Hello everyone and welcome. This video we're going to be talking about what is
double clutching when referring to the driving technique.
So we're going to talk about what the process of it is and then talk about why
it's necessary and its really only necessary with cars which don't have
synchronizers with a manual transmission and so I think the why
question is the part that kind of confuses people the most, that's the most
difficult to understand, but first let's go ahead and walk through the process of
what you're actually doing. So here we have our accelerator pedal, our brake
pedal, and our clutch pedal.
The first thing you're going to do is let your foot off of the accelerator pedal,
the second thing you're going to do is press in the clutch, third thing you're
going to do we're going in our scenario be going from fourth year to third gear
so we're going to pull it out of fourth and put it into neutral.
The fourth thing we're then going to do is release the clutch and the important
thing to realize here is that this isn't you know this like tedious step-by-step
process a lot of this is kind of happening simultaneously there's overlap
between these steps so it's actually a very smooth and quick process it's not
like you know first step let off accelerator seconds that press in clutch
like those are kind of happening simultaneously there's overlap between
these steps
so it's a very quick smooth process. Moving on to number five because we're
down shifting we need to raise up the engine speed to match the gear speed
so we're going to blip the throttle that's for number five. If you were up
shifting going from 3 to 4 then you would leave your foot off the gas and
let that engine speed dropped down to your gear speed because will be rotating
lower so you wouldn't put the throttle in that case but we're going from fourth
to third so we blip the throttle,
then we press in our clutch, and then we put it into our third gear and then we
release the clutch and then you go on about your way driving it in third gear.
So that's the process of double clutching and as I mentioned it smooth
there's overlap between these steps and it's a very quick process but why is it
necessary
and so that's the part here that's all about these synchronizers and you know
how they're involved in this process.
So in order to understand why we need to look at, you know, the inside of a
transmission so here we've got our engine which is coupled to the flywheel
it's got a pressure plate around the clutch so there's your clutch disc and
then that clutch disc is going to gear up to
a layshaft which will rotate your gears three and four
here is your output shaft with a collar on it and then here is your gear
selector so you can see if it's about this point and you pull that fourth back
it's going to push this forward pushing this forward and pushing that collar into
fourth gear
so if we're going to be going into the third year we push it forward and that
would slide it into there. so the important thing to realize looking at
this diagram is that each individual color can rotate at its own speed
so in red red will always rotate together so the engine flywheel the
pressure plate those are always rotating together in blue
some of these gears can rotate on their own because these are on bearings on the
output shaft but they will always be rotating with the layshaft so their
speed may differ but they'll always rotate with the layshaft and so
everything in blue is always rotating together and then everything in green so
your collar which is splined to the output shaft will always be rotating
with the output shaft
so in different scenarios everything can be rotating together that's all
synchronized for example when you're in gear or everything can rotate separate
so if you're in neutral and you have your clutch pressed in everything is
rotating at its own speed
ok so let's walk through this process again but looking at what's going on
inside
so first we're releasing the accelerator pedal second were pressing in our clutch
so now this and this are no longer rotating at the same speed and so that
means also at that time when we pressed in that clutch
the collar is also rotating at a different speed from the gear so
everything is rotating at a different speed at that time once you have your
clutch pressed in
so you release the clutch and now what you've done is you've linked up the
engine to everything in blue so everything in blue and red is now
rotating together and so what your goal with doing that is you can press the
throttle
so that when you go into gear 3 you now have influence over gear three's speed
because it's connected to the engine
so you blip the throttle you bring this up to speed with the collar and then once
these two speeds are close you press in that clutch and the reason you're doing
that is because you don't want all of the mass
of the engine influencing that gear shift and so once you press in the
clutch
these two are relatively the same speed you press them in together
you don't have that influence from the engine so it's you know it's not much
mass that you have to actually bring to the same speed
so you connect those together and then you've already you know this is a very
quick process and so then you let out the clutch
once you have that in gear and that's going to be a very smooth process for
shifting the gear
so the reason why you do it is because you
you let out the clutch and that gives you control over the gear speed versus
the synchronizer speed and you want to match those press in your clutch engage
them
release your clutch and then have everything moving together
so if you have a regular transmission which most of you out there you know
driving a regular production car on public roads
that's what it's going to have it will have synchronizers in there the process
is a bit different so you release the gas
you press in the clutch and now when you're shifting over to the next gear
what's happening is everything is at a different speed
so you've released the clutch you're in neutral and you're about to go into the
next gear
so your engine is at one speed your transmission as far as these gears are
in another speed and your output shaft is at a completely different speed this
is that your wheel speed of course because this is going to your
differential
so what that synchronizer is doing is as you bring this to third gear
it's going to match the speed of the gear to the collar and so that will
allow you to get in gear and then once you're in gear
you can blip the throttle these are now all rotating together and the only speed
differential is between your engine and your clutch and so you blip the throttle
if you're down shifting you will match your engine speed to your clutch speed and
then you'll release and then you'll have that smooth engagement so the the
benefit here of the synchronizer is that you don't have to have the clutch
engaged in order to match the speeds and so you know that's why with modern cars
you don't ever have to do this double clutching technique because you have
synchronizers that match the speed of the gear
so what is this technique useful for well basically if you have a
transmission that doesn't
have synchronizers or if you do have a transmission with synchronizers but
they're completely worn out
this is a method that you could use to shift gears where you had wouldn't have
to worry about replacing that synchronizer if you got good enough at it
and you could match your engine speed to that collar speed and then get in gear
without using the synchronizer simply by matching the speeds so thank you guys
for watching if you have any questions or comments feel free to leave those
below