16 replies to this topic

[Backbowlsbilly]

Hello all, I am currently involved with a project regarding a large aerial tramway system (large cabins and towers, haul rope with two track ropes, etc.), however I am pretty inexperienced with the nuances and workings of complex tramway systems. As I will guaranteed have many questions about trams throughout this project, I wanted to set up a new topic where I could ask tram specific-questions and learn as much as I can. I also wanted to start this thread for other people who might have questions about trams to create a kind of learning platform about tramways. Any and all help is much appreciated, thank you!

The first couple questions.
1. Why do tram cars sway as they pass over the saddles on towers?
2. What is a track rope shoe?

[vons]

Short answers
1) Radial Acceleration
2) The brass saddle/rail that the track rope rests in on a tower or other fixed support.

[Backbowlsbilly]

3. What is the purpose of the cabin guide rails on tram towers? It seems to me like the tram wouldn't be running in a scenario where it was gusty enough to hit the guide rails.
4. How to track rope bollards work? I am confused on how/if they "unspool" or maintain stationary, and if track rope tension is also provided by the counterweight or if that is just for the haul rope.
5. On modern tram systems where the two cabins can run independent of each other, such as the new Roosevelt Island Tram, is the tram essential just two mechanical tram systems or can they share some components, like tensioning systems?

[Kelly]

Billy - thanks for all of your questions, I would like to suggest you purchase this book on tramways...it pretty much covers all aspects of tramway terms, design and engineering.
http://www.skilifts....showtopic=10910

1. Huge leaps in design technology in addressing swing damping in modern tramway - much like motocross shocks
3. Consider them like seatbelts - only used in extreme cases
4. By the term "bollard" do you mean " haul rope carrier" or "slack rope carrier" that is attached to the track rope?
5. They share the "drive" rope...

ISR has in-depth tramway information: http://de.isr.at/new...ierte-raeumung/

[JSteigs]

Backbowlsbilly, on 30 October 2017 - 11:47 AM, said:

3. What is the purpose of the cabin guide rails on tram towers? It seems to me like the tram wouldn't be running in a scenario where it was gusty enough to hit the guide rails.
4. How to track rope bollards work? I am confused on how/if they "unspool" or maintain stationary, and if track rope tension is also provided by the counterweight or if that is just for the haul rope.
5. On modern tram systems where the two cabins can run independent of each other, such as the new Roosevelt Island Tram, is the tram essential just two mechanical tram systems or can they share some components, like tensioning systems?

The Bollard end is fixed, it doesn't unspool. They are just there to privide enough friction to keep the track rope from going downhill. The other end is tensioned by counterweight or hydraulic rams, seperate from the haul rope, and separate to each side.

[Backbowlsbilly]

Thank you everyone for all of your help. I have been having some trouble recently visualizing the drive machinery of a tramway, take for example the drive at the Squaw Valley High Camp Cable Car (picture from Remontees Mechaniques). Why is it necessary to have the dual bullwheel system? How does the haul rope move through a system like this? What is the benefit of this/ why is it necessary to have on a tram instead of just one bullwheel?I do understand that each bullwheel is double grooved, and the deflection sheaves in the middle shift the haul rope from one groove to another, but I am confused on how the haul rope travels through this system. Also sorry if the language I use is not correct tram terminology, I am trying to use the corrects terms but please feel free to correct anything that was misused.

This post has been edited by Backbowlsbilly: 06 November 2017 - 11:55 AM

[Liftkid99]

The dual bullwheels provide a stronger and more snug grip on the haul rope than just a single bullwheel would since it allows the rope to contact more surface area on the drive bullwheel by wrapping around most of it as opposed to around half of it like it would with just one. Not 100% sure on the path of the haul rope but I’m sure someone here can explain it better than I can.

[Kelly]

Adding to JSteigs post...
Ok I was thinking you meant a short row of pipes. Term is also called pollern (German for rope tie-off) or drum end connection. Most trams have bollards (short pipes or bumpers etc) at the terminal to stop the car if it swings excessively.
 Tram-tyback-1.jpg (98.53K)
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 Tram-tyback-2.jpg (98.54K)
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Notice the extra rope on reel next to the pollern...
 Tram-Port-top-term-drum.jpg (99.01K)
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To prevent fatigue of the track rope at tower saddles and terminals... at roughly a 10-year time interval a short distance of rope is released from reel then moved “around” the drum then “slid” downhill.
 Tram-Port-track-reel.jpg (87.94K)
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The “old” section is removed at the bottom and the “newer” rope is reattached to the counterweight. The technical term for this process is called “rope slipping” or slipped as the rope slips through the shoe/saddles.
Picture of Squaw’s drum ends, notice the towers in the background... this is one of Yan’s first chairlifts (Links). Drum ends or pollers at Squaw are now under a “decorative” cover.
 Tram tybacks with old yans.jpg (837.23K)
Number of downloads: 110  Tram-SV-drum-covered.jpg (84.17K)
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The haulrope transmits power to accelerate the load and also can provide braking.
For needed traction the haulrope must contact the bullwheel with a large (long) surface to establish the necessary friction; a 180 degree wrap or better helps successfully transmit those forces.
If you look closely you can see the rather large caliper brake on the bullwheel flange...
 Tram-mtr-room.jpg (118.04K)
Number of downloads: 106

[JSteigs]

To add a bit more about the odd bullwheel setup, the use of multiple bulwheels also helps get the rope to such a wide gauge. One bullwheel would be massive for it to be at gauge of the lift. Even at the return, there are multiple bulwheels on the counterweight to get it to gauge.

[Backbowlsbilly]

Thanks once again, that information about the friction and track rope slipping really makes sense. The same is true for the friction and bullwheel wrap at the drive terminal. I was looking at images (courtesy of Remontees Mechaniques) of the old Roosevelt Island Tram in New York, and more specifically the tension station in Manhattan. In the image below, I believe I understand what the yellow bullwheel is, a deflection sheave for the haul rope, but I am confused on what the row of small wheels around it is. I know that it is likely involved with track rope tensioning and I believe it is called a shear wall, but am unclear on how it works. What is the purpose of these wheels? How do they factor into tensioning the track rope? Is this a common feature of tramway tension systems, or is there another more typical system?




An additional question is why would counterweights need to be damped, rather than just be suspended in the counterweight pit?

This post has been edited by Backbowlsbilly: 13 November 2017 - 11:36 AM

[liftmech]

The small wheels are indeed for the track rope. They allow it to move during normal operation. The counterweight is damped to avoid sudden changes in the sag between towers on line, if I recall correctly.

[Backbowlsbilly]

What are the benefits of using a drum anchor as the grip from the haul rope to carriage of a tram? If clamps are still necessary on the haul rope, then why go have an anchoring drum in addition to the clamps? Also, what kind of connection from the haul rope to the carriage is common on modern aerial trams?

[Kelly]

Quote

What are the benefits of using a drum anchor as the grip from the haul rope to carriage of a tram?

I don't understand the question, would you mind rewording...

[Backbowlsbilly]

Yes sorry. One type of connection from the carriage to the haul rope that I have come across is called "drum anchoring of the haul rope". It appears that the haul rope is wrapped around a drum on the carriage to connect the two, instead of a clamp. A tram with an anchoring drum is the old Roosevelt Island system, compared with the clamps used to attach the carriage to the haul rope on other trams like the new one in Jackson Hole. I was wondering why an anchoring drum would be used instead of a simple clamp, since it seems like a clamp would be easier to design and construct. The terminology also seems to suggest that there are two separate haul ropes that are attached at the drum on both carriages, rather than one rope that had been spliced into a continuous loop and threaded through the drums. I could very well be misunderstanding the wording, but is this possible?

Sorry for any confusion or wording mixups, please feel free to correct anything that was misused.

Edit: Why would a different diameter rope be used for the haul rope (lead through the drive) and counter rope (lead through the counterweight)? I think that is the piece of information that made drum anchoring seem oddly unnecessary that I was missing before, it would be necessary if there was slightly different diameter ropes connecting at it.

This post has been edited by Backbowlsbilly: 07 December 2017 - 11:33 AM

[Kelly]

See Topic #10
Roosevelt rope diagram courtesy via our good friends at remontees-mecaniques.net then via Poma...
 Roosevelt-Tram-diagram.jpg (98.78K)
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[Kelly]

Here is a typical diagram of a ropeway with track ropes – only one track rope is shown for clarity.
 Tram-rope-diagram-with-lett.jpg (99.44K)
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TR = Track rope
HR = Haul rope
Cr = Car carriage
The term carriage is sometimes problematic as it can be used to denote the carriage for the haulrope tension system and track rope tension system.
Blue square is one area that you can have a haulrope carriage...
Getting back to Billy’s questions
The haulrope attachment at the car carriage has a lot to do with track slope, passenger capacity, oversight codes, track rope brakes and newer rope clamp designs. Full socketed connections have full rope strength capacity and are (relatively) maintenance free but are more difficult to place exactly. Shown below are weaves, clamps and socketed connections.

A track rope is a group of “locked" wires that can only be “bent” a certain degree – they are usually socketed to a “twisted wire” rope that has more flex ability as it passes over the deviation sheave before the vertical counter weight path. – See red blob in upper picture for this connection. The short twisted rope holding the counterweight is called the counterweight rope. It is slightly bigger diameter because the individual wires are not as tightly packed together as a locked wire or locked coil rope which are very close to solid rods of steel. Both have similar breaking and fatigue strengths.
 Cwt-Rope-to-TR-connection.jpg (98.04K)
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Billy time to buy the book :)

Attached File(s)

•  Carriage-rope-weave.jpg (99.79K)
  Number of downloads: 93
•  Carriage-rope-clamp-1.jpg (90.18K)
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•  Carriage-rope-socket.jpg (99.92K)
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[Kelly]

https://www.youtube....h?v=ShDGIQMbx4I
This video shows many tram aspects and gives a “voice-over” interview with Austen Edwards the manager for the Portland tramway.
There is a nice view of the rope dynamics in the upper span (shown in fast-motion) that isn’t as apparent when you ride the tram (starts at 1:19).
Haulrope carriage system can be seen at :48 – blue device is a hydraulic dampener to control the counterweight “carriage” movement.
Yellow numbers show the carriage position (some movement of the carriage can also be seen).
Speaking with Garaventa engineers they are quite proud of this hidden device.