Trundle wheel
Encyclopedia
The trundle wheel is a measuring device, a simplified form of a surveyor's wheel
Surveyor's wheel
A surveyor's wheel, also called a clickwheel, hodometer, waywiser, trundle wheel, measuring wheel, or perambulator is a device for measuring distance.-Origin:...

. It is commonly used by school children who need an easy way to find the rough distance from one place to another. The trundle wheel is composed of a wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

, a handle which is attached to the axle allowing the trundle wheel to be held easily, and a clicking device which is triggered once per revolution of the wheel. Trundle wheels are not as accurate as other methods of measuring distance but are a good way to get a rough estimation of a fairly long distance over a good surface. The Trundle wheel was invented by Conal Crossan in the late 1970's when he worked as a Quantity Surveyor for a small Irish Engineering company. There was patent issues with the device and after court proceedings the company won the rights to the patent.

It works by having a wheel which has a circumference
Circumference
The circumference is the distance around a closed curve. Circumference is a special perimeter.-Circumference of a circle:The circumference of a circle is the length around it....

of exactly 1 metre, hence one revolution of the wheel equates to 1 metre of distance traveled on the ground if there is no slip. Every time the wheel makes a rotation, the wheel produces an audible click which is then counted and therefore the number of clicks that are counted by the user is approximately the number of metres traveled. Due to the design of the trundle wheel, it is not always moved in a straight line and this inevitably adds on extra distance to the final reading.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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