From roundabout to roller coaster: drives and motors are making it all
work
Les Hunt goes behind the scenes at Britain's premier tourist attraction
to see how modern motor and drives technology, coupled with a vigorous
maintenance regime, is helping to keep the magic alive for hundreds of
thousands of visitors throughout the summer season
Blackpool Pleasure Beach is probably the only leisure ride theme park in
the UK where you can choose to ride the magnificent 90 year-old, Grade 1
Listed 'Carousel' to the strains of its original pipe organ, or
experience the multi-G forces of the very latest white-knuckle ride, all
on the one site. The undoubted success of this extraordinary amusement
park, established on the South Shore of Blackpool over 100 years ago,
relies on a relentless regime of maintenance, repairs and upgrades to
keep an extraordinary variety of rides in a thoroughly safe and
fully-functioning condition.
Blackpool Pleasure Beach employs a small army of mechanical and
electrical technicians to carry out the daily morning checks and regular
strip-downs that are necessary to meet the strict safety requirements.
Over the past three to four years, the onsite maintenance team has been
aided in its work by Preston based Wyko Electro Maintenance Services
(WEMS), under the leadership of WEMS' regional director, Keith Hargreaves
and electronics development director, Vic Harris, who was DPA's host
during a recent visit.
The Monorail
A favourite veteran attraction is the Monorail, which actually first saw
service at the 1964 Worlds Fair in Lausanne, Switzerland before being
dismantled and shipped to Blackpool, where it has since proved a
particularly popular ride. As Mr Harris explained, the Monorail trains
comprise 12 cars, each powered via geared dc motors fed by a venerable
Ward Leonard dc power source. For those of you too young to remember,
this is a dc generator continuously driven by an ac induction motor -
essentially a big electromechanical 'transistor' that satisfies the wide
ranging current demands of these individual car motors (from start-up to
coasting) by means of dc generator field control.
Whilst effective, this technology is now obsolete and the trains had
become more and more difficult to maintain. Despite extensive repairs to
various drive cards, field control modules and tachometer generators, not
to mention the replacement and rewiring of contactors and the manufacture
of replacement bridge rectifiers, it became evident that these problems
were likely to return. At the park's request, Wyko proposed a solution
that would see the entire dc field control system replaced by the very
latest in digital dc field control technology. The upgrade involved the
installation of a Sprint Electric PLA Applications digital drive
front-end, connected to an analogue Sprint Electric SLX dc drive, used in
torque mode to effectively eliminate the obsolete drive control elements
and allow better integration of the train safety systems. The complete
rewire job that this entailed enabled a number of key electrical systems
- including contactors and control circuits - to be relocated within a
custom panel in the driver's cab, vastly improving access for maintenance
and repair.
The upgrade work to the first of the four available trains was carried
out over a three-week period at the end of February/early March of this
year. With a few teething problems ironed out, the train ran immediately
on start-up under the new control system. Tests to simulate the train's
performance and match it to that of the other three took just a few days.
Now in full service since May, its performance and reliability will be
closely monitored over the busy summer period before similar upgrades are
undertaken on the remaining trains.
Grade 1 Listed Carousel
The Grade 1 Listed Carousel was posing another maintenance headache for
the onsite engineering team, so Wyko was enlisted to help replace the
ride's maintenance-intensive drive system. Formerly comprising a
slip-ring dc motor and viscous coupling (the latter being required to
overcome the ride's huge inertia on start-up), the drive is now provided
by a standard 7.5kW ac induction motor under vector control. The vector
control continuously matches the motor torque to the load and is provided
by a Control Techniques Commander SE drive, chosen for its proven
reliability and ready availability from stock.
Magic Mountain
A perennial problem of snatch on start-up was successfully resolved on
another ride popular among younger visitors to the park - the 'Magic
Mountain'. This carries its riders on short trains through a succession
of enclosed attractions and experiences, and is based on a 48V dc motor
drive system. Realising that a 48V dc soft starter was going to be a very
difficult beast to track down, Wyko decided to tackle the snatch problem
by designing a custom-built current-limiting circuit. This comprises two
shunts, one of 0.4ohm (2kW) and the other, 0.8ohm (3kW), placed in series
in the 48V dc feed to the pick-up rail. By means of timers and
contactors, the 0.4ohm shunt is bypassed after three seconds, followed by
the 0.8ohm shunt after six seconds. This relatively simple expedient was
designed by Mr Harris and ensures that the initial motor loading is
sufficiently limited to produce a smoother start-up without the unwanted
snatch.
Looking after the motors
In addition to providing motor control expertise for the Blackpool
Pleasure Beach engineering team, WEMS' other key responsibilities include
helping with the periodic maintenance and replacement of motors, and
occasionally finding solutions to particularly irksome motor problems
such as those that were being encountered on the spectacular 'Valhalla'
experience (there's more about this one on page 20). Water ingress was
causing weekly failures in some of the car drive system's submerged
0.75kW ac brake motor gearbox units. Wyko undertook a successful
programme of repairs to these motors that entailed stripping each one
down and replacing all seals with high grade silicone alternatives and
coating the motors externally with a waterproof rubber compound.
At the other end of the scale, the company is also entrusted with the not
insignificant task of maintaining the big dc motors and gearboxes on what
is arguably the scariest ride in the park - the 'Spin Doctor'. Located at
a height of around 20m, at the hub of the spinning arms, these components
have to be removed with the help of a crane before being shipped to WEMS'
Preston facility for a complete electrical and mechanical overhaul.
Last winter, WEMS conducted its fourth major electrical and mechanical
overhaul of Blackpool Pleasure Beach's most popular ride, the Pepsi Max
'Big One' - the tallest and fastest roller coaster in Europe. This annual
task involves electrically and mechanically disconnecting the main drive
motor (a 300hp Reliance dc unit) from its Dodge Maxum reduction gearbox.
This is replaced by an identical spare motor (refurbised at Preston),
which is laser aligned to the gearbox (itself replaced every two years)
on reassembly. This year, maintenance of the Big One involved removal of
the main drive sprocket and replacement of its associated bearing
assemblies, plus the fitting of an all-new Renold drive chain and
auto-lubrication system, the latter being carried out by Blackpool
Pleasure Beach's own maintenance team.