設(shè)計(jì) ZL120型整體動(dòng)臂裝載機(jī)設(shè)計(jì),學(xué)生姓名: 指導(dǎo)教師:,(課題來(lái)源： ),裝載機(jī),裝載機(jī)屬于鏟土運(yùn)輸機(jī)械類，是一種通過(guò)安裝在前端一個(gè)完整的鏟斗支承結(jié)構(gòu)和連桿，隨機(jī)器向前運(yùn)動(dòng)進(jìn)行裝載或挖掘，以及提升、運(yùn)輸和卸載的自行式履帶或輪胎機(jī)械。 它是工程機(jī)械中不可缺少的裝備之一。,裝載機(jī)的分類,1) 按行走裝置不同可分為履帶式和輪胎式兩種。右圖是一種履帶式裝載機(jī)。這種裝載機(jī)堅(jiān)固耐用、與地面附著力大、接地比壓力小、越障礙物能力強(qiáng)，但其質(zhì)量大、運(yùn)動(dòng)慣性大、結(jié)構(gòu)復(fù)雜、磨損嚴(yán)重、維修量大、運(yùn)行速度受限制，而且不能起吸收振動(dòng)和緩和沖擊的作用。,,右上圖是一種輪式裝載機(jī)。這種機(jī)型采用雙臂支承鏟斗，鏟斗工作平穩(wěn)性好，受力狀況也較好，但兩臂之間有一定尺寸，這導(dǎo)致結(jié)構(gòu)尺寸擴(kuò)大，可能與輪胎等發(fā)生干涉，結(jié)構(gòu)不好布置。 右下圖也是一種輪胎式裝載機(jī)。這種機(jī)型采用單臂支承鏟斗，鏟斗工作平穩(wěn)性及受力狀況均不如雙臂支承，但此型式結(jié)構(gòu)緊湊，結(jié)構(gòu)易與布置。,2)按裝載方式不同分類按裝載方式不同可分為前卸式、后卸式、側(cè)卸式和回轉(zhuǎn)式。輪式裝載機(jī)基本上都是采用前卸式。 3)按轉(zhuǎn)向方式不同分類按轉(zhuǎn)向方式不同可分為整體式和鉸接式。 4)按使用場(chǎng)合不同分類按使用場(chǎng)合不同分為露天用裝載機(jī)和井下用裝載機(jī)。 此外，還有一些分類方式。如按傳動(dòng)形式不同可分為機(jī)械傳動(dòng)、液壓傳動(dòng)、電傳動(dòng)等。,主要設(shè)計(jì)參數(shù):,1）斗容量4 m3 ； 2）額定載重量80kN； 3）發(fā)動(dòng)機(jī)功率200kW； 4）最大掘起力210kN； 5）最大卸載高度3500mm；6）動(dòng)臂提升時(shí)間6.5s； 7）三項(xiàng)和時(shí)間12s； 8）最大轉(zhuǎn)向角35°； 9）最小轉(zhuǎn)彎半徑6800mm；10）行駛速度：前進(jìn)第4擋36km/h；后退第3擋 20km/h； 11）后橋擺動(dòng)角10°； 12）外形尺寸8500×3200×3450mm 13）整機(jī)質(zhì)量18500kg。,裝載機(jī)總體設(shè)計(jì),裝載機(jī)的總體布置應(yīng)從保證其主要性能出發(fā)，在總體設(shè)計(jì)和各總成部件設(shè)計(jì)的密切配合下，根據(jù)使用要求和橋荷分配來(lái)協(xié)調(diào)各總成的性能 ，并確定和控制它們的位置、尺寸和重量。總體布置不僅應(yīng)使裝載機(jī)具有良好的使用性能，而且必須保證操作輕便、拆裝容易和維修方便。,1）車架連接和傳動(dòng)軸的布置① 鉸接車架鉸銷中心布置在前后橋軸線中間偏前位置 。 如右圖所示，采 用這種布置方式， 裝載機(jī)轉(zhuǎn)彎時(shí)， 前輪轉(zhuǎn)彎半徑大 于后輪轉(zhuǎn)彎半徑， 作業(yè)阻力增大， 作業(yè)效率低，操 作性能不好。,② 鉸接銷布置在前后橋軸線的中心。如右圖所示，采用 這種布置方式，裝載 機(jī)轉(zhuǎn)彎時(shí)，前后輪軌 跡相同，這不僅在松 軟地面上可以減小轉(zhuǎn)向阻力矩和行駛阻力， 而且前輪能通過(guò)狹小的 場(chǎng)地，后輪也能順利通 過(guò)，司機(jī)操作性能好， 但是這種布置方式就整 個(gè)傳動(dòng)系統(tǒng)來(lái)說(shuō)，排列 比較困難。,傳動(dòng)軸布置在裝載機(jī)的縱向?qū)ΨQ平面內(nèi)，并盡可能成水平布置，使中間傳動(dòng)軸的中點(diǎn)和車架的鉸接銷中心線重合，這樣才能保證轉(zhuǎn)向時(shí)，萬(wàn)向節(jié)作等速轉(zhuǎn)動(dòng)。 2）工作裝置的布置工作裝置布置在裝載機(jī)的前部，工作裝置各構(gòu)件的布置主要是確定動(dòng)臂的長(zhǎng)度和各鉸接點(diǎn)的位置。動(dòng)臂和車架連接的鉸接點(diǎn)的位置，應(yīng)不影響駕駛員的視線。鉸接點(diǎn)前后位置選取時(shí)，若鉸接點(diǎn)位置前移，卸載的距離增大，穩(wěn)定性降低。因此，在不影響卸載距離的條件下，盡可能向后布置。,輪式裝載機(jī)工作裝置設(shè)計(jì),輪式裝載機(jī)工作裝置 由鏟斗、連桿、搖臂、 動(dòng)臂、轉(zhuǎn)斗油缸、舉升 油缸組成。 如圖，1為搖臂，2為 動(dòng)臂，3為鏟斗， 4為 連桿。,輪式裝載機(jī)工作過(guò)程,輪式裝載機(jī)是一種鏟、裝、運(yùn)、卸一體化的自行式設(shè)備，它的工作過(guò)程由六種工況組成。 1）插入工況 動(dòng)臂下放，鏟斗放置于地面，斗尖觸地，斗底板與地面呈3°～5°傾角，開動(dòng)裝載機(jī)，鏟斗借助機(jī)器的牽引力插入料堆。 2）鏟裝工況 鏟斗插入料堆后，轉(zhuǎn)動(dòng)鏟斗鏟取物料，待鏟斗口翻至近似水平為止。,3）重載運(yùn)輸工況 鏟斗鏟裝滿物料后舉升動(dòng)臂，將鏟斗舉升至運(yùn)輸位置，然后驅(qū)動(dòng)機(jī)器駛向卸載點(diǎn)。 4）舉升工況 保持轉(zhuǎn)斗缸長(zhǎng)度不變，操縱舉升缸，將動(dòng)臂舉升至上限位置，準(zhǔn)備卸載。 5）卸載工況 在卸載點(diǎn)，在舉升工況下操縱轉(zhuǎn)斗油缸使鏟斗翻轉(zhuǎn)，向運(yùn)輸車輛中卸載，鏟斗物料卸凈后下放動(dòng)臂，使鏟斗恢復(fù)至運(yùn)輸位置。 6）空載運(yùn)輸工況 卸載結(jié)束后，裝載機(jī)由卸載點(diǎn)空載返回裝載點(diǎn)。,工作裝置設(shè)計(jì)要求:要具有較強(qiáng)的工作能力，鏟斗插入料堆的阻力要小，在料堆中鏟掘的能力大，能耗低。工作機(jī)構(gòu)的各桿件受力狀態(tài)良好，強(qiáng)度壽命合理。要保證必要的卸載角、卸載高度。輪式裝載機(jī)工作機(jī)構(gòu)屬于連桿機(jī)構(gòu)，設(shè)計(jì)中要特別注意防止各個(gè)工況出現(xiàn)構(gòu)件相互干擾、“死點(diǎn)”、“自鎖”和“機(jī)構(gòu)撕裂”等現(xiàn)象 。,連桿系統(tǒng)設(shè)計(jì),連桿系統(tǒng)有以下幾種類型：1）正轉(zhuǎn)八桿機(jī)構(gòu) 2）轉(zhuǎn)斗油缸后置式反轉(zhuǎn)六桿機(jī)構(gòu) 3）轉(zhuǎn)斗油缸后置式正轉(zhuǎn)六桿機(jī)構(gòu)4）正轉(zhuǎn)四桿機(jī)構(gòu) 5）轉(zhuǎn)斗油缸前置式正轉(zhuǎn)六桿機(jī)構(gòu) 6）正轉(zhuǎn)五桿機(jī)構(gòu) 綜合考慮各種機(jī)構(gòu)的優(yōu)缺點(diǎn)，本次設(shè)計(jì)選用轉(zhuǎn)斗油缸后置式反轉(zhuǎn)六桿機(jī)構(gòu)。,機(jī)構(gòu)分析,右圖所示裝載機(jī)采用反轉(zhuǎn)六桿機(jī)構(gòu)。反轉(zhuǎn)六桿機(jī)構(gòu)由轉(zhuǎn)斗機(jī)構(gòu)和動(dòng)臂舉升機(jī)構(gòu)兩個(gè)部分組成。轉(zhuǎn)斗機(jī)構(gòu)由轉(zhuǎn)斗油缸、搖臂、連桿、鏟斗、動(dòng)臂和機(jī)架六個(gè)構(gòu)件組成。舉升機(jī)構(gòu)主要由動(dòng)臂舉升油缸和動(dòng)臂組成。,根據(jù)要求，采用 圖解法作圖，得到 反轉(zhuǎn)六桿機(jī)構(gòu)如圖。在此數(shù)據(jù)的基礎(chǔ) 上，可設(shè)計(jì)出各構(gòu) 件。 各構(gòu)件如圖所示,搖臂,連桿,動(dòng)臂,鏟斗,動(dòng)臂實(shí)體網(wǎng)格圖,,動(dòng)臂應(yīng)力分析圖,,動(dòng)臂靜態(tài)位移圖,,,工作裝置設(shè)計(jì)完之后，則可畫出底座，完成 裝載機(jī)總圖，如下。,,,,,,,,,,,,,,,,,,結(jié)論,經(jīng)過(guò)三個(gè)月的忙碌，畢業(yè)設(shè)計(jì)至今已基本完成。在這段時(shí)間里，主要完成了以下工作。查閱各種資料，詳細(xì)了解了裝載機(jī)的現(xiàn)狀及發(fā)展趨勢(shì)、用途、分類、基本組成等相關(guān)知識(shí)。在此基礎(chǔ)上，完成了裝載機(jī)的總體設(shè)計(jì)及工作裝置設(shè)計(jì)，工作裝置結(jié)構(gòu)分析與校核以及整機(jī)穩(wěn)定性驗(yàn)算。繪出圖紙折合0號(hào)圖5張，設(shè)計(jì)計(jì)算書40余頁(yè)， 外文資料翻譯5000余字。,,所設(shè)計(jì)裝載機(jī)的特點(diǎn)：1、國(guó)內(nèi)現(xiàn)有的輪式裝載機(jī)大部分都是采用雙臂結(jié)構(gòu)，而此次設(shè)計(jì)的裝載機(jī)則是采用整體動(dòng)臂結(jié)構(gòu)。2、工作裝置選用反轉(zhuǎn)六桿機(jī)構(gòu)。,,謝謝各位老師參加我的答辯，敬請(qǐng)老師提出寶貴意見，謝謝！,0畢業(yè)設(shè)計(jì)（論文）任務(wù)書題目 ZL120 型整體動(dòng)臂裝載機(jī)設(shè)計(jì)專業(yè) 學(xué)號(hào) 姓名 主要內(nèi)容、技術(shù)參數(shù)、基本要求、主要參考資料等：1、主要內(nèi)容整體動(dòng)臂裝載機(jī)總體設(shè)計(jì)；整體動(dòng)臂裝載機(jī)的工作裝置設(shè)計(jì)；工作裝置的結(jié)構(gòu)分析；整機(jī)穩(wěn)定性驗(yàn)算。2、技術(shù)參數(shù)1） 、斗容量 4 m3；2） 、額定載重量 80kN；3） 、發(fā)動(dòng)機(jī)功率 200kW；4） 、最大掘起力 210kN；5） 、最大卸載高度 3500mm；6） 、動(dòng)臂提升時(shí)間 6.5s；7） 、三項(xiàng)和時(shí)間 12s；8） 、最大轉(zhuǎn)向角 35°；9） 、最小轉(zhuǎn)彎半徑 6800mm；10） 、行駛速度：前進(jìn)第 4 擋 36km/h；后退第 3 擋 20km/h；11） 、后橋擺動(dòng)角 10°；12） 、外形尺寸 8500×3200×3450mm13） 、整機(jī)質(zhì)量 18500kg。3、基本要求設(shè)計(jì)機(jī)器總體、鏟斗圖、動(dòng)臂機(jī)構(gòu)圖、主要零件圖、機(jī)器立體圖等，折合 0號(hào)圖紙 5 張；設(shè)計(jì)計(jì)算書 40 頁(yè)；外文資料翻譯 5000 字。4、主要參考資料相關(guān)三維設(shè)計(jì)與仿真軟件及參考書籍；相關(guān)機(jī)械設(shè)計(jì)手冊(cè)、液壓手冊(cè)、網(wǎng)上期刊文獻(xiàn)、相關(guān)樣本等。完成期限： 4 月 9 日～6 月 26 日 指導(dǎo)教師簽名： 專業(yè)負(fù)責(zé)人簽名：年 4 月 3 日 學(xué)生開題報(bào)告表課題名稱 ZL120 型整體動(dòng)臂裝載機(jī)設(shè)計(jì)課題來(lái)源 課題類型 A 指導(dǎo)教師姓名學(xué)生姓名 學(xué) 號(hào) 專 業(yè) 機(jī)自1、調(diào)研準(zhǔn)備拿到課題，通過(guò)查閱資料及實(shí)際調(diào)查，對(duì)裝載機(jī)有了一定的認(rèn)識(shí)。裝載機(jī)屬于鏟土運(yùn)輸機(jī)械類，是一種通過(guò)安裝在前端一個(gè)完整的鏟斗支承結(jié)構(gòu)和連桿，隨機(jī)器向前運(yùn)動(dòng)進(jìn)行裝載或挖掘，以及提升、運(yùn)輸和卸載的自行式履帶或輪胎機(jī)械。它廣泛用于公路、鐵路、建筑、水電、港口和礦山等工程建設(shè)。裝載機(jī)具有作業(yè)速度快、效率高、機(jī)動(dòng)性好、操作輕便等優(yōu)點(diǎn)，因此成為工程建設(shè)中土石方施工的主要機(jī)種之一，對(duì)于加快工程建設(shè)速度，減輕勞動(dòng)強(qiáng)度，提高工程質(zhì)量，降低工程成本都發(fā)揮著重要的作用，是現(xiàn)代機(jī)械化施工中不可缺少的裝備之一。裝載機(jī)按行走方式不同可分為輪胎式和履帶式裝載機(jī)；按使用場(chǎng)合不同可分為露天用裝載機(jī)和井下用裝載機(jī)；按傳動(dòng)形式不同可為機(jī)械傳動(dòng)、液力機(jī)械傳動(dòng)、液壓傳動(dòng)和電傳動(dòng)四種；按裝載方式不同可分為前卸式、后卸式、側(cè)卸式和回轉(zhuǎn)式。輪式裝載機(jī)基本上都是采用前卸式。按轉(zhuǎn)向方式不同可分為整體式和鉸接式。整體式利用偏轉(zhuǎn)后輪或前輪轉(zhuǎn)向，或者同時(shí)偏轉(zhuǎn)前后輪，鉸接式采用鉸接車架，利用前后車架之間的相對(duì)偏轉(zhuǎn)進(jìn)行轉(zhuǎn)向。標(biāo)志裝載機(jī)的主要技術(shù)性能參數(shù)有鏟斗容量、額定載重量、發(fā)動(dòng)機(jī)額定功率、整機(jī)質(zhì)量、最大行駛速度、最小轉(zhuǎn)彎半徑、最大牽引力、最大掘起力、最大卸載高度、卸載距離、工作裝置動(dòng)作三項(xiàng)和等。與此同時(shí)，我還特意上施工現(xiàn)場(chǎng)仔細(xì)觀察和研究了幾種型式的輪式裝載機(jī)，對(duì)其基本結(jié)構(gòu)、特點(diǎn)、原理等都有了一個(gè)大概的了解，對(duì)其各部件的布置、工作過(guò)程也有了一個(gè)直觀的印象，這給設(shè)計(jì)準(zhǔn)備了一定的基礎(chǔ)。2、設(shè)計(jì)目的本次畢業(yè)設(shè)計(jì)設(shè)計(jì)一個(gè)裝載機(jī)，我想設(shè)計(jì)目的主要有以下幾點(diǎn)：1） 、通過(guò)這次設(shè)計(jì)，熟練地掌握使用 solidworks 軟件，這是一大塊，需要花一定的時(shí)間。2） 、自己通過(guò)設(shè)計(jì)一個(gè)整機(jī)，對(duì)設(shè)計(jì)過(guò)程、思路、協(xié)調(diào)分配時(shí)間等等都是一個(gè)鍛煉。3） 、通過(guò)這次訓(xùn)練，達(dá)到鞏固以前所學(xué)知識(shí)，又學(xué)習(xí)新知識(shí)的目的，為以后工作或?qū)W習(xí)打下堅(jiān)實(shí)的基礎(chǔ)。3、設(shè)計(jì)要求 本次設(shè)計(jì)要求完成裝載機(jī)總體圖、鏟斗圖、動(dòng)臂機(jī)構(gòu)圖、主要零件圖、裝載機(jī)立體圖等，同時(shí)要完成設(shè)計(jì)計(jì)算書 40 頁(yè)，外文資料翻譯 5000 字。所有圖紙及計(jì)算數(shù)據(jù)都應(yīng)正確合理。4、設(shè)計(jì)思路此次畢業(yè)設(shè)計(jì)要求設(shè)計(jì)一臺(tái)裝載機(jī)，但裝載機(jī)是一個(gè)龐大的復(fù)雜機(jī)器，以我現(xiàn)在的水平，要想在 3 個(gè)月畢業(yè)設(shè)計(jì)期間完成所有的設(shè)計(jì)，無(wú)疑是完成不了的。因此，設(shè)計(jì)時(shí)就有主次之分了。裝載機(jī)主要是用來(lái)裝載工作的，而工作機(jī)構(gòu)是其完成工作任務(wù)的關(guān)鍵部位，因此，設(shè)計(jì)的主體就應(yīng)該是設(shè)計(jì)工作機(jī)構(gòu)，即設(shè)計(jì)完成鏟斗的動(dòng)作。而其它部分可參照同類裝載機(jī)畫出。設(shè)計(jì)思路具體如下：1）進(jìn)行裝載機(jī)總體設(shè)計(jì)。裝載機(jī)是由許多主要部件組合起來(lái)的一個(gè)有機(jī)整體，其整機(jī)性能不僅取決于每個(gè)部件的品質(zhì)，而且主要取決于各部件之間的相互協(xié)調(diào)，這種相互協(xié)調(diào)是通過(guò)總體設(shè)計(jì)實(shí)現(xiàn)的，所以裝載機(jī)的總體設(shè)計(jì)對(duì)它的整機(jī)性能起決定性作用?？傮w設(shè)計(jì)的內(nèi)容包括裝載機(jī)總體參數(shù)的確定、裝載機(jī)的總體布置等。這個(gè)過(guò)程要對(duì)裝載機(jī)的整體形狀，各部件形狀大小及位置布置等有個(gè)清晰的把握，力求做到結(jié)構(gòu)合理，布置得當(dāng)?？傮w設(shè)計(jì)完后，先快速將底座畫出，將各部件如駕駛室等布置上去，完成底座。2）進(jìn)行工作裝置設(shè)計(jì)。裝載機(jī)工作裝置主要由鏟斗和支持鏟斗進(jìn)行裝載作業(yè)的連桿系統(tǒng)組成，依靠這套裝置裝載機(jī)可以對(duì)汽車、火車等進(jìn)行散料裝載作業(yè)，也可以對(duì)散料進(jìn)行短途運(yùn)輸作業(yè)，還可以進(jìn)行平地修路等作業(yè)。裝載機(jī)工作裝置的結(jié)構(gòu)和性能直接影響整機(jī)的工作尺寸和性能參數(shù)，因此，工作裝置的合理性直接影響裝載機(jī)的生產(chǎn)效率、工作負(fù)荷、動(dòng)力與運(yùn)動(dòng)特性、不同工況下的作業(yè)效果、工作循環(huán)的時(shí)間、外形尺寸和發(fā)動(dòng)機(jī)功率等。所設(shè)計(jì)的裝載機(jī)應(yīng)具有較強(qiáng)的工作能力，鏟斗插入料堆的阻力要小，在料堆中鏟掘的能力大，能耗低。工作機(jī)構(gòu)的各桿件受力狀態(tài)良好，強(qiáng)度壽命合理。結(jié)構(gòu)和工作尺寸適應(yīng)生產(chǎn)條件需要，效率高。結(jié)構(gòu)簡(jiǎn)單緊湊，制造及維修容易，操縱使用方便。同時(shí)，工作裝置設(shè)計(jì)是本次畢業(yè)設(shè)計(jì)的主要設(shè)計(jì)內(nèi)容，因此，必須花大力氣，下苦功夫，努力完成，達(dá)到設(shè)計(jì)目的要求。3）工作裝置的結(jié)構(gòu)分析。工作裝置設(shè)計(jì)完成之后，其工作是否合理，是否發(fā)生干涉，強(qiáng)度是否符合要求等等都需要檢驗(yàn)。因此，要對(duì)其進(jìn)行結(jié)構(gòu)分析。主要包括工作裝置靜力學(xué)計(jì)算及強(qiáng)度校合，工作裝置結(jié)構(gòu)動(dòng)力分析等。4）整機(jī)穩(wěn)定性驗(yàn)算。裝載機(jī)設(shè)計(jì)完成之后，應(yīng)對(duì)其穩(wěn)定性進(jìn)行驗(yàn)算。裝載機(jī)的穩(wěn)定性是指裝載機(jī)在行駛過(guò)程中，不發(fā)生傾履和側(cè)滑的能力。設(shè)計(jì)出來(lái)的裝載機(jī)應(yīng)保證其能工作穩(wěn)定。5、預(yù)期成果。設(shè)計(jì)的預(yù)期成果是設(shè)計(jì)出來(lái)的裝載機(jī)總體方案合理，工作安全可靠且能很好地完成任務(wù)要求。6、階段內(nèi)容及時(shí)間安排1）收集查閱資料：第 1 周；2）設(shè)計(jì)總體方案：第 2-3 周；3）完成底座圖：第 4 周；4）設(shè)計(jì)工作機(jī)構(gòu)：第 5-7 周；5）檢查完善底座及工作機(jī)構(gòu)設(shè)計(jì)：第 8 周；6）完成裝配圖及各零件圖，并進(jìn)行分析：第 9-10 周；7）查缺補(bǔ)漏，完善設(shè)計(jì)：第 11 周；8）完成整理畢業(yè)論文及日志：第 12 周；9）準(zhǔn)備答辯：第 13 周。7、設(shè)計(jì)條件此次畢業(yè)設(shè)計(jì)采用計(jì)算機(jī)繪圖，備有計(jì)算機(jī)一臺(tái)，相關(guān)三維設(shè)計(jì)及仿真軟件如 solidworks 等，并備有機(jī)械設(shè)計(jì)手冊(cè)、液壓手冊(cè)及輪式裝載機(jī)等參考資料。指導(dǎo)教師簽名： 日期：1、課題來(lái)源：課題來(lái)源分為結(jié)合實(shí)際課題和自擬課題兩種，結(jié)合實(shí)際課題中來(lái)源于科研課題的要填寫確切基金項(xiàng)目、企事業(yè)單位項(xiàng)目，不能寫橫向、縱向課題等。2、課題類型：A—工程設(shè)計(jì)；B—科學(xué)實(shí)驗(yàn)；C—軟件開發(fā)；D—理論研究；E—應(yīng)用研究。WHEEL LOADERSCoal International January/February 2001Copyright @ 2001. All right reserved.16WHEEL LOADERSWorkhorses of the industry，with larger units adding flexibility to surface coal mining operations and smaller machines invaluable in stock-pile work，rehandling and other tasks． The primary choices today for open pit coal and overburden excavation and loading are between electric cable shovels，hydraulic excavators and wheel loaders．Wheel loaders carry 18-21% of their operating weight as payload，compared with 5-7% for electric cable shovels and 8- 11%for hydraulic face shovels．By fitting the bucket close to the carrier，designers of wheel loaders create a very favorable payload-to-operating weight ratio，allowing mobility around a mine．With comparably sized buckets，an electric shovel will weigh something like four times as much as a wheel loader，while a hydraulic face shovel，might weigh about twice as much as a wheel loader for the equivalent bucket capacity．Electric shovels can be expected to routinely achieve economic lives of 75,000-100,000 hours，with documented long-term operating costs in the range of $ 0．060-0．095/tonne．Hydraulic shovels and wheel loaders are generally considered to have economic lives in the 30,000-60,000 hour range ．They work in a wide range of conditions so their long-term operating costs are in a broader range of $ 0．0080-0．140/tonne．It should be noted that these long-term comparisons assume that costs are spread over the entire economic lives of the machines．It should also be remembered that the purchase of wheel loaders and hydraulic shovels could generally be considered to be reversible decisions．At almost any point in their working lives，they can be fairly easily resold and moved without a severe cost penalty．The same is unlikely to be true of electric shovels．In practice，it is unlikely that a mines choice would be between a wheel loader and an electric shovel．A more likely decision would be to make the choice between hydraulic excavators and wheel loaders．Choosing between these two options can have significant effects on truck maintenance costs．For example，controlled dumping of material into the truck has a great influence．Dumping heavy boulders into an empty truck can cause damage．However ，a hydraulic excavator WHEEL LOADERSCoal International January/February 2001Copyright @ 2001. All right reserved.17equipped with a bottom dump bucket can ensure a certain amount of dampening of the fall of the material into the truck by opening the bucket only slightly so as to allow smaller rocks to fall first and form a 'buffer' for the larger，heavier boulders．Reach and dump heights also play a considerable role in truck repair costs．A machine with a long reach greatly reduces and even eliminates the risk damage to tyre walls． Furthermore the better suited the dump height of the loading tool is to the truck， the lower the risk of damage to the truck's side wall．In the case of the wheel loader， the use of high lift versions can compensate somewhat for this．However ，a wheel loader will always，essentially ，be nearer to the truck during the dump phase．Versatility and mobility are other important considerations．In one minute a cable shovel will travel about 21 meters， a hydraulic shovel about 37 meters and a wheel loader about 370 meters．Mobility is a key factor in choosing wheel loaders，especially with large new models capable of producing in the 3,000-3,500 tonne/hour，range，and more．Blending，multiple faces and shove1 backup are all functions that can be performed well due to the wheel loader's mobility．However，a drawback to the mobility advantage of the wheel loader is its need for relatively smooth，flat floors，to prolong tyre life and provide machine stability．However ，those smooth，flat floors in the loading area are needed anyway，unless the mine is prepared to pay severely for damage to expensive truck tyres as they roll onto the loading area．The method of digging is different for all three machines．Because the cutting edge does not change angle on an electric cable shovel bucket，loading is accomplished by raking the face in a long sweeping arc rather than biting into it by combining boom，stick and bucket forces (as with hydraulic excavators)，or by combining power train，bucket crowd and rack back forces (as with wheel loaders)．A hydraulic shovel is considered a selective excavating tool and a wheel loader is considered a loading tool．This is because，due to geometry，a hydraulic excavator can apply its breakout force over its reach of the face，while a wheel loader’s best digging occurs low--from the toe of the face to about the height of the loader's bucket．Wheel loaders can get the best bucket fill factors in production rock face conditions，if used properly．Both they and hydraulic backhoes should achieve 100% (more with some wheel loaders)，compared with 90-100% for electric shovels and 80-85% for hydraulic face shovels．WHEEL LOADERSCoal International January/February 2001Copyright @ 2001. All right reserved.18A survey in the 1990s undertaken by Caterpillar of midsize wheel loaders provided an interesting insight into the factors involved in machine purchase decisions．The considerations brought into play，in descending order of priority were:● Performs tasks well● Can trust to run● ．Easy to operate● Easy to maintain● Lasts long time● Operator comfort● Competitive price● Repair cost low● Versatility● Good resale value● Fuel consumption● Easily transported● Design appearance Today，with fuel costs rising，we might expect to see fuel consumption having a higher priority ．The operating conditions that favor the selection of wheel loaders include．● Mobility● Versatility● Low pile profile● Smooth floorWHEEL LOADERSCoal International January/February 2001Copyright @ 2001. All right reserved.19● Level floor● Load-and-carry● Shop maintenanceWhy wheel loaders？In summary then，if wheel loaders have been selected as the primary loading tools， each unit should be capable of loading a truck in three to four passes．The cycle time per pass should be between 30 and 35 seconds．The loader should also achieve a 75-85% bucket fill factor in a single pass when loading blasted rock and 100% or more in rock-dirt mixtures．The ability of the chosen machine to achieve these performance criteria will be influenced by the loader's performance features and it is important to check that the machine has a high full-turn static top load capability，a high breakout force and fast hydraulic cycle times．The dump height clearance and forward reach of the loader should be compared with the truck side board height and body width．Wheel loaders are very mobile and are ideally suited to applications that demand selective mining and require the loader and haul trucks to move between various loading sites．It should，however ，be borne in mind that the loader tyres can become a high cost item and care should be taken to protect these as far as possible．However ，wheel loaders can provide their own clean-up support in the loading area，where required．The big onesHigh capacity wheel loaders are not new to the industry，LeTourneau has pioneered such machines for many years．As far back as 1982，at the Las Vegas American Mining Congress，Marathon launched its L-1000 diesel-powered and TCL-1000 training cable wheel loaders; both equipped with 13 cubic meter buckets as standard Clark Michigan，now part of the Volvo Construction Equipment group， also offered a large capacity wheel loader many years ago．More recently，both Caterpillar and Komatsu have launched monster units．LeTourneau is the specialist，offering all-wheel; electric drive wheel loaders based on concepts initially explored by founder R．G．LeTourneau back in 1923．The technology has been proven since 1950 and refinements since have included traction proportioning WHEEL LOADERSCoal International January/February 2001Copyright @ 2001. All right reserved.20that minimizes wheel slip and tyre wear by allocating power to the wheels that grip．The company claims still to be the only manufacturer of wheel loaders offering all-wheel drive，which，LeTourneau reports， “improves stability and increases operator comfort”．If LeTourneau has long been the major proponent of the large wheel loader，it was perhaps a Caterpillar development that got such machines widely accepted．A major milestone and a catalyst that led to much more widespread use of large wheel loaders was Caterpillar’s launch of the 994 back in late 1990．That was also a significant milestone in Cat’s programme of development of large mining machines which has seen the company take the mining world by storm，particularly in large trucks．Caterpillar has certainly proved that the mining industry is interested in large wheel loaders．Its first 994 went into operation at the Cyprus Sierrita open-pit copper mine in Arizona in November 1992，over 50 such units had been sold，and the first 12 had logged over 100000 operating hours．Announcing this at the Las Vegas American Mining Congress in1992，the manager of Caterpillar’s Mining Vehicle center，Don Hopkins，admitted that this volume of sales was higher than expected．That first 994 was a high-lift model equipped with a 16 cubic meters bucket，though buckets up to 31 cubic meters wear available depending on application． The 994 was then the largest mechanical drive wheel loader available in the world．The largest electric drive machine was a LeTourneau，as it is today．But today，the largest mechanical drive honor goes to Komatsu with the WA1200-3．Traditionally the much greater mobility of wheel loaders allows their use in secondary loading applications in very large open pits．They are also widely used in smaller operations such as eastern US coal mines and medium to smaller gold mines．But the large wheel loader has really taken off and a growing number of these machines are being put to heavy-duty loading requirements，especially in North America，Australia and selective markets in Latin America and elsewhere．The smaller units with bucket capacities of 10 to15 cubic meters are used only with the smaller truck sizes，but Komatau’s WA1200， Cat’s 994 and the bigger LeTourneaus can be matched with all but the very largest trucks．There are still only a few big mines that rely on these bigger wheel loaders completely． However，several hundred such machines are now working alongside，or in place of ， electric and hydraulic shovels．WHEEL LOADERSCoal International January/February 2001Copyright @ 2001. All right reserved.21By the time Caterpillar had achieved sales of well over 220 994s around the world， representing around 60% of all large wheel loader sales，it released the 994D．Significant among the technology updates were Cat’s Steering and Transmission Integrated Control (STIC) system that combines gear selection and steering into one control lever that requires less effort and makes shifting smoother．Caterpillar reports that this allows up to 10% greater productivity．A number of older machines were retrofitted before the 994 launch and displayed anything from 7 to 12% greater productivity in field trials．Retrofits are available for all 994s already operating．The rim pull control with new left-pedal operation also is important．This allows the operator to match rim pull to conditions for improved tyre life，loadability and increased control．Operator comfort is becoming more and more important．In the 994D，the new seven-way Contour Series air-suspension seat lets the operator adjust his or her seat to precisely the right position，optimizing movements and experiencing less fatigue over the shift．The 994D’s payload has been increased to 34．5 tonne for standard models and 31 tonne for the high-lift arrangement．Bucket capacities can be 14 to 31 cubic meters． The 994D should load 2800-3000 tonnes per hour and achieve a tyre life of 5000-6000 hours．LeTourneau’s monsters LeTourneau’s designers have been busy recently．First the company announced the L-1350 loader in 1999，with deliveries beginning in 2000，and then at MINExpo in Las Vegas last October，LeTourneau exhibited the monster L-2350．The 1120KW L-1350 has a 20cubic meter bucket capacity，6．6 meter lift height，and 2．9 meter reach．It rides on 49/75-51 tyres and has been specifically designed to minimize loading costs for 136 to 181 tonne capacity trucks and has the capability to load many of the 218 tonne capacity units．Many of the major components incorporated on the loader have already been field proven on the other LeTourneau loader models．At the time of its launch，LeTourneau said the introduction of the L-1350 would strengthen its position “as the market leader in high-performance，cost effective front-end loaders． ”The new 1715 kW LeTourneau L-2350 wheel loader，with a standard 40．5 cubic meter bucket capacity，a 7．3 meter lift height and 3．8 meter reach，is now，clearly ，the world’s largest wheel loader．The L-2350，like the L-1350，is WHEEL LOADERSCoal International January/February 2001Copyright @ 2001. All right reserved.22controlled and monitored by the LeTourneau Integrated Network Control System (LINCS)，which provides the most intelligent computerization available，LeTouneau claims．The information it provides includes bucket weights，cycle times，preventative maintenance data，self-diagnostics and more．LINCS manages all loader systems (including hydraulics，electrics，traction drive and engine) through the interactions of the Master System Manager (MCM) and multiple Remote Control Modules (RCMs)．The MCM combines ruggedised industrial hardware with a Pentium class microprocessor to direct the entire system from the cab．The RCMs are distributed around the machine providing the MCM with the hands and eyes needed to control and monitor the machine．The MCM is located in the cab of the loader．It has more than 350 input/output points and the ability to store more than a month’s worth of operating and production data．The RCMs use a high-speed 30-bit processor and connect directly to sensors，drive outputs and operator controls．They are housed in environmentally sealed enclosures，designed to withstand high-pressure hot water washes and drenching in any vehicle fluids．Other features include reliable gold-to-gold connections and short circuit and reverse polarity immunity．These EMC tested modules automatically programme themselves to the needs of the location．Thus they operate on a quick pull-out/plug-in procedure．Among the advances is that the second reduction gear is centre-hung between two bearings with a splined interface between this gear and the middle pinion．This design change results in more equal load share between the middle pinion and the three reduction counter-shaft gears．Better load share results in lower shaft and gear stress at the third and fourth reductions．The splined interface enables the middle pinion to be removed so that the loader can continue to run if a motor is disabled．In addition，the middle pinion can be replaced if the other driver gearing is in good condition．Both operations can be accomplished without removing the driver from the machine LeTourneau’s proven taper lock design and a unique timing method further ensure equal load share．The driver ratio minimizes the required motor torque while simultaneously minimizing the shock loads at the counter-shaft pinion．Before the L-2350，LeTourneau’s L-1800 was the largest wheel loader in the world， with a capacity of 454 tonne and able to centre-load trucks of 270 tonne capacity and larger．The L-1800 is offered with a 1342 or 1491 kW engine and，in WHEEL LOADERSCoal International January/February 2001Copyright @ 2001. All right reserved.23keeping with the trend to longer service intervals，its self-cleaning KLENZ air filtration system reduces maintenance costs and improves reliability．It can lift loads up to 50 tonne．Other features include full helical gearing in the final drive units and a cab designed for better operator comfort and visibility，enhanced by the machine’s sloped design which provides a superior rear view．There is an L-1800 at work at Triton Coal’s North Rochelle coal mine in Wyoming’s Powder River Basin (the proving ground for so many of today’s largest earthmovers) in the early stages of North Rochelle’s development (opened in December 1998)． Its narrow pits required manoeuvrability and this was ably supplied by the L-1800 with its 13．4 meter turning radius in high-lift configuration． Mobility is one of the reasons the mine purchased this loader．The other was capacity． Bucket capacities can be up to 42 cubic meters for coal mining and North Rochelle chose a 34-cubic-meter combo bucket to load both coal and overburden． Its 7．3-meter dump clearance allows it to load 218 tonne capacity trucks with ease．The world’s biggest mechanical drive loader today，Komatsu’s WA1200-3，is powered by Komatsu’s SDA16V160 electric-controlled engine．Its standard 16．3 cubic meter bucket will load 216 tonne trucks in just six passes．Its modulated clutch system offers adjustable travel speed，traction control and tyre specification settings for multiple applications．The Precise Dial Control of Travel Speed setting offers the operator variable travel speeds for tight ‘V’ cycles decreasing cycle times and increasing digging capabilities and tyre life．The Traction Control setting features a traction power selection of 20 to 100% to accommodate various application conditions．The Tire Saver setting controls tyre slip，preventing wear and prolonging tyre life．The WA1200-3 features the Remote Boom Positioner．This allows the operator to set maximum and minimum bucket positions， promoting smooth component movement and preventing spillage．The Variable Output Hydraulic System(VOHS) is a self-adjusting hydraulic system that reduces oil consumption and increases tractive effort and saves fuel．In addition，a new 65/65-67-62PR ultra-wide tyre with additional rubber on the ground and increased air volume is now available．As any good earthmover today，the WA1200-3 is designed for easy maintenance and service． To minimize maintenance and downtime the machine is equipped with a Vehicle Health Monitoring System (VHMS)，an integrated WHEEL LOADERSCoal International January/February 2001Copyright @ 2001. All right reserved.24maintenance system that employs self-contained diagnostics，a preventive maintenance scheduler and machine performance history．Caterpillar brought about a radical change in wheel loader design in 1997 when it launched the 992G．The 992 wheel loader has long been a workhorse of the mining industry，and widely used in stockpiling．The 992G began an innovative concept，the cast box section boom，the first major change in wheel loader design in about 20 years．This increases dump clearance， improves bucket visibility and requires no maintenance． It also offers three times the tortional strength of a traditional design，according to Caterpillar．Compared with previous models，Caterpillar reports a 15-20% increase in productivity from the 597 kw 992G，payload raised by 7%，and cycle times cut by 10%． Cab sound levels have been reduced and daily service costs cut by about 20%． This 91.8 toone unit can be equipped with 11.5 to 12.3-cubic-meter buckets and features a dump heignt of just over 4.6 meters and a reach of 2.3 meters．It will four-pass load a 90 toone payload 777D truck (around 2000 toones/hour) in the high reach version．Caterpillar’s testing of the machine showed that in truck loading it is 43% more productive than the 992C in coal operations．