资源描述
XXX设计(XXX)外文资料翻译院 系专业学生姓名班级学号外文出处http:/www.idealibrary.com附件：1.外文资料翻译译文（约3000汉字）； 2.外文资料原文(与课题相关的1万印刷符号左右)。指导教师评语：指导教师签名：年月日附件1：外文资料翻译译文J.agric. Engng Res. ,(2001) 78(1),43-60doi:10.1006/jaer.2000.0632,可在线获得于 http:/www.idealibrary.comPM-力量和机械通过去除大麻叶子和花头促进大麻的收获D. M.Bruce ; R. N. Hobson ; R. P.White; J. Hobson（2000年2月11日收到；2000年8月11日以校订形式接受；2年10月25日在线出版）种植麻（Cannabis sativa）是为了获得纤维，为了从茎杆中分离出纤维，大麻需要在被切之后沤麻而使其变软。无论是沤麻之前还是之后，晒干收割的大麻是必须的，但是茎杆的晒干极易被其上存在的叶子和花延迟。在沤麻之后，大麻晒干的延迟将会降低纤维的质量及在捆扎时造成大麻的损坏。而本项工作目的是决定是否能在大麻收割之前，通过一动力回转机械把大麻的叶子和花冠从直立的大麻茎杆上切去。我们做这样的一个实验，在实验室里向一台回转机械中推进了40株大麻。实验的效果确立了这种方法，而且转子的回转速度、大麻的推进速度、以及刀齿的设计都已通过验证。在设定的范围内，在离大麻顶部900毫米的范围内有92%以上的与它接触的叶子和花头被切去。本设备是为了试验田试制的，它由一个1.2米宽的安装在拖拉机牵引臂架上的转子组成，试验显示此机器在一定的前进速度，转速，和相关高度范围内非常有效。在它最适宜的三个参数的设定下，即前进转速为5.8千米/小时、转速645转/分和在1.6米高度范围内，本机可以去95%的与之相接触的叶子和花头。本机的实际执行部件是一个含有剥削转子的机构，它安装在切割原件的头部。2001 Silsoe 研究学会记号法Ma在正常剥削高度之上剩下的未剥削 h高度，米； 的叶子的质量，千克； Mb在正常剥削高度之下剩下的未剥削 m茎杆质量，克； 的叶子的质量，千克；Ms被剥削转子去除的材料的质量，千克； r转子速度，千转/分s总剥削效率； 正常剥削高度之上的剥削效率f 前进速度，千米/时；1.介绍在北欧种植的大麻是为了从茎杆中获取纤维产品，这种纤维具有高的伸缩强度，可用于造纸合成和生产工业纺织品。少量茎杆心部具有吸水的特性可用作动物的草垫。在当前的实验中，茎杆在仍然很绿的时候就开始被切开，这时大麻的种子仍然未完全成熟，大麻的叶子、花头及种头仍然存在，茎杆一旦被切开，就会被浸渍起来。收割后茎杆会被暴露在割道上晾干，然后浸渍起来，这样有利于韧皮部或外层的纤维束和周围细胞间化学粘结物的微生物解，这样做可以在纤维破坏最少的情况下把纤维从干茎中提取出来。当茎杆被浸渍到最佳程度时，纤维具有很高的强度，而且它们即将从茎杆的剩余部分中分离出来。假如浸渍再继续下去，纤维的强度将会因逐渐减弱而失去价值。因此，在最佳浸渍阶段把茎杆收集起来对保存和下面的进程来说是非常重要的。除非茎杆被收集并被烘干得极其干燥，以至于可以阻止微生物分解活动，否则在存储期间将会发生进一步的恶化。在英国，九月早期，大麻收获后，浸渍茎杆的烘干将花费3到6周的时间，而北欧发热天气状况常来说是不利于这此茎杆的烘干。所以，为了避免过度浸渍，当条件适宜时，浸渍的茎杆在割道上快速烘干是非常重要的。在茎杆切割前切去其上的叶子和花头就很可能促进烘干，并使浸渍后的茎杆在整个长度上显露出来，以利于更好的烘干。叶子和花冠的切削也可能提高茎杆从收获时的适度烘干到浸渍开始时的湿度的烘干速度，从而缩短了大麻作物占据田地的时间。空气将更易渗透到割道的大麻中去，否则叶子和花冠含有的附加水分必须蒸发掉中。这在捆扎浸渍后的作物时是非常重要的，因为种头很可能仍然潮湿，这将对捆好的大麻作物造成部分的损坏。另外，大麻叶子和种头的切割还可以减少捆扎、存储、运输和处理作物材料的量，从而降低成本。这样还可以返还一些作物材料给田地，从而提高土质的肥沃程度和结构，同时减少作物处理时的浪费及减少像工业垃圾那样分选作物废品而引起的高额处理费用。在荷兰的大部分地区，几乎关于如何从大麻作物上切去花头和叶子以提高茎杆的收获及其进程经济性的研究已经完成。而对于以种子和叶子作为主要产品进行回收的工作需要不同的方法，但这已不是本文的主题了，Huisman et al.(1988)利用一个改进的蚕豆收割机来切除大麻的种头（将切割刀具、卷轴及运送装置数加倍）。这种办法仅是部分的成功，因为它切割之后在大麻茎杆上留下了其种子和叶子的三分之一，并且成本很高。Bolkstein et al.(1991)进行了一次大麻收获的经济评估，得出顶层（种子和叶子）在高质量的大麻收获中是必须切除的。他同样报到了用改进的蚕豆切割机作的测试，结果是在包括8%的茎杆损失在内，共有25%的地方被漏掉了。Feitsam和Swinkels（1990）的设计同样利用了一台蚕豆收割机和一台安装在篱笆修剪机臂上的连枷割机。蚕豆机在大麻切割中运动缓慢（1.3千米每小时）并且运输器在将切割后的作物传送到另一边进会遇到妨碍。同时，连枷割草机虽然运作得很好，但却会引起不定量的茎杆损失，无论是用连枷的还是用手动的割草机去除种子和叶子，如果要去除大部分的叶子和种头，都将导致部分茎杆的损失。（Huisman et al，1988.Feitsma&Swinkels.1991)另外，手动切割机要求一种运输被切作物的通道，而种种阻碍将使工作效率降到很低。De Meayert和Husisman（1994）利用一旋转电刷去收割大麻，他们同样也进行了一次理论上的研究。利用旋转电刷来去除叶子和种头也仅仅是部分的成功。虽然在这种情况下损失的茎杆减少了，但是它在去除叶子时并不是足够的有效。在后期的收获中，每去除0.55千克的叶子，估计将损失0.02千克的茎杆，在田地里试验出每一千克的干燥作物中仅有0.04千克的叶子，这远小于模拟中的估计价值，上面出现的所有的方法都会因下面的一个或几个原因而无法成功。（1）切除或破坏的部分茎杆。（2）无法足够有效地去除叶子和花头。(3)工作效率低且容易受阻碍。以前开发出来的通过脱粒谷类头部来收获五谷的机器（Klinner et al，1987）是以带有销孔结构的脱粒元件的转子为基础的。这些脱粒元件是用高硬聚合材料制造的。除了能有效地切除农作物范围内的种子和谷粒外，这种脱粒系统 对落叶作物如薄荷、苜蓿，荨麻也同样有效，因此这种设备可作为大麻脱粒的一个潜在出发点。这项工作的目的是（a)确定是否能在不损失纤维的前提下有效地实现大麻叶子的花头剥削；（b）在一实验室模型中确定转子设计、运作速度和设计高度以及在作物中的前进速度对剥削工作的影响；（c)去开发，实地实验和评估此设备以证实它在纤维大麻中的剥削功能。2材料，机械及方法在实验室中，我们将生长于英国hertfordshire地区的经济作物Felina34大麻用普通收获方法手工从根部切除。然后用塑料袋包起来并在两小时内进行实验，以减少茎叶脱水对其性能的影响。用于实验的大麻是生长于英国Esswx地区的一种白垩砂土中的。在这里植株密度控制在180株每平方米，其产量为4.3t/ha。此实地试验发生于1997年9月15日。2.1实验室实验2.1.1设备图1所示的剥削设备是利用在模拟实地运作时将大麻推进到旋转剥削机里的原理开发出来的，它包含一个由电动马达驱动的经过一个多级变速器变速的转轴。在其上可安装一个范围为300毫米宽的转子，一个可在大麻和转子接触之前使大麻偏斜的引擎罩框架，一个水平8米长的传送道和一个由多级变速线性马达驱动的推车。在推车上40株大麻可被固定成株距100毫米、行距150毫米的两排，用它们来模拟密度为60株/平方米作物。大麻的底部被固定在允许他们倾斜的柔性套筒上，在柔性套筒上大麻倾斜的方式和田里的大麻很相似。线性马达可使推车在1米加速到选好的速度，并在接触期间使推车在作物和马达之间维持这一速度，以便模拟机器在田间的行走速度，此实验仪器的一面是没有障碍的，以便高速摄像头可用来研究作物在和马达及支架接触时的行为。转子是由一个平面八角形的柱体组成的，在它上面可以安装各种不同结构的由高密度聚合物构成的剥削原件。图3中三种结构的剥削元件已经通过审查，它们可安装在同一八角形中心基体上。这种八角形基体已应其销孔的结构而闻名，并早已用于五谷的脱粒，至于在这里是作为一个标准件而设计的。它是一个结构和以前相同，但横截面积只有原来的一半，孔数加倍，长度增加20%的元件，这些元件装配之后形成的转子直径分别为530，620和560毫米。2.1.2实验参数的确定研究不同结构的剥削元件的原因是因为转子的转齿要像转子与作物交战一样，能透过大麻束（如图4）。穿透的深度取决于前进方向上单位长度上大麻的数量和厚度，只要转齿被认为能更好地完成剥削工作就好了。前进速度是确定工作效率的一个主要因素。所以可以实现有效剥削的最高前进速度已在研究中。转子的速度被认为是有效剥削程度和茎杆破坏程度的折衷。2.1.3方法每运转一次机械，都会有40株大麻被选中。大麻的高度及顶部、中部和底部的直径以及最低的叶子的位置都被测了出来，同时，40株大麻中大多数的植株的总体结合形式也被记录下来。一旦大麻在小车上固定好，转子就调到相应的速度，小车将以选好的速度推进并经过转子，然后大麻被卸下来，称其质量，而大麻上仍然剩下的叶子和花头将被用手除去，最后再称一下质量。在上一步中，大麻上工作范围内依然剩下的叶子、花头和转齿能达到的最低点之下的叶子和花头的质量将被记录下来。这个程度是因为具有四种转速：400，550，700，及900转/分和四种前进速度3.5，4.3，5.5，及7.1千米/时的标准剥削元件而做的研究。双倍销孔的设计是在转速为550和700转/分的条件下测试的，而一半大小的设计是在400和500转/分的条件下测试的。在上面的所有情况下，转子的高度都是固定的，及转子的齿顶距大麻根部的距离都为900毫米。2.2实地实验2.2.1设备和实验室一样，Slisoe研究所设计并试制了一台机器来研究其在农田里剥削工作的情况（如图5和6所示）。此机器的设想是在一个原为篱笆修剪工作提供的由拖拉机带动的压力机臂上安装一个剥削工作头。剥削工作头包括一个1.2米长的由一下压力马达驱动的转子、一个引擎罩和作物分选装置。这台机器的工作情况是这样设计的：一旦地面上的作物被剥削完后，机臂就可以在能够到的情况下越过已剥削的地方进行下一次剥削工作。在这之后，所有被剥削过的作物就必须被收割掉，以进行下面的剥削工作。实验室的试验结果显示：田里工作的机器的参数已经被选定为500800转/分、转子的高度已由已知的作物的高度确定为2米、前进速度为7千米/时，这些值不允许任何变动。不幸的是我们无法获得足够的双倍销孔元件，所以在田地试验中标准剥削元件被投入使用。用于驱动转子的发动机在700转/分的转速下可提供15千瓦的功率，这个动力装置对于有可能遇到的任何情况都是足够的。2.2.2方法一个为实现有效土地进程而设计的实验已经完成，它的目的是对本设备在大麻茎杆上去除叶子和花头的有效性进行评价。它的控制变量为剥削转子的离地高度，转子速度和拖拉机的前进速度。每种变量都选出了三种级别（如表1所示）并用一个23 的因数结构来表示。中心点扩张需要一个二次方程来判断，以此来预测最佳设置值。每一块1.2米*10米的大麻地在处理之前和之后需要取样10株大麻。在初步取样之后，转子被驱动到适当的转速并开始进行小块地剥削，在小块地之间留下2米宽的大麻来让操作者改变前进速度。在地里的两部分作物被处理后。作物被收割以进行其它部分作物的收获。表1实地实验中的参数值高度（米）转速（转/分）前进速度（千米/时）1.35454.31.76455.82.07706.9用来评估剥削效率的方法是测量在齿顶能接触到的大麻的最低高度之上剩下的大麻叶和花头的数量。这在处理没小块地之前和之后都要测量10株。3结果3.1实验室结果剥削效率s是通过剥削的叶子和茎杆的数量来计算的。通过公式s=100MS/(Ms+Ma+Mb)(1)来计算。这里MS是剥削转子去除的材料的质量，单位为千克；Ma是在正常剥削高度上设剩余的未剥去的叶子材料的质量，单位千克；Mb是正常剥削高度以下的未剥叶子材料的质量，单位千克。这种测量方法非常准确，因为在正常剥削高度以下不可能剥掉任何叶子。第二种计算效率的方法是通过在正常剥削高度即转齿可接触到的高度之上的剥削来计算的。通过公式：s,=100MS/(Ms+Ma)（2）来计算。表2实验室剥削仪器的实验结果。表2实验室大麻剥削装置的测试次数转速转/分转子高度毫米转子类型前进速度千米/时平均茎杆直径毫米平均最低叶高度毫米植株高度毫米总剥削效率900毫米以上的剥削效率1700900std3.58.7706173584.795.22700900std4.38.6830171488.396.73700900std5.58.7846177589.496.04700900std7.18.6697175783.995.75700900std7.19.3815182884.592.56900900std7.19.4877181291.295.67700900dkh7.19.9830180390.696.98550900dhk7.110.2903184393.597.69550855lte7.19.41121189494.194.110700855lte7.19.4857177789.294.011400900std7.19.21137183575.377.512550900std7.19.41072184589.492.2转子类型（见图3）：std用于谷物的标准脱粒元件；dkh双销孔结构；lte深齿元件3.1.1剥削效率图7给出剥削前后的大麻模样的例子。三种类型的转子在在大麻叶子和花头的剥削中工作的都很好，以第二种方法来说，最低接触点以上的去除效率，像在表现转子好的工作特性似的，除了在400转/分的低转速是仅达到77%以外，其他的在整个运作过程中都超过了92%。对于标准齿来说，转子转速从550转/分提高到900转/分或前进速度从3.5千米/时升到7.1千米/时对剥削效率来说并没有过大的影响。所以建议前进速度取7.1千米/时是被普遍接受的。在高速的情况下，由小车最初加速过程而形成的大的偏斜惯性对大麻与剥削转子的良好接触来说是太大了，从而无法实现。当转速为550转/分或700转/分时，标准齿和一半大小的标准齿类型之间并没有什么不同。但是在前进速度为7.1千米/时时双倍销孔的齿形无论是在550转/分还是在700转/分的情况下都明显的比其它两种齿形好，这可能是因为双倍销孔类型有更多的和大麻接触的机会吧。这些额外的接触对剥削比本模拟实验中80株/平方米更密的大麻来说将更有优势。因为像图4所示的那样，较低的叶子的剥削是通过齿顶实现的，转齿之间的绝大部分空间是被较早接触的大麻的梢部所占据的。实验结果显示转子只能剥掉距顶部垂直距离为900毫米的范围内的大麻叶子和花头，这个范围的极限值是不可能被确定下来的，因为密集的缺乏光照的大麻会发出更低的叶子。但田地边缘的大麻应该需要这样的测试。3.1.2茎的损坏像预计的那样，剥削后的大麻茎显示出一定程度的损坏。通常来说，损害将随着转速的增大而增大，但即使是在最高转速时，大麻茎杆头部的损坏和下面收割时茎杆根部的损坏是类似的。在最严重的情况下，茎杆材料自身的损失象征着对一些潜在纤维的放弃，这种损失仅会出现在前进速度为3.5千米/时、转子转速为900转/分和700转/分大的情况下。4.说明本项工作是有ECFAIR1(priject PL 950396)和英国农业部及食品部门、渔业部门发动的，在此对Silsoe研究所的工程设计和建设小组的研究，Mr R Rucknall和种植大麻的Mr B Hills，以及在Hemcore Ltd的看守和在SRI的实验助理Mr N Jungk表示真诚的感谢。附件2：外文资料原文J.agric. Engng Res. ,(2001) 78(1),43-60doi:10.1006/jaer.2000.0632,available online oathttp:/www.idealibrary.comPM-Power and MachinaryStripping of Leaves and Flower Heads to improve the Harvestingof Fibre Hemp （Received 11 february 2000;accepted in revised from 11 August 2000；published online 25 October 2000）Hemp(Cannabis sativa) grown for fibre needs to be retted after cutting to allow the separation of fibre from the stem core.Drying of the mown stems in necessary both before and after retting but drying is likely to be hindered by the presence of leaves and flower heads on the stems.Delays in drying after retting have serious implications for fibre quality and core spoilage when baled.The aim of this work was to determine if leaves and flower heads could be removed from standing stams by powered rotor just prior to mowing.In a laboratory apparatus that propelled 40 stems past a rotor,the effectiveness of the method was established and the influence of rotor speed,forward speed and tooth design were examined.At every one of a range of setting ,more than 92% of the contacted leaf and flower head was removed form the top 900mm of the tested stems.A device constructed for field trials comprised a 1.2m wide rotor on a tractor-mounted arm.Trials showed it to be effective over a range of forward speed,rotor speed and contact height.At its optimum setting of these three variables,5.8km h-1,645min-1 and 1.6m,it removed 95% of the contacted leaf and flower head material.A practical implementation would probably comprise a single machine with stripping rotor mounted aheda of the stem-cutting elements.2001 Silsoe Research InstituteNotationMa mass of leaf material leaf unstripped above h height,m the nominal stripping height,kg m stem mass ,gMb mass of leaf material leaf unstripped below r rotor speed,min-110-3 the nominal stripping height,kg s overall stripping efficiencyMs mass of material removed by the stripping s stripping efficiency of Rotor,kg material above the f forward speed,km h-1 nominal stripping height1.IntroductionHemp(Cannabis sativa)is grown in northern Europe for production of fibres from the sten,which have a high tensile strength and can be used in pup products, composites and industrial textiles.Particles of stem core are absorbent and are used as animal bedding.In current practice, the stems are cut when still grenn and before full seed set when leaves,flower heads and seed heads are present.Once cut,the stems are retted,i.e. exposed in a swath to dry and rewet so that they undergo micro-biological digestion of the chemical bonds between the fibre bundles in the bast or outer layer and the surrounding cells.This makes possible the extraction of the fibre from the dried stems with minimal fibre damage. When the stems have retted to the optimum degree,the fibres are still of high strength but are readily separated from the remainder of the stem material. If retting is allowed to continue, the fibres are weakened and lose value.There fore,it is important to collect the stems at the optimum stage of retting for storage and later processing .Unless the stems are collected dry enough to prevent microbial action,further are generally not good for drying after retting,which takes some 3-6 weeks after harvest in early September in the UK, so it is important that swaths of retted stems dry quickly when conditions are favourable so as to avoid over-retting.Removal of the leaves and flower heads before the stems are swathed is also likely to promote more even retting by better exposing the whole length of the stems to drying.Leaf and flower head removal is also likely to increase the in-swath drying rate of the stems from harvested moisture to the moisture at which retting will start,thus minimizing the time for which the hemp crop occupies the field.Air can more easily penetrate the swath,and the leaves and flower heads contain additional moisture that must be evaporated.This is of particular importance when baling the retted crop because the seed heads tend to remain damp and later cause partial spoilage of the baled crop.In addition,the removal of the leaf and seed head also reduces the amount of material to be baled,stored,transported and processed,resulting in lower costs.It returns some plant material to the soil to improve soil fertility and structure and reduces waste at the processing plant, waste that may be classified as industrial waste and hence attract higher disposal charges.Several studies have been made on how to remove seed heads and leaf from hemp crops for the purpose of improved stem harvest, and on the economics of the process, mostly carried out in the Netherlands. The collection of the seeds or leaves as the primary product requires a different approach and so is not the subject of this paper.Huisman et al.(1998) used a modified broadbean topper (double cutterbar knife, reel and conveyor) to remove the seed heads.This was only partially successful because it left one-third of the seed and leaf, and was costly.Bolkstein et al.(1991） carried out an economic assessment of hemp harvesting and concluded that topping (seed and leaf removal) would be a necessary operation in the harvesting of good-quality hemp. He also reported on tests using a modified broadbean topper where 25% of the yield was lost including 8% loss of stem.Feitsma and Swinkels (1991) also used a broadbean topper and a flail mower mounted on a hedge trimmer arm. The bean topper was very slow in hemp (1.3km h-1) and suffered from blockages in a conveyor which transported the cut crop to one side,whilst the flail mower worked successfully but caused a loss of stem material, not quantified.If the seed and leaf are removed using a mower,either flail or cutterbar,then there will be a loss of stem if the majority of the leaf and seed head are removed (Huisman et al,1998;Feitsma & Swinkel,1991). In addition, the use of a cutterbar requires a means to remove the cut crop and blockages tend to make the work rate very slow.De Maeyer and Huisman (1994) used a rotary brush to defoliate hemp and also carried out a theoretical study.The use of the rotary brush to remove the leaf and seed head was partially successful in that less stem was removed but the brush was not sufficiently effective in removing leaf.In a late harvest,removal of 0.05kg of leaf caused a predicted loss of 0.02 kg of stem.In field trials only 0.04 kg of foliage was removed per 1 kg of plant dry matter,less than the estimated value in the simulation .As the combined ratio of leaf and seed head to above ground stem mass is typically between 0.15 and 0.30, a removal of 0.04 is not an effective performance. All these attempts appear to be less than successful for one or more of the following reasons(1) removal of or damage to part of the stem;(2) insufficient removal of enough of the leaf and seed head;(3) very low work rate and tendency to blockages.A device developed to harvest cereals by stripping the heads(Klinner et al. 1987)was bassed around a rotor with stripping elements of a keyhole design made of a stiff polymer .Besides being very effective for removing the seed and grain from a range of crops the stripping system has aiso proved to be very effective for defoliating crops,including mint,lucerne and nettles.Such a device therefore has potential as a staring point for hemp stripping.The objectives of this work were:(a)to determine whether stripping of hemp leaves and flower heads without losing fiber can be achieved effectively;(b) to determine at a laboratory scale the effect on stripping performance of rotor design,operating speed and height and forward speed in the crop;and (c) to develop,fieldtest and evaluate a device to demonstrate the stripping operation in a crop of fiber bemp.2. Material,apparatus and methodFor laboratory experiments,stems at the point of normal harvest were cut by hand at the base from commercial crop of hemp,cultivar Felina 34,grown in Hertforshire,UK . Stems were wrapped in polythene after cutting and used within 2 h to minimize the effects of dehydration on leaf and stem mechanical properties.For the field trial, a commercial crop of cultivar Felina 34 was grown in Essex,UK,on chalky boulder clay soil.Plant density at full establishment was 180 m- and yield was 4.3 t ha-1.The field experiment took place on 15 September 1997.2.1 Laboratory experiment2.1.1 ApparatusA stripping device,shown in Fig.1,was developed to propel whole hemp stems past the stripping rotor to simulate field operation . It comprised a shaft,powered by electric motor via a variable speed drive, on which could be fitted a range of rotor types,300 mm wide,a frame to support a hood that deflected the stems before contact with the rotor,a horizontal track 8m long,and a trolley,powered by a variable-speed linear motor,on which up to 400 stems could be mounted in two rows 150 mm apart and 100 mm apart along the row to simulate a crop of 600 plants m-.The stem bases were fixed into flexible sleeves that allowed them to deflect in a way similar to stems in the ground. The linear motor was capable of accelerating the trolley within 1 m to the selected speed and maintaining this speed during contact between crop and rotor ,so as to simulate forward movement of the field machine through the crop. The side of the laboratory device was unobstructed so that high-speed video could be used to study the crop behaviour on contact with the rotor and ， the hood.The rotor comprised an octagonal core which could be attached toothed stripping elements of various designs (Fig.2) formed from a high-density polymer.Three designs of stripping element ( Fig.3) were investigated,each attached to the same basic octagonal core: an element known as a keyhole design already used for cereal stripping(Klinner et ai.1987) and hence referred to here as a standard element; an element of the same design but with dimensions 50% larger; and a double keyhole type that had a 20% longer reach.These elements when mounted gave the rotor overall diameters of 530,620 and 560 mm,respectively. 2.1.2 Choice of experimental parametersThe reason why different designs of stripping element were investigated was that the teeth of the rotor had to be able to crop (Fig.4). The depth of penetration depends on the number and thickness of hemp stems per unit length in the direction of travel, so longer teeth were thought likely to give better stripping performance .Forward speed was a major determinant of work rate so the highest speed that also achieved effective stripping was investigated. Rotor speed was considered to be a compromise between the achieving sufficient stripping effect and restricting damage to the stems.2.1.3 MethodFor each run,40 stems were selected. The stem length,diameter at top,middle and bottom and the position of the lowest leaf were measured and the total combined mass of the 40 stems was recorded.Once the stems were mounted in the trolley.the rotor was run up to speed,and the trolley propelled past the rotor at the selected speed.The stems were then de-mounted,weighed,and any remaining leaf or flower head was removed by hand and weighed.The mass of leaf and head remaining on the stem above and the mass below the lowest point reached by the rotor teeth were recorded.This procedure was used for the standard stripping elements for four rotor speeds,400,550,700 and 900 min-1,and four forward speeds,3.5,4.3,5.5 and 7.1 km h-1.The double keyhole design was tested at 550 and 700 min-1 and the 50% larger designs at 400 and 550 min-1.In all cases, the rotor height was set so that the teeth tips were 900 mm above the base of the stem.2.2. Field experiments2.2.1. ApparatusFollowing the laboratory experiments, a machine was designed and built at Silsoe Research Institute to investigate the performance of stripping in a field crop (Fig 5 and 6).The concept was of a stripping head mounted on a tractor-mounted hydraulic arm supplied for hedge-trimming operations.The stripping head comprising a rotor of 1.2 m length powered by a hydraulic motor, a hood and crop dividers.The device was designed so that,with the reach available from the arm, once the crop next to the field edge had been stripped a second run could be made by reaching over the crop j
展开阅读全文