Isobar enhances disc brake performance

first_imgINTRO: German Railway’s ICE3 high-speed trains will have just two brake discs per axle, compared to four on earlier ICE generations. Use of advanced brake pads with an improved contact pattern offers lower noise and a 50% increase in energy absorptionBYLINE: Dr-Ing Xaver WirthSenior Manager, Design & DevelopmentKnorr-Bremse SfS GmbHTHE DEVELOPMENT OF friction brakes for high-speed trains suffers from one fundamental law of physics: the kinetic energy of a vehicle increases with the square of its velocity. With relatively heavy trains running in the 250 to 300 km/h speed band, a very large amount of kinetic energy must be absorbed every time the train slows or stops.Modern practice is to use electro-dynamic braking for most, if not all, service brake applications, and the ability to do this has been boosted by the current trend towards distributed traction drives, as on German Railway’s ICE3, with a greater number of motored axles spread through the train. However, it remains a condition of high-speed operation that, in the event of any failure of the electric brakes, during emergency brake applications virtually all of the energy will have to be absorbed by the friction disc brakes. Friction brakes must also absorb the bulk of the energy on loco-hauled vehicles, where dynamic braking is not available.Today’s state-of-the-art brake discs for high-energy applications are assembled from steel hubs mounted on the axle, and friction rings connected to the hub in a manner that allows them to expand as they heat up during brake applications. The friction rings are mainly made from steel or ductile cast iron, such as nodular cast iron.The brake pads normally used with these discs are made from organically-bonded composition materials, which can be pressed into large-area pad halves at reasonable cost (Fig 1a). However, these pads only provide an approximately uniform surface pressure and good contact pattern as long as their hardness and modulus of elasticity remain below specific limits. The contact pattern needs to be kept as constant as possible, so that the frictional energy, in the form of heat, is fed evenly into the brake disc. Otherwise the friction area will become overloaded in certain areas with a resultant risk of cracking.This is the crux of the problem: the higher the thermal loading capacity of an organic brake pad, the higher its modulus of elasticity, and therefore the greater the potential damage that can be done to the disc.Sinter pads harderMetal sinter pads are capable of withstanding much higher temperatures, being harder by a power of ten when compared with organic pads. Fig 1b shows a typical sinter brake pad with separate friction elements attached to an intermediate pad support which provides for a more or less flexible action. With a nominal size of 40000 mm2, this pad offers a contact pattern which is just about tolerable on brake discs of heat-treated steel at medium levels of braking energy.At high braking power levels, a poor contact pattern will result in local overheating of the friction surfaces, restricting the performance of the brake disc. Fig 3a (p480) is a thermographic picture of a disc during a brake application from 330 km/h using the sinter brake pads which are common today. It is noticeable that the disc shows hot spots at certain angles, with relatively cold areas in between. In the higher-temperature zones, thermal expansion of the disc results in the development of ’high spots’ which then receive a disproportionately large share of the energy because surface pressure is higher here than in the cooler ’valleys’ between. If the yield point of the disc material is exceeded, residual tensile stress will develop after the disc has cooled, leading to the formation of so-called heat cracks.Depending on the application and on material behaviour, heat cracks are only tolerable up to a specific length. Otherwise the forces of motion could cause the disc to break up, with fragments projected in all directions! Thus the risk of crack formation, along with the normal wear criteria, is a determining factor for the maximum permissible loading of a brake disc.For this reason, today’s TGV and ICE trainsets are equipped with four discs per axle (right). This results in a heavy unsprung weight penalty; the brake discs on an ICE1 trainset total 520 kg per axle, whilst the four actuating calipers in the suspended section of the bogie add another 260 kg.Lower weight and higher speedFor future vehicle generations, vehicle manufacturers are looking for lighter brake equipment able to operate at higher speeds. Knorr-Bremse decided that these specifications could not be met adequately by simply upgrading the conventional technology. Innovative solutions were required.The first development was the aluminium-ceramic brake disc (RG 6.95 p357) which is now in production for a wide range of applications. These discs have been in use on the prototype København S-bane EMUs since early 1996, and an ICE1 trainset fully equipped with aluminium discs has been in operation since January 1997. Disc brakes using fibre-composite materials will be ready for series production in a few years. But equally important has been the development of the innovative Isobar brake pad, which offers a considerable reduction in weight as well as enhanced performance.The name Isobar reflects the aim of equalising pressure at all points on the disc. The main objectives of the development project were:last_img read more

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Dustin Toops, 26, Osgood

first_imgDustin A. Toops, 26, of Osgood passed away Monday, February 18, 2019 in Aurora. He was born at Batesville on February 1, 1993. Survivors include his parents Roger and Terri Green Toops of Osgood; his children Caroline and Clayten; his brother Tanner Dilk of Osgood; sisters Missy Dilk of Batesville, Mandy (Jeff) Ronaldson of Manhattan, Illinois, Anna (David) Dougherty of New Palestine, Olivia McLaughlin of Dillsboro, and Lauryn Dilk of Osgood; nieces and nephews Aaron, Emma, Mollie, Madelyn, Parker, Grant, Ally, Ava, and Jack; also his paternal grandmother Mollie Toops of Osgood, along with several aunts, uncles, and cousins. He was preceded in death by his paternal grandfather Donald Toops, and his maternal grandparents Joseph and Ioata Green. Dustin helped his father on the farm and was an employee of Kraemer Construction in Aurora. He was a member of the Hopewell Baptist Church. Funeral services will be held on Friday, February 22nd at 11am at the Hopewell Baptist Church with Pastor Ty Choate officiating. Burial will be in the church cemetery. Visitation will be on Thursday from 5pm to 8pm at the Stratton-Karsteter Funeral Home in Versailles and from 10am until time of services Friday at the church. Memorials may be given to the donor’s choice in care of the funeral home.last_img read more

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Mayo battle back to beat Cork

first_img Mayo came from behind to defeat reigning champions Cork by 0-11 to 0-10 at Pairc Ui Chaoimh. Cillian O’Connor steered over a late winning free for the westerners, who had started the day with the threat of relegation hanging over them. Dublin will play Mayo and Tyrone will take on Kildare in the NFL semi-finals, as a result of a dramatic day of action. Daniel Goulding, Fintan Goold and Aidan Walsh shot the Rebels into a 0-7 to 0-1 lead, but second half scores from Donal Vaughan, O’Connor and Kevin McLoughlin helped Mayo claw their way back, before they stole a late winner. Kerry retained their Division One status after posting their best performance of the league with a 1-16 to 1-12 win over Tyrone at Healy Park. Tomas O Se’s 32nd minute goal, and a seven points tally shared between Declan O’Sullivan and Kieran Donaghy, sent wind-assisted Kerry in with a 1-13 to 0-5 interval lead Stephen O’Neill netted for Tyrone, and points from Conor Gormley and Conor Clarke and a Mark Donnelly goal narrowed the gap from 12 to one. All-Ireland champions Donegal were relegated to Division Two, along with Down. Dublin’s Paul Mannion scored a late equaliser to give Dublin a 1-10 to 0-13 draw with Donegal and secure top spot in the league table for the Dubs. center_img Press Associationlast_img read more

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Cantor says Boeheim still ‘our coach’

first_img Comments Facebook Twitter Google+ Published on November 29, 2011 at 12:00 pm Contact Debbie: [email protected] | @debbietruongcenter_img Chancellor Nancy Cantor expressed support for Jim Boeheim two days after the men’s basketball head coach backed down from earlier statements supporting Bernie Fine. ‘Coach Boeheim is our coach,’ Cantor said to a gathering of reporters, following an economic development conference with state officials in Albany on Tuesday, according to a blog post on the Albany Watch blog. Kevin Quinn, senior vice president for public affairs, confirmed the post. Boeheim initially defended Fine, former associate head coach of the men’s basketball team, when molestation accusations made by former Syracuse ball boys Bobby Davis and Mike Lang were brought to media attention. An additional accuser has since stepped forward and a recording of a phone conversation from 2002 between Fine’s wife, Laurie, and Davis was also released Sunday morning. In the phone conversation, Laurie Fine admitted she was concerned her husband molested Davis Boeheim released a second statement during the weekend, taking a step back from his original claims. Cantor addressed Boeheim’s second statement to reporters Tuesday.AdvertisementThis is placeholder text ‘Coach Boeheim is our coach; he’s getting the team ready tonight,’ Cantor said. ‘We’re very pleased with what he said Sunday night, and we stand by him.’ [email protected]last_img read more

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