , but if the batteries are charged already whats the point in
having the engine still running? It would then be no different to a
diesel car sitting in the jam with its engine idling.

surprises me somewhat. Instead of expensive large battery packs,
wouldn't it be better to build a trolley-bus network with trolley buses
with regenerating brakes? Larger initial investment costs probably but

That would involve long term commitment. Not something British
politicians are very comfortable with. Also though the usual Nimbys
would crawl out from under their rocks and start to whinge about the
"visual intrusion" (or some equivalent bull****) of the wires.

B2003

On Sat, 07 Jul 2007 21:20:34 GMT,
Olof Lagerkvist wrote:
wouldn't it be better to build a trolley-bus network with trolley buses
with regenerating brakes?

Regenerative braking depends on being able to guarantee that you can
dump the energy somewhere.

When you carry batteries with you it's not really a problem[1] - it's
reasonable to assume that your generator will maintain a good electrical
connection to the battery.

[1] Actually it is. Typically the batteries cannot take charge quickly
enough.

When you are connected to an external grid it is a bit of a problem (not
insurmountable, just difficult) because you can (and do) lose connection
from time to time. When you lose connection you also lose the brakes.

Super capacitors look promising for the future for regenerative braking
(regardless of what power source is used).

I'm wondering if we might start seeing something like this soon for
bicycles. I think that generator/motor plus supercapacitor ought to come
in at under 2kg[2] with the ability to store enough charge to stop (and
accelerate) a cyclist from 20-30mph to rest.

[2] not necessarily cheap, just possible.

Tim.

--
God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t,"
and there was light.

http://tjw.hn.org/ http://www.locofungus.btinternet.co.uk/

Tim Woodall wrote:

On Sat, 07 Jul 2007 21:20:34 GMT,
Olof Lagerkvist wrote:

wouldn't it be better to build a trolley-bus network with trolley buses
with regenerating brakes?


Regenerative braking depends on being able to guarantee that you can
dump the energy somewhere.


Yes, it is a bit complicated but (and as you say) it can be done. I was
thinking about some regulating combination of rheostatic brakes and
regenerating brakes like the technique used on some tube trains nowadays
(and also some other kind of railway and tram systems in different
places). London Underground claims that they save around 20-25% per cent
of energy on the lines equipped with regenerating braking.

I know however that we are talking about buses and not trains here and
that today most trolley-bus systems with regenerating brakes are
actually regenerating to a battery pack, either always or when wire
connection is lost, but still I think that trolley-buses are more the
right thing for the future than hybrid energy buses with battery packs are.

Super capacitors look promising for the future for regenerative braking
(regardless of what power source is used).


Yes, something like that will probably make the problems around
regulating regenerating brakes at least easier as it seems.

I'm wondering if we might start seeing something like this soon for
bicycles. I think that generator/motor plus supercapacitor ought to come
in at under 2kg[2] with the ability to store enough charge to stop (and
accelerate) a cyclist from 20-30mph to rest.


Funny, I saw a post about this idea in a mountainbike forum just a
couple of days ago. Seems like there are growing expectations on
supercapacitors for this kind of tasks.

--
Olof Lagerkvist
ICQ: 724451
Web: http://here.is/olof

On 6 Jul, 11:15, Boltar wrote:
On 6 Jul, 11:05, Adrian wrote:

Don't forget that the engine is basically just being used as a generator,
therefore can run at optimum revs for the specific output - there's no
requirement for any kind of useful rev range or torque curve.

True , and I suppose that will mitigate it somewhat. However
ultimately that engine will produce less power than a normal bus
engine so when relying on the engine alone its going to be slower
compared to the normal engine running at optimum gearing.

B2003

You might be right for an outer suburban bus route, or one going from
town to town. However, a bus in London will probably average about
15mph. Hypothesising a little, if a 6 litre engine can deliver 60mph,
a 1.5 litre engine should deliver 15mph. The battery is being used as
an accumulator so average speed determined average power requirement.

On 6 Jul, 11:26, Boltar wrote:
On 6 Jul, 11:16, Adrian wrote:

shrug
How often do bus engines require full power? Not very.

Agreed but when they do need it they really need it. The steep hills
around mill hill, highgate , hampstead and southgate spring to mind. A
hybrid bus with an exhausted battery going up one of those hills won't
be very popular with other motorists.

B2003

They've been trialling these for 2 years now. This hasn't been an
issue. It might be if the bus was used on a route going up a mountain
without a stop. Not many of these in London.

In article ,
(Paul Terry) wrote:

In message , John Rowland
writes

Rotherhithe tunnel

I doubt it... a normal single decker won't fit.

The double-deck route 82 used to run through the tunnel until the
1960s. Here's one just emerging from the northern exit:

http://www.busesatwork.co.uk/051-100...82_RTL1613.jpg

I have a feeling that the roadway through the tunnel was lower in
those days (as it was in the Blackwall tunnel), giving better
height clearance at the expense of (even) narrower width.
Apparently buses on route 82 were equipped with specially
reinforced tyres to mitigate the constant rubbing on the kerb while
going through the tunnel.

and an RTL was 7'6" wide, instead of the 8'2 1/2" of a modern bus.

--
Colin Rosenstiel

On Jul 8, 9:52 pm, alexterrell wrote:
On 6 Jul, 11:15, Boltar wrote:

On 6 Jul, 11:05, Adrian wrote:

Don't forget that the engine is basically just being used as a generator,
therefore can run at optimum revs for the specific output - there's no
requirement for any kind of useful rev range or torque curve.

True , and I suppose that will mitigate it somewhat. However
ultimately that engine will produce less power than a normal bus
engine so when relying on the engine alone its going to be slower
compared to the normal engine running at optimum gearing.

B2003

You might be right for an outer suburban bus route, or one going from
town to town. However, a bus in London will probably average about
15mph. Hypothesising a little, if a 6 litre engine can deliver 60mph,
a 1.5 litre engine should deliver 15mph. The battery is being used as
an accumulator so average speed determined average power requirement.

On the flat, and assuming your drag is mainly air resistance power
required to maintain a constant speed goes up as cube of speed.

So if we assume that a 1.5 ltr engine can deliver 1/4 the power of a 6
litre engine then the 1.5 ltr engine should be able to maintain a
speed of about 38mph if the 6ltr engine can maintain 60mph.


It's why there isn't a huge difference between the best in the world
cyclists and a reasonable club cyclist in average speed.

IIRC, a 90 year old has done a 25mile time trial in just under an hour
(so lets say 25mph). Saturday, the fastest rider managed a 5 mile time
trial in just under 9 minutes (lets say 34mph)

But Cancellara, all else being equal, was delivering 2.5x the power
that that 90 year old was managing.

Yesterday David Millar managed the first hour at 30mph. That's still
70% more power of that 90 year old for just a 20% increase in speed.

Tim.