自行車設計（含CAD圖紙）

自行車設計（含CAD圖紙）,自行車,設計,cad,圖紙 理工科類本科生畢業(yè)設計（論文）開題報告論文(設計)題目基于UG的死飛自行車設計作者所在系別機電學院作者所在專業(yè)作者所在班級作 者 姓 名作 者 學 號指導教師姓名指導教師職稱完 成 時 間畢業(yè)設計(論文)開題報告學生姓名專 業(yè)車輛工程班 級指導教師姓名職 稱副教授工作單位課題來源學生自擬課題課題性質課題名稱基于UG的死飛自行車設計本設計的科學依據（科學意義和應用前景，國內外研究概況，目前技術現狀、水平和發(fā)展趨勢等）1.死飛自行車的來源死飛自行車的由來最大歸功于美國，在80年代，歐美國家汽車的擁有量大，道路設施不健全，而信使的任務又加繁重，變通的信使便想到用轉向方便、快捷的自行車來運送信件。自行車的體積小，方便于在街道、擁擠的路上穿梭行駛，而這種自行車多是公路自行車。由于公路自行車擁有繁多的變速器、閘線等，在騎行的時候都需要緊密的配合，且在日常的騎行中又得保養(yǎng)，稍微損壞就會在騎行的過程造成不必要的傷害，而騎行過程中的各種配合又是對信使的一種負擔。于是他們開始對現有的公路自行進行改裝，對車架結構進行簡單化，不易損壞，也沒有多余的、錯綜復雜的閘線，并且擁有穩(wěn)定的速度便于在城市中平坦的公路上行駛，這種自行車便是死飛自行車的雛形。2.死飛自行車的現狀針對自行車行業(yè)的調查，技術含量，以及業(yè)界的死飛自行車行業(yè)現狀有以下幾點；1.行業(yè)亂象 因為節(jié)能能源使用，自行車需求趨于休閑健身行業(yè)。但是中國的自行車王國在歷經汽車時代的洗禮之后，淘汰產能依然存在。便宜就有市場的市場認知依然在收入有限的消費者購買動機下存在，而且普遍存在把休閑娛樂健身功能忽視的市場趨勢。2.行業(yè)技術 因為市場受眾，內銷自行車品質參差不齊，因價格戰(zhàn)導致市場黑洞，就是越節(jié)省成本，前沿技術的適應，產品的專業(yè)品質根本無需考慮。在這方面知名品牌的做法值得借鑒。3.行業(yè)服務 低價競爭的過剩產能銷售產品，售后無從談起，維權艱難。修補市場缺乏規(guī)范，實體店銷售終端經營以專賣服務有保障。設計內容和預期成果（具體設計內容和重點解決的技術問題、預期成果和提供的形式） 本論文主要是對死飛自行車進行三維建模，包括零部件的三維建模及最后的整體裝配，此論文的最大難點即重點是三維軟件的運用，如何正確的運用三維軟件中板塊和命令。最終以文件和照片的形式提交死飛自行車的所有零部件模型及整體三維模型。擬采取設計方法和技術支持（設計方案、技術要求、實驗方法和步驟、可能遇到的問題和解決辦法等）本論文的設計內容如下： （1）搜集現有相關的數據，對搜集到的數據進行歸類分析，研究各類數據并加以修改，加入自己創(chuàng)新點。（2）利用三維建模軟件，結合搜集、分析的數據，對死飛自行車的各部件進行三維建模、裝配。 在三維制圖軟件方面遇到的問題可以請教老師和同學們，也可通過網絡、論壇、各種群等來解決。 實現本項目預期目標和已具備的條件（包括過去學習、研究工作基礎，現有主要儀器設備、設計環(huán)境及協作條件等） 在選題時，選到本題目，我就能感覺到此次的畢業(yè)設計肯定能順利完成，能按照要求對死飛自行車進行三維建模。 以前在大一大二時感覺時間空余，就自學與本專業(yè)有關的軟件UG，通過自己的學習現已可以獨立完成一些比較簡單的三維建模。也恰好選對了一個自己比較熟悉的題目。各環(huán)節(jié)擬定階段性工作進度(以周為單位)開題報告外文翻譯搜集資料三維建模及裝配中期檢查擬寫說明書的初稿導師對初稿的指導定稿答辯整理入冊 開 題 報 告 審 定 紀 要時 間地點主持人參會教師姓 名職 務（職 稱）姓 名職 務（職 稱）論證情況摘要 記錄人：指導教師意見指導教師簽名： 年 月 日教研室意見教研室主任簽名： 年 月 日 32 本科生畢業(yè)設計(論文)文獻綜述設計 (論文)題目 基于UG的死飛自行車設計作者所在系別 機電工程學院作者所在專業(yè)作者所在班級作 者 姓 名作 者 學 號指導教師姓名指導教師職稱完 成 時 間2017年3月 說 明1根據學校畢業(yè)設計(論文)工作暫行規(guī)定，學生必須撰寫畢業(yè)設計(論文)文獻綜述。文獻綜述作為畢業(yè)設計(論文)答辯委員會對學生答辯資格審查的依據材料之一。2文獻綜述應在指導教師指導下，由學生在畢業(yè)設計(論文)工作前期內完成，由指導教師簽署意見并經所在專業(yè)教研室審查。3文獻綜述各項內容要實事求是，文字表達要明確、嚴謹，語言通順，外來語要同時用原文和中文表達。第一次出現縮寫詞，須注出全稱。4學生撰寫文獻綜述，閱讀的主要參考文獻應在10篇以上（土建類專業(yè)文獻篇數可酌減），其中外文資料應占一定比例。本學科的基礎和專業(yè)課教材一般不應列為參考資料。5文獻綜述的撰寫格式按畢業(yè)設計(論文)撰寫規(guī)范的要求，字數在2000字左右。文獻綜述應與開題報告同時提交。畢 業(yè) 設 計（論 文）文 獻 綜 述基于UG的死飛自行車設計摘要：死飛車（fixed gear bicycle，又稱 fixie bike，）后輪的齒輪與后輪直接用螺栓固接（不像普通自行車，后輪齒輪與后輪是通過棘輪棘爪連接，普通自行車反向踩腳踏板時后輪不受力）。所以曲柄的旋轉方向始終與后輪的運動方向保持一致。通常，死飛車是不能通過換檔來變速。利用UG技術可以對死飛機自行車進行相關設計。關鍵字：死飛自行車，UG技術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、 什么是死飛死飛車（Fixed Gear Bike），與場地自行車（Track Bike）是同類自行車，騎行地域并不只限制在體育館內。在日本則有古典 賭博形式的場地自行車比賽，被 稱為“競輪”，在中國被稱為“死 飛”或“固齒”，香港地區(qū)也有 稱為“梗牙”。死飛車（Fixed Gear Bike）來自New York Old School（紐約復古）單車文化，最初是由快遞工作者發(fā)起的快速單車文化，在日本原宿流行后， 就開始快速在全世界蔓延，成為街頭文化的代表。 “死飛”自行車只有一個車架、兩個輪子、一個車把和鞍座， 沒有閘線，沒有齒輪轉換器，也沒有擋泥板。也正因為飛輪是死的， 騎行的人便可以通過腳踏來控制后輪從而減速和剎車，也可以很 好地控車。主要是靠腳來控制車子的前進和后退，同時也可以做 出許多花樣動作，玩得好的騎手可以做出定桿、漂移、倒騎繞圈、 跳躍等花樣。 “死飛”運動作為一種結合時尚、街頭、環(huán)保、健康、挑戰(zhàn) 的運動，很快在國內年輕人里流行起來。由于外形酷炫、理念“前 衛(wèi)”，騎著“死飛”自行車上路的騎手往往成為人們目光的焦點。二、 死飛與普通自行車區(qū)別“死飛”屬于場地自行車的一種，并非一般意義上的代步工 具。 “死飛”講究簡約，沒有剎車，沒有變速，因此重量很輕， 目的只有一個，就是讓人把自行車騎得越來越快。 從結構來看，普通自行車的飛輪是“活的”,人踩腳踏時,輪 子跟著轉動,人停止踩腳踏后,車輪也可以繼續(xù)轉動,需要使用剎 車來停車;而“死飛”自行車是一種固齒飛輪自行車,需要腳踩腳踏來控制車速和剎車腳踏板轉動時帶動車輪轉動,而腳踏 板停止轉動時則車輪也停止轉動。除了停車外，騎行過程中人必 須一直不停地踩腳踏板。對于一般人來說，“死飛”自行車的騎 行時速可達40 km,是普通自行車最高時速的2倍。三、 理性看待死飛目前國內部分人對死飛的排斥主要來自對它的安全性沒有把 握。在這里我要說，死飛危險。只有危險的人，沒有危險的車。在上路之前，你首先必須學 習控制住自己的速度和節(jié)奏，而不是在技術還不成熟的情況下， 一味地追求炫耀。 關于剎車問題，死飛并非完全脫軌。目前有不少死飛愛好 者選擇了為死飛裝上了手動前剎，在這里也建議死飛新手可以使 用。愛好的同時，也要注意安全！ 所以安全問題并不全是剎車造成的,而是和自身的騎行技 術和水平有關系。汽車的速度很快，開車除了遵守交通法律和 規(guī)則以外，還一定要熟練掌握開車技能，還一定要有預判。熟 練掌握技能和預判就是經驗，經驗只有通過大量實踐才能獲得， 但是現在不少年輕人騎行時都沒有這個意識，這就存在著一定 的安全隱患。四、 死飛自行車的使用技術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、 結論死飛的文化理念接近中國那句古話：海納百川，有容乃 大?！八里w”不僅是對于愛好的一種追求，也是用來感受生 活的一個媒介。 “死飛”盡管出現了一些事故和一些讓人不 愉快的事情，但死飛不應該被粗暴地“一刀切”。這個騎行 群體和行業(yè)需要正確的引導和規(guī)范。經營者也應該和管理部 門相互配合，勸導大家安裝車閘，配戴頭盔，熟練特性，遵 守交通法規(guī)。 在這里呼吁一下，希望有能力的組織或者機構組織愛好者們 進入自行車場地騎行，讓大家能安全地體驗死飛的樂趣。參考文獻1中國自行車2013年11期2現代機械2012年10期3百度文庫死飛自行車的相關文章畢 業(yè) 設 計（論 文）文 獻 綜 述指導教師意見 指導教師： 年 月 日專業(yè)教研室審查意見 負責人： 年 月 日 54 地方官員常用的這樣的借口來拒絕電動自行車：鉛酸電池會污染環(huán)境；電動車會干擾機動車輛行駛，阻塞交通；特別是對公交系統(tǒng)造成巨大沖擊。積極為綠色交通奔走呼吁的請愿人士說，這些借口蒼白無力，不過是試圖去保護電動車的競爭者而已。中國科學院著名理論物理學家，院士何祚庥一針見血地指出：“真正的原因就是來自利益集團的競爭。”何院士在有關環(huán)境和能源政策的公共辯論中一向直言。他說反對電動車的理由沒有一條真正站得住腳：汽車上用的也是鉛酸電池，他特別補充：“真正的污染源不是電動車，而是汽車。”如果現有的交通運營者們和制造商們想與電動車競爭，就要為大眾提供效率更高，價格更便宜，更清潔的交通工具。但問題是，與其它競爭者相比，電動車廠商微不足道，特別是汽車產業(yè)，吸引了數十億美元的外國投資。在中國官方制定的五年計劃中，汽車生產已經被列為“支柱產業(yè)”。 盡管面臨著嚴酷的生存挑戰(zhàn)，但電動自行車廠商們并沒有退卻，而是知難而進，并取得了驚人成功。綠源電動車公司的董事長倪捷是代表電動車產業(yè)界的靈魂人物，他從一家小企業(yè)開始艱苦創(chuàng)業(yè)，以務實的態(tài)度開拓市場，并取得成規(guī)模的研究開發(fā)成果，對中國電動車的技術發(fā)展有獨到的見解。綠源電動公司一開始是從政府風險投資中分離出來的。九年前，綠源現任總經理胡繼紅(倪捷的妻子)制造出第一臺樣機，綠源公司成立了，隨后在倪捷和胡繼紅的領導下，公司改為私營，并且從最初的投資者手里買下了所有產權。公司成長迅猛，去年業(yè)績傲人，電動自行車和踏板電動車銷量達到了12萬輛，今年的銷售目標是30萬輛。去尋找綠源，要從上海市一路南下，來到金華。這是浙江省的一座城市，人口百萬，工業(yè)重鎮(zhèn)。順著金華市工業(yè)園的公路就可以找到綠源公司的總部。倪捷的辦公室坐落在辦公樓的一角，寬敞舒適，是公司里為數不多的帶暖氣的房間之一，寒冷的二月里，這一點顯得尤為突出。倪捷煙不離手，喝著泡著濃濃的綠茶的廣口杯，侃侃道來創(chuàng)業(yè)的艱辛與收獲。他說，在中國的大多數城市里，交通是個首要問題，電動車是昂貴的轎車和擁擠的公交車的首選替代品和補充品?！叭绻疀]有明確的解決方案，人民就可以按自己的辦法去行動，沒有理由去阻止人們這樣做。”倪捷非?？粗腥嗣竦牧α?，這一點在福州事件中得到了充分印證。2003年夏天，當時，綠源最大市場之一是毗鄰的福建省省會福州市，但是該市的政府卻要明令封殺電動車，不但不給電動車執(zhí)照，而且禁止銷售，他們沒收了綠源專賣店里的20輛電動自行車。倪捷就聯合了126家電動車廠家，將市政府(工商局)告上了法庭。此次，廠商聯手，迫使市政府無條件發(fā)還了無理沒收的電動車。這次聯手取得了局部的成功。 倪捷認為此次福州事件更深遠的意義在于贏得了全國媒體的廣泛關注和支持，并且也給其它(反對電動車的)地方政府有一點警示作用?！拔覀兿蚱渌胤秸畟鬟_的信息是，如果他們學習福州市政府的做法來反對電動車，他們就會有一些麻煩?！?圍繞電動車引發(fā)的沖突并不只局限于地方政府和生產廠家，中國自行車協會也和一些廠商(包括綠源)在產品細節(jié)上發(fā)生分歧，諸如何種兩輪車才可以上路等。自行車協會強調的是電動自行車的國家標準，如重量不能超過40公斤，腳踏之間的寬度不能超過220毫米，最高時速小于20公里等等，許多最新的電動自行車和踏板電動車都不符合這些指標。例如，很多踏板電動車配置了騎行功能不好的腳踏，并有限制速度的附加裝置。有些人買回去就可以自己把限速裝置拆掉。綠源公司的一款最新產品已經不再被現有的電動自行車標準所限制，綠源把這種新車型被稱做LEV，輕型電動車的縮寫。倪捷公開承認它已經不僅僅是“自行車”了。在綠源的網站上它被稱為“電動摩托車”：車重95公斤，配備48伏20安時的電池，電機的輸出功率高了一倍，達到500瓦，用CPU控制的電機可以將時速提高到35公里。 雖然目前國家還沒有出臺LEV統(tǒng)一標準，不過在金華，即使是銷售淡季，顧客還是首選LEV。在不到一個小時內，一位25歲的年輕人和一位上班族母親相繼開走了兩輛。在被問及選中這輛車的理由時，她指著城市上空的空氣污染解釋道她必須送塊頭大的兒子去上學，但是為了降低本地城市的空氣污染，她寧可選擇電動車，而不要燃油的踏板摩托車。 倪捷樂觀地相信，政府在看到LEV的普遍使用之后，會給予正式許可的?，F在不少人對該車重量增加是否會降低安全系數持懷疑態(tài)度。倪捷解釋道：LEV裝有電鼓閘，它的剎車效果比各種各樣電動車常用的懸臂閘要好得多。新的能量回收型制動系統(tǒng)也已開始使用，這種新系統(tǒng)在剎車時將把主動的電動機變成被動的發(fā)電機，一方面有利于迅速制動，另一方面也可以把剎車要消耗的能量提取出來對電池充電，從而擴大了車輛的行車里程。作為一名企業(yè)家，倪捷把在電動自行車和LEV上的成功看成是走向“更大和更好”的電動化交通工具的關鍵一步。他已經開始關注小型電動運輸車輛的市場，甚至夢想有一天，綠源能夠生產出自己的小型電動汽車，與大公司競爭?！八麄兛偸窃谡f，我們正在投入大量資金，我們將有計劃地把燃油系統(tǒng)改成電動系統(tǒng)?！蹦呓葜赋觯暗?，這些大公司他們真的愿意毀掉現有的工廠去建設新的工廠嗎？”依倪捷看來，一批富有進取心的小企業(yè)，就像綠源這樣的，更有可能推動電動車革命，因為這樣做他們一無所失。電動車廠家所面臨的最大挑戰(zhàn)，還不是部分地方政府的禁行令，保守的標準，甚至連技術也不是主要問題，最大困擾來自道路狀況。中國正遵循著西方發(fā)達國家的發(fā)展模式，圍繞著汽車來徹底重新規(guī)劃城市。中國的每一個城市都在摒棄機動車非機動車混合行使模式，實現嚴格的分道行使模式，農田改造成了工業(yè)園。住房從城市中心也逐漸向郊區(qū)遷徙以便讓位給亮麗的寫字樓，幾十年前西方國家就是這么干的。汽車成了這個模式中的國王。由于公共交通網很不健全，轎車成了從遠郊區(qū)居住地到辦公室或工業(yè)園的唯一工具。為了給更多的汽車讓路，中國的許多城市都將主路拓寬，并修建了高速公路。就像在世界其他地方發(fā)生的一樣，其后果只能是導致了汽車數量迅猛增長，新增的轎車馬上占據了新修的馬路。這種惡性循環(huán)在首都北京表現得十分明顯。1997年，北京只有1百萬輛轎車，有人曾經預計到2008年才達到2百萬輛。但事實是，去年已經突破了2百萬輛，新的預測是2008年將達到350萬輛。北京大學城市規(guī)劃專家俞孔堅尖銳地指出：“舉國上下，大家都認為馬路越寬交通狀況就越好，但是他們是錯的?！逼囄拿鞯呐d起對自行車是一個災難，馬路拓寬的代價是占用自行車道，高速公路不許自行車上道，而且?guī)缀醪豢纱┰健Ｕ稽c的馬路上，高峰時間的車流阻斷了自行車道和交叉路口，引起騎車人的強烈不滿。俞教授以前騎自行車從家到學校只需要20到30分鐘，但他現在開車，依據交通狀況，花費10到60分鐘不等。“騎自行車太危險了，所以許多人不騎車了，我也不騎了?！?不過俞教授相信從長遠來看，燃油的車輛終將會被迫給電動車讓路。一方面的原因是交通堵塞，另一方面的原因是中國的城市污染。在金華，即使污染不那么嚴重的日子，城市的天際線也都消失在煙塵之中，越來越多的大氣污染物是從機動車排氣管中排出的。 何院士之所以對電動車充滿信心，主要因為中國為石油所付出的戰(zhàn)略代價太高。中國石油進口增加速度和它的汽車數量增加速度并駕齊驅。中國已經超過了日本成為世界第二大原油進口國，開始與美國競爭世界上最大的石油消費國。為減少對進口原油的依賴，也為減輕沉重的環(huán)保負擔著想，中國已經制定了比美國更嚴格的燃料效能標準，同時正在考慮對零售汽油和柴油加征20%到50%的燃油附加稅。如果中國能找到一種解決辦法，能使得相對高效的電動車在交通系統(tǒng)中發(fā)揮更顯著的作用，這將為世界上其它發(fā)展中國家乃至發(fā)達國家樹立一個的典范。這也包括了全世界中最依賴汽車的國家美國。在日本和歐洲，自行車、火車和其它形式的公共交通工具還在積極地運轉，而美國是極少數絕大部分交通完全依賴汽車的國家之一，引用WaveCrest公司本杰明先生的話：“我們住在大泡沫里?！盜N 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.