July 3, 2020 7: 15 am
What slope can climb a tram ?
SCIENCE DAILY / “The route sub-field of the future tramway, in the district of Saint-Jean-Baptiste, was presented to residents and the media recently. To the question “Why a tunnel so that it would be so much more simple (and cheaper !) to borrow the Coast of Abraham ?”, the response of the City was that this slope is too steep for the trams modern. But how to explain then that the cars of old, from 1897 and until 1948, the rose without a problem ? The real reason, would it not be that this City wants to save the space already dedicated to cars ?”, asked Michel Beaulieu, Quebec.
Actually, the tram that circulated in the streets of Quebec during the first half of the Twentieth century who worked their way through the coast of Abraham without a problem, even if its inclination is about 10 %, with peaks of 12 % to go up to the Place D’youville. However in this project, we often heard the City to defend the idea of a tunnel under the district of Saint-Jean-Baptiste, saying that the trams so-called “modern” cannot climb slopes of more than 6 or 7 %. Since then, when the “trams” have so much difficulty with the ribs ?
When you are trying to figure out what can stop a train or “tram” to cross a slope, we say, naturally, that this must be a matter of grip, the wheels of metal must be finished by slipping on the metal rails. But in reality, explains the specialist of the public transport of the École polytechnique Pierre-Léo Bourbonnais, it is first and foremost a question of power — even if the grip might end up being a problem too, especially in certain weather conditions. For little that they are designed in the right way, “in theory trams can climb to 12 % or even 14 %, but this leads to additional costs and this remains quite rare,” he says.
In Lisbon, for example, the tramway climbs the slopes ranging up to 13.8 % and in the austrian city of Linz, with 11.6 %. And they do it only by the adhesion between wheels and rails, without the use of special systems as of the chains that pull the cars to the top or the rack (wheel indented, that are interleaved on a special track, serrated also, placed in the ribs particularly steep).
To develop enough power, however, the streetcars should be equipped with several “drive axles”. The axles, are essentially the “bars” that connect the two wheels, under the cars. They may be “passive” and serve simply to support the weight of the vehicle. Or they can be “engines” : the power of the engine is transmitted, it is they who are driving the car.
Gold, said Mr. Bourbonnais, “of our days, to the issues of universal accessibility, it uses smaller roads and the smaller equipment to have a low-floor full the entire length of the vehicle”, which prevents it from placing the axles under the vehicle, because they are larger than the axles “liabilities” and take up too much space.
This is not so “trams” in general who can’t climb slopes like the side of Abraham, but only the trams, the so-called “modern”, which keeps the floor as low as possible to accommodate the elderly and people with reduced mobility. The other, provided that their design allows, would be capable of it.
Or at least, they would be the only point of view of the inclination, because there are also many other factors that come into play. In addition to the coast, ” added Mr. Bourbonnais, to “negotiate the bends in the slopes to climb to the Upper Town is […] very complex. It is for this reason that the tunnel, though costly, dramatically reduces the complexity of the path”. Anyone who knows a little about the sector knows very well that there would have been pronounced corners to negotiate in the full slope, particularly at the junction between the côte d’abraham and Honore-Mercier, and then between the Honoré-Mercier and René-Lévesque.
“Limit the curves on the steep grades [would have asked] a redevelopment important to Quebec in my opinion,” says Mr. Bourbonnais, which would not have necessarily been more simple to make than a tunnel, since it is an area very densely built.
In addition, I was stated by the spokesman of the City Stephanie Gaudreau, “during the pre-project phase, different scenarios have been considered for the rise of the Lower Town to the Upper Town, including an insertion to the surface in the coast of Abraham, and a passage underground, in the area of Place D’youville. This option has not been chosen because of its impact on the traffic in the coast of Abraham, and access to the autoroute Dufferin-Montmorency. The City considers that the current path in the underground is the one that helps to ensure the best possible operation of the tram while reducing the impacts of inclusion in a historical area, and now the current traffic conditions”
So yes, as suspected, Mr. Beaulieu, a tunnel also serves to “save the space already dedicated to the automobile”, but this is really only part of the explanation.
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