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关键词：: RL7050H0 总布置设计汽车 cad图纸

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RL7050H0总布置设计

54页 26000字数+说明书+任务书+开题报告+外文翻译+5张CAD图纸【详情如下】

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RL7050H0总布置设计说明书.doc

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任务书.doc

外文翻译--基本概念的悬架和框架设计.doc

封皮.doc

开题报告封皮.doc

题目审定表.doc

摘要

　　　RL7050H0总布置设计是在中国大学生方程式汽车大赛的基础上进行的。首先通过充分准备和综合分析，选择一个合理的整车方案，并经过一定的程序将其定下来。方案确定后，进行准确布置和计算，并为各总成下一步开展的工作打好基础、准备条件、提出要求并与各专业组协同完成全部的设计，共同实现整车的总目标。

　　　汽车总布置设计参考同类车型有关数据作为借鉴，重新选定各总成部件，重新布置。提出汽车的长、宽、高、轴距等控制尺寸，轴荷的分布范围以及动力总成、散热器、前后悬架、传动轴与车轮等轮廓尺寸和位置，初步确定新车型的设计硬点。从而保证所设计的汽车不仅在预定的使用条件下具有良好的使用性能、重量轻、寿命长、结构简单、使用方便、效率高、经济性好，制造简单，便于维修。总布置设计在整车开发过程中起到非常重要的作用。

关键词：总布置设计；方程式赛车；总成匹配；车型；控制尺寸　

ABSTRACT

　　　RL7050H0 Layout Design Formula cars in the Chinese university students on the basis of competition. First, through the full preparation and comprehensive analysis of vehicle to select a reasonable solution, and after certain procedures to be laid down. Plan was finalized, the exact layout and calculation, and the next step for the assembly to lay the foundation work in preparation for the conditions, request and coordination with the professional group to complete all of the design together to achieve the overall objective of the vehicle.

　　　General layout of car design reference data as a reference on similar models, re-selected parts of the assembly, re-arranged. Proposed vehicle length, width, height, wheelbase and other control dimensions, axle load distribution range and power train, radiator, front and rear suspension, drive shafts and wheels outline size and location of initial hard to determine the design of new models point. Designed to ensure the car is not only the intended conditions of use with good performance, light weight, long life, simple structure, onvenient operation, high efficiency, good economy, manufacturing is simple and easy maintenance. Layout design in the vehicle development process play a very important role.　　

Key words：The layout design；Formula car；Assembly matching；Models；Control dimensions

　　　摘要I

　　　AbstractII

　　　第1章绪论1

　　　1.1 FSAE方程式研究现状1

　　　1.2 FSAE方程式目的、依据和意义2

　　　第2章总布置设计准备及整车型式选择4

　　　2.1 总布置设计的准备4

　　　2.1.1 市场调研4

　　　2.1.2 样车分析5

　　　2.1.3 制定设计目标6

　　　2.2 整车型式的选择6

　　　2.2.1 发动机的种类和布置型式6

　　　2.2.2 驾驶室的型式8

　　　2.2.3 轮胎的选型10

　　　2.2.4 转向机构型式的选择11

　　　2.2.5 制动器型式的选择13

　　　2.2.6 悬架布置形式16

　　　2.2.7 差速器型式的选择18

　　　2.3 本章小结20

　　　第3章新车型主要目标参数的初步确定21

　　　3.1 几个主要“目标参数”的确定21

　　　3.2 发动机最大功率及其转速21

　　　3.3 发动机最大扭矩及其转速22

　　　3.4 传动系速比的选择22

　　　3.4.1 最小传动比的选择23

　　　3.4.2 最大传动比的选择24

　　　3.4.3 变速器档位数的选择25

　　　3.5 本章小结25

　　　第4章尺寸参数与质量参数的初步确定26

　　　4.1 轿车的级别与载荷确定26

　　　4.2 轿车主要参数的确定26

　　　4.2.1 驾驶员单元26

　　　4.2.2 整车外形尺寸的确定29

　　　4.3 本章小结30

　　　第5章各总成的匹配及总布置图绘制31

　　　5.1 各相关总成的匹配31

　　　5.1.1 车身总布置设计31

　　　5.1.2 发动机总布置设计31

　　　5.1.3 转向节、车轮总成与前制动器总成的布置设计31

　　　5.2 整车总布置图绘制32

　　　5.2.1 整车布置的基准线32

　　　5.2.2 总布置图绘制的基本原则33

　　　5.3 本章小结33

　　　第6章主要总成的布置及其硬点概述34

　　　6.1 各总成的布置34

　　　6.1.1 发动机及传动系的布置34

　　　6.1.2 驾驶室及悬架的布置35

　　　6.1.3 车架总成外形及转向系的布置36

　　　6.1.4 制动系及进、排气系统的布置36

　　　6.2主要总成硬点概述37

　　　6.2.1 整车设计基准37

　　　6.2.2 总体设计方案及主要硬点37

　　　6.3 本章小结41

　　　第7章运动校核42

　　　7.1 轮胎运动校核42

　　　7.2 转向传动装置与悬架共同工作校核42

　　　7.3 制动力匹配校核42

　　　7.3.1 制动力匹配基本理论公式42

　　　7.3.2 RL7050H0赛车制动力匹配校核43

　　　7.4 本章小结45

　　　结论46

　　　参考文献47

　　　致谢49

第3章新车型主要目标参数的初步确定

3.1 几个主要“目标参数”的确定

　　　2010年第一届中国FSAE大赛中，部分车队赛参数：

　　　北京理工大学参赛赛车，最高车速可达135km/h，整车整备质量 208Kg；

　　　哈尔滨工业大学参赛赛车，最高车速可达160km/h，整车整备质量 265Kg。

根据以上参数初步选定RL7050H0最高车速为140km/h，整车整备质量210Kg。

一、设计（论文）目的、意义

　　　设计的小型汽车为一种乘用车，亦可易于比赛和娱乐休闲。

　　　本课题的选择充分考虑了研究课题对汽车车辆工程专业学生学习和工作的指导作用，对本课题的研究能够使学生了解专用汽车改装设计方法，通过本课题的研究学生可以完成理论课程的实践总结，获得一定的工程设计工作方法。

二、设计（论文）内容、技术要求（研究方法）

　　　进行一种微型乘用车的总体设计；面向单件生产；

　　　设计内容包括：整车总体参数的确定，总体方案的选择与分析，主要总成的计算选择和步骤，运动校核分析，整车性能的分析。

　　　要求：

　　　(1) 技术指标满足“FSAE”要求；

　　　(2) 不进行总成部件的详细设计；

　　　(3) 未详述指标和要求按“汽车设计”。

　　1.1 FSAE方程式研究现状

　　　近年来，汽车技术突飞猛进，方程式赛车也逐步被大多数人所了解，Formula SAE，是由各国SAE，即汽车工程师协会举办的面向在读或毕业7个月以内的本科生或研究生举办的一项学生方程式赛车比赛，要求在一年的时间内制造出一辆在加速、刹车、操控性方面有优异的表现并且足够稳定耐久，能够成功完成规则中列举的所有项目业余休闲赛车。自1981年创办以来，FSAE已发展成为每年由7个国家（美国、英国、澳大利亚、日本、意大利、德国及巴西）举办的9场赛事所组成，并有数百支来自全球顶级高校的车队参与的青年工程师盛会。

　　　SAE方程式（Formula SAE）系列赛源于1978年。第一次比赛于1979年在美国波斯顿举行，13支队伍中有11支完赛。当时的规则是制作一台5马力的木制赛车。SAE方程式（Formula SAE）系列赛将挑战本科生、研究生团队构思、设计与制造小型具有越野性能的方程式赛车的能力。为给车队最大的设计弹性和自我表达创意和想象力的空间，在整车设计方面将会限制很少。赛前车队通常用8至12个月组的时间设计、建造、测试和准备赛车。在与来自世界各地的大学代表队的比较中，赛事给了车队证明和展示其创造力和工程技术能力的机会。

　　　2009年中国国产汽车产销分别为1379.10万辆和1364.48万辆，首次成为世界汽车产销第一大国。汽车从中国人眼中的奢侈品到代步工具，到跃居世界汽车产销量第一的头把交椅，中国只用了短短十年时间。回顾十年来中国汽车工业的突飞猛进，一浪高过一浪的市场消费力，驱使中国一跃成为全球最大的汽车消费大国，而非真正意义上的汽车产业强国。中国汽车工业一直是在借鉴和应用，国外汽车一百多年来成熟的技术和制造工艺一路走来，而缺乏自主创新研发新技术的能力和人才培育。

　　　中国大学生方程式汽车大赛（以下简称"FSAE"）是中国汽车工程学会及其合作会员单位，在学习和总结美、日、德等国家相关经验的基础上，结合中国国情，精心打造的一项全新赛事。我国从2006年起开始组建FSAE车队。湖南大学、上海交通大学、厦门理工大学与同济大学自2007年至2009年共参加了在美国和日本举办的4场FSAE赛事，获得了多个单项奖及新秀奖。为搭建国内优秀汽车人才的选拔平台，培养和提高汽车专业学生的综合素质，2010年第一届中国FSAE由中国汽车工程学会、中国二十所大学汽车院系、国内领先的汽车传媒集团——易车（BITAUTO）联合发起举办。中国FSAE秉持“中国创造擎动未来”的远大理想，立足于中国汽车工程教育和汽车产业的现实基础，吸收借鉴其他国家FSAE赛事的成功经验，打造一个新型的培养中国未来汽车产业领导者和工程师的交流盛会，并成为与国际青年汽车工程师交流的平台。中国FSAE致力于为国内优秀汽车人才的培养和选拔搭建公共平台，FSAE要求各参赛队按照赛事规则和赛车制造标准，自行设计和制造方程式类型的小型单人座休闲赛车，并携该车参加全部或部分赛事环节。比赛过程中，参赛队不仅要阐述设计理念，还要由评审裁判对该车进行若干项性能测试项目，通过全方位考核，提高学生们的设计、制造、成本控制、商业营销、沟通与协调等五方面的综合能力，全面提升汽车专业学生的综合素质，为中国汽车产业的发展进行长期的人才积蓄，促进中国汽车工业从“制造大国”向“产业强国”的战略方向迈进。

1.2 FSAE方程式目的、依据和意义

汽车总布置设计是新车型开发的第一道工序，而新车型总体方案的确定是总布置设计的第一步。首先通过充分准备和综合分析，选择一个合理的整车方案，并经过一定的程序将其定下来。方案确定后，进行准确布置和计算，并为各总成下一步开展的工作打好基础、准备条件、提出要求并与各专业组协同完成全部的设计，共同实现整车的总目标。一种新车型的投产，除产品开发过程外，还要做大量的生产准备工作，如投入资金设备厂房、人员及制定一整套相关工艺等。这些都是为了保证整车能够稳定的大量的投入生产，并确保其整车性能和质量能被客户接受，所以整车总体方案和全部设计内容，也直接决定着工厂的投入。因此，总布置工作——方案选择、布置、和计算，都是非常重要的，而且是不可缺少的。做好整车设计工作，必须做好以下两点：第一、要能准确地分析市场形势、了解客户的心理状态、车辆使用特点，熟悉工厂的生产条件，以便真正确定出合理的整车方案；第二、要有独立工作的能力。因为方案确定后，实现该方案的所有布置、计算及整车的开发工作，基本上是由一个人来完成，所以要求设计者工作不应该有任何失误，否则会造成反工和浪费，甚至失掉抢占市场的机会。因此要求设计者必须具有严谨、认真、细致、负责的精神，在整个开发过程中能协调和解决各方面问题和矛盾，使设计产品质量达到设计要求。总布置工作虽然以完成全部图纸及技术文件资料来标志着阶段性的结束，但还应该进行整车装配图的校核工作，即利用已完成的全部图纸或三维数模进行全面的细致的整车装置的图面及运动校核，及时发现问题、解决问题，使设计中存在的问题消除在试制和试装第2章总布置设计准备及整车型式选择

2.1 总布置设计的准备

2.1.1 市场调研

　　　市场调研是制定商品规划的前提和基础，企业为了获取对外部环境的认识，需要设置专门机构，不断地进行认真、细致和规范的市场调查和预测。

　　　调研工作可以分为市场普查和专项调查。

　　　市场普查：可参与每年进行的市场情况调查，包括国内外制造厂家的产品开发生产销售国家政策地方规定、社会车辆运转情况统计、营运费用、管理维修、车辆性能、可靠性、寿命及备件供应等，从而掌握国内外市场情况、变化规律、发展趋势、用户的使用和需求状况，及时发现市场需求和预测未来。

　　　专项调查：参加为开发某车型而专门进行的市场调查，明确调查目标，细化调研提纲，对整车总成性能参数必须有初步的设想后，再对使用者和使用现场逐项进行的了解、找出差异，特别重点调研有关技术难点——性能要求、结构处理、特殊用途或要求等。

　　　调研的方法主要是通过听问看和测试手段，达到预期目的，通过研究思考达到完善和创新，形成一个比较完整的方案。

　　　中国FSAE赛车总体设计要求：

　　　1．赛车构造

　　　赛车必须是裸露式车轮和敞开式驾驶舱（方程式车型），以及四个车轮不能在一条直线上。

　　　2．车身

　　　从车的前端到主防滚架或者防火墙的这段空间里，除了驾驶舱必须的开口，车体上不允许有其他的开口。允许在前悬架处有微小的开口。

　　　3．轴距

　　　赛车必须有至少1525mm（60英寸）的轴距。轴距是指在车轮指向正前方时同一侧两车轮与地面的接触点之间的距离。

　　　4．轮距

　　　赛车较小的轮距（前轮或后轮）必须不小于较大轮距的75%。

　　　5．可视性

　　　检查表格上所有的条目必须在不使用工具，比如内窥镜或是镜子的情况下清楚地呈现给技术检察官看。呈示时可以拆卸车身外板或提供可拆卸的可见套件。　　　汽车常用的轮胎有普通斜交胎和普通子午线胎。普通斜交胎的胎体帘线层较多，胎侧厚，使用中不易刺破，侧向刚度大，但是缓冲性能差。而子午线胎的帘布层呈子午线排列，是帘布线的强度得到充分的利用，缓冲层也较多，加强了胎冠，所以提高了轮胎的缓冲性能、附着性能和使用寿命，滚动阻力比普通斜交胎要小，因而提高了整车的经济性。但是制造成本较高，由于胎侧较薄，侧向刚度小，太侧易被刺破。但是其优点较明显，相对斜交轮胎，子午线轮胎具备以下特点 : 良好的操纵稳定性能、安全的转弯性能、良好的耐磨性能、生热少、滚动阻力低，节省燃油费用、牵引能力强，打滑少、高速行驶时的乘车舒适感好。

　　　2010中国FSAE攒足轮胎相关参数见表2.1，赛事规定赛车可装备如下两套轮胎：

表2. 1 2010中国FSAE赞助轮胎的相关参数

规格180/530R13轮胎接地面宽(mm?inch)185?7.3

标准轮辋内距8.0轮胎半径(mm)244

轮胎胎面宽(mm?inch)223?8.8轮胎周长1626

轮胎外径(mm?inch)533?21.0轮辋内距7.5-8.5

　　　干胎——在检查时安装在赛车上的轮胎定义为干胎。干胎尺寸任意，型号任意。他们可以是光头胎，也可是有纹的

　　　雨胎——雨胎可以是如下规定的任何型号和尺寸的有花纹和沟槽的样式：

　　　（1）花纹和沟槽的图案必须是由轮胎厂商塑造成型的，任何被刻制的花纹沟槽必须有文件证明它是符合比赛的相关规定的。

　　　（2）沟槽最浅为2.4mm（3/32英寸）。

2.2.4 转向机构型式的选择

　　　1．齿轮齿条式转向器

　　　中小型轿车以及前轴轴荷小于1.2t的客车、货车，多采用该种型式，如图2.5所示。齿轮齿条式转向器的传动副为齿轮与齿条。转向轴带动小齿轮旋转时，齿条便做直线运动。有时，靠齿条来直接带动横拉杆，就可使转向轮转向。通常均布置在前轮轴线之后。转向传动副的主动件是一斜齿圆柱小齿轮，它和装在外壳中的从动件——齿条相啮合，外壳固定在车身或车架上。齿条利用两个球接头直接和两根分开的左、右横拉杆相联。横拉杆再经球接头与梯形臂相接。齿轮齿条式转向器是依靠齿条背部靠近主动小齿轮处装置的可调节压力的弹簧来消除齿轮齿条传动副的齿间间隙的。为了转向轻便，主动小齿轮的直径应尽量小。通常，这类转向器的齿轮模数多在2～3mm范围内，压力角为20。，主动小齿轮有5～8个齿，螺旋角为9°～15°。根据小齿轮螺旋角和齿条倾斜角的大小和方向的不同，可以构成不同的传动方案。

　　　齿轮齿条式液压助力转向器，是相对于机械转向器而言的，其增加了转向油泵、转向油壶、转向油管、转向阀、转向油缸等部件，以期达到改善驾驶员手感，增加转向助力的目的的转向装置。

　　　齿轮齿条式转向器结构简单、紧凑；布置方便；制造容易，成本低廉；壳体采用铝合金或镁合金压铸而成，转向器的质量较小；转向灵敏,传动效率高达90%；齿轮与齿条间因磨损出现间隙以后，利用装在齿条背部、靠近主动小齿轮处的压紧力可以调节的弹簧，能自动消除齿间间隙，能提高转向系统的刚度，防治工作时产生冲击和噪声；占用体积小,便于布置，制造容易。但转向传动比较小，(一般不大于15)，且齿条沿其长度方向磨损不均匀；逆效率高（60% ~70%），不易控制。

6.2.1 整车设计基准

　　　整车绝对坐标系采用右手坐标系，它是总布置设计和详细设计中的基准线。绝对坐标系的定义如下：高度方向，上正下负；宽度方向，取汽车的纵向对称中心线为 Y 零线，左负右正；长度方向，取通过汽车前轮中心的垂线为 X 零线，前负后正。

6.2.2 总体设计方案及主要硬点

　　　1．整车总体技术硬点

　　　以整车方案为指导，总体技术硬点如表6.1所示：

表6.1 总体技术硬点

基本形式裸露式车轮和敞开式驾驶舱（方程式车型）

驱动形式动力总成后置后轮驱动

外形尺寸长mm2968

宽mm1468

高mm1497

轴距mm1940

轮距前轮距mm1245

后轮距mm1180

前悬mm742.6

后悬mm285.4

质量参数整车整备质量Kg210

乘载质量Kg75

空载前后轴荷Kg前轴荷89.04（42.4%）后轴荷120.96（57.6%）

满载前后轴荷Kg前轴荷130.39（45.8%）后轴荷154.61（54.2%）

通过性数据接近角（满载）（°）20

离去角（满载）（°）88

最小离地间隙mm109

最小转弯半径m4.425

　　　2．动力传动系统设计硬点

　　　动力总成参数如表6.2所示：

表6.2 动力总成参数

基本型式横置中置后驱发动机排量（L）0.493

发动机CF188发动机最大功率（kw/rpm）24/6500

变速器CVT发动机最大扭矩（N.m/rpm）31.16/5500

　　　动力传动系统主要布置硬点如表6.3所示：

表6.3 动力传动系统主要布置硬点

动力总成BHC点坐标X：1377.3；Y：0；Z：190.0

发动机缸体对称中心面Y：65，平行于Y平面

差速器中心点坐标X：1959.6；Y：88.2；Z：106.1

发动机悬置中心点坐标前X：1212.9；Y：49.0；Z：494.9

后X：1553.8；Y：56.0；Z：356.9

左X：1345.3；Y：65.0；Z：50.0

右X：1601.8；Y：65.0；Z：37.0

发动机输出轴中心左传动轴X：1377.3；Y：-54.0；Z：19.0.0

右传动轴X：1377.3；Y：196.0；Z：190.0

后左半轴理论长度mm667.5

后右半轴理论长度mm491.2

油底壳最小离地间隙mm146.5

　　　3．底盘系统布置方案及主要硬点

　　　（1）悬架车轮系统

　　　悬架车轮系统的主要布置硬点如表6.4所示：

表6.4 悬架车轮系统的主要布置硬点

前悬架上支点X：428.0；Y：±194.2；

Z：530.0前轮总前束0.2o±30′

后悬架上支点X：1632.5；Y：±171.4；

±Z：563.0主销内倾12.6o±30′

轮胎类型子午线轮胎主销后倾2.5o±30′

轮胎规格180/530R13后轮外倾－0.6o±30′

轮辋规格13×8J后轮总前束0.2o±30′

前轮外倾－0.8o±30′

　　　前后悬架车轮系统：均采用空间多连杆、圆柱螺旋弹簧，双向作用筒式减振器结构，独立悬架。前车轮为非驱动轮，后车轮为驱动轮。

　　　（2）转向系统

　　　转向系统主要布置硬点如表6.5所示：

表6.5 转向系统主要布置硬点

转向器断开点X：170.3；Y：-157.4；Z：213.1

转向传动装置方向盘外径260mm

内外转角36.4°/26°

传动比44.6

转向管柱上下角度65o/68o/60o

方向管柱传动轴长度302.5mm

转向器行程140±1mm（厂家值）

管柱上顶点X：534.3；Y：0；Z：514.8

　　　（3）制动系统

　　　行车制动系统采用液压助力结构。前后制动器均为强制通风式盘式制动器。制动管路为 X 型双回路布置。

　　　驻车制动系统为拉索式手动结构，操纵手柄放置在座椅的右侧。

　　　制动系统主要布置硬点如表6.6所示：

表6.6 制动系统主要布置硬点

制动总泵安装面中心X：-200.0；Y：72.5；Z：170.0

前后轮缸数量2，2

前后轮缸直径（mm）57.15

前后制动半径（mm）92.5

制动踏板比5

驻车制动转动中心X：754.4；Y：239.7；Z：239.8

驻车制动手柄最大角度45°

6.3 本章小结

　　　本章主要是对总布置中的各总成部件，如发动机、传动系、悬架、转向系、制动系等进行详细的布置，以保证新车型运转平稳，不影响使用性能的发挥。简述了各总成的布置和各附件的硬点，主要包括确定车身、底盘与零部件相互关系的基准点、线、面及控制结构，为整车的详细设计提供依据和指导。

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内容简介：: 附录AFormula SAE is a student competition sponsored by Society of Automotive Engineers (SAE), were students design, build, and compete with a small formula style race car. The basis of the competition is that a fictitious company has contracted a group of engineers to build a small formula car. Since the car is intended for the weekend autocross racer, the company has set a maximum price of $8,500. The race car is also limited to a single 610cc displacement engine with a single inlet restrictor. Other major rules require that the car must have a suspension system with a minimum wheel travel of 50mm and a wheelbase greater than 1524mm. The remainder of the rules define safety requirements such as side impact protection . The competition is separated into static and dynamic events. The static events include the cost nalysis, sales presentation, and engineering design. The dynamic portions of the competition are the 15.25 m diameter skid-pad, 91.44 m acceleration event, 0.8 km autocross, 44 km endurance race, and fuel economy.The FSAE competition has been established to provide an educational experience for college students that is analogous to the type of projects they will face in the work force. To participate in FSAE, student groups work with a project from the abstract design until it is completed. The aspects of engineering design, team work, project management, and finance have been incorporated into the basic rules of Formula SAE.This paper is intended to cover some of the basic concepts of suspension and frame design and also highlights the approach UM-Rolla used when designing their 1996 suspension and frame. The suspension section addresses the basic design parameters and presents specific examples. Next, the frame section discusses how to achieve a compromise with the FSAE design constraints. Finally, the design section gives a brief overview of the design methodology used by UM-Rolla for the 1996 race car.1.Suspension GeometryFSAE suspensions operate in a narrow realm of vehicle dynamics mainly due to the limited cornering speeds which are governed by the racetrack size. Therefore, FSAE suspension design should focus on the constraints of the competition. For example, vehicle track width and wheelbase are factors governing the success of the cars handling characteristics. These two dimensions not only influence weight transfer, but they also affect the turning radius.Not only do the kinematics have to be considered for FSAE suspension, but the components must also be reasonably priced for the cost analysis and marketable for the sales presentation. For example, inboard suspension could be a more marketable design, while outboard suspension might cost less and be easier to manufacture.The suspension geometry section concentrates on some of the basic areas of suspension design and highlights what the UM-Rolla design team selected for their 1996 race car suspension geometry. UM-Rolla chose to use a four wheel independent suspension system with push rod actuated inboard coil over shocks. This decision was mainly because of packaging constraints. Furthermore, the appearance of inboard suspension was considered important for both the design judging and the sales presentation because of its similarity to modern race cars.Also, this section of the paper was written with short-long arm suspension systems in mind. However, many of the concepts are valid for other suspension types.2.Track Width and WheelbaseThe definition of track width is the distance between the right and left wheel centerlines which is illustrated in Figure 1. This dimension is important for cornering since it resists the Upper Ball JointTrack WidthLow Ball JointUpper Control ArmUpper Control ArmFigure 1. Track Widthoverturning moment due to the inertia force at the center of gravity (CG) and the lateral force at the tires . For the designer, track width is important since it is one component that affects the amount of lateral weight transfer . Also, the designers must know the track width before kinematic analysis of the suspension geometry can begin.When selecting the track width, the front and rear track widths do not necessarily have to be the same. For example, track width is typically wider in the front for a rear wheel drive race car. This design concept is used to increase rear traction during corner exit by reducing the amount of body roll resisted by the rear tires relative to the front tires. Based on the corner speeds and horsepower to weight ratio of FSAE cars, this concept should be considered by the designer.The wheelbase also needs to be determined. Wheelbase is defined as the distance between the front and rear axle centerlines, and also influences weight transfer, but in the longitudinal direction. Except for anti-dive and anti-squat characteristics, the wheelbase relative to the CG location does not have a large effect on the kinematics of the suspension system. However, the wheelbase should be determined early in the design process since the wheelbase has a large influence on the packaging of components.For track width and wheelbase starting points, the designers should research the oppositions dimensions to serve as a baseline for their own calculations. FSAE car specifications for the competing teams, including track width and wheelbase, are available in the event program published by SAE.The 1996 design team selected a 1727 mm wheelbase, 1270 mm front track width, and a 1219 mm rear track width, which were based on previous UM-Rolla cars. Although this wheelbase was adequate for the FSAE competition size courses, the UM-Rolla design team has decided to increase the wheelbase for the next car to 1854.2 mm. This increase in wheelbase is an attempt to improve stability for high speed corner entry at the competition.3.Tire and WheelAfter track width and wheelbase considerations have been addressed, tire and wheel selection is the next step in the design process. Since the tire is important to the handling of the vehicle, the design team should thoroughly investigate the tire sizes and compounds available. The tire size is important at this stage of the design since the height of the tire must be known before the geometry can be determined. For example, the tire height for a given wheel diameter determines how close the lower ball joint can be to the ground if packaged inside the wheel.Tire Size - The designers should be aware that the number of tire sizes offered for a given wheel diameter is limited. Therefore, considering the importance of the tire to handling, the tire selection process should be a methodical process. Since the amount of tire on the ground has a large influence on grip, it is sometimes desirable to use wide tires for increased traction. However, it is important to remember that wide tires add rotating mass which must be accelerated by a restricted FSAE engine. This added mass might be more detrimental to the overall performance than the increase in traction from the wider tires. Not only does a wider tire add mass, but it also increases the amount of rubber that must be heated. Since racing tires are designed to operate most efficiently in a specific temperature range, this added material may prevent the tires from reaching the optimum temperature range . The UM-Rolla team used tires for the 1996 competition that were designed to work most efficiently at a minimum of 71.During the selection process the designers must consider how the tires will influence the performance of the entire package. For example, the weather conditions for the FSAE dynamic events might determine which tire compound and tire size should be used for the competition. Another important consideration is the price of the tires since the cost can be a large portion of a teams budget.For the 1996 competition, UM-Rolla selected a 20 by 6-13 racing tire for both the front and rear of the car. Because of the low vehicle mass, a narrow tire was selected so tire temperatures would be greater than previous UM-Rolla designs. This tire selection increased the operating temperature from 48o to 60oC. For the competition, the weather was predicted to be cool, so the team brought a set of hard and soft compound tires. The team chose to use the harder compound since the weather for the endurance was predicted to be clear and warm.Wheel Selection - Once a decision has been made as to which tire sizes to use, the wheel selection should be next. Usually, the wheel dimensions are fixed and allow for little modification. Therefore, it is important to have some design goals in mind before investing in wheels. Generally, the upright, brake caliper, and rotor are placed inside the wheel which requires wheel offset for clearance. It is usually easier to design the suspension geometry if the wheel profile is known. For example, the ball joint location is limited to the area defined by the wheel profile. Some packaging constraints are shown in Figure 2.Other considerations for wheel selection include: cost, availability, bolt circle, and weight. For example, three-piece rims, although expensive, have the distinct advantage of offering many offsets and profiles that can be changed during the design process .Figure 2. 1996 Front SuspensionUM-Rolla designed the 1996 suspension geometry around a wheel profile from a previous car and then acquired a set of three-piece rims to meet the design specifications. All four wheels selected for the 1996 competition were size 6 by 13. This wheel selection allowed for tire rotations, reduced cost, and a wide selection of tire sizes, compounds, and manufacturers.4.GeometryThe designer can now set some desired parameters for the suspension system. These usually include camber gain, roll center placement, and scrub radius. The choice of these parameters should be based on how the vehicle is expected to perform. By visualizing the attitude of the car in a corner, the suspension can be designed to keep as much tire on the ground as possible. For example, the body roll and suspension travel on the skid pad determines, to a certain extent, how much camber gain is required for optimum cornering. The amount of chassis roll can be determined from roll stiffness while the amount of suspension travel is a function of weight transfer and wheel rates.Once a decision has been made about these basic parameters, the suspension must be modeled to obtain the desired effects. Before the modeling can begin, the ball joint locations, inner control arm pivot points, and track width must be known.The easiest way to model the geometry is with a kinematics computer program since the point locations can be easily modified for immediate inspection of their influence on the geometry. Should a dedicated kinematics computer program not be available, then a CAD program can be used simply by redrawing the suspension as the points are moved.When designing the geometry, it is important to keep in mind that designing is an iterative process and that compromises will be inevitable. For instance, the desired scrub radius might not be possible because of packaging constraints. When modeling the suspension, the designers should not aimlessly modify points without first thinking through the results. For example, the designer should visualize how the wheel will camber relative to the chassis when making the lower A-arm four times longer than the upper A-arm. One method that can be used to visualize the results is the instant center location for the wheel relative to the chassis. Another method is to use the arcs that the ball joints circumscribe relative to the chassis. For a complete explanation for determining suspension point locations from instant center locations refer to Milliken .Scrub Radius, KPI, and Caster - The scrub radius, or kingpin offset, is the distance between the centerline of the wheel and the intersection of the line defined by the ball joints, or the steering axis, with the ground plane which is illustrated in Figure 2. Scrub radius is considered positive when the steering axis intersects the ground to the inside of the wheel centerline. The amount of scrub radius should be kept small since it can cause excessive steering forces . However, some positive scrub radius is desirable since it will provide feedback through the steering wheel for the driver .Kingpin inclination (KPI) is viewed from the front of the vehicle and is the angle between the steering axis and the wheel centerline . To reduce scrub radius, KPI can be incorporated into the suspension design if packaging of the ball joints near the centerline of the wheel is not feasible. Scrub radius can be reduced with KPI by designing the steering axis so that it will intersect the ground plane closer to the wheel centerline. The drawback of excessive KPI, however, is that the outside wheel, when turned, cambers positively thereby pulling part of the tire off of the ground. However, static camber or positive caster can be used to counteract the positive camber gain associated with KPI.Caster is the angle of the steering axis when viewed from the side of the car and is considered positive when the steering axis is tilted towards the rear of the vehicle . With positive caster, the outside wheel in a corner will camber negatively thereby helping to offset the positive camber associated with KPI and body roll. Caster also causes the wheels to rise or fall as the wheel rotates about the steering axis which transfers weight diagonally across the chassis . Caster angle is also beneficial since it will provide feedback to the driver about cornering forces .UM-Rollas suspension design team chose a scrub radius of 9.5 mm, zero degrees of KPI, and 4 degrees of caster. This design required the ball joints to be placed near the centerline of the wheel, which required numerous clearance checks in the solid modeling program.Roll Center - Once the basic parameters have been determined, the kinematics of the system can be resolved. Kinematic analysis includes instant center analysis for both sets of the wheels relative to the chassis and also for the chassis relative to the ground as shown in Figure 3. The points labeled IC are the instant centers for the wheels relative to the chassis. The other instant center in Figure 3, the roll center, is the point that the chassis pivots about relative to the ground . The front and rear roll centers define an axis that the chassis will pivot around during cornering. Since the CG is above the roll axis for most race cars, the inertia force associated with cornering creates a torque about the roll center. This torque causes the chassis to roll towards the outside of the corner. Ideally, the amount of chassis roll would be small so that the springs and anti-roll bars used could be a low rate for added tire compliance . However, for a small overturning moment, the CG must be close to the roll axis. This would indicate that the roll center would have to be relatively high to be near the CG. Unfortunately, if the roll center is anywhere above or below the ground plane, a jacking force will be applied to the chassis during cornering forces . For example, if the roll center is above ground, this jacking force causes the suspension to drop relative to the chassis. Suspension droop is usually undesirable since, depending on the suspension design, it can cause positive camber which can reduce the amount of tire on the ground. Conversely, if the roll center is below the ground plane, the suspension goes into bump, or raises relative to the chassis, when lateral forces are applied to the tires. Therefore, it is more desirable to have the roll center close to the ground plane to reduce the amount of chassis vertical movement due to lateral forces .Figure 3. Front Roll CenterSince the roll center is an instant center, it is important to remember that the roll center will move with suspension travel. Therefore, the design team must check the migration of the roll center to ensure that the jacking forces and overturning moments follow a relatively linear path for predictable handling . For example, if the roll center crosses the ground plane for any reason during cornering, then the wheels will raise or drop relative to the chassis which might cause inconstant handling.The roll center is 35.6 mm below ground in the front and 35.6 mm above ground in the rear for UM-Rollas 1996 car. Since none of the previous UM-Rolla cars had below ground roll centers, the selection of the 1996 points was basically a test to understand how the below ground roll center affected the handling. Because of the large roll moment, the team designed enough camber gain into the suspension to compensate for body roll associated with soft springs and no anti-roll bar. The team was very happy with the handling but decided, for the next car, to have both roll centers above ground for a direct comparison between both designs.Camber - Camber is the angle of the wheel plane from the vertical and is considered to be a negative angle when the top of the wheel is tilted towards the centerline of the vehicle. Camber is adjusted by tilting the steering axis from the vertical which is usually done by adjusting the ball joint locations. Because the amount of tire on the ground is affected by camber angle, camber should be easily adjustable so that the suspension can be tuned for maximum cornering. For example, the amount of camber needed for the small skid pad might not be the same for the sweeping corners in the endurance event.The maximum cornering force the tire can produce will occur at some negative camber angle . However, camber angle can change as the wheel moves through suspension travel and as the wheel turns about the steering axis. Because of this change, the suspension system must be designed to compensate or complement the camber angle change associated with chassis and wheel movements so that maximum cornering forces are produced.The amount of camber compensation or gain for vertical wheel movement is determined by the control arm configuration. Camber gain is usually obtained by having different length upper and lower control arms. By using different length control arms, the ball joints will move through different arcs relative to the chassis. The angle of the control arms relative to each other also influence the amount of camber gain. Because camber gain is a function of link geometry, the amount of gain does not have to be the same for both droop and bump. For example, the suspension design might require the wheels to camber one degree per 25mm of droop versus negative two degrees per 25mm of bump.Static camber can be added to compensate for body roll, however, the added camber might be detrimental to other aspects of handling. For example, too much static camber can reduce the amount of tire on the ground, thereby affecting straight line braking and accelerating. Similarly, too much camber gain during suspension travel can cause part of the tire to loose contact with the ground.Caster angle also adds to the overall camber gain when the wheels are turned. For positive caster, the outside wheel in a turn will camber negatively, while the inside wheel cambers positively. The amount of camber gain caused by caster is minimal if the wheels only turn a few degrees. However, FSAE cars can use caster angle to increase the camber gain for the tight corners at the FSAE competition.UM-Rolla designed for a relatively large amount of camber gain since anti roll bars were not used in the 1996 suspension design. The use of low wheel rates with a large roll moment required the suspension to compensate for the positive camber induced by chassis roll and suspension travel. The camber gain for UM-Rollas 1996 car was from both the caster angle and the control arm configuration.5.Steering SystemThe steering geometry has a large influence on the handling characteristics of the vehicle. For example, if the system is not properly designed, then the wheels can unexpectedly toe in or out during suspension travel. This toe change is referred to as bump steer which is described in detail in both references . Bump steer is basically undesirable since the car changes direction when the driver does not expect the change .Ackermann steering must also be considered during the design process. Ackermann steering occurs when the outside wheel turns less than the inside wheel. This is possible since the amount of steering angle for each wheel is determined by the steering geometry. Reverse or anti-Ackermann occurs when the outside wheel turns more than the inside wheel during cornering .During a turn, the inside wheel travels around a smaller geometric radius than the outside wheel. Ackermann steering can be used so that the wheels travel about their corresponding radii, theoretically, eliminating tire scrub. However, designing for precise Ackermann steering might not provide the best handling since tire slip angles influence the actual turning radius . The designer must decide, based on the requirements, if the steering system design will include Ackermann geometry.UM-Rolla placed the rack and pinion in front of the axle centerline near the lower control arms because of packaging constraints. This placement required extra room in the frame design since the driver had to straddle the steering column. After building a test car that was hard to steer because of a half a turn lock to lock system, the 1996 steering system was designed to be one turn lock to lock. This was accomplished by changing the rack and pinion ratio instead of increasing the steering arm length because of packaging constraints. The system specifications for the 1996 car are: 76mm steering arms, 250mm diameter steering wheel, and 51mm of rack travel per one pinion revolution. These specifications were retained for the next race car design because of the handling characteristics. The 1996 UM-Rolla design has a small amount of anti-Ackermann due to packaging.FSAE suspension not only has to be competitive on the racetrack, but the suspension must also perform well in the static events. For the dynamic events, the designers should concentrate on the geometry so that most of the tire will stay in contact with the ground for all normal driving situations: braking, accelerating, and cornering. The suspension system must also be designed so that it is easy to manufacture and is reasonably priced for the cost analysis. To reduce the cost and complexity of the 1996 race car, UM-Rolla designed the system so that the wheels, hubs, and bearings were the same for each corner of the car.Designing the suspension geometry is only a small part of building a vehicle. A well engineered suspension system does not automatically make a fast race car. Although this paper has concentrated on the design aspect, development is just as important to the success of the package. Because the design process must take place within a given time constraint, the first suspension design might not provide the best handling. It is not uncommon to make design changes after the car is completed. It is more important for FSAE teams to compromise the overall design so that the car can be completed and tested prior to competition.6.FrameThe purpose of the frame is to rigidly connect the front and rear suspension while providing attachment points for the different systems of the car . Relative motion between the front and rear suspension attachment points can cause inconsistent handling . The frame must also provide attachment points which are not going to yield within the cars performance envelope.There are many different styles of frames; space frame, monocoque, and ladder are examples of race car frames. The most popular style for FSAE is the tubular space frame. Space frames are a series of tubes which are joined together to form a structure that connects all of the necessary components together. However, most of the concepts and theories can be applied to other chassis designs.Figure 4. UM-Rollas 1996 Frame Design7.StiffnessThe suspension is designed with the goal of keeping all four tires flat on the ground throughout the performance range of the vehicle. Generally, suspension systems are designed under the assumption that the frame is a rigid body. For example, undesirable changes in camber and toe can occur if the frame lacks stiffness. Superimposed images of a frame subjected to a torsional load and an undeflected frame and can be seen in Figure 5.Figure 5. Chassis DeflectionUM-Rolla has found that in most cases, a stiff chassis will not have a problem with yielding. However, some care should be taken to ensure that the attachment points of the frame do not yield when subjected to design loads. For example, the engine mounts should be made stiff enough to reduce the possibility of failure.Torsional Stiffness - Torsional stiffness is the resistance of the frame to torsional loads . UM-Rolla used FEA to analyze the torsional stiffness of the 1996 chassis. The solution of the simple rod and beam element model for the frame was roughly 2200 foot pounds per degree of deflection. The 1996 frame weighed approximately 27kg, which UM-Rolla believes is heavier than needed for a two day racing series. However, some extra structure was added to the frame to increase its safety. Also, the drivetrain mounts were significantly strengthened so that the car would be able to serve as a driver training tool for several semesters.As the 1996 frame evolved, the stiffness to weight ratios of different designs were compared. A chassis can be made extremely stiff by adding significant amounts of material to the frame. However, this additional material might degrade the performance of the car because of the added mass.Obviously, torsional rigidity is not the only measurement for analyzing the stiffness of a chassis. Bending stiffness can also be used to analyze the efficiency of a frame design. However, bending stiffness is not as important as torsional stiffness because deflection due to bending will not affect wheel loads . Because the design time is severely limited in FSAE, UM-Rolla has found that a torsional analysis is adequate to determine the relative stiffness of different frame designs.Triangulation - Triangulation can be used to increase the torsional stiffness of a frame, since a triangle is the simplest form which is always a structure and not a mechanism. Obviously, a frame which is a structure will be torsionally stiffer than a mechanism . Therefore, an effort should be made to triangulate the chassis as much as possible.Visualizing the frame as a collection of rods which are connected by pin joints can help frame designers locate the mechanisms in a design . Designers can also evaluate their frame by checking to see if each pin jointed node contains at least three rods which complement the load path.UM-Rolla chose to use thin wall steel tubing for the 1996 frame design. This required significant triangulation of the frame, since thin wall tubing performs very well in tension and compression but poorly in bending. The components which produce significant amounts of force, for example the engine and suspension, were attached to the frame at a triangulated point.Figure 6. Frame Triangulation(Frame, Side View)Previous UM-Rolla frames have lacked adequate triangulation for highly loaded components. These components were attached to the frame with load bearing tabs which were welded at the midpoint of a single section of tubing. As expected, this tube bent like a simply supported beam and caused unwanted movement of the attached component. Although these designs worked for the duration of the competition, they invariably failed by fracturing the tube or breaking the tab. For the 1996 car, all of the highly loaded components were attached to triangulated points.Area Moment of Inertia - The area moment of inertia has a large influence on the stiffness of a structure. Therefore, the farther material is from the axis of twist the stiffer the frame will be in bending and torsion. This concept is implemented by adding structural side pods to the basic frame.Figure 7. Structural Sidepods(Frame Top View)Figure 7 shows the triangulated side pods which were used to increase the torsional rigidity of the 1996 frame. This material also increased the side impact protection. The sidepods add structure as far from the centerline of the chassis as possible which increases the area moment of inertia between the front and rear suspensions. Most of the successful FSAE cars have structural side pods for safety and increased torsional stiffness.In addition to using the sidepods to increase the stiffness of the chassis, UM-Rollas 1996 entry used the roll hoop and down tubes to increase the rigidity of the frame. The 1997 FSAE rules state that the tubes from the top of the roll hoops to the base of the frame have to be 0.049 wall when fabricated from 4130 steel . Because these tubes are stiffer than 0.035 wall tubing, the frame stiffness can be substantially increased by properly placing the roll hoop tubes.8.Load PathDuring the design process, it is important to consider how loads are passed into the frame. A Load Path describes the path through which forces are dissipated into the frame. For example, Figure 8 shows how the vertical load generated by the weight on the wheel will travel through the upright, push rod, rocker, coil-over shock and into the structure of the frame. Of course, to properly investigate the forces involved, a freebody diagram for each component would have to be drawn. Nevertheless, this concept can be used by the designers to visualize how the frame should be constructed.9.Crash WorthinessIn the interests of safety for the drivers, the Formula SAE Rules Committee has written very specific rules to protect the driver from frontal, side, and roll-over crash situations. Figure 8. Load Path for Front Inboard SuspensionWhile designing the 1996 entry, the UM-Rolla team found that if the FSAE rules were followed and the frame was optimized for stiffness, it was obvious that the car would be adequate for most possible crash situations. Due to the possibility of a head on collision, more structure was placed in the nose of the frame than was necessary for the 1996 rules. Based on past experiences, the team believed that the probability of the vehicle running into a solid object, such as a curb or loading dock, was high. Therefore, considerable thought was given to the safety of the drivers feet during a frontal impact.10.PackagingEach of the systems of a FSAE car must be packaged within the frame. The placement of these components limits the available paths for tubes, which is usually detrimental to the chassis stiffness . For example, the driver occupies a section of the frame which could be used to significantly increase the stiffness of the frame.Suspension - Packaging of the suspension to the frame is generally not an interference problem since most of the components are exterior to the frame. However, it is especially important to attach the suspension components to stiff portions of the chassis to correctly dissipate the loads that will be created by these components .Designing the frame so the control arms are attached to a stiff portion of the chassis can sometimes be very difficult. UM-Rolla found that changing the distance between the control arm pivot points can help to optimize the load path for the control arms. This distance can be changed because it will not affect the suspension geometry, since the rotational axis of the control arm is not affected. However, decreasing the span of the control arms will reduce the arms ability to react to the forces which are generated by accelerating or braking.UM-Rolla found that the suspension should be designed concurrently with the frame. This allows the designer to concentrate on the load paths from the push rods and rockers so that the frame can efficiently react to the loads.Drivetrain - Correctly attaching the components of the drivetrain to the frame is very important for extended frame life. The relative stiffness between the engine, differential, and frame is not as critical as when attaching the suspension. This is due to the fact that most FSAE chassis layouts have short distances between the drivetrain components. The main design point is to ensure that the frame does not break during an incorrect downshift or a violent release of the clutch. Most of the frame failures which UM-Rolla has experienced were due to fractures in the engine mounts or differential mounts.When designing the frame around the motor and differential, on chain driven designs, sufficient clearance must exist so that several front and rear sprockets can be used. This will allow a wide selection of final drive ratios. Several UM-Rolla entries have been built with the inability to change the final drive ratio. This has proven to be a drawback when trying to drive the race car in the confined space of the FSAE competition and the more open spaces of autocrosses.Ease of maintenance is also an important design consideration when designing the frame around the drivetrain. UM-Rolla has found that providing clearance for direct removal of the engine will reduce the amount of mechanics stress involved with engine changes. It has also been found advantageous to provide simple access to all covers on the motor such as the clutch, alternator, and valve cover.11.ErgonomicsProperly incorporating the driver into a FSAE frame design can be very difficult because of wide variations in driver sizes. Each driver interface has to be designed so that it is comfortable for a wide variety of drivers. UM-Rollas 1996 entry is able to accommodate drivers who range in height from 1.58m to 1.90m.Controls - Designing the frame around the controls, such as the steering wheel and pedals, is a matter of ensuring that the structure of the frame does not interfere with the drivers task. Also, the controls must be adequately supported by the frame so that the attachment points do not yield while the car is being driven.The frame should not interfere with the drivers as they move through the full range of motion which is required to drive the car. The drivers arms are a particular problem in this area. In the past, UM-Rolla has designed cars which were very difficult for large drivers to keep their arms inside the cockpit. Fortunately, this was remedied on the 1996 chassis by increasing the cockpit cross sectional area.The frame designers should look beyond the structural considerations of the frame when designing it so major oversights are reduced. For example, a previous team encountered a packaging issue for their chassis when they placed the steering wheel directly over the rack and pinion. This was a design error because the universal joint between the steering wheel and the rack and pinion was not able to bend 90o.Safety Harness - Most importantly, the attachment points of the harness must be strong enough to ensure that they will not fail during a crash. They also must be positioned so that the buckles will not bind when the harness is tightened . This has been a problem for UM-Rolla in the past when trying to placing the attachment points for both large and small drivers.Egress - Rapid egress is very important since the 1997 rules mandate that the driver must exit the vehicle within five seconds . Past UM-Rolla cars had a difficult time with the egress requirement. These race cars were designed with structural tubes that left an area of only 165mm high for the drivers feet and legs to fit through. This was a situation were the designers compromised ergonomics for chassis stiffness.It is obvious that frame design is a compromise between stiffness, weight, and packaging. The stiffness of the frame is important because it affects the overall performance of the vehicle. If too much material is added to the frame in the quest for stiffness, the performance of the vehicle will be degraded because of the added mass. Not only must the frame be stiff and light, it must also package all of the vehicle systems. Therefore, the design of the frame will require many iterations to achieve a balance. The timeline of the competition will limit the number of iterations possible so that the car can be built and tested. If the basic design concepts have been applied to the frame and some thought has been placed into the integration of each sub-system, the end result will be a sound foundation for a FSAE car.UM-Rollas 1996 Design Methodology.Although it is simple to design a single part or system, it is more difficult to incorporate all of the parts and systems into a single package, such as a race car. The design team for each system or part must keep in mind how their design will affect the overall package. For example, the suspension design team must leave enough room between the left and right control arm pivot points so that the drivers legs will have enough room.This section explains the basic design sequence that UM-Rolla used for the 1996 car. This sequence is not the only avenue for the design of a vehicle. However, UM-Rolla has found that it is a logical sequence for the design of their FSAE cars.12.LayoutUM-Rolla started the 1996 design by determining the track width and wheel base dimensions of the vehicle. Once this was completed, the driver and engine placement was sketched into the design for an estimation of weight distribution. Some thought was given to the placement of other important or hard to packages systems. For example, the fuel system had to be packaged near the center of gravity to reduce the effects of its varying mass during the race.After the track width and wheelbase had been determined, the team made a preliminary decision on tire and wheel size. The design team settled on some basic suspension parameters: camber gain, caster, KPI, scrub radius, and roll center height. This was needed so that the design team could model the suspension geometry.UM-Rolla used a suspension modeling program to analyze camber change and roll center movement. The suspension was modeled with 0o of static camber, because static camber could be optimized during testing. During the modeling of the suspension, the team looked at vertical and lateral roll center movement and camber change as the chassis went through 25mm of vertical travel and 2 degrees of roll. It was necessary to perform several iterations before a satisfactory geometry was obtained.13.Solid ModelingOnce the preliminary suspension design was complete, the next step was to enter the suspension points into a 3-D computer model. Then the preliminary mechanical designs of the suspension components were drawn. The suspension was moved through its range of motion in a solid modeling package to check for interference between the control arms, tie rods, uprights, and wheels.After the suspension system had been checked for interference problems, the next step was to start designing the frame. UM-Rolla used a CAE package to model the frame structure. The major components, such as, engine and differential, were drawn into the model. To simplify this process, only mounting points or rough sketches were entered. Also, sufficient room was designed into the frame for the systems that had not been completed. For instance, ample room was left for the controls needed for various driver sizes.Figure 9. Major Frame ComponentsAfter the major components had been modeled, the first roll hoop design was placed into the model. This was needed because it represents a major component of the frame which is defined by the FSAE rules. Figure 9 represents this early frame model.Figure 10. Connecting the DotsAt this point, the inboard suspension system had not been designed. However, some preliminary designs for the inboard suspension allowed the load path theory to drive the design of the structure.14.Connecting the PointsOnce the main points of the frame were defined in the model, the connect the dots phase could begin. By using the concepts of triangulation and area moment of inertia, the defined points were connected with tubes. Connecting the dots, simply consists of attaching the front suspension to the rear suspension while providing attachment points for the systems of the car. Refer to Figure 10 for the final 1996 frame design.15.AnalysisOnce all of the points had been connected, the frame was ready for finite element analysis. This analysis was performed on a commercially available CAD/FEA software package. Beam elements were used for the major frame structure while rod elements were used for the suspension as illustrated in Figure 11. A more representative load could be applied by using a model with the suspension attached. Since accurately modeling a welded joint is beyond the undergraduate level, this model was strictly for determining if the frame was a structure.Figure 11. FEA ModelAfter the model was solved, the results could be viewed as an animation to expose any weak links. This approach allowed for quick what ifs. For example, if an area appeared to be over stressed, a different geometry for that joint could be substituted and modeled. Also, the UM-Rolla designers found that tubes with long versus short spans between joints should have a larger area moment of inertia to increase the stiffness.To reduce the cost of the race car, only a small selection of tube sizes were used, which made the modeling simpler since wall thickness optimization was limited. The 1996 UM-Rolla team used the following tubing sizes to construct the structure of the 1996 chassis: 1 x 0.065 (Roll Hoops)1 x 0.0353/4 x 0.0355/8 x 0.035To simplify the complexity of the frame construction, the number of tubes which had bends in more than one plane was reduced to only two.Although this is not the only sequence for designing a FSAE car, UM-Rolla has successfully used this basic method for the past three designs.Unlike the school environment, there are no right or wrong answers in the FSAE competition. The designers can make successive iterations on their designs until a satisfactory compromise has been reached. Constructing FSAE cars imparts to college students the knowledge of how to function in real world design groups while also introducing them to the entire design process involved in a products development.During the design process, the team must achieve a compromise between cost, manufacturing, performance, and design time so that their car will be competitive in all aspects of the FSAE competition. The timeline of the competition, combined with the rigorous schedule of college, limits the amount of iterations for each design. However, the team should understand that it will take several iterations to converge on a satisfactory design. The amount of time used for the design process subtracts from the time available for manufacturing and testing. Although this paper has concentrated on design, it is very important to test the car so that any design oversights will be highlighted before competition.A poorly engineered vehicle may not perform well at the competition. Conversely, a highly engineered car may not perform well unless there is time to manufacture and test. For the inexperienced FSAE team, concentrating on complex engineering techniques can be too time consuming for the amount of performance gained. Therefore, FSAE teams should use basic engineering concepts to design their car. This will simplify the design process and allow the team to finish the car as early as possible to allow for testing and redesign.附录B方程式SAE是由美国汽车工程师协会（SAE）的赞助，学生必须设计、制作并跟一个小公式风格赛车。竞争的基础是一个虚拟的公司承包的一组工程师建造一个小公式的车。由于汽车是专为周末赛车公司建立一个最大价格为8500美元。这赛车也局限于单一的610 cc排量发动机和一个进节流。其他主要规则要求汽车悬架系统必须具有最低车轮旅行50毫米和轴距大于1524毫米。剩下的规则定义的安全要求，如侧面碰撞保护等。竞争是分为静态和动态的活动。静态事件中包括成本分析，以及工程设计的销售报告。动态部分竞争是直径15.25米加速度的事件、91.44米耐力比赛， 0.8公里汽车交叉和44公里燃油经济性。竞争的FSAE已被建立，以提供一个大学生教育经验类似类型的项目也将面临在劳动力。参与FSAE学生团体的工作，从抽象的设计项目，直到它完成。这方面的工程设计、团队合作、项目管理、金融已纳入基本规则公式SAE。本文旨在介绍一些基本概念的悬架和框架设计，也凸显出罗拉设计方法时使用1996年暂停和框架。部分讨论悬架设计的基本参数，介绍了具体的例子。其次，框架部分将讨论如何实现的让步FSAE设计约束。最后，设计部门作了一个简要的概述罗拉设计方法采用1996年赛车。1.悬架系统的几何形状FSAE悬架在一个非常狭窄的领域操作对车辆动力学主要由于有限的转弯速度是受赛马场的尺寸。因此，FSAE悬架的设计应该集中在约束下的竞争。例如，车辆跟踪宽度和轴距的成功因素控制汽车的操纵特性。这两个维度不但影响重量转移，但他们也会影响的转弯半径。不仅运动学必须考虑FSAE悬架，但也必须价格合理成分的成本分析、市场销售的简报。例如，内悬架可能是一个更加卖座悬架设计中，当外更少、更代价更容易制造。悬架系统的几何形状的部分集中于一些基本的地区，强调了悬架的设计的设计团队罗拉选定其1996赛车悬架系统的几何形状。罗拉选择使用一个四轮独立悬架系统和推杆内线圈驱动的冲击。这一决定主要是因为组件的约束。此外，内悬架的出现被认为是重要的对于设计和销售报告来判断类似，所以人们把它称为现代赛车。2.轮距和轴距轮距的定义之间的距离中心线左、右两轮实例于本许可证图1。这个维度是很重要的，因为它抗拒转向颠覆时刻由于惯性力在引力中心(CG)、侧向力轮胎。为设计师，跟踪宽度是很重要的，因为它是一个部件的数量影响横向重量转移。同时，设计师必须知道在运动学分析轮距的悬架系统的几何形状可以开始了。轮距上控制臂下控制臂上球头下球头图1 轮距示意图当选择轮距、前方和后方，无需轮距不尽相同。例如，追踪是典型的宽宽度在前线的后轮驱动的赛车。这个设计理念用于增加后方牵引在角落的数量出口减少身体的滚动抵抗后方轮胎相对于前胎。基于角落里的速度和马力体重的比例FSAE汽车，这个概念应考虑设计者。轴距也需要的是确定的。轴距被定义为之间的距离轴中心线前方和后方，也影响重量转移，但在纵向方向。轴距相对的CG的位置不会有很大的影响悬架系统的运动学。然而，轴距应确定早在设计过程中有一个大轴距以来影响产品的组件组件。轮距和轴距的起点，设计师应当研究对手的尺寸来作为自己的计算基线。FSAE汽车规范竞争的团队，包括轮距和轴距，可在事件计划公布SAE。1996年的设计团队挑选了一个1727毫米轴距，1270毫米宽，前跟踪轨迹宽度1219毫米的后方，根据以往的罗拉汽车。虽然这轴距足够的FSAE大小的课程、竞争罗拉设计团队决定增加汽车轴距接下来1854.2毫米。这个增加是为了提高其稳定性，适合高速弯在竞争。3.轮胎和车轮在轮距和轴距考虑过演说、轮胎和车轮选择下一步的工作是在设计过程中。由于轮胎的处理是重要的车、设计团队要深入研究轮胎尺寸和化合物可用。轮胎的大小也是很重要的在这个阶段的设计达到高峰以来，杀伤力最大的轮胎几何之前，必须知道被确定。例如，对于一个给定的轮胎高度圆盘直径决定关闭低球接头可到地上如果组件内车轮。轮胎大小设计师应该知道号码不同尺寸的轮胎给一个给定圆盘直径是有限的。因此，考虑轮胎的重要性处理，轮胎的选择过程应该是一个井然有序的过程。由于数量的轮胎在地面上有一个很大的影响，它有时是理想控制使用广泛的轮胎增加抓地力。然而，重要的是要记住宽轮胎加旋转质量，必须加速了一个受限制的FSAE引擎。该附加质量可能更为有害于他们的整体性能比增加在牵引更广阔的轮胎。不仅是一个广泛的轮胎增加质量，但也增加了多少橡胶必须加热。因为赛车轮胎下运作而设计，最有效地在一个特定的温度范围内，该附加材料可以预防轮胎达到最适温度范围。罗拉小组使用的轮胎，为1996年的竞争的设计工作最有效地至少71 度。在选择的过程中如何设计必须考虑轮胎将会影响整个系列的性能。例如，天气条件的FSAE动态事件可能会决定哪个轮胎化合物和轮胎的尺寸应该用于竞争。另一个重要的问题是轮胎的价格从成本团队的一大部分的预算。在1996年的竞争，罗拉挑选了一个由613赛车轮胎20对于前方和后方的汽车。由于采用低汽车质量，一条狭窄的轮胎选择了所以轮胎温度会比以前的罗拉设计。这个轮胎选择操作温度增加48度至60度。比赛的天气预测，很酷，因此团队带来了一套硬软复合轮胎。项目组选择使用复合由于天气越努力在一场需要耐力的预计是明确和温暖。车轮选择一旦已决定以哪一个轮胎大小来使用，下一个应该是车轮选择。通常情况下，车轮尺寸是固定的，允许少量修改。因此，重要的是有轮子的投资前考虑的一些设计目标。一般来说，正直，制动钳，并放置在转子轮，要求清拆抵消轮。它通常是比较容易设计出悬挂几何如果车轮轮廓是众所周知的。例如，球接头位置限于由车轮配置文件定义的区域。一些组件的限制见图2。其他的考虑为轮选择包括成本、可用性、螺栓圆，和体重。例如，三件套，虽然昂贵，有钢圈的独特优点和型材提供多种抵消能改变在设计阶段。1996年罗拉设计悬架系统的几何形状在车轮轮廓，从汽车，然后获得一个先前的一套三件套的钢圈来满足设计要求。所有四个车轮被选为竞争的6号13分。这个轮子旋转允许轮胎选择，降低了成本，以及宽选择不同尺寸的轮胎，化合物，和生产商。4.几何尺寸设计师现在可以设置某种所需参数的悬架系统。这些通常包括曲面增益、轮中心的位置和洗涤半径。这些参数的选择应根据轮子是如何预期履行。观察的态度在一个角落，汽车悬架可设计成让尽可能多的轮胎在地面上是不可能的。例如，身体的滚动刷洗半径（+）车轮中心线转向轴线图2 1996年前悬挂示意图和悬挂旅行对打滑垫决定，在一定程度上获得多少曲面是需要优化转弯。底盘的数量可以确定轮轮的刚度，从数量的停牌的旅行是一个函数的重量转移和车轮的利率。一旦决定作出关于这些基本参数的确定、悬挂必须被提取出来获得预期的效果。在建模可以开始，球关节的位置、内部控制臂支点，并跟踪宽度一定要知道。最简单的方法是与几何模型的运动学计算机程序从点的位置，可以很方便地进行修改立即检验其对几何。要一个专门的运动学计算机程序无法得到，然后CAD程序可以用简单的通过刷新悬挂点的移动。几何设计时，重要的是记住设计是一个反复迭代的过程，妥协是不可避免的。例如，预期可能不可能取消半径由于组件的约束。建模时暂停，设计师应当不是漫无目的不先思考修改点的效果。例如，设计师应该如何曲面想象的摩天轮将相对较低的底盘时，长四倍多于上臂。一种方法可以用来观察结果都是瞬间的中心位置，为车轮相对的底盘。另一种方法是使用弧球关节限制相对的底盘。完整确定位置悬挂点从即时中心的位置是指米利肯一案。刷洗半径、KPI，施法者刷洗，或支撑半径之间的距离偏移，中线的车轮和交叉的线球接头的定义，或转向轴、实例的地线2中可以看出。刷洗半径是积极当转向轴与地面里面的轮中心线。刷洗半径的数量应保持小，因为它会导致过度转向部队。然而，一些积极的刷洗半径是可取的，因为它将提供反馈通过方向盘司机。KPI是支撑倾向从前面的汽车，是之间的角度和车轮转向轴中心线。减少刷洗半径、KPI可以收编到悬架的设计如果组件球接头近中线的车轮是不可能的。刷洗半径可减小KPI设计，它将会转向轴相交的地线接近轮中心线。过多的KPI的缺点，不过，就是外面的车轮，转过身来，从而将积极部分的轮胎从地面。然而，静态曲面或者积极施法者可以用来中和获得积极的曲面伴随KPI。施法者的视角转向轴当从侧面观察汽车，是积极转向轴倾斜时对车的后方。用积极的施法者，外面车轮在一个角落里将曲面从而有助于抵消负相关的积极曲面KPI与身体转动。施法者也造成了轮子的上升或下降的车轮转向轴旋转的转让重量对角线穿越底盘。施法者角度也是有益的，因为它将提供反馈给驾驶员转弯部队。罗拉的悬挂设计团队的一个灌木丛生的半径选择的9.5毫米，零摄氏度，4度及连铸机。本设计要求球关节附近放置中线的车轮，这要求多间隙实体模型检查程序。轮中心一旦基本参数的确定，运动学系统可以解决。运动学分析分析包括即时中心两套车轮相对的底盘和底盘与地面的相对如图3。集成电路是标记点即时中心轮相对的底盘。另一个即时中心图三轮中心，是指出底盘枢纽相关的地面。轧轮中心的前方和后方，定义一个轴支点周围底盘会转弯时。自从在滚动轴赛车，大多数惯性力联系在一起创造了一个扭矩的转弯轮中心。这样的扭矩使底盘，把对轮以外的角落。最理想的情况是，一定数量的底盘卷将小使弹簧和扭力杆可以低价使用以增加轮胎合规。然而，对于一个小倾覆的时刻，必须接近轮的轴。这将表明轮中心要相对高的让人无法靠近重心。如果轮中心是任何高于或低于地平面，“顶”力会应用到底盘转弯时部队。例如，如果轮中心是在地面上，这种“顶”力下降导致停赛，相对于底盘。悬挂下垂通常是不受欢迎的，因为根据悬架的设计，它会引起积极的曲面可减少大量的轮胎在地面上。反之，如果轮中心的地下，悬架飞机进入肿块，或提高相对的底盘，当侧向应用于轮胎。因此，它是更可取的轮中心靠近地面的飞机来减少大量的底盘由于侧向垂直运动的。右左轮中心图3 前轮中心从轮中心是一个即时中心，重要的是要记住轮中心将转会停牌的旅行。因此，设计团队必须检查迁移的轧轮中心，确保“顶”力量，倾覆的时刻跟一个相对线性可预测的处理途径。例如，如果轮中心穿过地平面转弯时因任何原因，然后将升高或下降车轮相对于底盘可能引起变化无常的处理。轮中心是35.6毫米地下在前排，35.6毫米在地面上的后方为罗拉 1996车。既然这里没有以前的罗拉汽车已卷中心地下的选择基本上是一个测试1996分，以了解其影响地下轮中心处理。因为液体到气体的大卷的时候，在获得足够的曲面团队设计的悬架来弥补相关身体滚动软弹簧和没有扭力杆。这支队伍很满意，但是决定处理的下一辆车，有这两卷中心地面了一个直接比较二者之间的设计。眉形曲面的角度和垂直轮飞机被认为是一个消极的角度的顶部时车轮对中心线倾斜的车辆。眉形调整倾斜方向盘轴垂直，通常由调整球关节的位置。因为数量的轮胎在地面上是受外倾角、拱应该容易，可调，悬架可调整为最大转弯。例如，将大量的曲面所需的防滑垫小可能不是同样的清扫角落耐力的事件。最大的轮胎能生产转向力将发生在一些负面外倾角。然而，外倾角可以改变为车轮通过时，车轮停牌的旅行转到转向轴。因为这种变化，悬架系统的结构必须赔偿或补充外倾角变化底盘和车轮运动联系在一起，产生最大转弯力量。补偿的金额或获得垂直曲面是由轮运动控制臂的配置。获得了曲面通常有不同长度的上、下控制臂。利用不同长度控制臂，将穿越球接头不同弧相对的底盘。控制臂的角度相对彼此的数量也影响曲面增益。因为曲面获得是一个函数的链接几何，一定数量的获得没有一样都耷拉下来的肿块。例如，悬架的设计也许需要一个度，每轮拱25毫米下垂和消极的两个学位，每25毫米的肿块。曲面可以被添加到静态补偿，然而，身体滚动增加可能会伤害到曲面其他方面的处理。例如，静电太多曲面可以减少大量的轮胎在地上，从而影响直线制动和加速发展。同样的，太多的曲面获得在停牌的旅行会造成部分的轮胎与地面接触宽松。施法者角度也增加了整体曲面获得当车轮是转变。对积极的施法者，外面车轮在一定的负面效应，而保持曲面内轮。曲面的数量获得施法者造成最小如果车轮只有把一些度。然而，FSAE汽车可以使用的角度对提高连铸机曲面为狭窄的角落获得在FSAE竞争。设计罗拉较大量的曲面自反轮酒吧获得没有被采用在1996年的悬架系统的设计情况。使用低利率与大型轮轮悬挂规定的时间来弥补积极诱导和底盘轮曲面停牌的旅行。中厚板轧机轮型有罗拉 1996车被两个施法者控制臂角度和配置。5.转向系统督导几何有大量的操作特性影响的车辆。例如，如果系统未能正确设计，然后竟然车轮可以在脚趾或停牌的旅行。这种变化是称为脚趾掌舵，基本上是撞以来避免不良会改变方向时，汽车司机不希望这样改变。阿克曼转向还必须考虑在设计过程。当外界发生阿克曼转向轮翻不到内轮。这是可能的因为数量转向角度是由各轮转向几何。阿克曼或逆转发生在外面超过内轮翻转弯时轮。在一个回合，绕着一个小轮内几何半径比外面轮。阿克曼转向可以用来使车轮旅行大约他们相应的半径，从理论上来讲，消除轮胎擦洗。但是，设计为精确的阿克曼转向可能不提供最佳的处理因为轮胎滑转角度影响实际的转弯半径。设计者必须决定，根据要求，如果转向系统设计包括阿克曼几何学。罗拉把齿条和齿轮在前面的轴中心线下游附近因组件控制臂的约束。这相位的需要额外空间框架设计自运司机不得不转向管柱。建立一个测试车后，很难避免由于半转锁锁系统，1996年的转向系统被设计用于一圈锁锁。完成了通过改变齿条和齿轮比的增加而转向节臂长度因为组件的约束。该系统规格的汽车是1996：直径76毫米转向臂、250毫米的方向盘和每一个小齿轮齿条51 mm。本规格书为下一场比赛保留了汽车设计由于处理特点。1996年罗拉设计有少量的阿克曼由于组件。FSAE悬挂不仅具有竞争力，但赛道上悬挂也必须很好地完成静态事件。动力事件，设计师应当集中精力几何，大部分的轮胎会保持接触地面让所有正常行车制动、加速、转弯。悬架系统也必须设计，很容易制造，

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