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Post by q8 on Oct 2, 2005 9:30:18 GMT
There seems to be a growing tendency among metro operators to build articulated trains and monomotor bogies.
What are the merits/demerits of both forms of technology?
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Post by Deleted on Oct 2, 2005 10:31:10 GMT
Articulation: Fewer bogies, thus fewer things to go wrong, and less maintenance on wheels, brakes, and other gizmos. Also it makes it easier to have wide connections between cars so that pax can move around. The current Sydney trams (sorry, Light Rail cars) are three shortish cars on four bogies, with no doors in the middle car. From inside, it looks like one long car.
Monomotor: Much the same, I guess. If one motor can produce enough power, why have two lower-power motors? It would just double the number of motors that can fail, need maintenance, or drop off because a bolt was not done up.
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Post by markextube on Oct 2, 2005 22:35:44 GMT
There was a plan for the new victoria line stock to have bendy trains called space train. They would have shorter carriages, all jointed with no end of carriage doors to make up one long unrestricted train you could walk through. The body was going to be slightly rounded to give more space and with a lower floor and smaller wheels.
It seemed quite a serious idea with diagrams, pictures and models but did'nt come about. But it will come about on the new surface line stock.
With designs at the moment there will not be any separate carriages. It'll either be one long train you can walk through or two separate units. With all double doors. The final design is due hopefully not too long in the future from Bombardier.
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Post by igelkotten on Oct 3, 2005 10:32:56 GMT
Actually, I cannot think of any large heavy metro project involving the use of monomotor bogies at the moment. Looking at the plans of the big manufactureres, the trend is instead to use as much distributed power as possible. Modern traction control packages have become so capable and dropped so much in price that the designers can opt for having every axle motored, thus giving an excellent degree of traction control, not least as regards adhesion and adhesive weight. Not to mention that that kind of setup gives an even distribution of smaller mass, which is a very good thing as far as vehicle vibration and track forces are concerned
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Colin
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Post by Colin on Oct 4, 2005 11:05:36 GMT
There was a plan for the new victoria line stock to have bendy trains called space train. They would have shorter carriages, all jointed with no end of carriage doors to make up one long unrestricted train you could walk through. The body was going to be slightly rounded to give more space and with a lower floor and smaller wheels. It seemed quite a serious idea with diagrams, pictures and models but did'nt come about. But it will come about on the new surface line stock. With designs at the moment there will not be any separate carriages. It'll either be one long train you can walk through or two separate units. With all double doors. The final design is due hopefully not too long in the future from Bombardier. And there was me thinking that it couldn't be done on LUL due to tight curves. Also differing stock lengths will surely preclude such an idea on the sub surface lines. IMHO it would also be unsafe - that is, with separate cars, people are limited to a certain part of the train; whereas with free movement you could end up with a crushing surge as seen at large events. At least the DLR has it right in that their articulated vehicles are only two cars long.
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Post by igelkotten on Oct 5, 2005 0:56:46 GMT
And there was me thinking that it couldn't be done on LUL due to tight curves. Also differing stock lengths will surely preclude such an idea on the sub surface lines. IMHO it would also be unsafe - that is, with separate cars, people are limited to a certain part of the train; whereas with free movement you could end up with a crushing surge as seen at large events. At least the DLR has it right in that their articulated vehicles are only two cars long. Long articulated units can actually be built to match the loading gauge more exactly, thus fitting in more train within the same tunnels. Compare a chain of lego bricks to a piece of string -the string can more or less wrap itself around a curve, while the lego bricks have edges sticking out everywhere. Same thing with trains. Likewise, long units with internal gangways or open saloons are considered to ease crush loadings if properly designed, since the passengers can spread out more inside. So, even if the critters will still insist on using the frontmost and rearmost doors of the train, just like before, they will still be able to spread out more once inside.
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Colin
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Post by Colin on Oct 5, 2005 2:36:45 GMT
I take your points onboard, IgelKotten, but I still don't like the idea.
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Post by igelkotten on Oct 6, 2005 10:10:12 GMT
I take your points onboard, IgelKotten, but I still don't like the idea. Resistance is futile. You will be assimilated. And bendy.
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Colin
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Post by Colin on Oct 7, 2005 3:12:36 GMT
Not if captain picard has anything to do with it ;D ;D ;D
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Post by Deleted on Oct 9, 2005 14:22:09 GMT
Could the solution be to have three sets of two-car bendy trains, or two sets of three car crains?
Dunno if it would work, but it might be an idea.
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Post by igelkotten on Oct 11, 2005 13:11:28 GMT
As always, it is a tradeoff.
Having a train formed out of a single articulated unit on the lines of the proposed "space train" gets rid of a lot of driver's cabs which cost money and take up room, as well as a lot of couplers and other equipment. Thus, it is cheaper, both to build and maintain, and has more space for passengers.
But from the operational side, it can have several drawbacks. What if your passenger loadings are uneven, with off-peak passenger levels very low? Then it is quite wasteful to lug around a whole train when just half a train would do. On the third hand (yes, I'm a mutant!), the staff costs assosciated with extra crews for splitting trains and driving parts of trains to and from stabling points etc, as well as the increased stock diagramming complexity can completely wipe out any advantages of splitting and coupling trains to fit passenger loadings.
And what happens if you get a fault on your train, such as a broken window or a faulty door? If you have a train composed of several carriages, you can perhaps isolate just one and continue in service.
Likewise, maintenace can become more difficult, or at least awkward. And you might have to invest in a completely new maintenance infrastructure -lifting roads, service roads and similar stuff.
Whether a "bendy train" is a good thing or not is something that, I suspect, differs from railway to railway, depending on local conditions.
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Post by trainopd78 on Oct 11, 2005 13:35:42 GMT
Tipping out must be a completed pain with a whole articualted train. Tipping out car by car has its pitfalls as a few of us can testify, but at least you know that people are all out of your train and the ones you can see aren't going to go very far. (why must the public insist on operating butterflies - the doors are closed for a reason )
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Post by q8 on Oct 11, 2005 13:38:51 GMT
I never knew why butterfly cocks weren't moved to the end of the car next to the porter button. That way they are not so obvious,
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Post by Deleted on Oct 11, 2005 18:16:44 GMT
But from the operational side, it can have several drawbacks. What if your passenger loadings are uneven, with off-peak passenger levels very low? Then it is quite wasteful to lug around a whole train when just half a train would do. On the third hand (yes, I'm a mutant!), the staff costs assosciated with extra crews for splitting trains and driving parts of trains to and from stabling points etc, as well as the increased stock diagramming complexity can completely wipe out any advantages of splitting and coupling trains to fit passenger loadings. We no longer split trains anyway, so that wouldn't matter. And what happens if you get a fault on your train, such as a broken window or a faulty door? If you have a train composed of several carriages, you can perhaps isolate just one and continue in service. We can't isolate individual cars now either. I believe the arguement is that in the event of a detrainment you may have to take passengers through the isolated car, so exposing them to whatever danger it was that made you isolate the car in the first place.
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Post by igelkotten on Oct 12, 2005 0:29:21 GMT
But from the operational side, it can have several drawbacks. What if your passenger loadings are uneven, with off-peak passenger levels very low? Then it is quite wasteful to lug around a whole train when just half a train would do. On the third hand (yes, I'm a mutant!), the staff costs assosciated with extra crews for splitting trains and driving parts of trains to and from stabling points etc, as well as the increased stock diagramming complexity can completely wipe out any advantages of splitting and coupling trains to fit passenger loadings. We no longer split trains anyway, so that wouldn't matter. And what happens if you get a fault on your train, such as a broken window or a faulty door? If you have a train composed of several carriages, you can perhaps isolate just one and continue in service. We can't isolate individual cars now either. I believe the arguement is that in the event of a detrainment you may have to take passengers through the isolated car, so exposing them to whatever danger it was that made you isolate the car in the first place. Well, I was speaking in general terms -but your answers give more reasons for LU to go for the "single-unit train", then, since that is what you in practice operates as. Of course, I can imagine the fleet maintenance people having a different opinion...
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