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CLUTCHES, BRAKES & COUPLINGS
FEATURE
MAGNETIC BRAKES: A THRILLING SOLUTION FOR ROLLERCOASTERS
With reliability
and safety essential, Bunting and Force Engineering have
worked together to develop a novel
magnetic brake for use on rollercoasters
DEVELOPING THE RIGHT SOLUTION
Using Finite Element Analysis (FEA), the design team determined the most cost-effective magnetic solution that generated the right amount of braking force. The eddy current brake relies on a massive permanent magnetic field between two permanent magnet arrays, with the attraction between these magnets being a key design criterion. Understanding the magnetic force through additional FEA was critical for determining the holding force needed to keep the magnets in place. A Halbach array is a useful magnetic tool,
W
hen it needed to find a brake suitable for use on rollercoasters, Force Engineering got in touch with Matthew
Swallow, Bunting’s technical product manager. The result was a two-year project in which both companies collaborated to design and build a suitable magnetic brake. The design brief identified a number of key
criteria, one of which was limiting weight. Rollercoaster track costs approximately £3,000 per meter due, in part, to the pylons and supporting structure. Subsequently, the weight determines the supporting structure design, with lighter systems lowering the overall cost. This also applies to permanent magnet wind turbines, where neodymium iron boron (NdFeB) permanent magnet motors are preferred to motors using ceramic ferrite magnets. Ceramic ferrite magnets are significantly cheaper but heavier, and a lighter weight motor means a lower cost support pylon, with cost savings outweighing the additional magnet cost. During the project a number of permanent magnet arrangements were considered. These included magnetic Halbach arrays, which are a great way of focusing the flux in a specific direction. These, however, are difficult to build and need expert handling. Four to five segment Halbach arrays are the best at focusing the field but, once again, more segments lead to more material and labour cost.
but it causes adhesive bond lines to be put into a twisting peel effect, producing a form of ‘pull force’ that adhesives do not like. Many iterations of the design looked at bonding the magnets with different coatings to the lightweight carbon fibre structure. However, despite the adhesives’ data sheet specifications stating suitability to surviving the environment, none were up to the task when tested in a real-world simulation. The investigation of alternative methods of magnet retention led the design team to review manufacturing techniques used at one of Bunting’s sister companies in Redditch. Bunting manufactures magnetic separators including hundreds of plate magnets which are installed in chutes and over conveyors to capture and hold ferrous metal contamination found in
Magnetic braking systems
feature on rollercoaster rides such as Rita at Alton Towers
foodstuffs and other dry granular materials. With the Redditch engineers joining the design team, and in collaboration with the Force Engineering team, Bunting adapted the eddy current brake magnet assembly to incorporate a more comprehensive twist-tolerant design which retained the magnets indefinitely. Magnetic braking systems such as this feature on many famous rollercoaster rides such as Rita at Alton Towers and Stealth at Thorpe Park. “Knowing magnetic braking systems are on the coaster I am riding makes me feel safer, especially on X-Scream on top of the stratosphere tower in Las Vegas – this is one ride you really want to trust!” said a long-time member of the European Coaster Club.
Bunting-Berkhamsted
www.bunting-berkhamsted.com
BESPOKE BRAKES MEET 24HR LE MANS DEMANDS
NASCAR entered the 24 hours of Le Mans race in June for the first time since 1976, competing as an experimental Garage 56 entry. A joint venture from IMSA, Hendrick Motorsports, Chevrolet and Goodyear, the vehicle includes a braking system from Coventry-based AP Racing. The car, a Chevrolet Camaro ZL1, closely resembles its NASCAR cup series next generation counterpart, but with significant modifications to meet the requirements of the race. Using a modified version of the standard Radi-CAL caliper as
fitted to the cup cars, AP Racing used its experience with Formula 1 and IMSA Carbon/Carbon brake systems to design a bespoke disc and pad combination. The Carbon/Carbon system is a crucial part of the Garage 56 project, providing an unparalleled combination of performance, endurance and weight reduction. David Hamblin, managing director of AP Racing, said: “The
Garage 56 entry doesn’t look too different than a normal cup series car, but under the skin there are a lot of changes. We are proud to have been selected as the exclusive braking supplier for this prestigious Garage 56 entrant in this special centenary year.”
AP Racing
www.apracing.com
JULY/AUGUST 2023 DESIGN SOLUTIONS 23
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