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Hybrid buses
I saw on TV not long ago something about Hybrid buses being used in
London - not those hopeless fuel cell things but a diesel engine plus electric motor. Are these out and about yet? B2003 |
Hybrid buses
Boltar ) gurgled happily, sounding much like they
were saying : I saw on TV not long ago something about Hybrid buses being used in London - not those hopeless fuel cell things but a diesel engine plus electric motor. Are these out and about yet? February 2006. http://www.tfl.gov.uk/corporate/medi...ntre/3680.aspx And double-deckers since November 2006. http://news.bbc.co.uk/1/hi/england/london/6102806.stm |
Hybrid buses
On 6 Jul, 09:56, Adrian wrote:
Boltar ) gurgled happily, sounding much like they were saying : I saw on TV not long ago something about Hybrid buses being used in London - not those hopeless fuel cell things but a diesel engine plus electric motor. Are these out and about yet? February 2006.http://www.tfl.gov.uk/corporate/medi...ntre/3680.aspx And double-deckers since November 2006.http://news.bbc.co.uk/1/hi/england/london/6102806.stm Anyone know what routes? B2003 |
Hybrid buses
On 6 Jul, 09:56, Adrian wrote:
February 2006.http://www.tfl.gov.uk/corporate/medi...ntre/3680.aspx From the article: "The battery pack is kept at optimum power by a 1.9 litre diesel Euro IV engine. In other words, an engine which would normally be found in a family car keeps the battery" 1.9 sounds a bit too small. I'm sure in start and stop traffic it might be ok but ultimately the energy all comes from that engine. Seems to me the bus would be hopeless for any long or even middle distance runs especially if any hills are involved, since once the battery has been used up its relying on the engine only and a 10 ton (probably more) bus won't be going anywhere fast with an engine that size. B2003 |
Hybrid buses
"Boltar" wrote in message ups.com... On 6 Jul, 09:56, Adrian wrote: February 2006.http://www.tfl.gov.uk/corporate/medi...ntre/3680.aspx From the article: "The battery pack is kept at optimum power by a 1.9 litre diesel Euro IV engine. In other words, an engine which would normally be found in a family car keeps the battery" 1.9 sounds a bit too small. I'm sure in start and stop traffic it might be ok but ultimately the energy all comes from that engine. Seems to me the bus would be hopeless for any long or even middle distance runs especially if any hills are involved, since once the battery has been used up its relying on the engine only and a 10 ton (probably more) bus won't be going anywhere fast with an engine that size. Do the buses have regenerative braking as well? Paul |
Hybrid buses
Boltar ) gurgled happily, sounding much like they
were saying : "The battery pack is kept at optimum power by a 1.9 litre diesel Euro IV engine. In other words, an engine which would normally be found in a family car keeps the battery" 1.9 sounds a bit too small. I'm sure in start and stop traffic it might be ok but ultimately the energy all comes from that engine. Seems to me the bus would be hopeless for any long or even middle distance runs especially if any hills are involved, since once the battery has been used up its relying on the engine only and a 10 ton (probably more) bus won't be going anywhere fast with an engine that size. 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. |
Hybrid buses
Boltar ) gurgled happily, sounding much like they
were saying : I saw on TV not long ago something about Hybrid buses being used in London - not those hopeless fuel cell things but a diesel engine plus electric motor. Are these out and about yet? February 2006.http://www.tfl.gov.uk/corporate/medi...ntre/3680.aspx And double-deckers since November 2006.http://news.bbc.co.uk/1/hi/england/london/6102806.stm Anyone know what routes? sigh From the first link... The hybrids will operate on route 360, run by London Central, from tomorrow, Wednesday, 8 February 2006. From the second link... When it returns to London it will operate on the route between Wood Green and London Bridge. |
Hybrid buses
On 6 Jul, 11:06, Adrian wrote:
Boltar ) gurgled happily, sounding much like they were saying : I saw on TV not long ago something about Hybrid buses being used in London - not those hopeless fuel cell things but a diesel engine plus electric motor. Are these out and about yet? February 2006.http://www.tfl.gov.uk/corporate/medi...ntre/3680.aspx And double-deckers since November 2006.http://news.bbc.co.uk/1/hi/england/london/6102806.stm Anyone know what routes? sigh From the first link... The hybrids will operate on route 360, run by London Central, from tomorrow, Wednesday, 8 February 2006. I had spotted it. That was 18 months ago however. From the second link... When it returns to London it will operate on the route between Wood Green and London Bridge. And that is the number what? B2003 |
Hybrid buses
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 |
Hybrid buses
Boltar ) gurgled happily, sounding much like they
were saying : 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. shrug How often do bus engines require full power? Not very. Don't forget that one thing electric motors are very good at is producing large amounts of torque from rest. |
Hybrid buses
On Fri, 06 Jul 2007 02:35:46 -0700, Boltar
wrote: On 6 Jul, 09:56, Adrian wrote: Boltar ) gurgled happily, sounding much like they were saying : I saw on TV not long ago something about Hybrid buses being used in London - not those hopeless fuel cell things but a diesel engine plus electric motor. Are these out and about yet? February 2006.http://www.tfl.gov.uk/corporate/medi...ntre/3680.aspx And double-deckers since November 2006.http://news.bbc.co.uk/1/hi/england/london/6102806.stm Anyone know what routes? Single decks are on the 360 (South Ken - Elephant) and the double deck is normally scheduled for the 141 (London Bridge - Palmers Green) but I believe it is away for further mods at present. An ethanol powered Scania double deck is scheduled for use on the 148 but it's not been passed for operation yet. -- Paul C Admits to working for London Underground! |
Hybrid buses
Boltar ) gurgled happily, sounding much like they
were saying : From the first link... The hybrids will operate on route 360, run by London Central, from tomorrow, Wednesday, 8 February 2006. I had spotted it. That was 18 months ago however. I doubt they've been moved to another route, because to do so would make the long-term trial results more difficult to interpret. From the second link... When it returns to London it will operate on the route between Wood Green and London Bridge. And that is the number what? http://www.google.co.uk/search?q=woo...don+bridge+bus |
Hybrid buses
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 |
Hybrid buses
Boltar ) gurgled happily, sounding much like they
were saying : 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. Nor would a diesel bus with an empty fuel tank... I really don't think it's going to be an issue. |
Hybrid buses
In article , aooy65
@dsl.pipex.com says... Single decks are on the 360 (South Ken - Elephant) and the double deck is normally scheduled for the 141 (London Bridge - Palmers Green) but I believe it is away for further mods at present. An ethanol powered Scania double deck is scheduled for use on the 148 but it's not been passed for operation yet. From LOTS News Sunday 24 June 1) The Wrights Hybrid d/d HEV1 with Arriva was taken back to Wrights at Ballymena on 18th June for mods to the system that keeps the traction battery pack cool and which needs to be replaced by a more robust system. It is unlikely to be back in London much before the end of July. |
Hybrid buses
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. Even if the buses were unsuitable for those areas, that's only about a dozen routes. You wouldn't say that double deckers will never work in London because of the Rotherhithe Tunnel. |
Hybrid buses
On 6 Jul, 11:35, Adrian wrote:
Boltar ) gurgled happily, sounding much like they were saying : 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. Nor would a diesel bus with an empty fuel tank... I really don't think it's going to be an issue. A buses diesel fuel probably lasts all day. If these hybrid buses are anything like hybrid cars then the battery would run down after only a few miles without topping up which means its quite possible the bus could be relying on engine power alone on difficult routes such as I mentioned if the engine doesn't have the surplus to charge the battery as well as supplying the motors. B2003 |
Hybrid buses
Boltar ) gurgled happily, sounding much like they
were saying : 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. Nor would a diesel bus with an empty fuel tank... I really don't think it's going to be an issue. A buses diesel fuel probably lasts all day. And...? If these hybrid buses are anything like hybrid cars then the battery would run down after only a few miles without topping up which means its quite possible the bus could be relying on engine power alone on difficult routes such as I mentioned if the engine doesn't have the surplus to charge the battery as well as supplying the motors. But the engine'll be keeping the batteries brimmed as much as possible, so it'll arrive at the bottom of the hill with full charge - which will be perfectly adequate for the ascent. Don't forget that the only real restriction on battery capacity in hybrid cars is the physical packaging constraints - which just don't apply to a bus. |
Hybrid buses
On Fri, 06 Jul 2007 03:13:00 -0700, Boltar
wrote: When it returns to London it will operate on the route between Wood Green and London Bridge. And that is the number what? http://just****inggoogleit.com/ |
Hybrid buses
On 6 Jul, 16:01, James Farrar wrote:
On Fri, 06 Jul 2007 03:13:00 -0700, Boltar wrote: When it returns to London it will operate on the route between Wood Green and London Bridge. And that is the number what? http://just****inggoogleit.com/ Thanks for the useful input to the discussion. B2003 |
Hybrid buses
On Fri, 6 Jul 2007 12:26:49 +0100, "John Rowland"
wrote: 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. Even if the buses were unsuitable for those areas, that's only about a dozen routes. You wouldn't say that double deckers will never work in London because of the Rotherhithe Tunnel. True, as double deckers have been used in it, haven't they? |
Hybrid buses
In article . com,
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. Yes, but busses (especially in London) are very stop-start; if the engine is busy recharging the battery when at a bus stop and/or red lights, it will mitigate that to some extent. Plus the regenerative braking, of course. Exactly how far those effects help is something they will find out as part of the trial, I guess. -- Shenanigans! Shenanigans! Best of 3! -- Flash |
Hybrid buses
I am no bus crank but am interested in this alternative technology
stuff. Can anyone supply me with list of vehicle identities - registration number or whatever - so I can identify them - or do the buses have huge adverts on them announcing they are hybrids ? Bear in mind that since I am incapable of telling one makers bus type from another, anorak answers like ''hyrbids have one extra rivet on the fourth panel below the third grommet on the offside when compared to a standard model'' are completely useless as I won't actually know which types to look at. I'm sure this gen is on the web somewhere, I'm just not familiar enough to pick it out. -- Nick |
Hybrid buses
"Boltar" wrote in message
ups.com On 6 Jul, 09:56, Adrian wrote: February 2006.http://www.tfl.gov.uk/corporate/medi...ntre/3680.aspx From the article: "The battery pack is kept at optimum power by a 1.9 litre diesel Euro IV engine. In other words, an engine which would normally be found in a family car keeps the battery" 1.9 sounds a bit too small. I'm sure in start and stop traffic it might be ok but ultimately the energy all comes from that engine. Seems to me the bus would be hopeless for any long or even middle distance runs especially if any hills are involved, since once the battery has been used up its relying on the engine only and a 10 ton (probably more) bus won't be going anywhere fast with an engine that size. I was in Seattle a couple of months ago and noticed that all their bendy buses proudly claim to be hybrids. The buses certainly didn't look new, so presumably have older technology than the London buses, and Seattle is a lot more hilly than central London. They seemed to get up the hills all right, though I've no idea what size diesel engines they have. Seattle has another pro-public transport featu buses are free in the central area, so encouraging people to park their cars and then move around by bus (I doubt that many people get into town other than by car). |
Hybrid buses
Ken Wheatley wrote:
On Fri, 6 Jul 2007 12:26:49 +0100, "John Rowland" wrote: 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. Even if the buses were unsuitable for those areas, that's only about a dozen routes. You wouldn't say that double deckers will never work in London because of the Rotherhithe Tunnel. True, as double deckers have been used in it, haven't they? I doubt it... a normal single decker won't fit. |
Hybrid buses
On Fri, 06 Jul 2007 08:28:38 -0700, Boltar
wrote: On 6 Jul, 16:01, James Farrar wrote: On Fri, 06 Jul 2007 03:13:00 -0700, Boltar wrote: When it returns to London it will operate on the route between Wood Green and London Bridge. And that is the number what? http://just****inggoogleit.com/ Thanks for the useful input to the discussion. My pleasure. |
Hybrid buses
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. -- Paul Terry |
Hybrid buses
In message . com, D7666
writes Can anyone supply me with list of vehicle identities - registration number or whatever - so I can identify them - or do the buses have huge adverts on them announcing they are hybrids ? They are branded in quite large letters front and rear: http://www.busandcoach.com/featureStory.aspx?id=640 -- Paul Terry |
Hybrid buses
In message , Recliner
writes I was in Seattle a couple of months ago and noticed that all their bendy buses proudly claim to be hybrids. The buses certainly didn't look new, so presumably have older technology than the London buses, and Seattle is a lot more hilly than central London. They seemed to get up the hills all right, though I've no idea what size diesel engines they have. Seattle's dual-mode Breda buses date back to 1989, but were not very reliable and have been phased out to be replaced by a system developed by General Motors, in which the diesel engine powers the wheels as well as charging the battery. Unfortunately, they haven't delivered the expected reductions in diesel usage: http://seattlepi.nwsource.com/transp...9_metro13.html -- Paul Terry |
Hybrid buses
"Paul Terry" wrote in message
In message , Recliner writes I was in Seattle a couple of months ago and noticed that all their bendy buses proudly claim to be hybrids. The buses certainly didn't look new, so presumably have older technology than the London buses, and Seattle is a lot more hilly than central London. They seemed to get up the hills all right, though I've no idea what size diesel engines they have. Seattle's dual-mode Breda buses date back to 1989, but were not very reliable and have been phased out to be replaced by a system developed by General Motors, in which the diesel engine powers the wheels as well as charging the battery. Unfortunately, they haven't delivered the expected reductions in diesel usage: http://seattlepi.nwsource.com/transp...9_metro13.html Yes, they certainly have a lusty diesel roar as they climb the Seattle hills. I wouldn't have guessed they were hybrids if the signs hadn't said they were. I suppose this is yet another episode of hybrid vehicles not achieving the economy that they claim. |
Hybrid buses
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 |
Hybrid buses
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 |
Hybrid buses
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 |
Hybrid buses
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 |
Hybrid buses
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/ |
Hybrid buses
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 |
Hybrid buses
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. |
Hybrid buses
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. |
Hybrid buses
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. |
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