📚 Year 8 OCR Engineering: Case Study Practical Exercise | Year 8 OCR 工程：案例分析实战演练
In this article, you will step into the role of an engineer tackling a real design challenge. We will follow a complete engineering cycle – from reading a design brief, researching existing solutions, generating ideas, selecting materials and manufacturing a prototype, right through to testing, evaluating and improving the final product. This case study is based on a typical Year 8 OCR Engineering classroom task: building a simple catapult that can launch a ping-pong ball accurately. Every stage is modelled as a practical exercise, so you can apply the same thinking to your own projects.
在本文中，你将扮演工程师的角色，解决一个真实的设计挑战。我们将走完一个完整的工程循环——从阅读设计任务书、调研现有解决方案、产生创意、选择材料、制造原型，一直到测试、评估并改进最终产品。本案例研究基于一个典型的八年级 OCR 工程课堂任务：制作一个能准确发射乒乓球的简易投石器。每个阶段都以实践练习的方式呈现，因此你可以将相同的思维方式运用到你自己的项目中。
1. Understanding the Context | 理解案例背景
The school is hosting a STEM challenge and needs a low-cost device that can launch a standard ping-pong ball over a distance of 3 metres. The device must be built using only the materials provided: craft sticks, rubber bands, a plastic spoon, hot glue, a small wooden block and masking tape. You have two 60-minute workshop sessions to build and test your prototype. The brief also requires that the catapult stands on a table and remains stable during launch.
学校正在举办一次 STEM 挑战赛，需要一个低成本装置，能将一个标准乒乓球投射到 3 米以外。该装置只能使用提供的材料制作：工艺棒、橡皮筋、塑料勺子、热熔胶、一个小木块和遮蔽胶带。你有两次 60 分钟的工作坊时间来制造并测试原型。任务书还要求投石器放置在桌子上发射，并在发射过程中保持稳定。
The engineering cycle you will follow is: investigate, design, make, evaluate. This mirrors the real-world process used by professional engineers, where testing often leads to design improvements. By the end, you will have a deeper understanding of forces, energy transfer and the importance of iterative testing.
你将遵循的工程循环是：调研、设计、制造、评估。这与专业工程师使用的真实流程一致，测试往往促使设计改进。到最后，你将对力、能量传递以及迭代测试的重要性有更深刻的理解。
2. The Design Brief in Detail | 详细的设计任务书
A well-written design brief turns a general idea into measurable targets. For this case study, the brief states: ‘Design and make a working catapult that launches a ping-pong ball at least 3.0 m across a flat classroom floor. The catapult must be operated by hand, powered only by elastic energy, and must not exceed the dimensions 150 mm × 100 mm × 100 mm. It should be robust enough to survive five launches without breaking.’
一份写得好的设计任务书能把一个笼统的想法变成可衡量的目标。就本案例而言，任务书写道：“设计并制作一个可工作的投石器，将乒乓球发射到超过教室平坦地面至少 3.0 m 远处。投石器必须手动操作，仅由弹性能量驱动，且长宽高尺寸不得超过 150 mm × 100 mm × 100 mm。它应足够坚固，能经受五次发射而不损坏。”
Key constraints from the brief are the limited material list, the size restriction and the performance target. These constraints act like the ‘design specification’ that engineers always work to. They define what success looks like and help you decide when a design idea is good enough to take forward.
任务书中的关键约束条件包括受限的材料清单、尺寸限制和性能目标。这些约束就像工程师始终遵循的“设计规范”。它们定义了成功的样子，并帮助你判断一个设计想法是否足够好，可以进一步推进。
3. Researching Existing Solutions | 研究已有的解决方案
Before sketching your own design, it is important to look at how similar problems have been solved. Engineers call this ‘product analysis’. You might study pictures of medieval trebuchets, modern torsion catapults, or even simple elastic-band launchers made from popsicle sticks. Notice how they store energy and release it rapidly to propel a projectile.
在草绘你自己的设计方案之前，重要的是看看类似的问题是如何被解决的。工程师称之为“产品分析”。你可以研究中世纪投石机、现代扭力弹射器甚至是冰棍棒做的简单橡皮筋发射器的图片。注意它们是如何储存能量并快速释放以推进发射物的。
From your research, you will notice two common catapult types: the tension catapult that uses stretched rubber bands pulling a lever arm forward, and the torsion catapult that twists rubber bands to create torque. For the available materials, a tension design using a spoon as the arm is a practical choice. Record your findings with simple labelled sketches and notes on how each part functions.
通过研究，你会发现两种常见的投石器类型：利用拉伸橡皮筋拉动杠杆臂向前的张力型，以及扭转橡皮筋产生扭矩的扭力型。根据现有材料，使用勺子作为弹射臂的张力型设计是一个实用选择。用简单的带标注草图记录你的发现，并注明每个部分的功能。
4. Generating Design Ideas | 提出设计方案
Now it is time to put pencil to paper. Aim to produce at least three distinct ideas. One could use a single craft stick as the lever pivoted on a triangular fulcrum. Another might stack several sticks to create a stronger base and use a spoon nested in a slot. A third idea might explore using the wooden block as a vertical frame with rubber bands stretched downwards. Annotate each sketch with notes on how the elastic force is generated and how the ball will be held.
现在该拿起笔了。目标是提出至少三种截然不同的设想。一种可以使用单根工艺棒作为杠杆，支点为一个三角形支架。另一种可以将多根棒叠加制作更强底座，并把勺子嵌在一个槽中。第三种设想可以尝试用木块作为竖框，将橡皮筋向下拉伸。在每个草图上标注弹力是如何产生的以及如何固定球。
Good engineers always justify their preferred idea against the design specification. Once you have three ideas, evaluate them using a simple decision matrix. Rate each idea from 1 (poor) to 5 (excellent) on criteria such as: likely launch distance, stability, ease of manufacture, and efficient use of materials. This structured approach removes guesswork and helps you pick the most promising design.
好的工程师总是对照设计规范来论证自己的首选方案。一旦有了三个设想，就用一个简单的决策矩阵来评估它们。根据可能的发射距离、稳定性、制造难易程度和材料利用效率等标准，给每个设想打分，从 1 分(差)到 5 分(优秀)。这种结构化的方法消除了猜测，帮助你选出最有潜力的设计。
5. Developing the Chosen Design | 细化选定的方案
Let us assume you have selected a tension catapult design with a spoon arm. The base will be a layered sandwich of four craft sticks glued together for weight and stability. Two upright posts will hold a pivot rod made from a shortened craft stick, with the spoon arm free to rotate. Rubber bands will be stretched between the front of the base and the spoon handle, creating the launching force.
我们假设你已经选定了一种带有勺子臂的张力投石器设计。底座将是一个由四根工艺棒粘合叠成的三明治结构，以增加重量和稳定性。两个立柱将固定一根由短工艺棒制成的转轴，勺子臂可以自由转动。橡皮筋将拉伸连接在底座前端和勺子柄之间，产生发射力。
At this stage, produce a detailed orthographic drawing and a 3D sketch. Label the pivot point, the rubber band attachment point, the ball cup, and the stop bar that limits the arm’s forward travel. Add important dimensions. This technical drawing acts as your manufacturing plan and must be clear enough for someone else to build from.
在这个阶段，要绘制详细的正投影图和三维草图。标注出转动点、橡皮筋连接点、球杯以及限制弹射臂前移的挡杆。加入关键尺寸。这份技术图纸就是你的制造计划，必须足够清晰，以便他人可以按图施工。
6. Selecting Materials and Understanding Their Properties | 选择材料并理解其特性
Our material list is fixed, but you still need to decide how each part will be used. Craft sticks are made of birchwood or basswood; they are stiff, lightweight and have reasonable tensile strength. Rubber bands provide high elasticity – they can be stretched repeatedly and return to their original shape. The plastic spoon is flexible but tough, making it ideal for the ball cup. Hot glue bonds well to wood and plastic, but it is brittle under sudden shock loads.
我们的材料清单是固定的，但你仍需决定每个部件如何使用。工艺棒由桦木或椴木制成；它们坚硬、轻质，且具有相当好的抗拉强度。橡皮筋提供高弹性——它们可以反复拉伸并恢复原状。塑料勺子具有弹性且坚韧，非常适合做球杯。热熔胶对木料和塑料的粘合性很好，但在突然的冲击载荷下会变脆。
A useful engineering habit is to create a simple material property table. This helps you anticipate where failures might occur. A sample table for the catapult is shown below.
一个有用的工程习惯是制作一个简单的材料特性表。这可以帮助你预测可能发生故障的位置。下面展示了一个投石器的示例表格。
| Component | Material | Key Property | Risk |
|---|---|---|---|
| Base | Craft sticks + glue | Compressive stiffness | Glue joint cracking |
| Pivot | Short craft stick | Shear strength | Breaking under sudden load |
| Launcher arm | Plastic spoon | Flexibility, impact resistance | Snapping at handle joint |
| Spring | Rubber band(s) | Elastic potential energy | Permanent deformation (losing elasticity) |
Understanding these risks feeds directly into your construction plan – for example, reinforcing glued joints with extra tape, or deciding to double-loop the rubber band for more power.
理解这些风险会直接影响你的施工计划——例如，用额外胶带加固粘接处，或决定用双圈橡皮筋以获得更大的动力。
7. Planning the Manufacturing Process | 规划制造流程
Before touching any material, write a step-by-step manufacturing plan. This should be a numbered list of instructions, including all measurements and safety notes. For example: Step 1 – Glue four craft sticks together in a stack, ensuring the edges are flush. Step 2 – While the base dries, cut the pivot holes in the two upright sticks using a small hand saw (with teacher supervision).
在接触任何材料之前，先写一份逐步制造计划。这应该是一个包含编号的指令清单，包括所有测量值和安全注意事项。例如：步骤1——将四根工艺棒叠放粘合在一起，确保边缘齐平。步骤2——在底座干燥的同时，用小手锯在两块立柱棒上开轴孔(在老师监督下操作)。
Identify every tool you will need: scissors, a saw, a ruler, a protractor for setting the launch angle, clamps and a well-ventilated space for the hot glue gun. Predict how long each step will take. Given two 60-minute sessions, you might allocate 30 minutes for building the frame, 20 minutes for attaching the spoon arm and rubber bands, and 10 minutes for initial adjustment and safety checks.
明确所需的每一种工具：剪刀、锯子、尺子、用于设定发射角度的量角器、夹钳以及热熔胶枪所需的良好通风空间。预测每一步需要多长时间。在两节 60 分钟的课内，你可以安排 30 分钟用于搭建框架，20 分钟用于安装勺子臂和橡皮筋，还有 10 分钟用于初始调整和安全检查。
8. Building and Test-Rig Set-Up | 组装与测试台设置
With your plan approved, begin construction. Pay close attention to the alignment of the pivot – if the arm twists sideways, the ball will fly off course. Once the glue has fully set, attach the rubber band. Start with a single band, hooking it from the front edge of the base to a notch on the spoon handle. You can add more bands later if you need more force. Always wear safety goggles when testing.
计划获得批准后，开始施工。特别注意转轴的对齐——如果弹射臂偏向一侧，球就会飞偏。等胶水完全凝固后，装上橡皮筋。先用一根皮筋，将它从底座前缘勾到勺子柄上的一个凹口上。如果之后需要更大的力，你可以再增加皮筋。测试时务必要佩戴护目镜。
Set up a testing range on the classroom floor with a start line and target markers at 1 m, 2 m, 3 m and 4 m. A simple ruler or a phone camera set to slow motion can capture how the ball leaves the spoon. Record the launch angle that seems to work best. The standard equation for the range of a projectile is:
在教室地板上设置一个测试区，标出起射线，以及 1 m、2 m、3 m 和 4 m 处的目标标记。用一个简单的尺子或手机的慢动作摄像头捕捉球离开勺子时的状态。记录下看起来效果最好的发射角度。抛射体射程的标准方程是：
Range = v² sin(2θ) / g
where v is the launch speed, θ is the launch angle measured from the horizontal, and g is the acceleration due to gravity (9.8 m/s²). While you do not need to calculate exact values now, this formula shows that the maximum range is achieved at an angle of 45°, provided air resistance is small. This theory will guide your adjustment of the stop bar position.
其中 v 是发射速度，θ 是从水平方向测量的发射角度，g 是重力加速度 (9.8 m/s²)。虽然你现在不需要计算精确值，但这个公式表明，只要空气阻力很小，最大射程是在 45° 角时获得的。这一理论将指导你调整挡杆的位置。
9. Collecting Test Data | 收集测试数据
Carry out a systematic set of test launches. For fairness, use the same ball and the same pull-back distance for the rubber band each time. Measure how far back you pull the spoon – this is directly related to the amount of elastic potential energy stored, given by the equation:
进行系统的测试发射。为了公平起见，每次使用同一个球，并保持相同的橡皮筋后拉距离。测量你将勺子后拉了多远——这与储存的弹性势能的多少直接相关，其公式为：
E_elastic = ½ k x²
where k is the spring constant of the rubber band and x is the extension length. Create a data table like the one below to record your results.
其中 k 是橡皮筋的弹性系数，x 是拉伸长度。创建一个如下所示的数据表格来记录结果。
| Trial No. | Pull-back (cm) | Launch Angle (°) | Distance (m) | Observations |
|---|---|---|---|---|
| 1 | 5 | 45 | 2.4 | Ball veered left, glue joint creaked |
| 2 | 6 | 45 | 2.9 | Slight wobble, near target |
| 3 | 7 | 45 | 3.3 | Successful, base jumped 1 cm |
| 4 | 7 | 55 | 2.7 | High arc, less horizontal distance |
From this data you can see that a 7 cm pull-back with a 45° angle hits the target, but the base lifted slightly. This indicates a stability problem that needs to be solved – perhaps by adding weight or clamps to the base.
从这些数据中你可以看到，7 cm 的后拉距离配合 45° 角度就能命中目标，但底座轻微翘起。这表明存在一个需要解决的稳定性问题——或许可以通过给底座增加配重或使用夹持器来改善。
10. Evaluating Against the Specification | 根据规范进行评估
Now go back to your design brief and ask: did the catapult meet all the requirements? It achieved a 3.3 m launch, which exceeds the 3.0 m target, but the base lifting means it is not completely stable. The size remained within the allowed dimensions, and the device survived five launches without critical damage. On the whole, it is a successful prototype, but there is room for improvement.
现在回到你的设计任务书，问一问：投石器满足所有要求了吗？它达到了 3.3 m 的发射距离，超出了 3.0 m 的目标，但底座翘起意味着它并非完全稳定。尺寸保持在允许的范围内，装置在五次发射后没有关键损坏。总体而言，这是一个成功的原型，但仍有改进的空间。
A formal evaluation should include both quantitative data (distance measurements) and qualitative observations (wobble, noise, glue cracks). Identify two strengths and two weaknesses of your final design. For instance, strength: simple, robust construction; weakness: base needs to be heavier. Then explain what you would do differently next time. This reflective evaluation is what distinguishes a good engineer from a great one.
正式的评估应包括定量数据(距离测量)和定性观察(晃动、噪音、胶水开裂)。指出你最终设计的两个优点和两个缺点。例如，优点：简单、结构坚固；缺点：底座需要更重。然后解释你下次会做出哪些改变。这种反思性的评估正是区分优秀工程师和出色工程师的关键。
11. Iterative Improvement and Redesign | 迭代改进与重新设计
Based on your evaluation, sketch a modified version. To solve the stability issue, you could tape the base to a large cardboard sheet, or glue additional craft sticks crosswise to widen the footprint. To increase consistency, replace the single pivot rod with two small nails (where permitted by safety rules) to reduce friction and wobble. Every change is a new hypothesis waiting to be tested.
根据你的评估，画出修改版草图。为解决稳定性问题，你可以用胶带将底座固定在一块大卡纸上，或者横向粘接更多的工艺棒以扩大底座面积。为了提高一致性，可将单根转轴换成两颗小钉子(在安全规则允许的情况下)以减少摩擦和晃动。每一次改动都是一个等待检验的新假设。
Engineers rarely get a design right the first time. The ‘make-test-improve’ cycle is at the heart of engineering. In industry, this is called ‘rapid prototyping’. Re-test your improved catapult and compare the new data with your original results. You will likely see a tighter spread of distances and a much steadier base. Document your changes with before-and-after images or diagrams.
工程师很少能一次性把设计做对。“制造-测试-改进”循环是工程学的核心。在工业界，这叫做“快速原型制作”。重新测试你改进后的投石器，并将新数据与原来的结果进行比较。你可能会看到距离的分布范围更集中，底座也稳多了。用改造前后的图片或示意图记录你的更改。
12. Presenting the Final Solution | 展示最终方案
An engineer must be able to communicate their design clearly. Prepare a short presentation or a poster showing your journey: the design brief, initial sketches, the chosen design with key dimensions, a photo of the finished catapult, test data and your evaluation. Use engineering vocabulary such as ‘elastic potential energy’, ‘fulcrum’, ‘trajectory’ and ‘torque’.
工程师必须能够清晰地传达自己的设计。准备一个简短的演示或一张海报，展示你的历程：设计任务书、初步草图、带关键尺寸的选定方案、成品投石器的照片、测试数据以及你的评估。要使用工程术语，例如“弹性势能”、“支点”、“轨迹”和“扭矩”。
Finally, reflect on how this case study has trained you to think like an engineer. You have learned that a good design emerges from careful research, structured idea generation, skilful making and honest evaluation. The same process can be applied to any Engineering project, from a bridge-building challenge to a programmable robot. Keep your portfolio as evidence for your OCR Engineering progression.
最后，反思本案例研究是如何训练你像工程师一样思考的。你已经学到，一个好的设计来自于仔细的调研、结构化的创意产生、娴熟的制作和诚实的评估。同样的过程可以应用于任何工程项目，从造桥挑战到可编程机器人都一样。保存好你的作品集，作为 OCR 工程课程进阶的证据。
Published by TutorHao | Engineering Revision Series | aleveler.com
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