Multi Stop PLC controlled Cable car
(click to enlarge)
Car departing terminal building
Access Automation
Multi Stop PLC controlled Cable car
(click to enlarge)
Car departing terminal building
Manufacturing self-leveling incline elevators for Wellington's hillside properties
Techlink would like to thank Mark Galvin and Paula Smith for their contributions to this case study.
Introduction
Access Automation's Managing Director Mark Galvin likens his cable cars to trains or lifts running in the open, each on an inclined track, to improve access to hillside sites. A cable car is pulled up the hill by an electric winch and a wire rope, on either a single track or dual tracks.Now a flourishing mechanical engineering business, Access started as a hobby and part-time business. For the first five years Mark produced one cable car a year out of his garage, while he was working for the Industrial Crown Research Institute. For the last 12 years, however, it has been a full-time venture, and has become New Zealand's leading cable car manufacturer of self-leveling incline elevators “and yes I still enjoy it, absolutely."
The concept was born in Wellington, with its hilly suburbs presenting all manner of access challenges. The city's “wild properties" have been an ideal Research and Development proving ground as Access Automation has evolved their product range. The lineup of self-leveling incline elevators covers nearly every operational requirement, from a 10-12 seat commercial gondola car to a basic two-person car ideally suitable for bringing home the shopping.
Clients come from right across the spectrum – old people, retired people, young people. Young professional couples ask why struggle carrying up the shopping, and why wait until 65 years of age before considering a cable car? “It's usually when the second child comes along that is the trigger point," says Mark.Access Automation ensures there is no compromise by designing, managing, and installing their product themselves. Every cable car gets the same innovative thinking, attention to design and construction, rigorous testing of critical safety components, and state-of-the-art control systems.
Improved access can unlock a site's development potential. Designers and architects can gain flexibility, and save space and the cost of more extensive earthworks due to the ability of Access Automation cable cars to turn corners and negotiate multiple gradients. The innovative cantilever car has no under-floor machinery, which allows easy access to the car without the need for an elevator pit in most installations.
Pre-planning
Oriental Bay gondola site
(click to enlarge)
Oriental Bay gondola
Workshop at Lower Hutt
Most people approach Access Automation because they want to improve their access. Mark Galvin will meet the potential client at the site and discuss their specific requirements (where they need to get to and from, and, for example, whether wheelchair access is needed). An estimated cost is given at the initial meeting.
If the prospective client is still interested Access Automation prepares a written quotation. This involves a detailed site survey and often puts the location for the cable car in a very different place from the one the client had in mind. Once the quote is complete and the client is satisfied a contract is signed.
A residential style cable car now costs around $35,000, and the gondola style anything from $60,000 up.
The cable car's location
From a technical perspective a cable car can be positioned almost anywhere. From a safety viewpoint it's not the gradient of the land that is the biggest issue, but rather the requirement for clear space. A safe running clearance or movement corridor is required – narrow gaps between homes, or perhaps balustrades or trees or other obstacles, could potentially create a crush hazard. There are no regulations that state safe clearance measurements so this is an area requiring ongoing clarification.Steepness may offer construction challenges, but does not cause operating problems. In relation to gradient the biggest problem is a lack of steepness because the cable car descends using gravity. Any gradient less than 12 degrees is not practical in windy locations as the wind can stop the car descending.
The kitset approach
A thorough, accurate and detailed site survey is necessary because of the way Access Automation manufactures each cable car as a complete kit set. There is no welding or fabrication of components on site. Everything is made in the workshop. The rails consist of five-metre-long modules of galvanized steel bolted together on site like a giant mechano set. A 30-metre rail can be erected in two days.
The site survey is crucial because everything must line up and fit together accurately when assembled on site. In some situations involving complex geometry the rail has to curve or change gradient. Also for sites away from Wellington, a registered surveyor's site data allows Access Automation to manufacture the cable car in the workshop and then have it trucked to its location.
Preparation of the site
(click to enlarge)
Examples of manufacturing on site
Access Automation has no registered surveyors and so cannot define boundaries, but they can measure the topography of the site. On big commercial sites, such as a block of town houses, there is a surveyor allocated to the project, along with other subcontractors, and boundary pegs are positioned around the site, which assists in the placement of the cable car. The surveyor would identify the centerline reference where the cable car rails are to go so that there is a datum to work from.
Cable car tracks can be constructed on various foundations.
If a little two-passenger cable car is to run over an existing concrete path which is sound, because the rail structure is not particularly heavy the rails can literally be bolted down onto the existing concrete.
Most often Access Automation lay their own foundations, which involves augering/boring a hole down to solid ground, on average 1.0 to 1.5 metres. Concrete pads are then put into the ground to hold the galvanized steel tubes to which the rails are attached. Access Automation employs a labourer to work on site.
On very steep sites or unstable ground a rock-drilling company is sub-contracted. Often they have to drill 4 to 6 metres into a bank to insert galvanized rock anchors.
A recent job on the hilly southern Wellington coastline offered a real challenge relating to unstable ground. Rock anchors were drilled six metres straight into the rock face. Two weeks were spent working on the foundations before construction of the track could begin.
The “terminal building" at the end of the track which houses the cable car is the responsibility of a builder contractor. Access Automation does, however, give clear instructions on clearances, spatial requirements, and recommended designs, but not aesthetic design.
Manufacture
Preparation of rails that bend and curve in workshop
Bogie frames in manufacture
A Bogie system
COP Outcome development and evaluation
Design and most of the manufacturing take place in Access Automation's modest Lower Hutt workshop. After searching without success to find a suitable contract manufacturer, Access has employed staff who are multi-skilled and/or are specialist in one or two areas. A few areas require outside contractors; but to maintain quality control Access Automation insists that Mark Galvin and his team take responsibility for overall co-ordination and production.
Producing a cable car is a very labour intensive craft-type job. Among the tradespeople required are a glazier, a stainless steel manufacturer, a plastics person, a painter, a coachbuilder, an electrician, and an upholsterer.
Innovative technologies
Access Automation has developed its own products, to be able to supply a range of well engineered and safe cable car options. They have developed, for example, rails that bend and curve, dual safety braking systems, wheels and other mechanical components. It's a constant process of refinement, innovation and improvement. Stop improving, Mark Galvin says, and “someone will catch up with you."
People want access but they also want a system that will not detract from a property. With this come potential problems: existing pathways may clash with the obvious movement corridor, or it may not afford enough clearance. Access Automation has developed a range of innovative technologies that make rails bend and curve to custom fit a site. The rails don't have to be straight any more. The cable cars can turn corners to the extent of negotiating a 180-degree spiral; and technology patented by Mark Galvin allows the cars to remain level despite gradient changes.
This fundamental part of the safety system is needed to provide the greatest range of protection. It consists of two independent brakes:
The Compact Bogie System
A carriage on a train has a set of wheels at the front and another at the back; the wheelsets are called bogies and they support the carriage. Access Automation uses the same terminology for their cable cars. The bogie is the compact unit about the size of an average briefcase. The whole cable car sits on and is supported by the bogie, which incorporates the wheels and the braking system.
There are about 3 different designs of bogie for the different models.
Standard Mechanical Models
As Access Automation do not know what the exact specifications of their next cable car will be, they have developed their own mechanical models in three basic designs that will allow components to be used in multiple gradients and installations. Standards ensure efficient use of resources, because economies of scale are possible when making multiples rather than one-offs.
Control electronics
Electronic control system
(click to enlarge)
On a tonnage and volume basis steel is the biggest raw product purchased but in dollar terms the electronic control equipment, weighing only a few kilos, makes up a greater proportion of the overall cost of a cable car.
One of the attractions of the cable car for the engineering mind is the interaction of the mechanical machine with the electronic controls. Many of the cable cars use a programme logic controller or PLC. For example a 10-stop cable car has gates, timers, and very complex control systems to govern the ramping speed up and down the rail.
COP Outcome development and evaluation
The design of the electronic systems is subcontracted to a specialist firm. Over the years Access Automation has developed, in partnership with this firm, a robust safe control system specific to their needs.
The mechanical fail-safe systems are backed up with electronic monitoring. In addition to the two mechanical safety brake systems positioned on the cable car itself, there is an electronic speed monitoring system located on the winch. This monitors the speed of the winch, which pulls the cable car up and down the hill. So if the car starts to over-speed, the electronics will be activated, and if necessary also the mechanical back up safety systems. There are other proactive safety systems. For example when the car is coming in to the landing the computer checks that it is slowing down in the correct manner. The systems have evolved through experience; there are no regulations or standards governing them. They cost a little extra money but Access Automation puts a high priority on safety .
Management Perspective
A safe movement corridor
The team at work
“I'm always struggling to manage time!" smiles Mark Galvin.
He believes in a well-trained staff who are passionate about their work. His team get great satisfaction about putting a really nice machine together which works smoothly.
Mark explains that he doesn't have any formal management training. He feels that if you have like-minded people they tend to get on well and perform well as a team.
“We've got a small tight team and we all get on well. We've got a culture within the company. People know they have to do their job right, I trust the guys, they know what's expected of them, they've been well trained and it s a pretty relaxed sort of a culture."
Access Automation now have seven staff, three with NZCE in Mechanical Engineering, three fitters and turners, and an apprentice studying diagnostics and instrumentation (the new name for fitting and turning), and an administrator.
Communication
Clear written communications and good verbal site instructions are very important in making a job run smoothly. Communication must be effectively maintained with various stakeholders – clients, staff, suppliers, sub- contractors. This can get complex especially on bigger jobs where several subcontractors may be involved (such as landscape architect, surveyor, builder, electrician, site excavators, civil engineer), and misunderstandings can arise.
Maintenance
Different landscapes
COP Outcome development and evaluation
Access Automation has a planned maintenance programme. The cable cars have a two-year warranty. During and after that period the client is offered a planned maintenance contract at a modest cost, covering two visits per year. A checklist is gone through at each visit, like a car's warrant of fitness process, followed by a written report to the client.
Maintenance is essential to keep the cable car running well and ensure its maximum life. The safety of the cable car is a function not only of the design of the original equipment but also of the ongoing maintenance, which is absolutely critical. A lot of the wheel bearings are now sealed but the ropes require regular greasing. One of the items on the checklist is checking the components of the emergency braking system. Normally they aren't required to move, so they must be checked to make sure they haven't seized up.
Feedback
Feedback occurs mainly when something goes wrong. The cable cars and their operating machines/systems are running in the open, exposed to aspects of the environment beyond anyone's control. Salt spray corrosion around Wellington creates a very hostile environment. After a few years on south coastal properties even galvanized steel will start to corrode.
Access Automation log every fault, observe any patterns of recurring problems and respond accordingly.
The commonest problem would be the safety braking system activating when the client doesn't want it to. This can be triggered by a stick the size of a pencil caught in the wheels, which is enough to alert the control systems that something isn't right and trigger the brakes. This probably happens about once every year or 18 months. Access Automation accepts that from time to time this “nuisance trigger" will occur, as they like to have their systems calibrated quite finely. As Mark Galvin says, “Its very easy to make a cable car in which the brakes never come on. That's the easiest thing in the world, but it's not a lot of use to people if it's ever needed."
Not all the feedback is about trouble, “we do also get people who ring up and say what a great job we've done," says Mark.