Streetcars / Trams / Light Rail

They’re awesome, yet problematic. In the early 1900s, Los Angeles had an extensive streetcar and light rail network (the red and yellow cars), but it was dismantled, like in many other american cities in the thirties, forties and fifties. One of the reasons was a conglomerate of car manufacturers and oil and tire companies that bought the streetcar companies, trashed their vehicles and changed them to buses. Of course, there were many other reasons as well, and it’s a subject far too large to handle here.

Turku, Finland’s old capital and currently fourth largest city, had trams as well but they were dismantled in the sixties. A large investment in the track and electricity network was lost, new buses had to be bought and the roads had to be reinforced to carry the buses. It was the irresistible zeitgeist that the automobile would be the future – ironically, only a few years before the oil crisis.

Thankfully, Helsinki never did that. There were awful plans of putting a highway overpass right in the scenic main market by the seaside and other absolutely horrible things. It is sometimes very hard to understand that time. Making a huge graffiti to a beautiful Jugend building is next to nothing compared to some of the architectural and city ideas of the sixties.

What New?

That was the past. What about now? Well, Turku has been pining for the streetcars for a long time, and now it seems the inland city of Tampere (Turku’s arch rival no less) that never had trams is actually planning to upstage Turku in building a network. Both have populations of about 200,000.

And in multiple US cities, tram networks are being brought back. Los Angeles has built it anew and is expanding it, although it’s still far smaller than what it was in the old times.

What are the issues?

Well, tracks cost some, compared to buses that can run on roads, but tram tracks are actually not that expensive since they can be laid on roads, can make sharper corners than heavier rail tracks (trains, metro) and don’t require over/underpasses. And the “default” alternatives, cars and buses need roads and affect other traffic as well, so the difference might not be large. In Helsinki, trams are actually the most profitable of the city’s transportation sectors. They cost very little to run. Trams are also more flexible than heavier rail systems in a city development timescale (5 years) because the new tracks are quite quick and cheap to lay down. You can also leave old tracks in place without them doing any harm, to keep them in reserve in case they will be used later again.

What about the utility factor problem? Buses can have a larger network and transition a bit better from line to line. But still, most vehicles stand outside the rush hour. But it’s the same issue with everything, personal automobiles included.

Technology

It’s curious that newer trams in Helsinki actually seem to be noisier than older ones. This, I gather is from different technology – the new ones have high torque motors right in the wheels, and are designed for modern international rails that have ample lead-in to corners, meaning the sideways acceleration starts slowly. In contrast, Helsinki’s tracks are old, have sharp corners with no lead in. And sometimes the tracks are even uneven because of cobblestones, like in the senate square. This means that the older Finnish trams from seventies and eighties and the recently “stop-gap” purchased old Mannheim trams actually travel smoothly while the 2000:s Bombardier low floor trams bang really hard and are in constant need of repair.

One weird thing about trams is that they are very heavy. 30 tons for a vehicle carrying 100 people is a lot. Since the investment cost is high already and it will last for a long time, wouldn’t it make sense to actually spend some extra on structures and construct them out of aluminium and/or composites? Of course, since trams are operated much longer than for example buses, fatigue issues must be taken into account very carefully. You could then do with smaller motors, less reinforced tracks and many other beneficial things that would then reduce the cost. It seems trams, like local passenger trains have some mental legacy from the old czar era steam trains when everything was constructed of mild steel and weighed absolutely humongously – so that when a freight train or a building and a passenger rail vehicle collide, the passengers survive unharmed. Yet these trams move among ordinary traffic with “flimsy” buses and ordinary motor cars (that at times are crushed like soft drink cans in collisions with the heavier rail vehicles). Hence the high impact survivability traditions make less sense for rail vehicles moving among road traffic and could actually result in less safety overall.

Another alternative to the tram is the trolley bus. You still avoid pollution and fuel cost compared to buses and avoid the need to build a track compared to tram. The trolley buses might not last as long as trams and they have an image problem though – they’re seen as Eastern or Southern European and a poor man’s alternative. I haven’t studied the subject that much.

Ideas

Use large pultruded* carbon fiber tubes to construct a triangular truss space frame, reinforced by a carry-around at the door openings. Separate the wheels from the motors with axles (jointed axle or a cardan) and use very accurately tailored suspension (possibly with active components for varying loads) to ensure very low vibration levels. Use separable high impact plastic panels on the outside and inside, attached with a large number of very sturdy fasteners.

Modern frequency converters and high torque permanent motors are a natural choice of course.

This should result in a light, quickly accelerating, silent, easily maintainable, reliable and low operations cost tram. It’s also going to cost a lot to buy, but since trams are going to be used for thirty or even fifty years, it pays itself back in a fraction of that time.

The space frame construction can be customized easily by varying the number of frame triangles, and the number of panels can be varied as well. The door reinforcements and doors need to be standard components though. They potentially need metal or in-place cured composites.

*: the pultrusion industrial process results in very straight fibers that can handle both tension and compression. A good use for the expensive carbon fiber, compared to layups where the strength is much less.

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