Yes , Porsche opted to use the GT1 sized rear wheels for the RSR in exchange for the weight penalty imposed by the ACO .

The use of the larger GT1 tires in the rear improved the traction  and balance of the car, but also contributed to some under-steering problems (in fast turns), that were later corrected by front suspension and aerodynamic redesign, as well as posing some problems with rear tire ware.

The ACO will also have change the rules to allow the front wheels to be driven.

It's good to hear that the transition from flywheel to a accumulator storage system is feasible if the ACO demonstrate their usual flare for the erratic!

Mike

2005 Carrera GT - Signal Yellow + 2008 Tesla Roadster - Thunder Gray +1972 BMW 3.0 CSi - Nachtblau +2009 Bentley Arnage T - Black Saphire

Flywheel Background

Flywheels have been used to store and stabilise energy for hundreds of years. Early examples include the potter's wheel and spinning wheels. More recently advances in bearing technology, power electronics and vacuum enclosures have substantially improved their performance characteristics. The first modern flywheel systems were large stationary installations used to provide uninterruptible power supply and the production of very large pulses of electricity for scientific or industrial use.

Only in the last two decades has flywheel technology been seriously considered for use in mobile applications. It was held back by prohibitive weight and unwanted precession forces. Both of these characteristics are determined by the specific tensile strength (the ratio of the hoop stress to material density) of the flywheel. Advances in carbon fibre composite technology has allowed the specific tensile strength to be greatly improved leading to the development of light, high-speed flywheel systems. Test vehicles, particularly buses, have been produced using mechanical flywheel systems with a continuously variable transmission (CVT) to transfer power to and from the flywheel.

The next evolution was electrically-driven flywheels which do not require a CVT system thus avoiding added weight and reduced efficiency. Electrically-driven flywheels have another important advantage over their mechanically driven relatives in that vacuum integrity is easier to maintain as no high speed mechanical seal is needed. WHP's MLC flywheel is electrically driven.

Mike

2005 Carrera GT - Signal Yellow + 2008 Tesla Roadster - Thunder Gray +1972 BMW 3.0 CSi - Nachtblau +2009 Bentley Arnage T - Black Saphire

Thanks man! Now, that's why I love Rennteam!

Still don't really understand... the "energy storing capacity" of a flywheel stemms from it's inertia, right?

I understand that you want to use carbon fibre, especially with the fillament winding method, as all your fibres can be oriented in the correct direction, yielding enormous strength against centrifugal forces. However, using a lighter material will also reduce the inertia, and thus the energy storing capacity.

Joost:

Still don't really understand... the "energy storing capacity" of a flywheel stemms from it's inertia, right?

I understand that you want to use carbon fibre, especially with the fillament winding method, as all your fibres can be oriented in the correct direction, yielding enormous strength against centrifugal forces. However, using a lighter material will also reduce the inertia, and thus the energy storing capacity.

 But inertia has two components: mass and the square of velocity.

Using high-tensile-strength materials allows the speed of rotation of the flywheel to be increased.

fritz

fritz:

 But inertia has two components: mass and the square of velocity.

Using high-tensile-strength materials allows the speed of rotation of the flywheel to be increased.

Exactamente!!!!!

Mike

2005 Carrera GT - Signal Yellow + 2008 Tesla Roadster - Thunder Gray +1972 BMW 3.0 CSi - Nachtblau +2009 Bentley Arnage T - Black Saphire

2010 Porsche 911 GT3 R Hybrid...

"Porsche Intelligent Performance"

fritz:

 But inertia has two components: mass and the square of velocity.

Using high-tensile-strength materials allows the speed of rotation of the flywheel to be increased.

... thus yielding more than by adding more weight...

Thanks guys, think I've got it (finally) ;-)

fritz:

Joost:

Still don't really understand... the "energy storing capacity" of a flywheel stemms from it's inertia, right?

I understand that you want to use carbon fibre, especially with the fillament winding method, as all your fibres can be oriented in the correct direction, yielding enormous strength against centrifugal forces. However, using a lighter material will also reduce the inertia, and thus the energy storing capacity.

 But inertia has two components: mass and the square of velocity.

Using high-tensile-strength materials allows the speed of rotation of the flywheel to be increased.

High-tensile materials may help lowering the mass and allowing high rotation velocity, but... the gyroscopic effect is still there, being proportional to the angular momentum and therefore the rotational velocity. It will work great on flat corners, but watch out any banked one.

_________________________________________________________ 

A. Dias --- 997.2S (ordered). Previous cars: Corvette C6,  996 C4.

ADias:

High-tensile materials may help lowering the mass and allowing high rotation velocity, but... the gyroscopic effect is still there, being proportional to the angular momentum and therefore the rotational velocity. It will work great on flat corners, but watch out any banked one.

 I was intrigued by this statement above from WHP:

Only in the last two decades has flywheel technology been seriously considered for use in mobile applications. It was held back by prohibitive weight and unwanted precession forces.

I wonder what exactly has been done to prevent "unwanted precession forces"?

Mike

2005 Carrera GT - Signal Yellow + 2008 Tesla Roadster - Thunder Gray +1972 BMW 3.0 CSi - Nachtblau +2009 Bentley Arnage T - Black Saphire

W8MM:

I wonder what exactly has been done to prevent "unwanted precession forces"?

 Maybe counter-rotating masses, so that equal and opposite forces cancel each other out.

fritz

- PRESS RELEASE -

WILLIAMS HYBRID POWER CONTRACTS WITH PORSCHE AG FOR 911 GT3 R HYBRID

Oxford, UK, February 11, 2010. Williams Hybrid Power Limited is pleased to confirm that the energy storage system as part of the new Porsche 911 GT3 R Hybrid, which was announced today by Dr. Ing. h.c. F. Porsche AG, Stuttgart, has been developed and supplied by Williams Hybrid Power. The 911 GT3 R Hybrid with innovative hybrid drive will make its debut at the Geneva Motor Show. Further details from Porsche follow in the attached press release.

The energy storage system was originally developed for use in Formula One by the AT&T Williams team but Williams Hybrid Power is now focused on applications in road vehicles. The technology will also be developed for larger, infrastructure applications by Williams F1 at its new research facility in the Qatar Science and Technology Park.

Ian Foley, Managing Director of Williams Hybrid Power said, "We are delighted to see our technology being adopted by one of the world's leading engineering companies and most prestigious automotive manufacturers in one of their racing cars. Partnering with Porsche on this project has been a very positive experience and we are grateful to them for choosing to work with us."

Alex Burns, Chairman of Williams Hybrid Power and Chief Operating Officer of Williams F1 said, "This is a milestone for both Williams Hybrid Power and Williams F1. Together we have worked to bring this technology forward to the point where it can be tested in a racing car and deployed in a road car. We hope that this will be just the start of the evolution of hybrid systems developed for Formula One moving across to applications where they can contribute to cleaner and more powerful vehicles."

Context:

Williams Hybrid Power Ltd (WHP) has developed a novel, patented electromechanical composite flywheel system that provides a high-power, cost-effective and environmentally friendly solution for mobile or stationary energy storage and recovery, originally developed for Formula One.

Through development of a flywheel for Williams F1’s Kinetic Energy Recovery System, WHP has proved its world-class engineering capabilities in the composite flywheel field as well as radically improving aspects of the technology in the process. WHP is today making the technology available to meet the high-power energy storage needs in a variety of applications including hybrid passenger vehicles, hybrid buses, electric trains, diesel-electric ships and wind power generation.

In November 2009, the company announced its involvement in a mild hybrid road car programme with Ricardo, CTG, JCB, Jaguar Land Rover, SKF and Torotrak. The project aims to demonstrate the potential of flywheel-based hybrid systems with the potential for 30 per cent fuel savings (and equivalent reductions in CO2 emissions) at an on-cost of less than £1000, to enable mass-market uptake of hybrid vehicles in price sensitive vehicle applications.

Source: Williams Hybrid Power Limited - Press Release

I don't know what precession forces mean, but flywheels (gyroscopes) have two strange effects:

1. They tend to want to stay in position (therefore, they were used in early navigational computer such as used in the german missiles of WW2)

2. When they rotate along axis X, and you rotate the entire wheel alongst axis Y, an acceleration in the Z-rotation appears.

I can imagine that the second effect results in high -difficult to predict- forces?

Joost:

I don't know what precession forces mean, but flywheels (gyroscopes) have two strange effects:

Precession of Spinning Top

A rapidly spinning top will precess in a direction determined by the torque exerted by its weight. The precession angular velocity is inversely proportional to the spin angular velocity, so that the precession is faster and more pronounced as the top slows down. The direction of the precession torque can be visualized with the help of the right-hand rule.

Spin a top on a flat surface, and you will see it's top end slowly revolve about the vertical direction, a process called precession. As the spin of the top slows, you will see this precession get faster and faster. It then begins to bob up and down as it precesses, and finally falls over. Showing that the precession speed gets faster as the spin speed gets slower is a classic problem in mechanics. The process is summarized in the illustration below.

This process involves a considerable number of physical and mathematical concepts. The angular momentum of the spinning top is given by its moment of inertia times its spin speed but this exercise requires an understanding of it's vector nature. A torque is exerted about an axis through the top's supporting point by the weight of the top acting on its center of mass with a lever arm with respect to that support point. Since torque is equal to the rate of change of angular momentum, this gives a way to relate the torque to the precession process. From the definition of the angle of precession, the rate of change of the precession angle q can be expressed in terms of the rate of change of angular momentum and hence in terms of the torque.

The expression for precession angular velocity is valid only under the conditions where the spin angular velocity w is much greater than the precession angular velocity w_P. When the top slows down, the top begins to wobble, an indication that more complicated types of motion are coming into play.

Mike

2005 Carrera GT - Signal Yellow + 2008 Tesla Roadster - Thunder Gray +1972 BMW 3.0 CSi - Nachtblau +2009 Bentley Arnage T - Black Saphire

Here's a pretty nice basic video on gyroscopes.

@ W8MM: "The precession angular velocity is inversely proportional to the spin angular velocity, so that the precession is faster and more pronounced as the top slows down."

Much of the explanation is over my head at the moment but can we conclude from the above that a fast spinning wheel, as that used in the WHP system, would therefore minimize precession forces?

Slow In, Fast Out

ADias:

It will work great on flat corners, but watch out any banked one.

 

Makes me think of the "Caroussel"  Also: what happens at the top of steep climbings on a track ? "Flugplatz" (airfield) at the Nordschleife may really earn it's name  The Eifel roller coaster will be the perfect test terrain for the new technology.

public roads: Porsche 987 S Seal/Cocoa, toll road  : Porsche 997 GT3 Arctic/Black

fritz:

W8MM:

I wonder what exactly has been done to prevent "unwanted precession forces"?

 Maybe counter-rotating masses, so that equal and opposite forces cancel each other out.

Ummm. I suspect that the solution is easier than that. 

Looking at the images above, the axis of rotation of the flywheel is vertical, not horizontal as would be the case in gyroscopes formerly used in navigation systems. 

Most drivers tend to keep their cars upright . The car's vertical axis is therefore generally maintained in a more or less vertical alignment. Precessional forces normally induced by varying the axis of rotation of  the flywheel when it is spooled up are kept within bounds, so that they are not an issue.  

Have I missed something? 

fritz

W8MM:

ADias:

High-tensile materials may help lowering the mass and allowing high rotation velocity, but... the gyroscopic effect is still there, being proportional to the angular momentum and therefore the rotational velocity. It will work great on flat corners, but watch out any banked one.

 I was intrigued by this statement above from WHP:

Only in the last two decades has flywheel technology been seriously considered for use in mobile applications. It was held back by prohibitive weight and unwanted precession forces.

I wonder what exactly has been done to prevent "unwanted precession forces"?

I wonder if they mounted the gyro/flywheel-generator on a gimbal decoupling it from the chassis. 

_________________________________________________________ 

A. Dias --- 997.2S (ordered). Previous cars: Corvette C6,  996 C4.

fritz:

fritz:

W8MM:

I wonder what exactly has been done to prevent "unwanted precession forces"?

 Maybe counter-rotating masses, so that equal and opposite forces cancel each other out.

Ummm. I suspect that the solution is easier than that. 

Looking at the images above, the axis of rotation of the flywheel is vertical, not horizontal as would be the case in gyroscopes formerly used in navigation systems. 

Most drivers tend to keep their cars upright . The car's vertical axis is therefore generally maintained in a more or less vertical alignment. Precessional forces normally induced by varying the axis of rotation of  the flywheel when it is spooled up are kept within bounds, so that they are not an issue.  

Have I missed something? 

That is OK in a perfectly flat road. Try driving on a banked turn and the gyro will pull the chassis up towards the outside of the corner - not good. As I offered above, I wonder if the gyro/flywheel-generator is mounted in a gimbal decoupling it from the chassis.

_________________________________________________________ 

A. Dias --- 997.2S (ordered). Previous cars: Corvette C6,  996 C4.

ADias:

fritz:

Looking at the images above, the axis of rotation of the flywheel is vertical, not horizontal as would be the case in gyroscopes formerly used in navigation systems. 

Most drivers tend to keep their cars upright . The car's vertical axis is therefore generally maintained in a more or less vertical alignment. Precessional forces normally induced by varying the axis of rotation of  the flywheel when it is spooled up are kept within bounds, so that they are not an issue.  

Have I missed something? 

 

That is OK in a perfectly flat road. Try driving on a banked turn and the gyro will pull the chassis up towards the outside of the corner - not good. As I offered above, I wonder if the gyro/flywheel-generator is mounted in a gimbal decoupling it from the chassis.

You are still thinking in terms of the flywheel having a horizontal axis, causing the car to tend to continue in a straight line in a turn.

Unless I am mistaken, a vertical axis would just cause a little more force to be applied to the offside wheels in a turn, due to precession.

I say "just cause a little more force" because a banked turn might cause an angular displacement of the vertical axis of maybe 20 degrees, whereas a turn could take a horizontal axis through anything up to 180 degrees.

Come to think of it, depending on the direction of rotation of the flywheel, shouldn't it be possible to use the precession force to reduce weight displacement to the offside wheels and load up the inside wheels instead? 

This is just speculation on my part, not gospel. It's a long time since I got involved with the intricacies of gyroscopic effects, and I didn't even enjoy the experience the first time around. 

fritz

Sounds about right to me. I also believe these cars will make some pretty cool matrix-esque slow motion moves when crashing and flying through the air.

denn:

Sounds about right to me. I also believe these cars will make some pretty cool matrix-esque slow motion moves when crashing and flying through the air.

 Uhu?  

I don't remember predicting that scenario. 

fritz

fritz:

denn:

Sounds about right to me. I also believe these cars will make some pretty cool matrix-esque slow motion moves when crashing and flying through the air.

 Uhu?  

I don't remember predicting that scenario. 

 I'm just joking 

fritz:

You are still thinking in terms of the flywheel having a horizontal axis, causing the car to tend to continue in a straight line in a turn.

Unless I am mistaken, a vertical axis would just cause a little more force to be applied to the offside wheels in a turn, due to precession.

I know fully well the flywheel axis is vertical. That's why it will be stable only on a perfectly flat surface. And I am not referring to precession. Even if precession is zero the flywheel will unbalance  a car on a banked turn, because it will try to maintain its axis vertical. Precession is a second order effect and adds a random component to the stability problem.

--

_________________________________________________________ 

A. Dias --- 997.2S. Previous cars: Corvette C6,  996 C4.

2010 Porsche 911 GT3 R Hybrid...

In preparation for a race debut at the famous Nurburgring Nordschleife, the Porsche 911 GT3 R Hybrid undergoes further testing...

Great Thanks!

BTW - Roman Dumas at the wheel!

--
997 GT3 clubsport

 Thanks rantanplan.

 I'm trying to get hold of some times and also confirmation of who was testing it.