棘輪機構(ratchet)

棘輪機構(ratchet)：[防倒轉的] 棘齒。使線性往復運動或旋轉運動保持單一方向的機械機構,用以

防止傳動機構逆轉。它主要由搖杆、棘爪和外棘輪所組成。搖杆為運動輸入構件，棘輪為運動輸出構件。當搖杆順時針擺動時，鉸接在杆上的棘爪插入棘輪的齒內，使棘輪同時轉過一定角度。當搖杆逆時針擺動時，棘爪在棘輪的齒上滑過，棘輪靜止不動。這樣，當搖杆作連續的往復擺動時，棘輪便得到單向的間歇轉動。

「棘輪機構的多重應用」：課程先說明棘輪機構的相關知識與應用實例，釐清機件、機構、機械。了解間歇運動機構之棘輪機構。並利用實際的教案作品，分享可能的創作與適合的學習階段。接著引導製作一個可以用在教學現場的棘輪教具以及棘輪陀螺與發射器。接著製作趣味棘輪釣竿，先說明各個設計要點後；再讓老師們實際以尺規作圖的方式，設計棘輪。棘輪的運用：

• 絞盤
• 時鐘
• 千斤頂
• 雲霄飛車
• 束線帶
• 驗票閘門
• 手銬
• 棘輪套筒扳手

棘輪構造

1. 齒輪
2. 棘爪
3. 固定用的基底

A ratchet mechanism is based on a wheel that has teeth cut out of it and a pawl that follows as the wheel turns. Studying the diagram you will see that as the ratchet wheel turns and the pawl falls into the 'dip' between the teeth. The ratchet wheel can only turn in one direction - in this case anticlockwise.

起重棘輪·千斤頂

棘輪條B上之齒與槓桿A上的棘爪相契合,另一個棘爪D用來防止棘齒條向下滑落0起重棘輪常用於千斤頂,是汽車換胎的工具。

利用棘輪機構製作橡皮筋手槍

樂高_橡皮筋手槍組裝圖

樂高達芬奇的彈射器Catapult

Model of one of the Leonardo da Vinci’s less famous inventions: a catapult using a leaf spring to fire projectiles, which makes it unique in terms of Medieval technology. The original catapult was to use a single wooden leaf spring – an idea probably inspired by a bow. It did not become popular due to high manufacturing costs at the time. There was a number of full-size models recreated today, and they proved capable of throwing stone projectiles just under a quarter mile. My model, whose scale is difficult to determine, can throw a regular Lego ball just under two meters.

It took me a while to find a Lego element of proper elasticity – I eventually settled for two 12 L axles. It seemed that the axles will get bent permanently from the tensions present in the model, but eventually the did not – they turned out to be perfectly straight after disassembly. I believe a catapult using the same principles to work without risking damage to any Lego pieces could be made with two rigid levers mounted on tension bars, but that would look very much different from Leonardo’s original design. I wanted the model to be mechanically accurate; this is also why I didn’t include any arm-stopping mechanism that could potentially increase the range – I simply haven’t found any in the original drawings.

	班級：
	座號：
	姓名：
	標題：機構之棘輪釣竿玩具
	備註：Woody
活動: 機構之棘輪釣竿玩具
	班級：生科
	座號：一
	姓名：活動
	標題：機構之棘輪釣竿玩具
	備註：研習