"... If it were not subsidized with tax payer dollars, it would fail?"

Most U.S. mass transit systems are, I believe, subsidized.

<...Is it cost effective?...>

What's the cost of not using it?

The logic of the cable pull drive system is the fact that the grades are too steep for steel wheels to grip steel rails.

The draw back is the maintenance of the underground cable chases and centralized drive system.

I lived in San Francisco for 27 years and relied on the SF trolley, cable car and trolley buses to get me around. A lot of other people did also besides the tourists. The system is old, but paid for in pre war dollars. I can't imagine SF without it's trolley system. It wouldn't be SF without it. Bart takes care of the long distance travel. You could also ask the same about New Orleans. The system works and as they say, "if it ain't broken, don't fix it".

Ronsetto wrote: "You could also ask the same about New Orleans."

Ronsetto, New Orleans is not just an anachronism, IMO it is a bizarre collection of the illogical and the irrational.

Not just in those who knowingly insist on exposing themselves to certain death but to a Federal Government and the Army Corp of Engineers who encourage such risk by throwing billions of dollars at badly designed dikes, admits it and builds them anyway.

Why doesn't Congress put up cigarette ads while they are at it!

I know this is a rant and apologize ahead of time but some things are an instant ignition source for me and as much as I love visiting New Orleans, what it costs all of us to support such a risk laden life style violates my sensibilities.

Perhaps this a source for another discussion string.

L.J.

Take your pick. They'll both get you around town.

I think the old one is a tourist trade anachronism that is an effective way of moving around the steep hills of San Francisco

Agreed but the nice air conditioned bus better not have the usual stinking, smoking, diesel or SF will be more smoggy than LA.

Does the system in San Francisco recover energy from cars that are descending the slopes to power ones ascending? If so it is a very efficient system and should be kept! If not...convert it to utilizing dynamic braking to transfer energy from one car to another.

Drew K

Does the system in San Francisco recover energy. . . ?

I visited a trolley system power unit that was set up as a museum and studied the mechanics of the design thoroughly. While the details have been lost to memory, had there been a recovery system such as you asked about, I'd have remembered.

Incorporating such a device is not likely as while there are cars going downhill on any given cable, there are others climbing at the same time.

Whether or not such distribution "balances" the load is hard to say as each car has a gripper which releases the cable when stopping in traffic or for passengers and grabs the cable again when starting up. Given the independent nature of each operator and his trolley, it's hard to predict where any one will be at any given moment.

What I see as more likely is tearing out the cables and replacing them with electrical conductors and then equipping the trolleys with "shoes" and electric motors. That alone would increase energy efficiency and enable more trolleys on any given route. It would also reduce the monstrous maintenance that is inevitable on so complex and old a design. The power needed to run that steel cable is, by itself, enormous, before it even starts to move a trolley.

Load limits on the cable system preclude "improvements" on the basic nature of the system.

L.J.

Looks like Ram has some information...I may have to read up on it to be convinced (sry ram).

What I was describing is not something you would actually see and since I don't know how a cable trolly system works I would need to read about it. The system I was thinking uses a motor that can also generate. When there is a load on the motor it consumes electricity and moves the load, when the car is going downhill you generate electricity with the work done by the descending car. When a load is placed on the generator it slows the car, so you distribute the generated energy to other cars going uphill.

Drew K

Given the constant speed nature of the cable, energy recovery becomes more like energy balance. If we assume that the overall loading of the "up" cars exactly matched the loading of the "down" cars then the "only" load on the drive motors would be the friction of the cables being dragged around the route. However this friction is enormous, representing over 95% of the total load on the drive motors! in reality the cable is a huge flywheel where the loading/unloading of a single car has little effect on the speed/power requirements of the system and subsequently only a tiny opportunity for energy recovery equal to the change in the mass/inertia of the overall system. So under the extremes of all "down" cars or all "up" cars we would expect the system to speed up or down incrementally respectively. This is exactly how our modern interconnected utility system autonomously maintains its frequency when loads are randomly switched on and off.

From Wikipedia: http://en.wikipedia.org/wiki/Cable_car_%28railway%29

"...One apparent advantage of the cable car is its relative energy efficiency, because of the economy of centrally located power stations, and the ability of descending cars to transfer energy to ascending cars. However, this advantage is totally negated by the relatively large energy consumption required to simply move the cable over and under the numerous guide rollers and around the many sheaves. Approximately 95% of the tractive effort in the San Francisco system is expended in simply moving the four cables at 9.5 miles per hour..."

Good information, but do you know if there is a energy recovery system designed in? Do cars going down hill help pull the uphill ones?

Drew K

Cool, sounds like an interesting system that would be difficult but not impossible to increase efficiency on. But efficiency is not quite the same as efficacy right? One is a quantifiable calculation of energy consumed, monetary overhead compared to profit. Efficacy is a measure of how effective the system is? If that is the case it sounds like the system is effective, it transports people but may or may not be profitable in itself. Trouble is there are many difficult to quantify aspects of the trolly system, mainly being the tourism industry. I wouldn't be surprised if someone out there has already calculated the number of tourists it brings and how much they spend, that would help complete understanding. If the tourists pay enough in sales tax and / or bring in enough business to offset the subsidy then it is a wash. I would bet that this is the case and that the city even makes a tidy profit from the tourism.

Drew K

I'll give you a GA mainly for pointing out the advantage of a smaller more open design. Large buses are comparatively slow and inconvenient for passengers who only want to travel 5 or 6 blocks. Plus, the more passengers that are stuck in a bus, the more the odor of those passengers tends to linger inside the bus.

When I visited San Francisco last year I left my rental car in the garage for most of the trip because I could get around the city more quickly using street cars. The cable cars charge more and go slower, so I only rode one once and that was for the enjoyment of the ride rather than for any practical reason.