Mechanical Energy transmission system (gears)

A gear is a drive mechanism used to transmit mechanical power from one point to the other. It is a wheel fixed in machines to make different parts move at different speeds or in different directions. Gears have toothed edges that help them to engage or mesh with one another. When two gear-wheels are fitted, engaged or meshed, one wheel turns one way, while the other turns the other way that is, in the opposite direction.

If you take two corks and arrange them in such a way that each tooth enters into each space, you have arranged a simple gear. Notice that the teeth will mesh properly if they are equally spaced

You must have noticed that when the engine of a vehicle is turned on, the vehicle does not start moving immediately. To move the vehicle, the driver engages the gear system. The gear is used to transmit the power being developed by the engine to the road being developed by the engine to the road wheels. Nowadays, some bicycles also have gears to help make pedaling as relaxing as possible. You should perform the simple illustrative experimental described below.

Get a bicycle that has gears. Turn it upside down so that it rests on the saddle and the handlebars. Locate the gear wheels attached to the pedals. Notice that the small gear wheel on the back road-wheel is driven by wheel of a chain drive, this shall be discussed later. Now, turn the pedals with your hands and watch the back road-wheel move. Take note of the engaged gears. Change gear, turn the pedal again and watch the back road-wheel move. Take note of the engaged gears. Change gear, turn the pedal again and watch the back wheel move. Repeat this experiment until all the gears are used in turn. You can easily feel the difference in the effort required to keep the wheel moving at speed. Greater effort is required to move at speed with bigger gear than with smaller gear. Hence, When going down a hill at speed, the cyclist selects a higher gear(this means that the cyclist engages a smaller gear wheel), which provides a high speed in turn for slower pedaling. For climbing hills, the cyclist changes to a lower gear (this means that he selects a bigger gear wheel), which makes pedaling easier in turn for a lower speed. It should be pointed out that this situation is less tasking as it requires less effort to turn the pedals, thereby enabling the cyclist to climb through the hill without getting tired soon.

The principle described above forms the basis for gear change in motor vehicles.

Gears are not only used for changing speed of rotation of connected shafts, they can also be used to change the direction of rotation.

The system of gears in the back axle of a motor vehicle is shown below. The shafts connected to the road wheels are at 90 degree angle to the transmission shaft from the engine. The bevel gears shown below are used to transmit mechanical energy from the transmission shaft from the engine to the road wheel shafts.

When two gears mesh with one another, one usually drives the other. Hence, one is called the driving gear while the other is called the driven gear. If the driving gear has fewer teeth than the driven gear will turn more slowly than the smaller gear will turn more slowly than the smaller gear driving it. On the other hand, if the driving gear has more teeth than the driven gear will turn more rapidly than the driving gear. To put it in another way, if gear wheel A has to teeth and gear wheel B has 20 teeth, the smaller gear wheel B will turn twice to everyone rotation of the bigger wheel B. Therefore, the ratio of gear A to gear B is said to be 2:1 (i.e. 40:20).

This property of gears (gear ratio) is made use of in the design of gear mechanisms for different uses. For example, clocks have different sized gear wheels arranged such that they move the clock hands at different speeds. The number of teeth on the various gears is arranged in such a way that the minute hand travels round the clock once an hour while the small “hour” hand goes round the clock face in twelve hours. As an exercise, draw the gear system that will operate a clock that the second hand as well as the minute and hour hands.https://googleads.g.doubleclick.net/pagead/ads?guci=2.2.0.0.2.2.0.0&client=ca-pub-1661929042807246&output=html&h=280&slotname=9757662299&adk=1561942993&adf=3100146925&pi=t.ma~as.9757662299&w=700&fwrn=4&fwrnh=100&lmt=1604154294&rafmt=1&psa=1&format=700×280&url=http%3A%2F%2Fstoplearn.com%2Fcourses%2Fsecondary-school%2Fjunior-secondary-school%2Fjss3-second-term-basic-technology-junior-secondary-school%2Flessons%2Fmechanical-energy-transmission-system-gears%2F&flash=0&fwr=0&fwrattr=true&rpe=1&resp_fmts=3&wgl=1&adsid=ChEI8Jb0_AUQms_jh5KIqv7UARJIAA7JAC_GO2FC6iznaMEwNw4hlJQdlpkBDDCBn2NYYMtNiVRO3A6cs2leJEGAH_Dq4SLFL-IsXiR6-z89Dqd0f0HDyiBGXFhY&tt_state=W3siaXNzdWVyT3JpZ2luIjoiaHR0cHM6Ly9hZHNlcnZpY2UuZ29vZ2xlLmNvbSIsInN0YXRlIjowfSx7Imlzc3Vlck9yaWdpbiI6Imh0dHBzOi8vYXR0ZXN0YXRpb24uYW5kcm9pZC5jb20iLCJzdGF0ZSI6MH1d&dt=1604154230789&bpp=6&bdt=200&idt=79&shv=r20201029&cbv=r20190131&ptt=9&saldr=aa&abxe=1&cookie=ID%3D3b5c0a4b352ccd7b-2255262b41a60032%3AT%3D1602230088%3ART%3D1602230088%3AS%3DALNI_MaWUG7yiaaHthyGgrREyU5I0uWdRw&prev_fmts=0x0%2C1200x90_0ads_al&nras=1&correlator=1520896014141&frm=20&pv=1&ga_vid=1725423649.1604154231&ga_sid=1604154231&ga_hid=458694218&ga_fc=0&iag=0&icsg=599886135210&dssz=59&mdo=0&mso=0&u_tz=60&u_his=3&u_java=0&u_h=768&u_w=1366&u_ah=728&u_aw=1366&u_cd=24&u_nplug=3&u_nmime=4&adx=609&ady=727&biw=1518&bih=730&scr_x=0&scr_y=0&eid=21067981%2C21067655%2C21066705&oid=3&psts=AGkb-H_s_Redq2dOVRFft-_7Pm891IXbXJ-gUyLiiIfoXbXj-1L-qjgyMw&pvsid=3178410213663545&pem=804&ref=http%3A%2F%2Fstoplearn.com%2Fcourses%2Fsecondary-school%2Fjunior-secondary-school%2Fjss3-second-term-basic-technology-junior-secondary-school%2Flessons%2Fmechanical-energy-transmission-system%2F&rx=0&eae=0&fc=896&brdim=0%2C0%2C0%2C0%2C1366%2C0%2C1366%2C728%2C1517%2C730&vis=1&rsz=%7C%7CaoeE%7C&abl=CA&pfx=0&fu=8320&bc=31&ifi=1&uci=a!1&fsb=1&xpc=CO67a0OabD&p=https%3A//stoplearn.com&dtd=64151

Gear train for clock

Reducing Friction Effects between Meshing Gears

As mentioned earlier, when two surfaces move relative to one another, friction comes into play. When two gear teeth are engaged as described above, they rub against one another, frictional effect generates heat and the wearing of the surfaces. In order to reduce wear and loss of power in   transmission, friction between the meshing teeth must be reduced. This is achieved by lubricating the gears with suitable oil often called “gear oil”. You can now appreciate why it is necessary for motorists to check their gear oil levels regularly.