0005-10t橋式起重機(jī)總體設(shè)計(jì)
0005-10t橋式起重機(jī)總體設(shè)計(jì),10,橋式起重機(jī),總體,整體,設(shè)計(jì)
本科畢業(yè)設(shè)計(jì)（論文）開(kāi)題報(bào)告
題目名稱
10t橋式起重機(jī)總體設(shè)計(jì)
學(xué)生姓名
學(xué)號(hào)
一、選題的目的和意義：
起重機(jī)是現(xiàn)代工業(yè)在實(shí)現(xiàn)出產(chǎn)過(guò)程機(jī)械化、自己主動(dòng)化，改善物料搬運(yùn)前提，提高勞動(dòng)出產(chǎn)率必不可少的重要機(jī)械設(shè)備。它對(duì)于發(fā)展國(guó)民經(jīng)濟(jì)，改善人們的事物、文化生活的需要都起著重要的作用。隨著經(jīng)濟(jì)建設(shè)的迅速發(fā)展，機(jī)械化、自己主動(dòng)化程度也在不停提高，與此相適應(yīng)的起重機(jī)技能也在高速發(fā)展，產(chǎn)物種類不停增加，使用規(guī)模越來(lái)越廣。一些企業(yè)由于沒(méi)有起重機(jī)械，不僅工作效率低，勞動(dòng)強(qiáng)度大，甚至難以工作。高層建筑的施工，上萬(wàn)噸級(jí)或幾十萬(wàn)噸級(jí)的大型船只的建造，火箭和導(dǎo)彈的發(fā)射，大型電站的施工和安裝，大重件的裝卸與搬運(yùn)等，都離不開(kāi)起重機(jī)的作業(yè)。
通過(guò)畢業(yè)設(shè)計(jì)，能從各個(gè)方面綜合考查大學(xué)四年所學(xué)過(guò)的專業(yè)知識(shí)。能代表機(jī)械選型設(shè)計(jì)的一般過(guò)程?？梢蚤_(kāi)闊視野，提高我們的解決問(wèn)題和分析問(wèn)題的能力，以及提高綜合運(yùn)用理論知識(shí)的能力；通過(guò)此次畢業(yè)設(shè)計(jì)，更能激發(fā)學(xué)習(xí)和探索問(wèn)題的興趣，為未來(lái)的學(xué)習(xí)和工作打下良好的基礎(chǔ)；通過(guò)此次的畢業(yè)設(shè)計(jì)，我們可以把學(xué)過(guò)的課本知識(shí)在設(shè)計(jì)工作中綜合地加以應(yīng)用，使這些知識(shí)得到鞏固和發(fā)展；通過(guò)畢業(yè)設(shè)計(jì)，能夠初步培養(yǎng)我們對(duì)機(jī)械設(shè)計(jì)的獨(dú)立工作能力，為以后進(jìn)行設(shè)計(jì)工作打下良好的基礎(chǔ)；通過(guò)畢業(yè)設(shè)計(jì)，我們能夠熟練應(yīng)用有關(guān)參考資料、計(jì)算圖表、手冊(cè)；熟悉有關(guān)的國(guó)家標(biāo)準(zhǔn)和部頒標(biāo)準(zhǔn)，以完成一個(gè)工程技術(shù)人員在機(jī)械設(shè)計(jì)方面所必須具備的基本技能訓(xùn)練。
二、國(guó)內(nèi)外研究綜述：
目前，在工程起重機(jī)械領(lǐng)域，歐洲、美國(guó)和日本處于領(lǐng)先地位。歐洲作為工程起重機(jī)的發(fā)源地，輪式起重機(jī)生產(chǎn)技術(shù)水平最高。該地區(qū)的工程起重機(jī)械業(yè)主要生產(chǎn)全地面起重機(jī)、履帶式起重機(jī)和緊湊型輪胎起重機(jī)，也生產(chǎn)少量汽車起重機(jī)。其中，全路面起重機(jī)、履帶起重機(jī)以中大噸位為主；緊湊型輪胎起重機(jī)則以小噸位為主；汽車起重機(jī)一般為通用底盤(pán)組裝全地面上車，即以改裝為主。國(guó)外專業(yè)生產(chǎn)大型起重機(jī)廠家很多。其中利勃海爾、特雷克斯-德馬格、馬尼托瓦克與神鋼等公司產(chǎn)品系列較全， 市場(chǎng)占有率較高。利勃海爾公司的產(chǎn)品技術(shù)先進(jìn)、工作可靠，其生產(chǎn)的LR系列履帶起重機(jī)最大起重量已達(dá)1200t。其桁架臂履帶式起重機(jī)系列在2007年又喜添新品LR1600/2，使其產(chǎn)品型譜更加完善。
國(guó)內(nèi)專業(yè)生產(chǎn)大型起重機(jī)的也廠家很多。其中以中聯(lián)重科、三一重工、撫挖等公司產(chǎn)品系列較全，市場(chǎng)占有率較高。中聯(lián)重科在2007年12月宣布實(shí)行品牌統(tǒng)一戰(zhàn)略后?，F(xiàn)已成功開(kāi)發(fā)了50t~600t履帶式起重機(jī)產(chǎn)品系列。作為中國(guó)起重機(jī)行業(yè)的領(lǐng)跑者，徐州重型機(jī)械有限公司現(xiàn)在已經(jīng)形成了以汽車起重機(jī)為主導(dǎo)，履帶式起重機(jī)和全路面起重機(jī)為側(cè)翼強(qiáng)勢(shì)推進(jìn)的龐大型譜群。國(guó)內(nèi)最具歷史的履帶式起重機(jī)生產(chǎn)企業(yè)撫挖現(xiàn)已擁有35t~350t的履帶式起重機(jī)產(chǎn)品系列。QUY350是撫挖2007年推出的國(guó)產(chǎn)首臺(tái)350t履帶式起重機(jī)，填補(bǔ)了國(guó)內(nèi)350t履帶式起重機(jī)的產(chǎn)品型譜空白。
三、畢業(yè)設(shè)計(jì)（論文）所用的主要技術(shù)與方法：
所用技術(shù)：在這次設(shè)計(jì)中將采用機(jī)械圖形設(shè)計(jì)軟件AutoCAD2007 進(jìn)行繪圖，并參考相關(guān)設(shè)計(jì)和專業(yè)書(shū)籍，進(jìn)行設(shè)計(jì)。
方法：首先對(duì)產(chǎn)品進(jìn)行總體設(shè)計(jì)，確定系統(tǒng)的要求，選擇工作原理；其次，計(jì)算和確定主要尺寸，繪制部件裝配圖和總圖；最后，繪制全部零件工作圖，編寫(xiě)說(shuō)明書(shū)。如果設(shè)計(jì)的過(guò)程中如果發(fā)現(xiàn)遺漏我還會(huì)及時(shí)補(bǔ)充上去。
四、主要參考文獻(xiàn)與資料獲得情況
[1] 《起重機(jī)設(shè)計(jì)手冊(cè)》 起重機(jī)設(shè)計(jì)手冊(cè) 編寫(xiě)組，機(jī)械工業(yè)出版社，1980
[2] 《機(jī)械設(shè)計(jì)師手冊(cè)》 吳宗澤主編，機(jī)械工業(yè)出版社，2002
[3] 《起重機(jī)課程設(shè)計(jì)》 北京鋼鐵學(xué)院編，冶金工業(yè)出版社，1982
[4] 《焊接手冊(cè)》 中國(guó)機(jī)械工程學(xué)會(huì)焊接學(xué)會(huì)編，機(jī)械工業(yè)出版社，1992
[5] 《起重運(yùn)輸機(jī)械》 張質(zhì)文 劉全德中國(guó)鐵道出版社 1983年
[6] 《最新國(guó)內(nèi)外起重機(jī)械實(shí)用技術(shù)性能手冊(cè)》 田復(fù)興 中國(guó)水利水電出版社，2004年
五、畢業(yè)設(shè)計(jì)（論文）進(jìn)度安排（按周說(shuō)明）
1）6～8周：生產(chǎn)實(shí)習(xí)、期間還收集部分資料。
2）9～10周：寫(xiě)開(kāi)題報(bào)告，進(jìn)行畢業(yè)設(shè)計(jì)的基本計(jì)算。
3）11～13周：排版整理畢業(yè)設(shè)計(jì)說(shuō)明書(shū)和用CAD軟件進(jìn)行繪圖。
4）14～15周：對(duì)畢業(yè)設(shè)計(jì)進(jìn)行修改、完善，準(zhǔn)備答辯。
六、指導(dǎo)教師審批意見(jiàn)（對(duì)選題的可行性、研究方法、進(jìn)度安排作出評(píng)價(jià)，對(duì)是否開(kāi)題作出決定）：
指導(dǎo)教師： （簽名）
年 月 日
摘 要
本次畢業(yè)設(shè)計(jì)是針對(duì)畢業(yè)實(shí)習(xí)中橋式起重機(jī)所做的具體到噸位級(jí)別的設(shè)計(jì)。我國(guó)現(xiàn)在應(yīng)用的各大起重機(jī)還是仿造國(guó)外落后技術(shù)制造出來(lái)的，而且已經(jīng)在工廠內(nèi)應(yīng)用了多年，有些甚至還是七八十年代的產(chǎn)品，無(wú)論在質(zhì)量上還是在功能上都滿足不了日益增長(zhǎng)的工業(yè)需求。如何設(shè)計(jì)使其成本最低化，布置合理化，功能現(xiàn)代化是我們研究的課題。本次設(shè)計(jì)就是對(duì)小噸位的橋式起重機(jī)進(jìn)行設(shè)計(jì)，主要設(shè)計(jì)內(nèi)容是10t橋式起重機(jī)的結(jié)構(gòu)及運(yùn)行機(jī)構(gòu)，其中包括橋架結(jié)構(gòu)的布置計(jì)算及校核，主梁結(jié)構(gòu)的計(jì)算及校核，端梁結(jié)構(gòu)的計(jì)算及校核，主端梁連接以及大車運(yùn)行機(jī)構(gòu)零部件的選擇及校核包括: 輪壓計(jì)算及強(qiáng)度驗(yàn)算, 運(yùn)行阻力計(jì)算,選擇電動(dòng)機(jī),減速器的選擇驗(yàn)算,運(yùn)行速度及實(shí)際功率,選擇制動(dòng)器,選擇聯(lián)軸器,低速浮動(dòng)軸的驗(yàn)算,緩沖器的選擇等計(jì)算。還有小車的運(yùn)行和起升機(jī)構(gòu)零部件的選擇及校核包括: 運(yùn)行阻力計(jì)算，選電動(dòng)機(jī)，選擇減速器驗(yàn)算起動(dòng)時(shí)間，按起動(dòng)工況校核減速器功率，選擇制動(dòng)器，選擇高速軸聯(lián)軸器及制動(dòng)輪，驗(yàn)算低速浮動(dòng)軸強(qiáng)度，鋼絲繩的選擇，滑輪、卷筒的計(jì)算，聯(lián)軸器的選擇。
關(guān)鍵詞: 起重機(jī)；大車運(yùn)行機(jī)構(gòu)；小車運(yùn)行結(jié)構(gòu)；小車起升結(jié)構(gòu)；橋架 ；主端梁 。
Abstract
The graduation design is aimed at the graduation fieldwork medium-sized crane do specific to tonnage level of design. Our country is the application of the big crane or counterfeit foreign backward technology out of manufacture and has within the plant for many years, some even application or the 70s and 80s products, both in quality and in on the function can't satisfy the growing industrial demand. How to design makes it the lowest cost, decorate rationalization, functional modernization is our topic. This design is on small tonnage design of bridge crane, the main design content is 10t bridge crane structure and operation organization, including bridge structure arrangement calculation and checking the structure of the girder, the calculation and checking, calculated and checked the beam structure, the main girders connection and cart mechanism parts selection and checking including: wheel pressure calculation and intensity checking, running friction calculation, the choice of motor, gear reducer is checked, choose speed and actual power, choose brakes, choose coupling calculating speed floating axis, buffer choice calculation, etc. And car running and lifting mechanism parts selection and checking including: running friction calculation, choose motor, choose reducer, by starting checked start-up time check reducer power, choose working brakes, choose high-speed couplings and brake wheel, the checking low-speed axial intensity, the wire rope floating choice, pulley, drum calculation, coupling choice.
Keywords: cranes; During operation organization; Car running structure; Car hoisting structure; Bridge; Main girders.
該方案是10t橋式起重機(jī)總體設(shè)計(jì)，橋式起重機(jī)是橫架于車間和料場(chǎng)上空進(jìn)行物料調(diào)運(yùn)的起重設(shè)備。由于它
兩端坐落在高大的水泥柱或金屬架上，形狀似橋，所以俗稱“天車”。橋式起重機(jī)是現(xiàn)代工業(yè)和起重運(yùn)輸中實(shí)
現(xiàn)生產(chǎn)過(guò)程機(jī)械化、自動(dòng)化的重要工具與設(shè)備，可減輕操作者的勞動(dòng)強(qiáng)度，可大大提高生產(chǎn)率。橋式起重機(jī)在
工礦企業(yè)、鋼鐵化工、鐵 路交通、港口碼頭以及物流周轉(zhuǎn)等部門(mén)和場(chǎng)所應(yīng)用的最為廣泛，是人們生產(chǎn)生活不
可或缺的一種設(shè)備。
對(duì)于起重量大、跨距大的起重設(shè)備多采用箱型 式，箱型 橋式起重機(jī) 一 由兩 箱型 和兩 橫
端 的 橋架，在橋架上運(yùn)行 車，可起 和水 運(yùn) 物 。它 用于機(jī)械 工和 車間、
和料場(chǎng)等場(chǎng)所。 箱型 具 工 、工 、通用 及 方 等 ?，￠￡在生產(chǎn)中
廣泛?用。
河南理工大學(xué)萬(wàn)方科技學(xué)院
本科畢業(yè)設(shè)計(jì)（論文）中期檢查表
指導(dǎo)教師： 張 燕 職稱： 副教授
所在院（系）： 機(jī)械與動(dòng)力工程系 教研室（研究室）： 機(jī)械樓團(tuán)委108
題 目
10t橋式起重機(jī)總體設(shè)計(jì)
學(xué)生姓名
鄭子亮
專業(yè)班級(jí)
07機(jī)制二班
學(xué)號(hào)
0720150147
一、選題質(zhì)量：（主要從以下四個(gè)方面填寫(xiě)：1、選題是否符合專業(yè)培養(yǎng)目標(biāo)，能否體現(xiàn)綜合訓(xùn)練要求；2、題目難易程度；3、題目工作量；4、題目與生產(chǎn)、科研、經(jīng)濟(jì)、社會(huì)、文化及實(shí)驗(yàn)室建設(shè)等實(shí)際的結(jié)合程度）
1、本題目符合機(jī)械設(shè)計(jì)專業(yè)的培養(yǎng)目標(biāo)，能夠充分鍛煉和培養(yǎng)分析問(wèn)題和實(shí)際操作能力，能夠體現(xiàn)綜合訓(xùn)練的要求；
2、本題目難易適中，符合本科畢業(yè)設(shè)計(jì)要求；
3、本題目工作量適中，能在規(guī)定的時(shí)間內(nèi)完成；
4、所選題目10t橋式起重機(jī)總體的設(shè)計(jì)與實(shí)際貼合比較緊密，在實(shí)際的應(yīng)用中比較廣泛。在設(shè)計(jì)過(guò)程中，對(duì)機(jī)器的零件的設(shè)計(jì)和計(jì)算對(duì)我來(lái)說(shuō)是以往所學(xué)知識(shí)的總結(jié)和應(yīng)用，所以能夠滿足綜合訓(xùn)練的要求
二、開(kāi)題報(bào)告完成情況：
根據(jù)自己在各方面資料的收集和整理，通過(guò)對(duì)可行性的分析，結(jié)合老師給的題目的選擇，我完成了這次設(shè)計(jì)的選題。在選題結(jié)束之后，通過(guò)自己認(rèn)真查閱相關(guān)的資料，最后結(jié)合本身的實(shí)際情況和設(shè)計(jì)的時(shí)間任務(wù)完成了開(kāi)題報(bào)告。
三、階段性成果：
1、通過(guò)對(duì)10t橋式起重機(jī)的了解，再加上老師對(duì)我們的講解，算是對(duì)10t橋式起重機(jī)有了一個(gè)大概的了解。前期階段主要是對(duì)有關(guān)于10t橋式起重機(jī)的各方面的文獻(xiàn)和資料進(jìn)行搜集，為設(shè)計(jì)以后的設(shè)計(jì)做了必要的準(zhǔn)備。
2、中期階段主要是依據(jù)參考資料，從上面找到一些關(guān)于關(guān)于10t橋式起重機(jī)的信息，首先對(duì)其零部件有了大致的了解，其次是已有了大概的設(shè)計(jì)方法，并開(kāi)始了一些基本的結(jié)構(gòu)設(shè)計(jì)。
3、正在進(jìn)行裝配圖的CAD畫(huà)圖和設(shè)計(jì)說(shuō)明書(shū)。
四、存在主要問(wèn)題：
由于這是我第一次單獨(dú)進(jìn)行10t橋式起重機(jī)總體設(shè)計(jì)，所以剛開(kāi)始進(jìn)展的并不是很順利。而我對(duì)這方面的知識(shí)掌握比較少，所以需要在圖書(shū)館和網(wǎng)上查找更多的相關(guān)資料，對(duì)有關(guān)起重機(jī)的知識(shí)進(jìn)行更深入的了解。不過(guò)我堅(jiān)信，只要自己努力和在指導(dǎo)老師的指引下，我能把各方面的問(wèn)題逐個(gè)擊破，最終順利完成畢業(yè)設(shè)計(jì)。
五、指導(dǎo)教師對(duì)學(xué)生在畢業(yè)實(shí)習(xí)中，勞動(dòng)、學(xué)習(xí)紀(jì)律及畢業(yè)設(shè)計(jì)（論文）進(jìn)展等方面的評(píng)語(yǔ)
指導(dǎo)教師： （簽名）
年 月 日
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河南理工大學(xué)萬(wàn)方科技學(xué)院本科畢業(yè)論文
The Use and History of Crane
Every time we see a crane in action we remains without words, these machines are sometimes really huge, taking up tons of material hundreds of meters in height. We watch with amazement and a bit of terror, thinking about what would happen if the load comes off or if the movement of the crane was wrong. It is a really fascinating system, surprising both adults and children. These are especially tower cranes, but in reality there are plenty of types and they are in use for centuries. The cranes are formed by one or more machines used to create a mechanical advantage and thus move large loads. Cranes are equipped with a winder, a wire rope or chain and sheaves that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human. Cranes are commonly employed in the transport industry for the loading and unloading of freight, in the construction industry for the movement of materials and in the manufacturing industry for the assembling of heavy equipment.
1. Overview
The first construction cranes were invented by the Ancient Greeks and were powered by men or beasts of burden, such as donkeys. These cranes were used for the construction of tall buildings. Larger cranes were later developed, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbor cranes were introduced to load and unload ships and assist with their construction – some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron and steel took over with the coming of the Industrial Revolution.
For many centuries, power was supplied by the physical exertion of men or animals, although hoists in watermills and windmills could be driven by the harnessed natural power. The first 'mechanical' power was provided by steam engines, the earliest steam crane being introduced in the 18th or 19th century, with many remaining in use well into the late 20th century. Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilized where the provision of power would be uneconomic.
Cranes exist in an enormous variety of forms – each tailored to a specific use. Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing high buildings. For a while, mini - cranes are also used for constructing high buildings, in order to facilitate constructions by reaching tight spaces. Finally, we can find larger floating cranes, generally used to build oil rigs and salvage sunken ships. This article also covers lifting machines that do not strictly fit the above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes.
2. History
Ancient Greece
The crane for lifting heavy loads was invented by the Ancient Greeks in the late 6th century BC. The archaeological record shows that no later than c.515 BC distinctive cuttings for both lifting tongs and lewis irons begin to appear on stone blocks of Greek temples. Since these holes point at the use of a lifting device, and since they are to be found either above the center of gravity of the block, or in pairs equidistant from a point over the center of gravity, they are regarded by archaeologists as the positive evidence required for the existence of the crane.
The introduction of the winch and pulley hoist soon lead to a widespread replacement of ramps as the main means of vertical motion. For the next two hundred years, Greek building sites witnessed a sharp drop in the weights handled, as the new lifting technique made the use of several smaller stones more practical than of fewer larger ones. In contrast to the archaic period with its tendency to ever-increasing block sizes, Greek temples of the classical age like the Parthenon invariably featured stone blocks weighing less than 15-20 tons. Also, the practice of erecting large monolithic columns was practically abandoned in favor of using several column drums.
Although the exact circumstances of the shift from the ramp to the crane technology remain unclear, it has been argued that the volatile social and political conditions of Greece were more suitable to the employment of small, professional construction teams than of large bodies of unskilled labor, making the crane more preferable to the Greek polis than the more labor-intensive ramp which had been the norm in the autocratic societies of Egypt or Assyria.
The first unequivocal literary evidence for the existence of the compound pulley system appears in the Mechanical Problems (Mech. 18, 853a32-853b13) attributed to Aristotle (384-322 BC), but perhaps composed at a slightly later date. Around the same time, block sizes at Greek temples began to match their archaic predecessors again, indicating that the more sophisticated compound pulley must have found its way to Greek construction sites by then.
Ancient Rome
The heyday of the crane in ancient times came during the Roman Empire, when construction activity soared and buildings reached enormous dimensions. The Romans adopted the Greek crane and developed it further. We are relatively well informed about their lifting techniques, thanks to rather lengthy accounts by the engineers Vitruvius (De Architectura 10.2, 1-10) and Heron of Alexandria (Mechanica 3.2-5). There are also two surviving reliefs of Roman treadwheel cranes, with the Haterii tombstone from the late first century AD being particularly detailed.
The simplest Roman crane, the Trispastos, consisted of a single-beam jib, a winch, a rope, and a block containing three pulleys. Having thus a mechanical advantage of 3:1, it has been calculated that a single man working the winch could raise 150 kg (3 pulleys x 50 kg = 150), assuming that 50 kg represent the maximum effort a man can exert over a longer time period. Heavier crane types featured five pulleys (Pentaspastos) or, in case of the largest one, a set of three by five pulleys (Polyspastos) and came with two, three or four masts, depending on the maximum load. The Polyspastos, when worked by four men at both sides of the winch, could already lift 3000 kg (3 ropes x 5 pulleys x 4 men x 50 kg = 3000 kg). In case the winch was replaced by a treadwheel, the maximum load even doubled to 6000 kg at only half the crew, since the treadwheel possesses a much bigger mechanical advantage due to its larger diameter. This meant that, in comparison to the construction of the Egyptian Pyramids, where about 50 men were needed to move a 2.5 ton stone block up the ramp (50 kg per person), the lifting capability of the Roman Polyspastos proved to be 60 times higher (3000 kg per person).
However, numerous extant Roman buildings which feature much heavier stone blocks than those handled by the Polyspastos indicate that the overall lifting capability of the Romans went far beyond that of any single crane. At the temple of Jupiter at Baalbek, for instance, the architrave blocks weigh up to 60 tons each, and one corner cornice block even over 100 tons, all of them raised to a height of about 19 m. In Rome, the capital block of Trajan's Column weighs 53.3 tons, which had to be lifted to a height of about 34 m (see construction of Trajan's Column).
It is assumed that Roman engineers lifted these extraordinary weights by two measures (see picture below for comparable Renaissance technique): First, as suggested by Heron, a lifting tower was set up, whose four masts were arranged in the shape of a quadrangle with parallel sides, not unlike a siege tower, but with the column in the middle of the structure (Mechanica 3.5). Second, a multitude of capstans were placed on the ground around the tower, for, although having a lower leverage ratio than treadwheels, capstans could be set up in higher numbers and run by more men (and, moreover, by draught animals). This use of multiple capstans is also described by Ammianus Marcellinus (17.4.15) in connection with the lifting of the Lateranense obelisk in the Circus Maximus (ca. 357 AD). The maximum lifting capability of a single capstan can be established by the number of lewis iron holes bored into the monolith. In case of the Baalbek architrave blocks, which weigh between 55 and 60 tons, eight extant holes suggest an allowance of 7.5 ton per lewis iron, that is per capstan. Lifting such heavy weights in a concerted action required a great amount of coordination between the work groups applying the force to the capstans.
Middle Ages
During the High Middle Ages, the treadwheel crane was reintroduced on a large scale after the technology had fallen into disuse in western Europe with the demise of the Western Roman Empire. The earliest reference to a treadwheel (magna rota) reappears in archival literature in France about 1225, followed by an illuminated depiction in a manuscript of probably also French origin dating to 1240. In navigation, the earliest uses of harbor cranes are documented for Utrecht in 1244, Antwerp in 1263, Brugge in 1288 and Hamburg in 1291, while in England the treadwheel is not recorded before 1331.
Generally, vertical transport could be done more safely and inexpensively by cranes than by customary methods. Typical areas of application were harbors, mines, and, in particular, building sites where the treadwheel crane played a pivotal role in the construction of the lofty Gothic cathedrals. Nevertheless, both archival and pictorial sources of the time suggest that newly introduced machines like treadwheels or wheelbarrows did not completely replace more labor-intensive methods like ladders, hods and handbarrows. Rather, old and new machinery continued to coexist on medieval construction sites and harbors.
Apart from treadwheels, medieval depictions also show cranes to be powered manually by windlasses with radiating spokes, cranks and by the 15th century also by windlasses shaped like a ship's wheel. To smooth out irregularities of impulse and get over 'dead-spots' in the lifting process flywheels are known to be in use as early as 1123.
The exact process by which the treadwheel crane was reintroduced is not recorded, although its return to construction sites has undoubtedly to be viewed in close connection with the simultaneous rise of Gothic architecture. The reappearance of the treadwheel crane may have resulted from a technological development of the windlass from which the treadwheel structurally and mechanically evolved. Alternatively, the medieval treadwheel may represent a deliberate reinvention of its Roman counterpart drawn from Vitruvius' De architectura which was available in many monastic libraries. Its reintroduction may have been inspired, as well, by the observation of the labor-saving qualities of the waterwheel with which early treadwheels shared many structural similarities.
Structure and placement
The medieval treadwheel was a large wooden wheel turning around a central shaft with a treadway wide enough for two workers walking side by side. While the earlier 'compass-arm' wheel had spokes directly driven into the central shaft, the more advanced 'clasp-arm' type featured arms arranged as chords to the wheel rim, giving the possibility of using a thinner shaft and providing thus a greater mechanical advantage.
Contrary to a popularly held belief, cranes on medieval building sites were neither placed on the extremely lightweight scaffolding used at the time nor on the thin walls of the Gothic churches which were incapable of supporting the weight of both hoisting machine and load. Rather, cranes were placed in the initial stages of construction on the ground, often within the building. When a new floor was completed, and massive tie beams of the roof connected the walls, the crane was dismantled and reassembled on the roof beams from where it was moved from bay to bay during construction of the vaults. Thus, the crane ‘grew’ and ‘wandered’ with the building with the result that today all extant construction cranes in England are found in church towers above the vaulting and below the roof, where they remained after building construction for bringing material for repairs aloft.
Less frequently, medieval illuminations also show cranes mounted on the outside of walls with the stand of the machine secured to putlogs.
Mechanics and operation
In contrast to modern cranes, medieval cranes and hoists - much like their counterparts in Greece and Rome - were primarily capable of a vertical lift, and not used to move loads for a considerable distance horizontally as well. Accordingly, lifting work was organized at the workplace in a different way than today. In building construction, for example, it is assumed that the crane lifted the stone blocks either from the bottom directly into place, or from a place opposite the centre of the wall from where it could deliver the blocks for two teams working at each end of the wall. Additionally, the crane master who usually gave orders at the treadwheel workers from outside the crane was able to manipulate the movement laterally by a small rope attached to the load. Slewing cranes which allowed a rotation of the load and were thus particularly suited for dockside work appeared as early as 1340. While ashlar blocks were directly lifted by sling, lewis or devil's clamp (German Teufelskralle), other objects were placed before in containers like pallets, baskets, wooden boxes or barrels.
It is noteworthy that medieval cranes rarely featured ratchets or brakes to forestall the load from running backward. This curious absence is explained by the high friction force exercised by medieval treadwheels which normally prevented the wheel from accelerating beyond control.
Harbor usage
According to the "present state of knowledge" unknown in antiquity, stationary harbor cranes are considered a new development of the Middle Ages. The typical harbor crane was a pivoting structure equipped with double treadwheels. These cranes were placed docksides for the loading and unloading of cargo where they replaced or complemented older lifting methods like see-saws, winches and yards.
Two different types of harbor cranes can be identified with a varying geographical distribution: While gantry cranes which pivoted on a central vertical axle were commonly found at the Flemish and Dutch coastside, German sea and inland harbors typically featured tower cranes where the windlass and treadwheels were situated in a solid tower with only jib arm and roof rotating. Interestingly, dockside cranes were not adopted in the Mediterranean region and the highly developed Italian ports where authorities continued to rely on the more labor-intensive method of unloading goods by ramps beyond the Middle Ages.
Unlike construction cranes where the work speed was determined by the relatively slow progress of the masons, harbor cranes usually featured double treadwheels to speed up loading. The two treadwheels whose diameter is estimated to be 4 m or larger were attached to each side of the axle and rotated together. Today, according to one survey, fifteen treadwheel harbor cranes from pre-industrial times are still extant throughout Europe.[28] Beside these stationary cranes, floating cranes which could be flexibly deployed in the whole port basin came into use by the 14th century.
Renaissance
A lifting tower similar to that of the ancient Romans was used to great effect by the Renaissance architect Domenico Fontana in 1586 to relocate the 361 t heavy Vatican obelisk in Rome. From his report, it becomes obvious that the coordination of the lift between the various pulling teams required a considerable amount of concentration and discipline, since, if the force was not applied evenly, the excessive stress on the ropes would make them rupture.
Early modern age
Cranes were used domestically in the 17th and 18th century. The chimney or fireplace crane was used to swing pots and kettles over the fire and the height was adjusted by a trammel.
3. Mechanical principles
There are two major considerations in the design of cranes. The first is that the crane must be able to lift a load of a specified weight and the second is that the crane must remain stable and not topple over when the load is lifted and moved to another location.
Lifting capacity
Cranes illustrate the use of one or more simple machines to create mechanical advantage.
? The lever. A balance crane contains a horizontal beam (the lever) pivoted about a point called the fulcrum. The principle of the lever allows a heavy load attached to the shorter end of the beam to be lifted by a smaller force applied in the opposite direction to the longer end of the beam. The ratio of the load's weight to the applied force is equal to the ratio of the lengths of the longer arm and the shorter arm, and is called the mechanical advantage.
? The pulley. A jib crane contains a tilted strut (the jib) that supports a fixed pulley block. Cables are wrapped multiple times round the fixed block and round another block attached to the load. When the free end of the cable is pulled by hand or by a winding machine, the pulley system delivers a force to the load that is equal to the applied force multiplied by the number of lengths of cable passing between the two blocks. This number is the mechanical advantage.
? The hydraulic cylinder. This can be used directly to lift the load or indirectly to move the jib or beam that carries another lifting device.
Cranes, like all machines, obey the principle of conservation of energy. This means that the energy delivered to the load cannot exceed the energy put into the machine. For example, if a pulley system multiplies the applied force by ten, then the load moves only one tenth as far as the applied force. Since energy is proportional to force multiplied by distance, the output energy is kept roughly equal to the input energy (in practice slightly less, because some energy is lost to friction and other inefficiencies).
Stability
For stability, the sum of all moments about any point such as the base of the crane must equate to zero. In practice, the magnitude of load that is permitted to be lifted (called the "rated load" in the US) is some value less than the load that will cause the crane to tip (providing a safety margin).
Under US standards for mobile cranes, the stability-limited rated load for a crawler crane is 75% of the tipping load. The stability-limited rated load for a mobile crane supported on outriggers is 85% of the tipping load. These requirements, along with additional safety-related aspects of crane design, are established by the American Society of Mechanical Engineers in the volume ASME B30.5-2007 Mobile and Locomotive Cranes.
Standards for cranes mounted on ships or offshore platforms are somewhat stricter because of the dynamic load on the crane due to vessel motion. Additionally, the stability of the vessel or platform must be considered.
For stationary pedestal or kingpost mounted cranes, the moment created by the boom, jib, and load is resisted by the pedestal base or kingpost. Stress within the base must be less than the yield stress of the material or the crane will fail.
4. Types of the cranes
Mobile
Main article: Mobile crane
The most basic type of mobile crane consists of a truss or telescopic boom mounted on a mobile platform - be it on road, rail or water.
Fixed
Exchanging mobility for the ability to carry greater loads and reach greater heights due to increased stability, these types of cranes are characterized that they, or at least their main structure does not move during the period of use. However, many can still
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