Do F1 engines have flywheels?

[63l8qrrfy6]

and otoh ....
how can taking no action to modulate PU behaviour give a quicker shift ? (than taking action designed to help shift)
also now the gearbox is required to have a long life
rpm change within 1 rev (eg by cutting) is a significant proportion of the nominally required 15% rpm swing for shifts

What limits shift time is the fact that reducing the time increases the accelerations required to synchronize the inertias either side of the meshing gears, therefore the 'stab' torque increases. The clutch preload springs effectively cap this torque. Of course another limit is the actuator response time.

During an upshift for example, part of the rotational energy stored in the engine cranktrain assembly is passed on to the driveline once the gears engage and manifests as a short burst of wheel torque. Slowing down the engine during the upshift (spark/ fuelling/ K ,etc) significantly decreases the rotational energy (as it is proportional to the square of angular velocity) so the initial wheel torque spike decreases which is not great for performance.

[Big Tea]

shifts (then called gearchanges)

Sorry for the OT, but I´m curious about this. Did you call it gearchanges when it was a manual H-style gearbox and shifts with new semi-automatic gearboxes?

In spanish we´ve not changed the term, so I´ve never noticed this before

Started changing name around the the time Beachboys and Jan & Dean started singing about it

[Caito]

iirc Mudflap's view is that the quill shaft enables shifting without use of throttle, ignition cut or fuelling cut ....
but yesterday I heard Mr Coulthard say that Alonso had a problem as he had lost his throttle blip

Scootin is of course correct. The preload on these clutches is adjusted so that the clutch slips at excessive inertial torques, protecting the driveline during harsh shifts. Interestingly, I am pretty sure I have heard F1 have experimented with motorcycle style ramp slipper clutches although I am not sure if the purpose was to avoid rear wheel slip or protect the driveline (or both?).

Is this why you hear some oscillation when changing gears?

This was more noticeable with V8 engines that upon upshifting you'd hear some oscillation.
Very noticeable in this video:
https://youtu.be/aolTbZkysW8?t=24

[PlatinumZealot]

Here is excellent engineering perspective on torque variation vs. crankshaft angular position. In 4, 6, 8, 12 cyl engines. Current F1 engine probably best represented by the chart for "odd-fire V-6"--

http://www.epi-eng.com/piston_engine_te ... ngines.htm

An even-fire 6-cyl engine still has moments of negative torque (rotational deceleration). You have to go to ~ 8 cyls to maintain positive torque all the time. A heavy flywheel on a 6-cyl would reduce the severity of its peaks vs. valleys, but it would not prevent the negative-torque valleys from existing.

Conventional wisdom is that engines produce more steady-state power with a heavy flywheel, and this is due to crank vibration modes messing up timing and other issues. F1 engine people understand the torsional vibrations quite well, plus now they monitor individual cylinder pressures (!!) as the crank turns, so by sensor/computational brute-force they eliminate power advantage of flywheels. If clutches and spec-dimension gearsets can handle the torque fluctuation with no flywheel, then I guess no reason to have one?

The flywheel should reduce the negative dips like how a capacitor smoothens rectfied AC current. There is no extra power as your rightly say but there is stored eneergy being added back helping to turn the engine when it is going against negative torque like friction, vibrations and compression etc.
Engine sensors and firing modes wont do anything to stop the dips because there is simply no external addition of power to help it. MGUK is a different story though.. It can reduce the dips.. but at a cost in life of it not sure if teams risk that. The Flywhweel is a great invention and is alost zero loss. It is easier and more logical to make the MUGK help overcome the weakness of the flywheel inertia than for to replace the role of it.

[63l8qrrfy6]

Well, i would not call that almost 0 loss but rather a significant loss.

By definition a flywheel has a high inertia. The higher the inertia the higher the torque required to accelerate it - torque that is taken away from the wheels that is.

[strad]

On the other end of things. Do they run any kind of harmonic balancer on the front? I have never noticed one.

[PlatinumZealot]

On the other end of things. Do they run any kind of harmonic balancer on the front? I have never noticed one.

I hear there are many of them. Cosworth V8 had in the teens balancers all over the engine! Not sure how many on these V6's though.

[63l8qrrfy6]

A damper is most effective where the amplitude of torsional vibration is highest.
In a conventional engine the amplitudes are low at the flywheel end due to its high inertia and high at the crankshaft nose which is why the dampers usually sit at the front. Same reasoning for cam dampers located at the end of the cam shaft.

Since we've established F1 engines don't have flywheels, the damper does not have to be at the front - in fact the Cosworth CA had a viscous damper at the rear.

I'm sure the V6 must have some form of driveline damper as the very low excitation frequency produced by uneven firing (and lower engine speed and reduced cylinder count) is bound to hit a resonance at some point.

[strad]

Guess I was thinking of something similar to what's on the front of a Chevy.. Ford.. Chrysler crankshaft.

[Tommy Cookers]

[quote=PlatinumZealot]
The flywheel should reduce the negative dips .....
Engine sensors and firing modes wont do anything to stop the dips because there is simply no external addition of power to help it. MGUK is a different story though.. It can reduce the dips.. but at a cost in life of it not sure if teams risk that. The Flywhweel is a great invention and is alost zero loss. It is easier and more logical to make the MUGK help overcome the weakness of the flywheel inertia than for to replace the role of it.[/quote]


the electrical machine has some limit in (rpm) acceleration and usually torque variability is limited by this acceleration limit
the EM is in principle attractive as it can smooth ICE torque variations in-cycle as when no great rpm acceleration is involved

but in an F1 type shifts rpm accelerations are great and the (active) EM's response slightly degrades overall (PU) response
this degradation would be worse with a more powerful EM

if the EM was direct-drive its torque cycle would need adaption by design specific to any in-ICE-cycle application


btw iirc
the Hele-Shaw clutch had adjustable and safe slip torque
it was used in Eldridge's Fiat that took the so-called LSR almost 100 years ago

[roon]

The flywheel should reduce the negative dips .....
Engine sensors and firing modes wont do anything to stop the dips because there is simply no external addition of power to help it. MGUK is a different story though.. It can reduce the dips.. but at a cost in life of it not sure if teams risk that. The Flywhweel is a great invention and is alost zero loss. It is easier and more logical to make the MUGK help overcome the weakness of the flywheel inertia than for to replace the role of it.

the electrical machine has some limit in (rpm) acceleration and usually torque variability is limited by this acceleration limit
the EM is in principle attractive as it can smooth ICE torque variations in-cycle as when no great rpm acceleration is involved

but in an F1 type shifts rpm accelerations are great and the (active) EM's response slightly degrades overall (PU) response
this degradation would be worse with a more powerful EM

if the EM was direct-drive its torque cycle would need adaption by design specific to any in-ICE-cycle application


btw iirc
the Hele-Shaw clutch had adjustable and safe slip torque
it was used in Eldridge's Fiat that took the so-called LSR almost 100 years ago

I'm reminded of our exchange last year, Tommy. viewtopic.php?p=728846#p728846

Regarding the K and shift time responsiveness. The K rotates something like three times per full crank rotation. This should aid control relative to the injection and ignition sequences available to the more slowly moving pistons. The K can provide more than 1/6 engine power while seemingly offering higher control resolution.

[Tommy Cookers]

in this moment and fwiw I think that .....

EMs can torque fill in-cycle at road car-useful rpm eg 1200 rpm - and be 'flywheel-neutral' in this low rpm shifting
EMs might even torque fill in-cycle at race car rpm eg 12000 rpm - but act as passive flywheels detrimental to high rpm shifting

because the synchronous EM (K) torque response time is fundamentally limited by the associated rpm acceleration
(and max rpm accelerations outside the cycle (in shifting) are clearly much greater than in-cycle rpm accelerations)

ok if clutch slip behaviour during shifts accomodates PU inertia then a larger K machine may be tolerable wrt shifts

[gruntguru]

Any idea how quickly the the K can respond to a step input? Is its time constant small enough to significantly contribute during upshifts by slowing the engine?

[roon]

because the synchronous EM (K) torque response time is fundamentally limited by the associated rpm acceleration
(and max rpm accelerations outside the cycle (in shifting) are clearly much greater than in-cycle rpm accelerations)

What do you mean by "in-cycle" and "outside the cycle"?

[Tommy Cookers]

a largeish servomotor (2 phase AC peak power 5 kW) that I bought - its mechanical time constant was about 25 millisec
(installed, the system time constant was iirc c.50 mSec at max acceleration-related load)
only now do I wonder whether it always acted synchronously

the synchronous machine would not be given a step controlling signal
to maintain synchrony the signal slew (rate of change) would be related to the (system) acceleration
(eg torque-fill capability would depend on the system (combined EM and ICE) rpm acceleration)
ok for some F1 purposes torque collapse from excessive slew rate could be useful but it's not useful for shifting or fill