03
Jan

2010

Grip Module, Lesson 4: Corners

Post by Steven Dale

Gondolas turn corners by automatically switching from one cable line (blue) to another in intermediary angle stations (orange circles)

Corners are important because all cities have them. If your transit technology cannot turn corners, you cannot exist in cities. It’s just that simple.

As I said before, however, no one has taken the time to explicitly and simply explain how cable deals with them. For those who’ve never encountered Cable Propelled Transit before, you may not even believe CPT can turn corners.

For the sake of ease, I’m just going to talk about Gondola systems. Cable Cars are a whole other issue, one that I will get to in the future. Know, however, that Cable Cars can turn corners with or without detachability.

For Gondola systems to turn corners, however, detachability is an absolute prerequisite. An attached gondola, for all intents and purposes, cannot turn corners because corner-turning is dependent upon detachability (let’s pretend that’s a word, okay?).

If you’ll recall from Grip Module, Lesson 2 detachable grips allow cable gondola systems to stop at intermediary “angle” stations. This same technique is used to allow gondolas to turn corners by locating the opposing terminals of two separate cable lines in the same station. A gondola enters the station, detaches from the first cable line, is decelerated then moved through the station so that it aligns perpendicularly with the second cable line. The gondola is then reaccelerated, attaches to the second cable line and departs the station.

A Gondola Angle Station

This technique allows gondolas the flexibility to realize an almost infinite number of configurations. Furthermore, deceleration at the angle station is not a prerequisite. Gondolas can switch lines in angle stations at operating speed without the need to slow down.

Most (but certainly not all) turning stations are too large right now, admittedly (as the image above implies). The above image, it should be noted, is not merely a turning station, but a turning station coupled with a maintenance bay. It is therefore a very large station. Unfortunately it is the only photo I have of the internal workings of a turning station. One thing the cable industry should pay attention to is slimming the profile of their stations which is entirely possible given the technology.

Proceed to Grip Module, Lesson 5 (coming soon)

Return to Grip Module, Lesson 3: Atttachable Grips



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Comments

  1. Unnecessary complex system for an urban environment. Another reason cities continue to the embrace the simplicity and flexibility of rail? Gondola technology is far too complex, and all those moving parts means a great chance of breakdown. Rail wins again.
  2. Ron Wm. Hurlbut
    This is pretty elaborate for turning a tight corner. 45 degree or tighter. However, I would imagine that 30 degree or wider turns could be handled by the support towers without the need to Detach the Grip.
  3. Ron Wm. Hurlbut
    Hi Steven, I'm not concerned with the size of the turning station. I didn't say that it was big, I said it was "elaborate": As in "Complex". I'm thinking in terms of an LRT. The track can curve back and forth to follow the road and turn on a radius of track. What you show is like having a turn-table at each intersection. It's like turning an old steam locomotive at a roundhouse. A 2 degree turn is very restrictive. It is one thing to travel from point A to point B on a straight line. However, if you are travelling from point A to point B on a curve, you will have to pass through several Turning Zones along the way... To be fair, the Gondola will pass over most obsticles instead of going around them. Also: If the Gondola is a substitute for the LRT's as proposed by Transit City, then there would be a Station/Stop every few hundred meters. Each Station/Stop would also likely be a Turning Zone as well.
  4. Hi Steven, It occured to me that Gondolas are a strange transportation technology. You need special mechanisms in order to negotiate horizontal curves. [To turn Left and Right] But vertical curves are a cinch. They excel in going up and down, but not great side to side. The City of Toronto isn't particularly hilly and our vallies aren't canyons. So a transportation technology designed to excel at going up and down seems to be overkill. Almost all of the modern Gondola installations that you refer to are applied to hilly/mountainous locations, or where they cross wide bodies of water. Hmmmm.... Maybe we should forget about bridges or tunnels to the Toronto Island and install a Gondola there!
  5. Hi Steven, I have been on a fixed grip gondola that goes around a corner at a tower. It is a pulsed gondola at Squaw Valley, and the corner is probably around 15 degrees. It doesn't work all that well, but apparently it can be done. I don't remember how it works mechanically, but it has to slow down for the corner, and since the corner isn't in the middle it has to slow down twice. Also the gondolas can't swing as they go around the corner, so there are these metal guides to stabilize the cars. (The gondolas hit the guides pretty hard if it's at all windy, especially the first car in the chain.) -Kelly
  6. The Original David
    It surprises me that this is such an difficult problem. What are the reasons for requiring an angle station at each turn? Why not thread the cable around a pulley on the support tower and use some kind of flexible grip that bends as it passes around the pulley? I imagine there would be complications with cable tension and side forces on the support towers, but I don't see why these would necessarily be insurmountable.
  7. To reduche the speed of a Reversible Ropeway (they are braking outside the station) from 7,5 m/s = 16,8 mph to standstill you need (at -1 m/s² deceleration) 66 m braking distance with the gondola on the rope ! To reduce the speed from a slower detachable ropeway from (for example) 4 m/s = 8,9 mph to standstill you need only 26 m, but INSIDE the station. And you need a braking section of (for example). 26 m, a slow velocity section of 10 m and an acceleration section of 26 m, in sum you need 62 m. So you need much space to build such a destination stop. I' ve designed a solution for this problem at my research project http://www.abcde-institute.org/urban_ropeways_destination_stops.html Slow motion of 4 m/s is not a problem for transportation. Underground trains are faster. Walking to a suburb station, you have to walk hundred of meters and you need time therefore. Gondola destination stops (entering and exit) are small, but the gondolas arrive every 12 seconds.With a gondola you save this walking time, so a gondola ist fast too.
  8. Aerial tram is probabily the best high capacity transport system now available. Our association has been working for 5 years now to impulse the use of aerial tramway, and some projects are now beiing studied in France. I think we should join our actions to be more efficient, and share our experiences. On our web site, you will find some of the papers that we wrote on rope transport to be used as public transports. You can contact us by mail or by phone (our phone number may be downloaded from our web site. Best wishes Pierre Jaussaud
  9. Detachability is absolutely a word. It means the quality of being detachable. See the Shorter OED.
  10. Even if the already avalaible technology is competitive - small curves are possible on different types of gondola , a technology breathrough is necessary to step up . I am thinking to three new opportunities : - Self-propelled gondolas , so solving several limitations of current ropeway system , to have a function exactly like a LRT or Metro - Intermodal transport : the ropeway systems have an intrinsic possibility of carrying , loading and unloading palletized goods or containers in an full automatized way, combining in this way a logistic distribution network inside the gondola network , multipling the ROI and reducing the emissions in a significant way (and also lower operating costs ... no vans, no handlers etc.) - Use of the gondola poles as support for solar energy panels , already feasible with very good results (low-cost possibility to have an orientation system for day and season, increasing the power output ... and the infrastucture is already paid for...)