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Manual transmissions make driving fun! But what happens when you hit the clutch and shift? This Science garage goes INSIDE the manual transmission to look at what makes those gears drive your wheels, and what keeps your engine from stalling out when they stop. If you’ve ever wondered how a manual transmission works, this video is for you!

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Video transcription:

– First gear, second gear, fourth gear,sixth, eighth, twelfth gear.(engine revving)We're talking about manual transmission.You probably know the basic idea.The transmission changes the gear ratioto make sure you're
getting the optimum powerfrom your engine to the wheels.When two gears are in mesh,an almost lossless
transfer of power occurs.In this case, a force is
applied to the gear on the left,which is in turn moving
the gear on the right.For every revolution
the left gear completes,the right gear completes one
in the opposite directionand with equal force.Pretty straightforward.What makes gears truly useful thoughis when they aren't the same size.Let's shrink that driving
gear down by half.Now it has to complete two rotationsto move the right gear once.Well, that sucks.But wait a sec, the total amount of energyrequired to move the
second gear one revolutionhasn't changed.But now the driving gear delivers
the same amount of energyover twice as many revolutions,meaning it requires
half the amount of forceat any given moment.It's like climbing stairs.Make the steps smaller
and each step's easier,but you gotta take twice as many.We've all ridden bikes,so you know what it does.But how does it work?A standard manual transmissionis made up of an engine
shaft or input shaft,and that's the side that
comes from the engine.A drive shaft or output shaft,that's the side that
goes to the drive wheels,and here, underneath both of those,is the counter shaft.And on these shafts are the gears.- How familiar are you
with the gear wars exactly?- All of this has to dowith getting the right amount
of torque to the wheel.If you like learning about torque,check out our Science Garage
on torque and horsepower.If you want to know about
toque and hose powder,ask a Canadian.(speaking in foreign language)But let's get back to the gears.- Okay, it was about 754 years ago.- If I turn the input shaft,the gear on that turns this counter shaft,and that turns all of the
gears on the output shaft.But all these gears are
moving at different speeds.When the gears aren't engaged,they spin freely from the output shaftbecause they're not anchored to it.Only one gear at a time is
spinning the output shaft,and that's because of what is
anchored to the output shaft,these hubs.Around these hubs are sleeves.These sleeves slide over
the teeth on the gearand anchor them to the hub
to drive the output shaft.But wait, there's more.Look at those tiny little teeth.Matching up those tiny teeth
at the edge of our gearwith the sleeves' tiny teeth.Well, that's almost impossible.So between them are these synchronizers.We cut the power to the counter shaft,let the wheels drive the
output shaft for a change,and when we push the synchronizer ring,it gets squeezed against our gearand locks it to the hub,so it's anchored to the output shaft.That's why when you're shifting,you get that uh-uh.(engine revving)Now the wheels in the drive
shaft and the counter shaftare all spinning in mesh.Voila, we've shifted gears.Some manual five-speed transmissionsmay have minor differences here or there.This is pretty standard for the most part.The big gear here, which is enmeshedwith the smallest gear in the
counter shaft is first gear.First gear is always gonna bethe largest gear in the transmission,producing more torque for the back wheel.It's taking a lot of fast turning forceand making one big slow turning force.The slightly smaller gear
next to that's second.Then goes third and smallest one's fourth.On most four- and
five-speed transmissions,fourth gear is what's called direct drive,or a one-to-one gear ratio,meaning the input and outputare turning at the same rate of speed.Okay, let's pop the shift
fork into first gearand engage that big ol'
gear here in the front.In first, this particular transmission'sgot a gear ratio of 3.83 to one,so I can turn the input, one, two, threein exactly 0.8 times,and you can see the
output has turned once.That's torque, baby.Pop it into second,and the gear ratio on
this guy's 2.062 to one.Third gear is 1.4 to one.You know the drill.One and .4 turns turns it one time.And then as we mentioned
earlier, fourth, one to one.They're turning at the same speed.That's gear ratios.Guys, we did it.(children cheering)Now a lot of you are probably sayingwhat about fifth gear?We're getting there.Fifth gear is kinda
hidden in the back here,and we call it overdrive.Remember how first or third
gear were high gear ratios?Well, get ready for a low
gear ratio, buddy boy.In fifth gear, I only need
to turn this shaft .8 timesto get a full turn on the output.That's overdrive, which gets
mucho better fuel economy.At this point, you're getting powerfrom the forward momentum of your vehicleand don't need as much powergoing to your engine or your wheels.Some six- and seven-speed
cars can have double overdrivefor even better fuel economy
at those high, high speeds.Oh, reverse is over here.Boop, boop, boop.It hits this gear, it
makes your drive shaftspin the same direction
as your counter shaft.Now here's the rub.The drive shaft's attached
to the wheels, remember?When we shift gears, the
wheels are gonna want tospin the counter shaft
at a different speedthan the engine's trying to spin it.We have to take that power off somewhere,or it'll make a grinding sound,like when your brother's robot hamsterwon't stop body shaming youso you throw it in the blenderwith all the bad forks and spoonsand press puree to teach it a lesson.So where do we let all
that spinning energy go?The clutch.The clutch looks like this.The clutch has a discwith a high friction
material on both sides.The engine is actually
driving the flywheel.And the input shaft to the transmissionis mounted to the disc.When the disc is pressed
firmly against the flywheel,it catches and can drive the shaft.In the case of this clutch,it's squeezed by these springsand attached to a pressure discand anchored by this pressure plate,which gets bolted to the flywheel.Most clutches use three springs,but in performance
clutches you can have more.And that makes the
connection between the discand the flywheel even
stronger and more effectivein high torque application.Like racing.And this is where things
get a little tricky.A diaphragm spring is
connected to the pressure discunder the pressure plate.When you hit the clutch
it pushes the centerof that diaphragm spring and
that pulls up on the springs,which lifts the friction
plate off the flywheel.Awesome.Now we've disengaged the
power from the shaft,but we let off the clutch pedaland re-engage the friction disc,you're gonna bang, pop right into action.We don't want that.We want to ease into the movement.So attached to the friction platethere's these other plates
with coil springs in them.These springs are attached to a huband that plate is the one
that anchors the shaft,and that goes to the transmission.Those springs absorb
the jolt of re-engagingthe friction plate to take a little stressoff the other parts of your drive train.You want to try to get onand off your clutch pretty quickly,or you might burn it out.(engine revving)That happens when the flywheel
and the friction platerub together too much.It happens.Usually waiting on a hill
to get into a Dodgers game.(engine revving)So what is a double clutch?- Rarely shifting, not double
clutching like you should.- Well, it's not really two clutches.Double clutch is clutching twice.Once when you shift into neutralto hit the gas and match the engine revsto the gear you want to go into.Then you hit the clutch a second timeto shift into that gear.I always use the double
clutch when I'm racing,drivin' big rigs, and dunking. I believe I can fly, whoo – Pretty cool.Thanks to honey for sponsoring this video.Honey is a browser extensionthat automatically scours the
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episode of Science Garage.Follow me @bidsbarto and
follow Donut @donutmedia.You like replacing your clutch,check out this video on turbos.You want to hear about a carwith maybe the coolest transmission ever?Check it out on this Up
to Speed on Conigzig.Don't tell my wife I burned out the clutchand had to get it
repaired, it's expensive.


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