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参与翻译: 一叶障目 (3)

介绍

你是否有过驾车驶过坑洼或缓坡的经历?你会感觉车子摇摇晃晃,上下颠簸,但除了启用悬架,你什么也做不了。试试这个工程项目,看悬架能给你带来怎样顺畅的驾驶体验。

背景

当你在顺滑平稳的道路上驾驶时或许感觉不到,但一旦汽车驶入崎岖坎坷的地方,汽车悬架就发挥了它的重要作用。在极其颠簸的道路上行驶时,它能保护汽车(和乘客)免受伤害。汽车的车身并没有直接与车轮相连,不然,车轮每次的地面的接触碰撞都会直接传递给车身,给车内乘客带来极差的乘车体验。相反,车轮通过弹簧(金属在拉伸或压缩时能弹回原来的位置)和阻尼器(通过摩擦减缓部件运动,通常以充满粘性油的活塞形式存在)的组合与汽车其他部分连接,也称为减震器。这些部件组合起来,能吸收和减少路面震动。在这个项目中,你将建立自己的简单模型车,并设置一个悬架系统, 以帮助防止货物(包装花生)在颠簸时被抛出车外。

第 1 段(可获 3.16 积分)

材料

这是一个工程设计项目,也就是说你不一定要使用清单中提供的材料。以下只提供参考建议,您可随意替换成其他材料

用办公和工艺材料来搭建汽车。(或者,如果你不想自己做,也可以去买个中型玩具车) 在线搜索“气球车”或“橡皮筋车”,您会发现许多设计理念。 一般来说,您将需要准备:

  • 用作汽车轮子的东西,如 CD 或塑料饮料盖
  • 用作车轴的东西,如木棍和铅笔
  • 用作汽车框架的东西,如塑料瓶,纸板管或吸管
  • 将零件连接在一起的胶水或胶带
  • 和车身差不多大的小卡纸箱
  • 袋装花生
  • 线/绳
  • 各种橡皮筋和/或小弹簧(当然,在(大人)允许的情况下,你也可以通过拆卸圆珠笔来获取弹簧。)
  • 吸管或铅笔
  • 胶带
  • 剪刀
第 2 段(可获 2.16 积分)

准备

  • 组装车身(如购买玩具车,请跳过此步骤)
  • 组装车轴,使之可转动——如,将螺纹木串穿过吸管
  • 将车轮链接车轴。如,在塑料瓶盖上小心地钻个孔,然后将木串穿过瓶盖孔
  • 搭建一个车架,连上车轴和车轮。保证车轴能自由滚动,不受过大阻力影响
  • 将线/绳系在车身前,方便拉动车子运行
  • 如果小纸箱有襟翼,将其去除,保持顶部无遮挡
  • 使用磁带将盒子连接到汽车顶部,并用包装花生装满纸箱
第 3 段(可获 1.65 积分)

Procedure

  • Set up “speed bumps” for your car to drive over. For example, tape several straws or pencils to a tabletop, parallel to one another and a few inches apart.
  • Pull the car quickly across the speed bumps. What happens?
  • Now try to design a suspension for your car to prevent the packing peanuts from falling out of the box. For example, you could suspend the cardboard box from rubber bands. This is where the engineering design process really comes in to play!
  • Once you have built your suspension, try pulling your car over the speed bumps again. Try to do it at the same speed. What happens this time? Do fewer packing peanuts fall out?
  • Don’t get discouraged if your suspension doesn’t work on the first try! The engineering design process is iterative, meaning engineers often go back and redesign, rebuild and retest their devices to improve them. There are many different things you can tweak about your design. For example:
  • Try changing the type of rubber bands. What happens if you use thicker or thinner rubber bands, or longer or shorter ones?
  • Try changing the tightness of the rubber bands. What happens if the box is hanging from them loosely or if the rubber bands are pulled tight?
  • Try changing the weight of different parts of the car. (Weight has a big impact on vibrations.) For example, what happens if you tape a bunch of coins to the cardboard box to make it heavier? What happens if you tape the coins to the frame of the car instead?
  • Keep iterating and tweaking your design. Can you get to a point where no packing peanuts fall out of the box?
第 4 段(可获 3.54 积分)

Observations and results

You should find that when you attach the cardboard box directly to the frame of your car, many of the packing peanuts are tossed out of the box when you pull it over the speed bumps. This occurs because the vibrations from the wheels are transferred directly to the cardboard box. This would be like riding in a car with no suspension—quite an uncomfortable ride! When you add a suspension, it helps absorb some of the vibrations, so the cardboard box does not bounce up and down as much and doesn’t toss out as many of the packing peanuts. It might take some tweaking, however, to get your suspension working well. The stiffness (thickness/length/tightness of the rubber bands or springs) and weight of an object (for example, adding coins) have a big impact on how it reacts to vibrations. Real engineers carefully design a car’s suspension to optimally absorb vibrations on the road, just like you did in this project!

This project was inspired by the Trash Sliders activity, by Larry Richards, via eGFI.

第 5 段(可获 2.28 积分)

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