[Tech Issue] KERS - all over already?

[fourWheelDrift]

Originally Posted by JamesH

Agreed the speed is a exponential relationship, but you very quickly get to problems of flywheel materials not being strong enough to cope with the forces involved. Bigger and slower means less danger and also cheaper. But more difficult to package.

Perhaps you should have a leccy generator/motor on each wheel, and a motor/generator attached to the flywheel, which you use to store the energy. Yes, lots of losses in the conversion to leccy and back and forth, but (and I am guessing), perhaps only of the order of the friction losses of the CVT and driveshafts required to physically connect wheels to the flywheel. You capture the energy from all the wheels that way, not just the driven ones. Still, I am sure many people smarter than me have gone through all this stuff!

I don't think there is any particular virtue in using all wheels or non driven wheels for KERS unless the vehicle is close to traction limited or braking/cornering at the limit, while this is normal use for a racing car I hope it is pretty unusual on the road. Consequently I think there is no disadvantage for mechanical systems connecting to the exisitng drive train.

I do agree with earlier posters that electrical systems are too inefficient and clumsy to be the way forward other than for electric/hybrid cars which already have the hardware in place and in most cases already recover energy under braking anyway.

It is precisely because of the engineering challenges in those high speed spinning flywheels, there bearings and packaging that having a devleopment race around them in F1 could be so good for pushing the technology forward, a process which is well on the way.

It is also worth remembering that to be effective as a fuel saving measure on a road car you don't neccesarily need to store the amount of energy that is already allowed in the F1 systems. Substantial savings could be made in urban driving simply by storing enough energy to get from 0 to 30mph (the in town speed limit at least in the UK). The F1 system gives 80hp for 6.7 seconds which is near enough 400kJ, the energy required to accellerate an 1100kg road car to 30mph is only 100kJ, ie only a quarter the energy allowed in F1. Of course more energy storage=more savings but the relationship is not linear and would rapidly reach the point of diminishing returns, how much energy to store is yet another design trade off. At a fuel efficiency of 30% and an energy content of 38.4 MJ/l this would mean that for every 100 times you used that 100kJ of energy you would save 1l of petrol in round figures.

[stedevil]

Originally Posted by JamesH

Agreed the speed is a exponential relationship, but you very quickly get to problems of flywheel materials not being strong enough to cope with the forces involved. Bigger and slower means less danger and also cheaper. But more difficult to package.

It sure does, but we dont really have such huge forces involved.
We need to store about (80hp for 6s =) 350kJ
For a rotational mass of 4kg at radius of 50cm we reach that at about 133revs/s (8000revs/min). Considering even the engine revs at more than twice as much, it should be reasonably easy to reach that.

As for packaging, had a discussion on a forum with a guy 5-10 years back that had a really interesting idea. He was envisioning a flywheel sealed inside a vacuum container resting on magnetic bearings. Adding and removing of energy would be done via a magnetic coupling. The 2 main advantages would be virtually 0 energy loss due to friction as well as relatively good resistance to vertical movement of the flywheel due to bumps on the road.

Perhaps you should have a leccy generator/motor on each wheel, and a motor/generator attached to the flywheel, which you use to store the energy. Yes, lots of losses in the conversion to leccy and back and forth, but (and I am guessing), perhaps only of the order of the friction losses of the CVT and driveshafts required to physically connect wheels to the flywheel. You capture the energy from all the wheels that way, not just the driven ones.

With a 67-33 brake balance, the question quickly becomes (for a FWD car if we are talking road relevant), do you lose more in the multiple conversions than you gain from trying to recover from all 4 wheels? 2/3rds in any case comes from the wheels connected to the engine. Would be interesting to know if it's worth it.

Still, I am sure many people smarter than me have gone through all this stuff!

Im sure they have, but it doesnt stop 2 amatures theorizing on a forum.

[crmalcolm]

Reading this thread reminded me of this car. It uses the 'motor in each wheel' setup and if the claims are half true, seems to have good promise.

[JamesH]

Originally Posted by stedevil

It sure does, but we dont really have such huge forces involved.
We need to store about (80hp for 6s =) 350kJ
For a rotational mass of 4kg at radius of 50cm we reach that at about 133revs/s (8000revs/min). Considering even the engine revs at more than twice as much, it should be reasonably easy to reach that.

I made that 11k rpm for a solid flywheel. Still achievable of course. Big problem would be the gyroscopic affect I would think.

[fourWheelDrift]

Further hopefully constructive descussion of some of your points.

Originally Posted by stedevil

It sure does, but we dont really have such huge forces involved.
We need to store about (80hp for 6s =) 350kJ
For a rotational mass of 4kg at radius of 50cm we reach that at about 133revs/s (8000revs/min). Considering even the engine revs at more than twice as much, it should be reasonably easy to reach that.

A flywheel with a radius of 50cm would take a hell of a lot of packaging, for safety reasons it would have to have a strong casing around it so we are talking of a diameter for the system of maybe 1.1m, the only place it could go is probably under the floor so the whole car needs a redesign. Flybrid is certainly looking at a much smaller flywheel at a much higher speed in a unit you could just fit into the engine bay connected to the transmission.

Originally Posted by stedevil

With a 67-33 brake balance, the question quickly becomes (for a FWD car if we are talking road relevant), do you lose more in the multiple conversions than you gain from trying to recover from all 4 wheels? 2/3rds in any case comes from the wheels connected to the engine. Would be interesting to know if it's worth it.

Hard braking (should) only represent a handul of braking events in the life of a road car (unless it is unfortunate enough to be owned by a hormone filled male in his late teens or early twenties) and you would never design a KERS system to recover energy under these conditions. I suspect with suitable control systems and for normal in traffic braking you could put all the retardation through the driven axle (sort of engine braking plus) so having it on all four wheels may be all cost and no benefit. Of course if the driver brakes hard or conditions are icy the system would have to detect this and put the best braking possible on all wheels like any ABS system

[Racer 35]

http://www.autosport.com/news/report.php/id/74714

No KERS for Kimi this weekend, but Massa's persevering it seems.

[stedevil]

Originally Posted by JamesH

I made that 11k rpm for a solid flywheel. Still achievable of course. Big problem would be the gyroscopic affect I would think.

Solid flywheels would be a waste of material and weight. Any solution will be of the "bicycle wheel" type with just the minimal amount of material in the center areas to supports it's own weight. Likely even 2 main materials would be used, 1 low weight high strength, the other high density, to maximize the center of mass - rotational axis distance.

For the gyroscopic effect, it shouldn't be too bad. As long as we have horizontal spinning flywheel it should have mostly negligible effect on a car.

Originally Posted by fourWheelDrift

A flywheel with a radius of 50cm would take a hell of a lot of packaging,

Yes, for sure, that size would fit a lot better integrated into a car platform than in a racecar. The size was mostly chosen out of lazyness since 4 and 0.5^2 cancels each other out in the equasion

But I assume r of 0.25m could fit under the fule tank or fit somewhere else if needed, which gives us 400kJ at 200rps (12k rpm).
If we make it really tiny, eg r 0.1m, the speed increases considerably to above 1400rps (85k rpm) which seems a tad too high.

[JamesH]

Originally Posted by stedevil

For the gyroscopic effect, it shouldn't be too bad. As long as we have horizontal spinning flywheel it should have mostly negligible effect on a car.

Hmm. Not sure about that. It would turn left and right OK, but would be very reluctant to pitch forward and back. (i.e. start to go up or down a hill), or tilt side to side (camber on the road)

Try a power ball to really see what high rpm gyroscopic effects are like! (my record is 13k rpm)

[stedevil]

Originally Posted by JamesH

Hmm. Not sure about that. It would turn left and right OK, but would be very reluctant to pitch forward and back. (i.e. start to go up or down a hill), or tilt side to side (camber on the road)

Yes, up and down hills would be affected, especially downhill corners might be affected negatively by increasing understeer I presume (uphill conversely should increase downforce). So if overall laptime would increase or even decrease I guess depends on the track.

But sideways tilting in a corner is a necessary evil. The less of it you can have, the better (think active suspension). So in this case I can even imagine the effect, if it matters on laptime, would be positive.

[Marbot]

FOTA want total ban on KERS for 2010.

http://www.autosport.com/news/report.php/id/74793

[Glen]

If the fIA waas serious about green credentials they would demand KERS on the team trucks, not the race cars. Also, try reducing by half the number of personnel sent to each race, and the amount of equipment. And so on - the amount of energy consumed by two cars on track is irrelevant against what is wasted by the teams as a whole.

While they're at they should lead by example too - Max and Bernie should share a car when they go about their business - a Smart car perhaps, or a Tata Nano. And travel economy class.

[VIVA GT]

Originally Posted by Glen

If the fIA waas serious about green credentials they would demand KERS on the team trucks, not the race cars. Also, try reducing by half the number of personnel sent to each race, and the amount of equipment. And so on - the amount of energy consumed by two cars on track is irrelevant against what is wasted by the teams as a whole.

While they're at they should lead by example too - Max and Bernie should share a car when they go about their business - a Smart car perhaps, or a Tata Nano. And travel economy class.

Damned valid points there Glen, and well made as usual.

[duke_toaster]

http://www.autosport.com/news/report.php/id/74793

Flav wants KERS banned for 2010.

[Marbot]

Originally Posted by duke_toaster

http://www.autosport.com/news/report.php/id/74793

Flav wants KERS banned for 2010.

You're a bit late with that!

[stedevil]

I would not trust Flavio to truthfully represent/convey an accurate shared opinion of the FOTA. My guess is Flav is probably just whining as usual, grossly exaggerating the FOTA opinion. He even keeps whining about the diffusers even though his own team was, together with BMW, the main opposers to proper rules that would have banned them.

[Sodemo]

I heard that Flav wants KERS banned for 2010.

[Kiwi3]

Flav is a whining sore loser. He says we need to get back to 'equality', while every team has the opportunity to run KERS, every team had the opportunity to develop a double deck diffuser. Somehow all of this is embarrasing for fans, in actual fact that Renault have not built a very good car isn't embarrasing for anyone other than Renault. Nice try at deflecting attention Flav , but anyone with intelligence won't buy it. Renault's failure is your problem!

[JeremySmith]

This is no surprise....

http://www.autosport.com/news/report.php/id/74793

I believe it to be not much more than a gimmick..IMHO

[Knowlesy]

When did Flavio start having this logic bypass?

[JeremySmith]

On the subject of KERS I have to agree with him Knowlesy..

[Knowlesy]

I agree that it may be expensive, but this 'same footing' he speaks of: where in the regs does it say Renault can't use KERS?

[JeremySmith]

It does not, but Flavio sees KERS as not cost effective and just plain gimmicky I think..

[Burnsie]

Originally Posted by JeremySmith

...Flavio sees KERS as not cost effective and just plain gimmicky I think..

A quote from Briatore talking to Gazzetta dello Sport. "The season starts here. I'm talking about Renault, we have these new diffusers, and we'll be able to take advantage of the KERS".

At least he has acknowledged that there is an advantage to be gained by running with KERS, although the qualifying times from today's session don't exactly agree with that theory...

[JeremySmith]

So who is running with and who is not?

We know the Brawn cars are not using it along with the Toyota's, and also the Willams

[Burnsie]

Originally Posted by JeremySmith

So who is running with and who is not?

McLaren, Ferrari, BMW Sauber and Renault - to the best of my knowledge, both drivers from each team.