- What is super hot,
needs a specialist for optimal function,
and has 18 fingers?
This guy.
Actually, it's a Top Fuel Dragster clutch.
And today we're getting deep into its mini layers
and what can cause it to get so hot.
And it welds itself together.
Freaking laying down dimes on the old clutch, let's go.
(chill music)
Top field Dragsters produce an absolutely insane
11,000 horsepower.
Enough to trash their entire engine
in just under four seconds.
Pistons, rings, connecting rods and spark plugs,
all have to be tossed after a single run,
but we're not talking about all those components.
Oh no.
We're talking about their clutches.
Those clutches can reach 4,000 degrees Fahrenheit,
twice as hot as lava,
and just a little bit hotter than your boy.
Because of all that horsepower, these clutches get so hot
that they can weld themselves together.
So to figure it out,
we first gotta see how a Top Fuel clutch works.
Not to oversimplify things,
but you probably know what a clutch does.
It regulates power from the engine to the drive shaft,
and ultimately to the wheels.
Now the purpose of a Top Fuel clutch is the same
as in any other car.
You can think of a Dragster clutch setup like a sandwich.
Within the bell housing,
you'll find the highly tuned Top Fuel centrifugal clutch.
I call it centrifugal sometimes,
sometimes people say the same words differently.
I'm gonna call it centrifugal.
'Cause some kid yelled at me on Instagram about it.
At the engine in is the flywheel,
which forms that all important connection
to the Dragster's 11,000 plus horsepower.
And in this case, the flywheel will be a lot like
the bottom bread of our sandwich.
Then we have the filling, the nice meat that's inside,
and that is the five or six discs clutch pack.
The clutch pack is an alternating stack
of six clutch disks and five steel floater plates.
It really is the meat of the centrifugal clutch system
and the source of a lot of the friction and heat
that can cause the plates to weld themselves together.
The base metal melting and a Top Fuel clutch is iron,
and iron is super dense, it melts around 2,800 degrees.
Now typically more mass, especially dense mass like iron,
means more heat energy dissipation,
otherwise known as cooling.
So heat energy dissipation across a dense surface
means the heat energy is diminished
as it spreads across that surface.
And this is why the clutch doesn't weld itself together
on every single run, but it does happen.
And when it does it's because of friction.
That friction causes the clutch temperature to rise
above the melting point of the clutch pack materials.
The manufacturer and material type are tippy top
Top Fuel secrets when it comes to the plates and the disc.
Steel floater plates are actually a blended steel
unique to each team's tuning and performance calculation.
A steel is just an alloy of iron and carbon.
And the choice of ratios of metals in that steel
will obviously have an effect on the clutch performance
based on the friction or slippage that they provide.
That blend can also be more or less prone
to heat damage or welding.
So, that's the steel plates, right?
But you also have clutch discs and those are made of iron.
Specifically made of sintered iron.
Well, what is sintered iron?
Well, so freaking glad you asked.
Here's some hot footage.
(romantic music)
Oops, sorry about that.
That was just me with my shirt off.
Here's some sintering footage, sorry.
I don't know why just keep hitting a wrong button.
For real, here's some sintered footage.
Sintering is the process
of putting parts made of compressed iron powder
through a very toasty furnace and adding high pressure.
The goal is to control the temperature
so it reaches just below the melting point of iron
without actually liquefying.
The heat and pressure works at a molecular level
causing the metal particles to bond together
so you get a stronger disc
with enhanced properties from the original metal.
It diffuses other elements like carbon
that may be in the mix and reduces pore size,
increasing the strength of the bonds between the particles,
and because the discs are so dense from being heated
and compacted during the sintering process,
they can absorb and dissipate a lot of heat energy
before their temperature goes up.
Not only that, but sintered iron discs
also have a super strong grip.
It has a high coefficient of friction
compared to standard iron disc.
They grip even better when they get hot.
That's why you'll see a really quick burnout before a run.
That not only gets the tires ready for the run,
but it also warms up the clutch disc enough
to start engaging better.
That gives the disc the heat that they need
to withstand slippage without sacrificing
the all important coefficient of friction
that makes a clutch work.
There are many different types of friction
that we could get into here.
There's static friction, sliding friction, rolling friction.
The obvious friction between me and James
on the subject of wheel.
- You're making me regret having you on the show!
- The obvious friction between me and my girlfriend
when deciding where we're gonna go eat on Tuesday nights.
It's B2B day, baby, okay?
I get to pick, Tuesday's my day.
You get all the other days.
You get Wednesday, Thursday,
Friday, Saturday, Sunday, Monday.
I get Tuesday, B2B day, my day.
But let's talk about the coefficient of friction,
or how well or how poorly friction exhibits itself
between two objects.
In even simpler terms, just remember it like this,
a higher coefficient of friction
means the better a disc will be able to do its job.
It also means a super harsh engagement.
So more parts are sacrificed, but it's worth it
so you can go faster down the track.
That being said, the same sintering process
that strengthens the material for more grip
makes it ideal for welding.
The lower the carbon content present,
the easier it is to weld,
and generally low carbon metals have good weldability,
and do not require special process measures
in order to weld with another metal.
So when you combine the low carbon sintered iron
with the steel blend plates, you're only a few factors away
from a welded panini press of a clutch sandwich.
Mm, mm, mm, mm, yum.
On the other end of the clutch sandwich
is a pressure plate hat or cap,
and it has many names and roles
including providing the pressure onto the clutch pack
and the flywheel.
There's a titanium donut.
Yes, a donut, underneath the clutch hat as well.
Speaking of donut, if you want some cool, (beep)
I'm not wearing a donut shirt.
Speaking of donut, why don't you go to donutmedia.com?
Get some cool merch like this donut pen.
I don't have a donut shirt,
'cause I'm going to ninja practice today.
So I had to wear my Ninja shirt, no big deal.
(Japanese battle music)
The two parts of the cap are held together
with six stall springs.
The springs can be adjusted to be free or loose
so that the crew can push the vehicle to the burnout.
Then because the clutch has heated,
the springs expand enough to make the clutch stickier.
Now mounted on the top of the hat,
are up to 18 clutch fingers,
which sound creepy, little frigging salad fingers,
but they are essential to the operation.
A traditional clutch uses springe steel arms
to create the plate load needed to hold the clutch disc.
A Top Fuel clutch uses centrifugal force
and pistons to compress the clutch pack
using a set of weighted levers on the pressure plate.
Sound confusing?
Well, it sort of is and it's also why the clutch
is really where tuning makes such a difference
between wins and losses.
Yeah, that's right.
This clutch needs to be tuned.
And the art of clutch tuning lies in the hands
of a clutch specialist and crew chief,
or more accurately their fingers.
They calculate the weights needed on the fingers
as well as the timing map
that will release the throwout bearing.
The clutch fingers act as levers
being forced out against the pressure plate,
compressing the clutch and locking the friction disc
and floaters together.
So you have one hole assembly from the engine,
to the flywheel, to the clutch, to the wheels.
Now that allows more power to be transmitted gradually
to the wheels, as opposed to all at once.
You don't want that.
You want a smooth operation,
so you can get that power to the wheels
and not break traction so you can get a nice run
down the drag strip.
Later sucker, oh, you burned out?
Get a new clutch man, dude,
you need to tune your fingers more.
Each of the clutch fingers can be adjusted individually
to control locking of the plates.
The six primary fingers, they'll all be the same length,
all made of tool steel,
but the secondary fingers, they can vary in length.
That vary in length will mean different timing
for reaching engagement with the clutch.
The addition of weights, usually in the form of nuts
can fine tune the rate of clutch engagement too.
So adding weights means the clutch will engage
at a lower RPM on the initial hit of the throttle.
Whereas taking weight off,
will allow the motor to reach higher RPMs
before fully engaging.
Thinking about this in terms of centrifugal force
present in the clutch, the more weight,
the faster a lever will swing out.
You can try it at home, hold your arms in front of you
and bend your elbows so that your hands
are now in front of your face, okay?
Now spin around as fast as you can, okay?
Do you feel forced trying to pull your arms out
away from your body like this?
If you do the same thing while you're holding
say five or 10 pound weights,
it'll be even tougher to keep your hands up
and your arms in.
That's cental force at play.
It's the apparent force felt by an object
moving in a curved path that acts outwardly
away from the center of rotation.
It's that pullout when you're rotating,
and it's what forces the levers out to engage the clutch.
Now, if a track has plenty of grip,
the crew chief will add weight to the clutch.
Meaning the power will be deployed quicker,
resulting in a faster run.
But if a track is slippery or it's wet,
they will remove weight to provide a softer hit
from the clutch.
There truly is a fine line
between pulling a fast run and just smoking the tires.
And the interesting thing is the driver has no control
over the clutches engagement.
I guess it doesn't matter if you're a good or bad driver.
It's all up to the old engineers who are working on the car.
The level of locking is really controlled
by pneumatic release bearing.
As the driver hits the throttle,
a micro switch initiates a pneumatic timer
that controls the release bearing,
sometimes called the cannon.
This bearing limits movement of the clutch fingers
and locks in the clutch.
As the clutch timer counts down, pressure is released
from the system, moving the release bearing
and allowing the fingers to lock the clutch up.
Since only a very basic mechanical system is allowed,
the timer sequence cannot be adjusted
once the Dragster is set to the starting line.
So all these elements are set ahead of time.
No adjustments can be made once the time is punched in
and everything has to go right, unless it doesn't.
And then that can lead to, you got it, welding.
Technology has changed over the years though.
And most teams have upped the number of plates they use
and improved the materials as well.
But a clutch failure is still catastrophic.
It means no power goes to the wheels and the run is over.
You're also looking at costs, which add about 10,000 bucks
per run to replace all those parts.
It's not a cheap fix.
There's so many things that can go wrong in a Dragster run,
that it's sort of amazing when things don't go wrong.
And out of all the components involved in a successful run
ask any team's crew, and the clutch will be at the top
of their list for prioritized parts.
The secrecy around materials used in the clutch
and the calculations for each team is well founded.
A factor of mere grams on the clutch levers
can make or break a run.
So when you do see a win,
know that there wasn't just nitro fuel
and turbocharge engine power behind it.
There's a little revenge there for us nerds,
determining all the weather and track conditions,
inputting data into complex equations
to determine weight ratios on levers, et cetera, et cetera.
All that science and math that might not seem super cool,
actually wins or loses a run for the turbocharge Dragster.
Thank you guys so much for watching this episode of B2B.
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hit that subscribe button, that really helps us out.
If you guys wanna see more Dragster content,
leave comment down below, let us know.
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Follow me at Jeremiah Burton,
and until next week, bye for now.