SAE Vehicle Electrification Magazine features the Model S

[ckessel]

According to the SAE article cited, the Model S body in white has a 42Hz torsional frequency.

I found a wiki page on torsional frequency and still don't really get it. What's the torsional frequency mean in end-user terms? Less noise? Smoother ride?

 

[Todd Burch]

+1 to GSP's comments.

The weight distribution and stiffness is completely different from traditional ICE cars, so drawing a direct comparison to using McPherson's on an ICE is probably not so valid.

 

[Doug_G]

I found a wiki page on torsional frequency and still don't really get it. What's the torsional frequency mean in end-user terms? Less noise? Smoother ride?

Resonant frequency correlates with stffness. Torsional means twisting. The body of the model S will strongly resist twisting.

 

[TEG]

I found a wiki page on torsional frequency and still don't really get it. What's the torsional frequency mean in end-user terms? Less noise? Smoother ride?

Saab 9-4x Technical Highlights

...A stiff body structure, with a {high} torsional rigidity ... is key to ensuring refined ride characteristics and good suppression of noise, vibration and harshness, as well providing a solid foundation for the location of suspension mountings...

http://www.autosteel.org/~/media/Files/Autosteel/Programs/ULSAB/ulsab_eng_rpt_complete.ashx

...The main factors affecting the ride and handling of the vehicle are Noise, Vibration and Harshness, known as NVH behavior. To achieve the desired levels of comfort for the occupants, the vehicle body must have high static and dynamic rigidity. In other words, the auto body should have high stiffness. This is required because the increased rigidity improves the vehicle resistance to excitement caused by the drive train, the engine or by road conditions such as bumps and potholes. When excited, the car body vibrates at particular frequencies, called its natural frequencies, and also in a particular manner called its mode shape. The mode shapes are for instance on: global torsion mode, global bending mode and front end lateral mode...

 

[TEG]

2005 Maserati Quattroporte - First Look - European Car Magazine

...And a very stiff chassis it is-it is totally new and features the latest technology in aluminum and tailored blanks. The Quattroporte's chassis dynamic flexional rigidity in first mode is 47 Hz and its dynamic torsional rigidity is 49 Hz. Translation: This is an incredibly tight-feeling car that handles like a much smaller and lighter one...

​

 

[TEG]

http://www.wak-tt.com/tt_intro/intro4_2.html

[FONT=arial, geneva][SIZE=-1]Higher rigidity, greater sporting character[/SIZE][/FONT]
[FONT=arial, geneva][SIZE=-1]

[/SIZE][/FONT][FONT=arial, geneva][SIZE=-1]Body rigidity is a decisive factor when designing a good sports car: the aim is clearly to transmit the output from a powerful engine efficiently to the road in the form of precise handling and roadholding. This in turn means choosing the most suitable running-gear settings, and for these to have their maximum effect - the body itself must act as an extremely rigid "backbone"...
...[/SIZE][/FONT][FONT=arial, geneva][SIZE=-1] The Audi TT Coupé achieves outstanding results in this area. Its static torsional rigidity is 19,000 Nm per degree of angle and the first intrinsic bending frequency is as high as 50 Hz. This latter value in particular is reliable proof of a genuinely rigid bodyshell with a "clean" vibration pattern, and therefore a guarantee of the safe, comfortable ride...

[/SIZE][/FONT]
[FONT=arial, geneva][SIZE=-1]
[/SIZE][/FONT]

 

[TEG]

From the SAE article:

Haas said in the preliminary CAE the Model S’s body structure displays 57 Hz in bending, 42 Hz in torsion, including the battery pack and fixed glazing. Overall body frequency is 58 Hz.

From here:

...
Infinity M35/45 is 52 Hz first bending and 58.1 first tortional
Infinity G35 is 46.6 Hz first bending and 55.6 first tortional
BMW 5 series is 45.6 Hz first bending and 44.7 first tortional
...

Do we know Nm/deg for Model S?

...
Aston Martin DB9 Convertible 15,500 Nm/deg
Aston Martin DB9 Coupe 27,000 Nm/deg
Audi A2: 11900 Nm/deg
Audi A8: 25,000 Nm/deg
Audi TT Coupe 19,000 Nm/deg
Audi TT: 10,000 Nm/deg
BMW E36 Touring 10,900 Nm/deg
BMW E36 Z3 5,600 Nm/deg
BMW E46 Convertible 10,500 Nm/deg
BMW E46 Coupe (w/folding seats) 12,500 Nm/deg
BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Wagon (w/folding seats) 14,000 Nm/deg
BMW Z4: 14,500 Nm/deg
Chrysler 300C 17,800 Nm/deg
Chrysler Crossfire 20,140 Nm/deg
Chrysler Durango 6,800 Nm/deg
Dodge Viper Coupe 7,600 Nm/deg
Ferrari 355: 10,042 Nm/degree
Ferrari 360 Spider 8,500 Nm/deg
Ferrari 360: 14,455 Nm/degree
Ferrari F50: 34,600 Nm/deg
Ford GT: 27,100 Nm/deg
Ford GT40 MkI 17,000 Nm/deg
Ford Mustang 2003 16,000 Nm/deg
Ford Mustang 2005 21,000 Nm/deg
Ford Mustang Convertible (2003) 4,800 Nm/deg
Ford Mustang Convertible (2005) 9,500 Nm/deg
Golf V GTI: 25,000 Nm/deg
Jaguar X-Type Estate 16,319 Nm/deg
Jaguar X-Type Sedan 22,000 Nm/deg
Koenigsegg CC-8: 28,100 Nm/deg
Lambo Gallardo: 23000 Nm/deg
Lambo Murcielago 20,000 Nm/deg
Lotus Elan 7,900 Nm/deg
Lotus Elan GRP body 8,900 Nm/deg
Lotus Elise 10,000 Nm/deg
Lotus Elise 111s 11,000 Nm/deg
Lotus Elise S2 Exige (2004): 10,500 Nm/deg
Lotus Esprit SE Turbo 5,850 Nm/deg
Mazda Rx-7: ~15,000 Nm/deg
Mazda Rx-8: 30,000 Nm/deg
McLaren F1 13,500 Nm/deg
Mini (2003) 24,500 Nm/deg
Pagani Zonda C12 S 26,300 Nm/deg
Porsche 911 Turbo (2000) 13,500 Nm/deg
Porsche 911 Turbo 996 Convertible: 11,600 Nm/deg
Porsche 911 Turbo 996: 27,000 Nm/deg
Porsche 959 12,900 Nm/deg
Renault Sport Spider: 10,000 Nm/degree
Rolls Royce Phantom: 40,000 Nm/deg
Volkswagen Fox: 17,941 Nm/deg
Volvo S60 20,000 Nm/deg
Volvo S80: 18,600 Nm/deg
...

 

[TEG]

The list: Torsional Rigidity

Alfa 159 - 31.400Nm/degree
Aston Martin DB9 Coupe 27,000 Nm/deg
Aston Martin DB9 Convertible 15,500 Nm/deg
Aston Martin Vanquish 28,500 Nm/deg
Audi TT Coupe 19,000 Nm/deg
Bugatti EB110 - 19,000 Nm/degree
BMW E36 Touring 10,900 Nm/deg
BMW E36 Z3 5,600 Nm/deg
BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
BMW E46 Wagon (w/folding seats) 14,000 Nm/deg
BMW E46 Coupe (w/folding seats) 12,500 Nm/deg
BMW E46 Convertible 10,500 Nm/deg
BMW X5 (2004) - 23,100 Nm/degree
BMW E90: 22,500 Nm/deg
BMW Z4 Coupe, 32,000Nm/degree
BMW Z4 Roadster: 14,500 Nm/deg
Bugatti Veyron - 60,000 Nm/degree
Chrysler Crossfire 20,140 Nm/deg
Chrysler Durango 6,800 Nm/deg
Chevrolet Corvette C5 9,100 Nm/deg
Dodge Viper Coupe 7,600 Nm/deg
Ferrari 360 Spider 8,500 Nm/deg
Ford GT: 27,100 Nm/deg
Ford GT40 MkI 17,000 Nm/deg
Ford Mustang 2003 16,000 Nm/deg
Ford Mustang 2005 21,000 Nm/deg
Ford Mustang Convertible (2003) 4,800 Nm/deg
Ford Mustang Convertible (2005) 9,500 Nm/deg
Jaguar X-Type Sedan 22,000 Nm/deg
Jaguar X-Type Estate 16,319 Nm/deg
Koenigsegg - 28.100 Nm/degree
Lambo Murcielago 20,000 Nm/deg
Lotus Elan 7,900 Nm/deg
Lotus Elan GRP body 8,900 Nm/deg
Lotus Elise 10,000 Nm/deg
Lotus Elise 111s 11,000 Nm/deg
Lotus Esprit SE Turbo 5,850 Nm/deg
Maserati QP - 18.000 nm/degree
McLaren F1 13,500 Nm/deg
Mercedes SL - With top down 17,000 Nm/deg, with top up 21,000 Nm/deg
Mini (2003) 24,500 Nm/deg
Pagani Zonda C12 S 26,300 Nm/deg
Pagani Zonda F - 27,000 Nm/degree
Porsche 911 Turbo (2000) 13,500 Nm/deg
Porsche 959 12,900 Nm/deg
Porsche Carrera GT - 26,000Nm/degree
Rolls-Royce Phantom - 40,500 Nm/degree
Volvo S60 20,000 Nm/deg
Audi A2: 11,900 Nm/deg
Audi A8: 25,000 Nm/deg
Audi TT: 10,000 Nm/deg (22Hz)
Golf V GTI: 25,000 Nm/deg
Chevrolet Cobalt: 28 Hz
Ferrari 360: 1,474 kgm/degree (bending: 1,032 kg/mm)
Ferrari 355: 1,024 kgm/degree (bending: 727 kg/mm)
Ferrari 430: supposedly 20% higher than 360
Renault Sport Spider: 10,000 Nm/degree
Volvo S80: 18,600 Nm/deg
Koenigsegg CC-8: 28,100 Nm/deg
Porsche 911 Turbo 996: 27,000 Nm/deg
Porsche 911 Turbo 996 Convertible: 11,600 Nm/deg
Porsche 911 Carrera Type 997: 33,000 Nm/deg
Lotus Elise S2 Exige (2004): 10,500 Nm/deg
Volkswagen Fox: 17,941 Nm/deg
VW Phaeton - 37,000 Nm/degree
VW Passat (2006) - 32,400 Nm/degree
Ferrari F50: 34,600 Nm/deg
Lambo Gallardo: 23000 Nm/deg
Mazda Rx-8: 30,000 Nm/deg
Mazda Rx-7: ~15,000 Nm/deg
Mazda RX8 - 30,000 Nm/degree
Saab 9-3 Sportcombi - 21,000 Nm/degree
Opel Astra - 12,000 Nm/degree
Land rover Freelander 2 - 28,000 Nm/degree
Lamborghini Countach 2,600 Nm/deg
Ford Focus 3d 19.600 Nm/deg
Ford Focus 5d 17.900 Nm/deg

 

[TEG]

(Beating a dead horse...)

Body flex - Wikipedia, the free encyclopedia

Body flex is a lack of rigidity in a motor vehicle's chassis. It is often something to be avoided by car manufacturers as higher levels of body flex is a sign of structural weakness, and means that the vehicle's suspension cannot work as efficiently - the body takes up some of the 'slack', rather than the parts of the car which were specifically designed for this purpose. A chassis that flexes may be prone to fatigue and further "softening" with use will eventually result in failure. Cars of a sporting nature are, therefore, often very 'stiff', while convertibles or cabriolets are not often considered to be good candidates for high-performance sports cars because of their lack of a rigid roof.
Although, for some time, body flex was a result of attempts to keep a car's weight down, makers such as Audi (the A8), and Jaguar (with the 2003 XJ8) have employed the use of aluminium in chassis production to get around this obstacle, ensuring the weight of these cars and their level of body flex can both be kept to a minimum.
Typically, the stiffness of the body is measured in torsion. The body is supported at the spring caps at the rear, and then a torque is applied to the front spring caps via a long beam and a fulcrum. Values achieved range from 1,000 lb·ft (1,400 N·m) per degree for pre-War racing cars, up to 25,000 lb·ft (33,900 N·m) per degree for some modern production vehicles.