人人文库网 > 图纸下载 > 毕业设计 > 10t桥式起重机的总体结构及运行机构设计【优秀起重机机械全套课程毕业设计含7张CAD图纸】

论文.doc

10t桥式起重机的总体结构及运行机构设计【优秀起重机机械全套课程毕业设计含7张CAD图纸】

资源目录

10t桥式起重机的总体结构及运行机构设计【优秀起重机机械全套课程毕业设计含7张CAD图纸】.rar

主梁A2.dwg

大车车轮A3轴.dwg

大车车轮组A1纸.dwg

大车轮A2纸.dwg

大车运行机构A1.dwg

端梁的装配A1.dwg

起重机总图A0.dwg

压缩包内文档预览：(预览前20页/共100页)

编号：474472 类型：共享资源大小：1.09MB 格式：RAR 上传时间：2015-08-27 上传人：QQ14****9609 IP属地：陕西

45
积分

版权申诉 word格式文档无特别注明外均可编辑修改；预览文档经过压缩，下载后原文更清晰！ 立即下载

关键词：: 桥式起重机总体结构运行机构机械设计起重机机械课程设计毕业设计 10t桥式起重机的总体结构及运行机构设计

资源描述：

10t桥式起重机总体设计

10t桥式起重机的结构及运行机构设计

桥式起重机总体设计

10t桥式起重机的总体结构及运行机构设计【优秀起重机机械全套课程毕业设计含7张CAD图纸】

【带开题报告+中期检查表+外文翻译】【99页@正文24200字】【详情如下】【需要咨询购买全套设计请加QQ1459919609】

中期报告.doc

中英文翻译.doc

开题报告.doc

论文.doc

主梁A2.dwg

大车车轮A3轴.dwg

大车车轮组A1纸.dwg

大车轮A2纸.dwg

大车运行机构A1.dwg

端梁的装配A1.dwg

起重机总图A0.dwg

中期检查表

题目 10t桥式起重机总体设计

一、选题质量：（主要从以下四个方面填写：1、选题是否符合专业培养目标，能否体现综合训练要求；2、题目难易程度；3、题目工作量；4、题目与生产、科研、经济、社会、文化及实验室建设等实际的结合程度）

1、本题目符合机械设计专业的培养目标，能够充分锻炼和培养分析问题和实际操作能力，能够体现综合训练的要求；

2、本题目难易适中，符合本科毕业设计要求；

3、本题目工作量适中，能在规定的时间内完成；

4、所选题目10t桥式起重机总体的设计与实际贴合比较紧密，在实际的应用中比较广泛。在设计过程中，对机器的零件的设计和计算对我来说是以往所学知识的总结和应用，所以能够满足综合训练的要求

二、开题报告完成情况：

根据自己在各方面资料的收集和整理，通过对可行性的分析，结合实际因素，我完成了这次设计的选题。在选题结束之后，通过自己认真查阅相关的资料，最后结合本身的实际情况和设计的时间任务完成了开题报告。

三、阶段性成果：

1、通过对10t桥式起重机的了解，再加上有关书籍的介绍，算是对10t桥式起重机有了一个大概的了解。前期阶段主要是对有关于10t桥式起重机的各方面的文献和资料进行搜集，为设计以后的设计做了必要的准备。

2、中期阶段主要是依据参考资料，从上面找到一些关于关于10t桥式起重机的信息，首先对其零部件有了大致的了解，其次是已有了大概的设计方法，并开始了一些基本的结构设计。

3、正在进行装配图的CAD画图和设计说明书。

四、存在主要问题：

由于这是我第一次单独进行10t桥式起重机总体设计，所以刚开始进展的并不是很顺利。而我对这方面的知识掌握比较少，所以需要在图书馆和网上查找更多的相关资料，对有关起重机的知识进行更深入的了解。不过我坚信，只要自己努力和在指导老师的指引下，我能把各方面的问题逐个击破，最终顺利完成毕业设计。

摘要

本次毕业设计是针对毕业实习中桥式起重机所做的具体到吨位级别的设计。我国现在应用的各大起重机还是仿造国外落后技术制造出来的，而且已经在工厂内应用了多年，有些甚至还是七八十年代的产品，无论在质量上还是在功能上都满足不了日益增长的工业需求。如何设计使其成本最低化，布置合理化，功能现代化是我们研究的课题。本次设计就是对小吨位的桥式起重机进行设计，主要设计内容是10t桥式起重机的结构及运行机构，其中包括桥架结构的布置计算及校核，主梁结构的计算及校核，端梁结构的计算及校核，主端梁连接以及大车运行机构零部件的选择及校核包括: 轮压计算及强度验算, 运行阻力计算,选择电动机,减速器的选择验算,运行速度及实际功率,选择制动器,选择联轴器,低速浮动轴的验算,缓冲器的选择等计算。还有小车的运行和起升机构零部件的选择及校核包括: 运行阻力计算，选电动机，选择减速器验算起动时间，按起动工况校核减速器功率，选择制动器，选择高速轴联轴器及制动轮，验算低速浮动轴强度，钢丝绳的选择，滑轮、卷筒的计算，联轴器的选择。

关键词: 起重机；大车运行机构；小车运行结构；小车起升结构；桥架；

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

摘要1

Abstract2

前言1

第1章桥式起重机的概述2

1.1 桥式起重机的特点2

1.2 桥式起重机的用途5

1.3 桥式起重机的基本参数5

1.4 桥式起重机主要零部件9

1.4.1吊钩9

1.4.2钢丝绳11

1.4.3 滑轮和滑轮组13

1.4.4 滑轮组类型及选配原则14

1.5滑轮组及其滑轮组的倍率15

1.6 卷筒16

1.7 位置限位器17

1.8 缓冲器18

1.9桥式起重机发展概述18

1.9.1 国内桥式起重机发展动向18

1.9.2 国外桥式起重机的发展动向19

第2章大车运行机构的设计21

2.1大车运行结构设计的基本思路及要求21

2.2 大车运行机构传动方案的确定21

2.3 大车运行机构具体布置时要注意的问题22

2.4 大车运行机构的设计计算23

2.4.1 大车运行结构的传动方案23

2.5轮压计算及强度验算24

2.5.1计算大车的最大轮压和最小轮压24

2.5.2 强度计算及校核25

2.6 运行阻力计算27

2.7 选择电动机28

2.8 减速器的选择30

2.9 验算运行速度及实际功率30

2.10 验算启动时间31

2.11 起动工况下校核减速器功率33

2.12 验算起动不打滑条件33

2.13 选择制动器36

2.14 选择联轴器37

2.15 低速浮动轴的验算38

2.16 缓冲器的选择40

第3章起升小车的计算43

3.1 确定机构的传动方案43

3.2小车运行机构的计算44

3.3选择车轮与轨道并验算起强度44

3.4运行阻力计算46

3.5 选电动机48

3.6 验算电动机发热条件49

3.7 选择减速器49

3.8 验算运行速度和实际所需功率49

3.9验算起动时间50

3.10 按起动工况校核减速器功率51

3.11 验算起动不打滑条件52

3.12 选择制动器53

3.13 选择高速轴联轴器及制动轮54

3.14 验算低速浮动轴强度56

3.15 起升机构的设计参数57

3.16 钢丝绳的选择58

3.17 滑轮、卷筒的计算59

3.18 根据静功率初选电动机61

3.19 减速器的选择61

3.20 制动器的选择63

3.21 启动时间及启动平均加速度的验算63

3.22 联轴器的选择65

第4章桥架结构的设计66

4.1 桥架的结构形式66

4.1.1 箱形双梁桥架的构成66

4.1.2 箱形双梁桥架的选材66

4.2 桥架结构的设计计算67

4.2.1 主要尺寸的确定67

4.2.2 主梁的计算69

4.3 端梁的计算76

4.4 端梁的尺寸的确定82

4.4.1 端梁总体的尺寸82

4.4.2端梁的截面尺寸82

第5章端梁接头的设计83

5.1 端梁接头的确定及计算83

5.1.1 腹板和下盖板螺栓受力计算84

5.1.2 上盖板和腹板角钢的连接焊缝受力计算85

5.2 计算螺栓和焊缝的强度86

5.2.1 螺栓的强度校核86

5.2.2 焊缝的强度校核87

总结91

致谢93

参考文献94

前言

桥式起重机是横架于车间和料场上空进行物料调运的起重设备。由于它两端坐落在高大的水泥柱或金属架上，形状似桥，所以俗称“天车”。桥式起重机是现代工业和起重运输中实现生产过程机械化、自动化的重要工具与设备，可减轻操作者的劳动强度，可大大提高生产率。桥式起重机在工矿企业、钢铁化工、铁路交通、港口码头以及物流周转等部门和场所应用的最为广泛，是人们生产生活不可或缺的一种设备。

随着工业的迅速发展和科学技术的不断进步，桥式起重机在结构设计及自动化程度上相继出现了一些新的变化和新的特点，在结构上，国内起重设备已采用计算机优化设计，以提高起重机的机械性能，在起重质量方面逐步向大型化发展，大型桥式起重机正在钢铁、水利、发电等行业不断出现，令人世人瞩目的三峡发电厂安装了两台1200T/125T的桥式起重机，2007年9月，起重量达2万吨的桥式起重机在山东烟台佛士船厂投入使用，它标志这我国起重机行业以达到世界先进水平。

总之，随着科技的迅速发展，国内各种先进的电气控制和机械技术正逐步应用到起重机上，起重机的自动化程度越来越高，结构日趋简单，性能愈加可靠，起重量越来越大，品种也越来越全。

对于起重量大、跨距大的起重设备多采用箱型双梁式，箱型双梁桥式起重机有一个由两根箱型主梁和两根横向端梁构成的双梁桥架，在桥架上运行小车，可起吊和水平搬运各类物件。它适用于机械加工和装配车间、仓库和料场等场所。箱型双梁结构具有加工零件少、工艺性好、通用性好及安装检修方便等优点，因而在生产中广泛使用。

第1章桥式起重机的概述

桥式起重机是桥架型起重机的一种，主要依靠起升机构和在水平面内的两个相互垂直方向移动的运行机构，能在矩形场地及其上空作业，是工矿企业广泛使用的一种其中运输机械。它具有承载能力大、工作可靠性高、制造工艺相对简单的优点。

桥式起重机一般有大车运行机构的桥架、起升机构和小车运行机构的起重小车、电气设备、司机室等机构组成，外形像一个两端支撑在平行的两条架空轨道上平移运行的单跨平板桥。起升机构用来垂直升降物品，起重小车用来带着载荷作横向移动，以达到在跨度内和规定高度内组成三维空间里做搬运和装卸货物用。

桥式起重机是使用最广泛、拥有量最大的一种轨道运行式起重机，其额定起重量从及吨到几百吨。最基本的形式是通用吊钩桥式起重机，其他形式的桥式起重机都是在通用吊钩桥式起重机的基础上派生发展出来的。

1.1 桥式起重机的特点

桥式起重机是横架于车间、仓库和料场上空进行物料吊运的起重设备。由于它两端坐落在高大的水泥柱上或金属支架上，形状似桥，所以俗称“天车”和“行车”。它是使用、范围最广、数量最多的一种起重机械。

桥式起重机是现代工业生产和起重运输中实现生产过程机械化、自动化的重要工具和设备，可减轻操作者的劳动强度，提高生常率。桥式起重机在工矿企业、钢铁化工、铁路交通、港口码头以及物流周转等部门和场所均得到广泛的运用，它是人们生产活动中不可缺少的一种设备。

桥式起重机的类型很多，其中通用桥式起重机和龙门起重机最为普遍，这两种类型起重机的结构和操作方法基本相同，不同之处在于大车运行轨道的位置，通用桥式起重机是在高空，龙门起重机在地面，由此带来支撑结构的不同。

参考文献

[1] 《起重机设计手册》起重机设计编写组，机械工业出版社，1980

[2] 《机械设计师手册》吴宗泽主编机械工业出版社，2002

[3] 《起重机课程设计》陈道南、盛汉中主编冶金工业出版社，1983

[4] 《焊接手册》中国机械工程学会焊接学会编，机械工业出版社，1992

[5] 《起重运输机械》张质文、刘全德中国铁道出版社 1983年

[6] 《机械原理》孙桓、陈作模高等教育出版社 1996年

[7] 《工程起重机》顾迪民中国建筑工业出版社，1988

[8] 《机械设计》濮良贵、纪名刚高等教育出版社，2000.12

[9] 《机械零件手册》周开勤高等教育出版社，2000.12

[10] 《机械设计课程设计手册》吴宗泽、罗圣国高等教育出版社，2006.5

大车车轮A3轴.gif

大车车轮组A1纸.gif

大车轮A2纸.gif

大车运行机构A1.gif

端梁的装配A1.gif

起重机总图A0.gif

主梁A2.gif

内容简介：: 河南理工大学万方科技学院本科毕业设计（论文）中期检查表指导教师：罗静职称：副教授所在院（系）：机械与动力工程学院教研室（研究室）：题目 10t 桥式起重机总体设计学生姓名牛翔专业班级 08 机设三班学号 0828070073 一、选题质量：（主要从以下四个方面填写： 1、选题是否符合专业培养目标，能否体现综合训练要求； 2、题目难易程度； 3、题目工作量； 4、题目与生产、科研、经济、社会、文化及实验室建设等实际的结合程度） 1、本题目符合机械设计专业的培养目标，能够充分锻炼和培养分析问题和实际操作能力，能够体现综合训练的要求； 2、本题目难易适中，符合本科毕业设计要求； 3、本题目工作量适中，能在规定的时间内完成； 4、所选题目 10t 桥式起重机总体的设计与实际贴合比较紧密，在实际的应用中比较广泛。在设计过程中，对机器的零件的设计和计算对我来说是以往所学知识的总结和应用，所以能够满足综合训练的要求二、开题报告完成情况：根据自己在各方面资料的收集和整理，通过对可行性的分析，结合实际因素，我完成了这次设计的选题。在选题结束之后，通过自己认真查阅相关的资料，最后结合本身的实际情况和设计的时间任务完成了开题报告。 nts 2 三、阶段性成果： 1、通过对 10t 桥式起重机的了解，再加上有关书籍的介绍，算是对 10t 桥式起重机有了一个大概的了解。前期阶段主要是对有关于 10t 桥式起重机的各方面的文献和资料进行搜集，为设计以后的设计做了必要的准备。 2、中期阶段主要是依据参考资料，从上面找到一些关于关于 10t 桥式起重机的信息，首先对其零部件有了大致的了解，其次是已有了大概的设计方法，并开始了一些基本的结构设计。 3、正在进行装配图的 CAD 画图和设计说明书。四、存在主要问题：由于这是我第一次单独进行 10t 桥式起重机总体设计，所以刚开始进展的并不是很顺利。而我对这方面的知识掌握比较少，所以需要在图书馆和网上查找更多的相关资料，对有关起重机的知识进行更深入的了解。不过我坚信，只要自己努力和在指导老师的指引下，我能把各方面的问题逐个击破，最终顺利完成毕业设计。五、指导教师对学生在毕业实习中，劳动、学习纪律及毕业设计（论文）进展等方面的评语指导教师：（签名）年月日 nts河南理工大学万方科技学院本科毕业论文 1 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 nts河南理工大学万方科技学院本科毕业论文 2 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 nts河南理工大学万方科技学院本科毕业论文 3 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. nts河南理工大学万方科技学院本科毕业论文 4 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 Trajans Column weighs 53.3 tons, which had to be lifted to a height of about 34 m (see construction of Trajans 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 nts河南理工大学万方科技学院本科毕业论文 5 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 nts河南理工大学万方科技学院本科毕业论文 6 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 ships 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 nts河南理工大学万方科技学院本科毕业论文 7 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 devils 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 nts河南理工大学万方科技学院本科毕业论文 8 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 nts河南理工大学万方科技学院本科毕业论文 9 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 loads 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 nts河南理工大学万方科技学院本科毕业论文 10 number is the mechanical advantage. The hydraulic cylinder. This can be use

温馨提示:
1: 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。

人人文库网所有资源均是用户自行上传分享，仅供网友学习交流，未经上传用户书面授权，请勿作他用。