自行车设计(含CAD图纸)
自行车设计(含CAD图纸),自行车,设计,cad,图纸
理工科类本科生毕业设计(论文)开题报告论文(设计)题目基于UG的死飞自行车设计作者所在系别机电学院作者所在专业作者所在班级作 者 姓 名作 者 学 号指导教师姓名指导教师职称完 成 时 间毕业设计(论文)开题报告学生姓名专 业车辆工程班 级指导教师姓名职 称副教授工作单位课题来源学生自拟课题课题性质课题名称基于UG的死飞自行车设计本设计的科学依据(科学意义和应用前景,国内外研究概况,目前技术现状、水平和发展趋势等)1.死飞自行车的来源死飞自行车的由来最大归功于美国,在80年代,欧美国家汽车的拥有量大,道路设施不健全,而信使的任务又加繁重,变通的信使便想到用转向方便、快捷的自行车来运送信件。自行车的体积小,方便于在街道、拥挤的路上穿梭行驶,而这种自行车多是公路自行车。由于公路自行车拥有繁多的变速器、闸线等,在骑行的时候都需要紧密的配合,且在日常的骑行中又得保养,稍微损坏就会在骑行的过程造成不必要的伤害,而骑行过程中的各种配合又是对信使的一种负担。于是他们开始对现有的公路自行进行改装,对车架结构进行简单化,不易损坏,也没有多余的、错综复杂的闸线,并且拥有稳定的速度便于在城市中平坦的公路上行驶,这种自行车便是死飞自行车的雏形。2.死飞自行车的现状针对自行车行业的调查,技术含量,以及业界的死飞自行车行业现状有以下几点;1.行业乱象 因为节能能源使用,自行车需求趋于休闲健身行业。但是中国的自行车王国在历经汽车时代的洗礼之后,淘汰产能依然存在。便宜就有市场的市场认知依然在收入有限的消费者购买动机下存在,而且普遍存在把休闲娱乐健身功能忽视的市场趋势。2.行业技术 因为市场受众,内销自行车品质参差不齐,因价格战导致市场黑洞,就是越节省成本,前沿技术的适应,产品的专业品质根本无需考虑。在这方面知名品牌的做法值得借鉴。3.行业服务 低价竞争的过剩产能销售产品,售后无从谈起,维权艰难。修补市场缺乏规范,实体店销售终端经营以专卖服务有保障。设计内容和预期成果(具体设计内容和重点解决的技术问题、预期成果和提供的形式) 本论文主要是对死飞自行车进行三维建模,包括零部件的三维建模及最后的整体装配,此论文的最大难点即重点是三维软件的运用,如何正确的运用三维软件中板块和命令。最终以文件和照片的形式提交死飞自行车的所有零部件模型及整体三维模型。拟采取设计方法和技术支持(设计方案、技术要求、实验方法和步骤、可能遇到的问题和解决办法等)本论文的设计内容如下: (1)搜集现有相关的数据,对搜集到的数据进行归类分析,研究各类数据并加以修改,加入自己创新点。(2)利用三维建模软件,结合搜集、分析的数据,对死飞自行车的各部件进行三维建模、装配。 在三维制图软件方面遇到的问题可以请教老师和同学们,也可通过网络、论坛、各种群等来解决。 实现本项目预期目标和已具备的条件(包括过去学习、研究工作基础,现有主要仪器设备、设计环境及协作条件等) 在选题时,选到本题目,我就能感觉到此次的毕业设计肯定能顺利完成,能按照要求对死飞自行车进行三维建模。 以前在大一大二时感觉时间空余,就自学与本专业有关的软件UG,通过自己的学习现已可以独立完成一些比较简单的三维建模。也恰好选对了一个自己比较熟悉的题目。各环节拟定阶段性工作进度(以周为单位)开题报告外文翻译搜集资料三维建模及装配中期检查拟写说明书的初稿导师对初稿的指导定稿答辩整理入册 开 题 报 告 审 定 纪 要时 间地点主持人参会教师姓 名职 务(职 称)姓 名职 务(职 称)论证情况摘要 记录人:指导教师意见指导教师签名: 年 月 日教研室意见教研室主任签名: 年 月 日 32 本科生毕业设计(论文)文献综述设计 (论文)题目 基于UG的死飞自行车设计作者所在系别 机电工程学院作者所在专业作者所在班级作 者 姓 名作 者 学 号指导教师姓名指导教师职称完 成 时 间2017年3月 说 明1根据学校毕业设计(论文)工作暂行规定,学生必须撰写毕业设计(论文)文献综述。文献综述作为毕业设计(论文)答辩委员会对学生答辩资格审查的依据材料之一。2文献综述应在指导教师指导下,由学生在毕业设计(论文)工作前期内完成,由指导教师签署意见并经所在专业教研室审查。3文献综述各项内容要实事求是,文字表达要明确、严谨,语言通顺,外来语要同时用原文和中文表达。第一次出现缩写词,须注出全称。4学生撰写文献综述,阅读的主要参考文献应在10篇以上(土建类专业文献篇数可酌减),其中外文资料应占一定比例。本学科的基础和专业课教材一般不应列为参考资料。5文献综述的撰写格式按毕业设计(论文)撰写规范的要求,字数在2000字左右。文献综述应与开题报告同时提交。毕 业 设 计(论 文)文 献 综 述基于UG的死飞自行车设计摘要:死飞车(fixed gear bicycle,又称 fixie bike,)后轮的齿轮与后轮直接用螺栓固接(不像普通自行车,后轮齿轮与后轮是通过棘轮棘爪连接,普通自行车反向踩脚踏板时后轮不受力)。所以曲柄的旋转方向始终与后轮的运动方向保持一致。通常,死飞车是不能通过换档来变速。利用UG技术可以对死飞机自行车进行相关设计。关键字:死飞自行车,UG技术Design of dead flying bicycle based on UGAbsrtact: Dead Speed (fixed gear bicycle, also known as Fixie bike,) rear wheel gear and rear wheel directly with bolts (unlike ordinary bicycles, rear wheel gears and rear wheels are connected by Ratchet Pawl, ordinary bicycle back pedal when the rear wheel is not force). So the rotation direction of the crank is always consistent with the movement direction of the rear wheel. Usually, a dead rook cannot be changed by shifting gears. The use of UG technology can be used to design the dead plane bicycle.Keywords: dead flying bicycles, UG technology一、 什么是死飞死飞车(Fixed Gear Bike),与场地自行车(Track Bike)是同类自行车,骑行地域并不只限制在体育馆内。在日本则有古典 赌博形式的场地自行车比赛,被 称为“竞轮”,在中国被称为“死 飞”或“固齿”,香港地区也有 称为“梗牙”。死飞车(Fixed Gear Bike)来自New York Old School(纽约复古)单车文化,最初是由快递工作者发起的快速单车文化,在日本原宿流行后, 就开始快速在全世界蔓延,成为街头文化的代表。 “死飞”自行车只有一个车架、两个轮子、一个车把和鞍座, 没有闸线,没有齿轮转换器,也没有挡泥板。也正因为飞轮是死的, 骑行的人便可以通过脚踏来控制后轮从而减速和刹车,也可以很 好地控车。主要是靠脚来控制车子的前进和后退,同时也可以做 出许多花样动作,玩得好的骑手可以做出定杆、漂移、倒骑绕圈、 跳跃等花样。 “死飞”运动作为一种结合时尚、街头、环保、健康、挑战 的运动,很快在国内年轻人里流行起来。由于外形酷炫、理念“前 卫”,骑着“死飞”自行车上路的骑手往往成为人们目光的焦点。二、 死飞与普通自行车区别“死飞”属于场地自行车的一种,并非一般意义上的代步工 具。 “死飞”讲究简约,没有刹车,没有变速,因此重量很轻, 目的只有一个,就是让人把自行车骑得越来越快。 从结构来看,普通自行车的飞轮是“活的”,人踩脚踏时,轮 子跟着转动,人停止踩脚踏后,车轮也可以继续转动,需要使用刹 车来停车;而“死飞”自行车是一种固齿飞轮自行车,需要脚踩脚踏来控制车速和刹车脚踏板转动时带动车轮转动,而脚踏 板停止转动时则车轮也停止转动。除了停车外,骑行过程中人必 须一直不停地踩脚踏板。对于一般人来说,“死飞”自行车的骑 行时速可达40 km,是普通自行车最高时速的2倍。三、 理性看待死飞目前国内部分人对死飞的排斥主要来自对它的安全性没有把 握。在这里我要说,死飞危险。只有危险的人,没有危险的车。在上路之前,你首先必须学 习控制住自己的速度和节奏,而不是在技术还不成熟的情况下, 一味地追求炫耀。 关于刹车问题,死飞并非完全脱轨。目前有不少死飞爱好 者选择了为死飞装上了手动前刹,在这里也建议死飞新手可以使 用。爱好的同时,也要注意安全! 所以安全问题并不全是刹车造成的,而是和自身的骑行技 术和水平有关系。汽车的速度很快,开车除了遵守交通法律和 规则以外,还一定要熟练掌握开车技能,还一定要有预判。熟 练掌握技能和预判就是经验,经验只有通过大量实践才能获得, 但是现在不少年轻人骑行时都没有这个意识,这就存在着一定 的安全隐患。四、 死飞自行车的使用技术the field of dead-flying, it is called drift, and drift is the opposite skill of pedal movement which can hardly stop the turn of the rear wheel. Putting all the weight on the front wheels can drift longer, and this action can impress others. If you want to stop quickly, you need the rider to make a jump stop, just like parking on a crowded road. Dead-flying bicycles are very beautiful, because they are simplified with only one frame, two wheels, a handlebar and a seat, usually without a brake line, no gear converter, no fender, no lights, no reflectors, no brakes, pure bicycles. Play Fixed gear Bike one of the great fun is the whole car 19 parts, each part is expensive, but the combination of a vehicles as a whole car is tailored to their own as a dress, pay attention to and car owners into one. Fixed gear absolutely can not light to buy a whole car directly on the ride, in the process of assembly is also the experience of Fixedgear, their own favorite color, and suitable for their parts these are essential processes. Because of this so a lot of people want to publicize the personality of the tide talent will be obsessed with it, this special belongs to their own fixed gear bike birth process, is bound to devote a great deal of energy and creativity, also is a personal art work it.五、 结论死飞的文化理念接近中国那句古话:海纳百川,有容乃 大。“死飞”不仅是对于爱好的一种追求,也是用来感受生 活的一个媒介。 “死飞”尽管出现了一些事故和一些让人不 愉快的事情,但死飞不应该被粗暴地“一刀切”。这个骑行 群体和行业需要正确的引导和规范。经营者也应该和管理部 门相互配合,劝导大家安装车闸,配戴头盔,熟练特性,遵 守交通法规。 在这里呼吁一下,希望有能力的组织或者机构组织爱好者们 进入自行车场地骑行,让大家能安全地体验死飞的乐趣。参考文献1中国自行车2013年11期2现代机械2012年10期3百度文库死飞自行车的相关文章毕 业 设 计(论 文)文 献 综 述指导教师意见 指导教师: 年 月 日专业教研室审查意见 负责人: 年 月 日 54 地方官员常用的这样的借口来拒绝电动自行车:铅酸电池会污染环境;电动车会干扰机动车辆行驶,阻塞交通;特别是对公交系统造成巨大冲击。积极为绿色交通奔走呼吁的请愿人士说,这些借口苍白无力,不过是试图去保护电动车的竞争者而已。中国科学院著名理论物理学家,院士何祚庥一针见血地指出:“真正的原因就是来自利益集团的竞争。”何院士在有关环境和能源政策的公共辩论中一向直言。他说反对电动车的理由没有一条真正站得住脚:汽车上用的也是铅酸电池,他特别补充:“真正的污染源不是电动车,而是汽车。”如果现有的交通运营者们和制造商们想与电动车竞争,就要为大众提供效率更高,价格更便宜,更清洁的交通工具。但问题是,与其它竞争者相比,电动车厂商微不足道,特别是汽车产业,吸引了数十亿美元的外国投资。在中国官方制定的五年计划中,汽车生产已经被列为“支柱产业”。 尽管面临着严酷的生存挑战,但电动自行车厂商们并没有退却,而是知难而进,并取得了惊人成功。绿源电动车公司的董事长倪捷是代表电动车产业界的灵魂人物,他从一家小企业开始艰苦创业,以务实的态度开拓市场,并取得成规模的研究开发成果,对中国电动车的技术发展有独到的见解。绿源电动公司一开始是从政府风险投资中分离出来的。九年前,绿源现任总经理胡继红(倪捷的妻子)制造出第一台样机,绿源公司成立了,随后在倪捷和胡继红的领导下,公司改为私营,并且从最初的投资者手里买下了所有产权。公司成长迅猛,去年业绩傲人,电动自行车和踏板电动车销量达到了12万辆,今年的销售目标是30万辆。去寻找绿源,要从上海市一路南下,来到金华。这是浙江省的一座城市,人口百万,工业重镇。顺着金华市工业园的公路就可以找到绿源公司的总部。倪捷的办公室坐落在办公楼的一角,宽敞舒适,是公司里为数不多的带暖气的房间之一,寒冷的二月里,这一点显得尤为突出。倪捷烟不离手,喝着泡着浓浓的绿茶的广口杯,侃侃道来创业的艰辛与收获。他说,在中国的大多数城市里,交通是个首要问题,电动车是昂贵的轿车和拥挤的公交车的首选替代品和补充品。“如果政府没有明确的解决方案,人民就可以按自己的办法去行动,没有理由去阻止人们这样做。”倪捷非常看中人民的力量,这一点在福州事件中得到了充分印证。2003年夏天,当时,绿源最大市场之一是毗邻的福建省省会福州市,但是该市的政府却要明令封杀电动车,不但不给电动车执照,而且禁止销售,他们没收了绿源专卖店里的20辆电动自行车。倪捷就联合了126家电动车厂家,将市政府(工商局)告上了法庭。此次,厂商联手,迫使市政府无条件发还了无理没收的电动车。这次联手取得了局部的成功。 倪捷认为此次福州事件更深远的意义在于赢得了全国媒体的广泛关注和支持,并且也给其它(反对电动车的)地方政府有一点警示作用。“我们向其他地方政府传达的信息是,如果他们学习福州市政府的做法来反对电动车,他们就会有一些麻烦。” 围绕电动车引发的冲突并不只局限于地方政府和生产厂家,中国自行车协会也和一些厂商(包括绿源)在产品细节上发生分歧,诸如何种两轮车才可以上路等。自行车协会强调的是电动自行车的国家标准,如重量不能超过40公斤,脚踏之间的宽度不能超过220毫米,最高时速小于20公里等等,许多最新的电动自行车和踏板电动车都不符合这些指标。例如,很多踏板电动车配置了骑行功能不好的脚踏,并有限制速度的附加装置。有些人买回去就可以自己把限速装置拆掉。绿源公司的一款最新产品已经不再被现有的电动自行车标准所限制,绿源把这种新车型被称做LEV,轻型电动车的缩写。倪捷公开承认它已经不仅仅是“自行车”了。在绿源的网站上它被称为“电动摩托车”:车重95公斤,配备48伏20安时的电池,电机的输出功率高了一倍,达到500瓦,用CPU控制的电机可以将时速提高到35公里。 虽然目前国家还没有出台LEV统一标准,不过在金华,即使是销售淡季,顾客还是首选LEV。在不到一个小时内,一位25岁的年轻人和一位上班族母亲相继开走了两辆。在被问及选中这辆车的理由时,她指着城市上空的空气污染解释道她必须送块头大的儿子去上学,但是为了降低本地城市的空气污染,她宁可选择电动车,而不要燃油的踏板摩托车。 倪捷乐观地相信,政府在看到LEV的普遍使用之后,会给予正式许可的。现在不少人对该车重量增加是否会降低安全系数持怀疑态度。倪捷解释道:LEV装有电鼓闸,它的刹车效果比各种各样电动车常用的悬臂闸要好得多。新的能量回收型制动系统也已开始使用,这种新系统在刹车时将把主动的电动机变成被动的发电机,一方面有利于迅速制动,另一方面也可以把刹车要消耗的能量提取出来对电池充电,从而扩大了车辆的行车里程。作为一名企业家,倪捷把在电动自行车和LEV上的成功看成是走向“更大和更好”的电动化交通工具的关键一步。他已经开始关注小型电动运输车辆的市场,甚至梦想有一天,绿源能够生产出自己的小型电动汽车,与大公司竞争。“他们总是在说,我们正在投入大量资金,我们将有计划地把燃油系统改成电动系统。”倪捷指出,“但是,这些大公司他们真的愿意毁掉现有的工厂去建设新的工厂吗?”依倪捷看来,一批富有进取心的小企业,就像绿源这样的,更有可能推动电动车革命,因为这样做他们一无所失。电动车厂家所面临的最大挑战,还不是部分地方政府的禁行令,保守的标准,甚至连技术也不是主要问题,最大困扰来自道路状况。中国正遵循着西方发达国家的发展模式,围绕着汽车来彻底重新规划城市。中国的每一个城市都在摒弃机动车非机动车混合行使模式,实现严格的分道行使模式,农田改造成了工业园。住房从城市中心也逐渐向郊区迁徙以便让位给亮丽的写字楼,几十年前西方国家就是这么干的。汽车成了这个模式中的国王。由于公共交通网很不健全,轿车成了从远郊区居住地到办公室或工业园的唯一工具。为了给更多的汽车让路,中国的许多城市都将主路拓宽,并修建了高速公路。就像在世界其他地方发生的一样,其后果只能是导致了汽车数量迅猛增长,新增的轿车马上占据了新修的马路。这种恶性循环在首都北京表现得十分明显。1997年,北京只有1百万辆轿车,有人曾经预计到2008年才达到2百万辆。但事实是,去年已经突破了2百万辆,新的预测是2008年将达到350万辆。北京大学城市规划专家俞孔坚尖锐地指出:“举国上下,大家都认为马路越宽交通状况就越好,但是他们是错的。”汽车文明的兴起对自行车是一个灾难,马路拓宽的代价是占用自行车道,高速公路不许自行车上道,而且几乎不可穿越。窄一点的马路上,高峰时间的车流阻断了自行车道和交叉路口,引起骑车人的强烈不满。俞教授以前骑自行车从家到学校只需要20到30分钟,但他现在开车,依据交通状况,花费10到60分钟不等。“骑自行车太危险了,所以许多人不骑车了,我也不骑了。” 不过俞教授相信从长远来看,燃油的车辆终将会被迫给电动车让路。一方面的原因是交通堵塞,另一方面的原因是中国的城市污染。在金华,即使污染不那么严重的日子,城市的天际线也都消失在烟尘之中,越来越多的大气污染物是从机动车排气管中排出的。 何院士之所以对电动车充满信心,主要因为中国为石油所付出的战略代价太高。中国石油进口增加速度和它的汽车数量增加速度并驾齐驱。中国已经超过了日本成为世界第二大原油进口国,开始与美国竞争世界上最大的石油消费国。为减少对进口原油的依赖,也为减轻沉重的环保负担着想,中国已经制定了比美国更严格的燃料效能标准,同时正在考虑对零售汽油和柴油加征20%到50%的燃油附加税。如果中国能找到一种解决办法,能使得相对高效的电动车在交通系统中发挥更显著的作用,这将为世界上其它发展中国家乃至发达国家树立一个的典范。这也包括了全世界中最依赖汽车的国家美国。在日本和欧洲,自行车、火车和其它形式的公共交通工具还在积极地运转,而美国是极少数绝大部分交通完全依赖汽车的国家之一,引用WaveCrest公司本杰明先生的话:“我们住在大泡沫里。”IN REJECTING ELECTRIC BIKES, the municipalities cited such concerns as the threat of pollution from spent lead-acid batteries, interference with automobiles resulting in accidents or slowed traffic, and the impact on the viability of public transit systems. Advocates for green transportation say these arguments amount to thinly veiled attempts to protect the electric-bicycle industrys competitors. The real reason is competition from interest groups, says He Zuoxiu, a renowned theoretical physicist and academician at the Chinese Academy of Sciences. An outspoken figure in public debates around environmental and energy policy, He says none of the arguments against electric bikes has merit. Lead-acid batteries, he points out, are used in cars, too. The real pollution source is not the electric bikes, its the automobiles, he adds. And he says transit operators and manufacturers should be forced to compete with the electric bikes by offering more efficient services and cheaper, cleaner vehicles. The problem, he explains, is that electric-bike manufacturers are insignificant next to the other interest groups, particularly the car makers that are attracting billions of dollars of foreign investment. The automotive industry is identified as a pillar industry in Chinas official five-year plans. Back with surpri Although the odds against them are daunting, electric-bike manufacturers are pushing sing success. The mastermind of one of the most high-profile battles is Ni Jie, president of Luyuan Electric Vehicle Co., a privately owned manufacturer that has a pragmatic approach to the market, a sizable R&D effort, and an ambitious vision for Chinese EV technology. Luyuan EV was a government venture-capital spinoff. Building from a prototype put together nine years ago by Luyuans general manager, Hu Ji Hong, Nis wife, Luyuan went private after Ni, Hu, and other principals bought out the initial investors. They have built a dynamic company that sold 120 000 electric bikes and scooters last year and expects to sell 300 000 this year see photo, Coming Off the Line. To find Luyuan EV, you must head off the beaten track to Jinhua, an industrial metropolis of 1 million people that is tucked into the unbroken sprawl south of Shanghai that is Zhejiang province. In the chairmans spacious corner office (one of the few heated rooms at Luyuan on a cold February day), Ni chain-smokes, sipping from a seemingly bottomless jar of well-steeped green tea. He says traffic is the top concern in many Chinese cities, and the electric bicycle fills a void by offering an affordable alternative to sitting in a stationary car or bus. If governments dont have the solution, the people will behave in their own ways, says Ni. Theres no way to stop that.! Ni took people power to surprising limits in 2003 when officials in Fuzhou, the capital of neighboring Fujian province, decided to ban electric bicyclesshutting off what until then had been one of Luyuans best markets. The city not only ceased issuing licenses for electric bicycles but also seized 20 electric bikes from a bicycle shop in the summer of 2003. Ni gathered a coalition of 126 electric-bike manufacturers and filed suit against the city in its own municipal court. The coalition scored a partial win against the city government, forcing it to return the seized bikes. Far more valuable, says Ni, was the sympathetic coverage they received from national media and the warning that attention sent to other municipalities. What we told other governments is that if they do the same as Fuzhou, there will be some trouble, he says. Conflict over electric bikes isnt limited to the municipalities and the manufacturers. Even the China Bicycle Association has been clashing with some companies, including Luyuan, over what types of electric two-wheelers should be on the road see photo, The Basic Bike. The bike group enforces a national standard for electric bicycles, and whichever parameter you chooseweight (no more than 40 kilograms), width (220 millimeters for the pedal shaft), speed (20 km/h, maximum)many of the latest electric scooters either flunk or thwart the standard. Lots of electric scooters, for example, are outfitted with nonfunctioning pedals and with speed-limiting devices designed for easy removal after purchase. Luyuans latest machine doesnt just skirt the electric-bike standard; it rumbles right over it. Luyuan calls its new product the LEV, short for light electric vehicle, and Ni openly admits that its more than a bicycle. Luyuans Web site calls it an electric motorcycle, and that seems fitting: the LEV weighs in at 95 kg; its 48-V, 20-AH battery packs double the energy of the standard bike; and its 500-watt CPU-controlled motor propels it to 35 km/h. The LEV has no official status in China. Nevertheless, on what should be a slow sales day at a Luyuan retail outlet in downtown Jinhua, the LEVs are flying out the door. In the space of an hour, one is snapped up by a 25-year-old man, and a working mother rolls out with another. Why did she choose an LEV? She drives her rather big-boned son to school and prefers an LEV to a gas-powered scooter, pointing to the endemic air pollution hanging over the city. Ni is betting that governments will sanction the LEV if it proves popular. He says he believes that Luyuan has addressed the one concern municipalities could level against the LEV that might have stuck: reduced safety due to the cycles greater weight. The LEV employs an electric drum brake that, Ni claims, stops it faster than the cantilever brakes used on garden-variety electric bikes could. A is also in the works that would boost braking power by using the in-hub motor as a generator to pull energy out of the wheels, extending the vehicles range by simultaneously charging the battery. Ever the entrepreneur, Ni sees the success of the LEV as a step toward bigger and better things. He already has his eye on the market for small delivery vehicles, and he even imagines Luyuan making electric cars and challenging the major automakers. They are investing money, saying we are going to change the gasoline system to electric, he points out. But will the big companies really be willing to destroy their own factories to build the new ones? In Nis view, small, aggressive Chinese companies like Luyuan are more likely to drive the EV revolution, because they have nothing to lose. THE BIGGEST CHALLENGE facing electric-bike makers may not be municipal bans, conservative standards, or even technology. It may be the roads. China is following the development path of Western countries like a map, rapidly redesigning its cities around the automobile. Across China, cities are rejecting a mixed-use model and redeveloping along a strict zoning model, razing residential buildings in center cities to make way for shiny office towers and paving farmland on the periphery to create large industrial parks. Displaced from the urban centers, houses and other residential buildings are springing up in sprawling suburbs, just as they did in the West decades ago. The automobile is king in this model, because in the absence of extensive public transit, cars are the only way to get from distant suburbs to offices and industry parks.To make way for more cars, Chinas cities are widening their main roads and building highways. The result has been a rapid increase in automobile use that, just as it does everywhere else in the world, almost instantly absorbs the extra roadways. The resulting gridlock has been especially acute in Chinas capital. Beijing had 1 million cars in 1997 and was once expected to reach 2 million in 2008. Instead, it hit 2 million last year and now expects 3.5 million to be in use in 2008. All over the country, they believe that wider roads are more efficient for traffic. Theyre wrong, says Yu Kon gjian, an urban planning expert at Beijing University. Car culture is a disaster for the bicycle. Road widening often comes at the expense of bike lanes, while highways are off-limits to bikes and nearly impossible to cross. On the smaller roadways, rush-hour traffic blocks the bike lanes and intersections, prompting outbursts of road rage from frustrated cyclists. Yu used to cycle 20 to 30 minutes between work and home, but he now drivesa 10- to 60-minute trip, depending on the traffic. Its too dangerous to bike, so people give up. I gave up, he says.5 b3 B! Yu is confident that, in the long run, it is the gas guzzlers that will be forced to give way. One reason is gridlock. Another is Chinas endemic urban pollution see photo, Pea Soup. On all but the best days in Jinhua, for example, the city skyline disappears behind a dense haze of smog and particulates; more and more of that atmospheric soup is pouring out of tailpipes.Its the strategic cost of petroleum that inspires professor Hes confidence in the electric bike. Chinas oil imports are on the same exponential growth path as its car fleet. China has eclipsed Japan as the second-biggest importer of oil, bringing it into direct competition with the worlds leading consumer of petroleum: the United States. With import dependence and environmental burdens in mind, China has promulgated fuel-efficiency standards that are stricter in principle than those currently in force in the United States, and it is considering imposition of a 20 to 50 percent national tax on retail gasoline and diesel. IF CHINA CAN FIND A WAY to make relatively efficient electric bikes a significant part of its transportation system, it could have major repercussions elsewhere in the developingand developedworld. That includes the United States, which has the worlds most car-dependent culture. Unlike Japan and Europe, where bicycles, trains, and other forms of transportation still thrive, the United States is one of the few places where people move almost exclusively by car. As WaveCrests Benjamin puts it, We live in a bubble.
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