Ideal weight balance - F1?
07-16-2008, 09:32 AM
#1
Drifting
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Ideal weight balance - F1?
Morning guys-
In an effort to get us back on topic
I'd like to ask a question that I've been wondering for a while:
What is the ideal front to rear weight balance for a race/track car?
In the press you always read about a "perfect 50/50 weight balance" but I believe, and I think most of you would agree, that a somewhat rear bias would be preferential.
The 944 S2 that I track has a 50/50 balance and it has a pretty good balance.
My Boxster S has a 45/55 balance I believe going by the axle ratings and has probably the best street car balance I have ever driven. I'm sure that the 911 have an even more rearward balance.
Does any one know what the F1 cars balance is? I'm sure that it varies team to team & race to race given the various conditions but I have to believe that the adjustments are relatively minor.
Discuss...
In an effort to get us back on topic
I'd like to ask a question that I've been wondering for a while:What is the ideal front to rear weight balance for a race/track car?
In the press you always read about a "perfect 50/50 weight balance" but I believe, and I think most of you would agree, that a somewhat rear bias would be preferential.
The 944 S2 that I track has a 50/50 balance and it has a pretty good balance.
My Boxster S has a 45/55 balance I believe going by the axle ratings and has probably the best street car balance I have ever driven. I'm sure that the 911 have an even more rearward balance.
Does any one know what the F1 cars balance is? I'm sure that it varies team to team & race to race given the various conditions but I have to believe that the adjustments are relatively minor.
Discuss...
07-16-2008, 09:36 AM
#2
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Should be easy to estimate, given the rough dimensions of an F1 car and a camera shot of the car being hoisted up by a crane and the resulting forward tilt angle.
Again, you just need to know dimensions/distances and you can get a pretty good estimate.
Again, you just need to know dimensions/distances and you can get a pretty good estimate.
07-16-2008, 10:01 AM
#3
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I think you'll find that a slight rearward bias on rear wheel drive cars is best, regardless of the car, and irrespective of marketing hype.
07-16-2008, 10:29 AM
#4
F1 has Front: 44-47%. It's a aerodynamical car - so it pretty much doesn't apply when going into details.
Taken from some old post about the M3 vs. GT3.
If we toss out driver skills, the optimum is quite different between a 911 and a M3. Both with pro's and cons. Major difference is of course the 911 has its engine behind the driver making a 50/50 WD a disaster for it. A rear bias WD will be able to brake later in and accelerate quicker out from corners.
If we don't include aerodynamically biased vehicles (like F1) since they have several more variables in aero setup and often are limited due to regulations rather than design - mid and rear engine cars with RWD will have a definite bias towards the rear. Even some front engine with RWD benefit from rear bias. Most successful atm would probably the ProDrive 550 where they move from the production cars 50/50 to a rear bias on the race cars. Talking about FWD and AWD cars this would be a bit different
Still the WD is so dependent on track design and race regulations it makes it very hard to optimize. For a 50/50 design to be optimum it requires all wheels to be the same size, same grip, same suspension, equivalent aerodynamics and of course a track where lateral and longitudinal G's that makes corner speed superior to deceleration and acceleration. Then there are some other variables to include to this if someone wants to go into details..
Taken from some old post about the M3 vs. GT3.
If we toss out driver skills, the optimum is quite different between a 911 and a M3. Both with pro's and cons. Major difference is of course the 911 has its engine behind the driver making a 50/50 WD a disaster for it. A rear bias WD will be able to brake later in and accelerate quicker out from corners.
If we don't include aerodynamically biased vehicles (like F1) since they have several more variables in aero setup and often are limited due to regulations rather than design - mid and rear engine cars with RWD will have a definite bias towards the rear. Even some front engine with RWD benefit from rear bias. Most successful atm would probably the ProDrive 550 where they move from the production cars 50/50 to a rear bias on the race cars. Talking about FWD and AWD cars this would be a bit different
Still the WD is so dependent on track design and race regulations it makes it very hard to optimize. For a 50/50 design to be optimum it requires all wheels to be the same size, same grip, same suspension, equivalent aerodynamics and of course a track where lateral and longitudinal G's that makes corner speed superior to deceleration and acceleration. Then there are some other variables to include to this if someone wants to go into details..
07-16-2008, 10:31 AM
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And yes, every "open wheel" or "proper" race car has a rearward bias to some degree: F1, Atlantic, Champ, Formula Ford, FIA Prototype, Daytona Prototype, Sports Racers, etc.
Now, does that mean you should go hang the engine behind the rear axle? Probably not.
07-16-2008, 10:32 AM
#6
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Race-prepped M3's will always have a slight rear bias if the rules allow, especially if allowed to move the engine rearward. "50-50" is 100% marketing hype to sell street cars.
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07-16-2008, 10:38 AM
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07-16-2008, 10:39 AM
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I think there have been a couple of similar threads on mid engined vs behind the axle threads in the past
"Rear Engine vs. Mid-engine
Engine location in the chassis is a direct contributor of performance capabilities as well as braking and traction. Rear engine cars are "tail heavy" causing the rear of the car to tend to swing out in a curve or turn. The faster the car is traveling the greater the tendency. More weight on the rear means less on the front. Since the primary brakes are on the front and the direction of the car is controlled from the front loss of weight there means less braking and steering control. The shorter wheelbase of the Speedster exacerbates this tendency. The more balanced a chassis the less swing out and the greater steering and braking on the front. Ideally, although unrealistic, a (50/50) bias would be preferred. Rear engine VW Speedsters typically have about 38% on the front and 62% on the rear (38/62), but our mid-engine Speedster is (45/55).
The point is best made by noting that virtually all world class high performance racing or road cars are mid-engine, and that includes Lamborghini, Ferrari, Jaguar, Maserti, Lotus, Porsche Boxster, Formula 1, Indy, and CART to name a few. The few that are not are deeply rear set front engine cars like the Corvette and Viper. The water-cooled Porsche 911 rear-engine car has alleviated the worst of the rear engine tendency by taking advantage of 40 years of design effort and making it an all wheel drive system with individual computer controlled wheel power distribution."
"Front/Rear weight Bias
Front/rear weight bias affects many aspects of performance. The most significant is the responsiveness of the car. Front biased cars tend to under steer heavily while rear biased cars tend to over steer heavily. Both of these types have a high polar moment of inertia, which is an engineering measure of the resistance of a rotating object to change direction.. These cars are usually altered to alleviate these tendencies, but those alterations cannot affect the responsiveness. Cars designed and built for performance responsiveness are typically mid-engine configuration which creates a low polar moment of inertia. Weight bias also has a large impact upon braking efficiency and traction. Front engine cars have most of the braking resistance carried by the front brakes. Although the greater weight is on the rear wheels of rear engine cars they still rely on the front brakes for controlled braking. The front brakes must be dominant in all cars or the car will tend to lose control on hard braking efforts. Since rear engine cars already have this tendency in turns great care must be taken to get the braking bias forward so as not to exacerbate an already sensitive situation. Mid-engine cars distribute the braking effort more evenly to front and rear allowing the brakes to run cooler, wear slower, and provide a balanced feel when braking"
"Rear Engine vs. Mid-engine
Engine location in the chassis is a direct contributor of performance capabilities as well as braking and traction. Rear engine cars are "tail heavy" causing the rear of the car to tend to swing out in a curve or turn. The faster the car is traveling the greater the tendency. More weight on the rear means less on the front. Since the primary brakes are on the front and the direction of the car is controlled from the front loss of weight there means less braking and steering control. The shorter wheelbase of the Speedster exacerbates this tendency. The more balanced a chassis the less swing out and the greater steering and braking on the front. Ideally, although unrealistic, a (50/50) bias would be preferred. Rear engine VW Speedsters typically have about 38% on the front and 62% on the rear (38/62), but our mid-engine Speedster is (45/55).
The point is best made by noting that virtually all world class high performance racing or road cars are mid-engine, and that includes Lamborghini, Ferrari, Jaguar, Maserti, Lotus, Porsche Boxster, Formula 1, Indy, and CART to name a few. The few that are not are deeply rear set front engine cars like the Corvette and Viper. The water-cooled Porsche 911 rear-engine car has alleviated the worst of the rear engine tendency by taking advantage of 40 years of design effort and making it an all wheel drive system with individual computer controlled wheel power distribution."
"Front/Rear weight Bias
Front/rear weight bias affects many aspects of performance. The most significant is the responsiveness of the car. Front biased cars tend to under steer heavily while rear biased cars tend to over steer heavily. Both of these types have a high polar moment of inertia, which is an engineering measure of the resistance of a rotating object to change direction.. These cars are usually altered to alleviate these tendencies, but those alterations cannot affect the responsiveness. Cars designed and built for performance responsiveness are typically mid-engine configuration which creates a low polar moment of inertia. Weight bias also has a large impact upon braking efficiency and traction. Front engine cars have most of the braking resistance carried by the front brakes. Although the greater weight is on the rear wheels of rear engine cars they still rely on the front brakes for controlled braking. The front brakes must be dominant in all cars or the car will tend to lose control on hard braking efforts. Since rear engine cars already have this tendency in turns great care must be taken to get the braking bias forward so as not to exacerbate an already sensitive situation. Mid-engine cars distribute the braking effort more evenly to front and rear allowing the brakes to run cooler, wear slower, and provide a balanced feel when braking"
07-16-2008, 10:42 AM
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Form good old Wikapedia
Mid-engine design
Benefits
The mid-engine layout is typically chosen for its relatively favorable weight distribution. The heaviest component is nearer to the center of the vehicle, reducing the vehicle's moment of inertia and making it easier and faster to turn the vehicle to a new direction. Also the engine weight is more evenly carried by all the wheels with this layout. As a result, vehicle stability, traction, and ride quality are naturally improved when turning, braking, and accelerating.
Mounting the engine in the middle instead of the front of the vehicle puts more weight over the rear tires so they have more traction and provide more assistance to the front tires in braking the vehicle, with less chance of rear wheel lockup and less chance of a skid or spin out. If the mid-engine vehicle is also rear-drive (as almost all of them are) the added weight on the rear tires can also improve acceleration on slippery surfaces, providing much of the benefit of all wheel drive without the added weight and expense of all wheel drive components. The mid-engine layout make ABS brakes and traction control systems work better, by providing them more traction to control. The mid-engine layout may make a vehicle safer, since an accident can occur if a vehicle cannot stay in its own lane around a curve or is unable to stop quickly enough. And additionally, mid-engine design is a way to provide additional empty crush space in the front of the automobile between the bumper and the windshield, which can then be used in a frontal collision to absorb more of the impact force to minimize penetration into the passenger compartment of the vehicle.
In most automobiles, and in sports cars especially, ideal car handling requires balanced traction between the front and rear wheels when cornering in order to maximize the possible speed around curves without sliding out. This balance is harder to achieve when the heavy weight of the engine is located far to the front or far to the rear of the vehicle. Some automobile designs strive to balance the fore and aft weight distribution by other means such as putting the engine in the front and the transmission and battery in the rear of the vehicle. Some of the same benefits are gained, but at the cost of greater moment of inertia compared to the mid-engine layout, making it harder and less responsive to turn the vehicle to a new direction.
Another benefit comes when the heavy mass of the engine is located close to the back of the seats. It makes it easier for the suspension to absorb the force of bumps so the riders feel a smoother ride. But in sports cars this benefit is once again utilized to increase performance and is usually more than offset by stiffer shocks.
This layout also allows the transmission and motor to be directly bolted to each other - with independent suspension on the driven wheels this removes the need for the chassis to transfer engine torque reaction.
[edit] Drawbacks
The largest drawback of mid-engine cars is packaging; most mid-engine vehicles are two-seat vehicles. The engine in effect pushes the passenger compartment forward towards the front axle (if engine is behind driver). Exceptions typically involve larger vehicles of unusual length or height in which the passengers can share space between the axles with the engine, which can be between them or below them, as in some Toyota vans, large trucks and busses.
Like any layout where the engine is not in the front of the car facing the wind, the traditional "engine-behind-the-passengers" layout makes engine cooling more difficult, and this has been a problem in some cars such as the Porsche 914, which is air cooled rather than having a front mounted coolant system. But this problem seems to have been largely solved in newer designs. For example, the Saleen S7 employs large engine-compartment vents on the sides and rear of the bodywork to help dissipate heat from its very high-output engine.
[edit] Variations
Traditionally, the term mid-engine has been applied to cars having the engine located between the driver and the rear drive axles. This layout is referred to here as RMR layout. Sports and racing cars typically have this mid-engine layout, as these vehicle's handling characteristics are more important than other features, such as practicality. Additionally the mechanical layout and packaging of a RMR car is substantially different than that of a front engine or rear engine car.
A subset of Front-Rear when the engine is in front of the driver, but fully behind the front axle line, the layout is sometimes called Front Mid engine Rear FMR layout instead of the less-specific term front-engine. In handling and vehicle layout FMR is substantially the same as FR. Some vehicles could be classified as FR or FMR depending on the factory installed engine (I4 vs I6). Historically most classical FR cars such as the Ford Models T and A would qualify as a FMR engine car/ Additionally, the difference between FR and FMR may be as little as a few millimeters of engine protrusion in front of the front axle line. Not all manufactures will use the Front-Mid designation.
Mid-engine design
Benefits
The mid-engine layout is typically chosen for its relatively favorable weight distribution. The heaviest component is nearer to the center of the vehicle, reducing the vehicle's moment of inertia and making it easier and faster to turn the vehicle to a new direction. Also the engine weight is more evenly carried by all the wheels with this layout. As a result, vehicle stability, traction, and ride quality are naturally improved when turning, braking, and accelerating.
Mounting the engine in the middle instead of the front of the vehicle puts more weight over the rear tires so they have more traction and provide more assistance to the front tires in braking the vehicle, with less chance of rear wheel lockup and less chance of a skid or spin out. If the mid-engine vehicle is also rear-drive (as almost all of them are) the added weight on the rear tires can also improve acceleration on slippery surfaces, providing much of the benefit of all wheel drive without the added weight and expense of all wheel drive components. The mid-engine layout make ABS brakes and traction control systems work better, by providing them more traction to control. The mid-engine layout may make a vehicle safer, since an accident can occur if a vehicle cannot stay in its own lane around a curve or is unable to stop quickly enough. And additionally, mid-engine design is a way to provide additional empty crush space in the front of the automobile between the bumper and the windshield, which can then be used in a frontal collision to absorb more of the impact force to minimize penetration into the passenger compartment of the vehicle.
In most automobiles, and in sports cars especially, ideal car handling requires balanced traction between the front and rear wheels when cornering in order to maximize the possible speed around curves without sliding out. This balance is harder to achieve when the heavy weight of the engine is located far to the front or far to the rear of the vehicle. Some automobile designs strive to balance the fore and aft weight distribution by other means such as putting the engine in the front and the transmission and battery in the rear of the vehicle. Some of the same benefits are gained, but at the cost of greater moment of inertia compared to the mid-engine layout, making it harder and less responsive to turn the vehicle to a new direction.
Another benefit comes when the heavy mass of the engine is located close to the back of the seats. It makes it easier for the suspension to absorb the force of bumps so the riders feel a smoother ride. But in sports cars this benefit is once again utilized to increase performance and is usually more than offset by stiffer shocks.
This layout also allows the transmission and motor to be directly bolted to each other - with independent suspension on the driven wheels this removes the need for the chassis to transfer engine torque reaction.
[edit] Drawbacks
The largest drawback of mid-engine cars is packaging; most mid-engine vehicles are two-seat vehicles. The engine in effect pushes the passenger compartment forward towards the front axle (if engine is behind driver). Exceptions typically involve larger vehicles of unusual length or height in which the passengers can share space between the axles with the engine, which can be between them or below them, as in some Toyota vans, large trucks and busses.
Like any layout where the engine is not in the front of the car facing the wind, the traditional "engine-behind-the-passengers" layout makes engine cooling more difficult, and this has been a problem in some cars such as the Porsche 914, which is air cooled rather than having a front mounted coolant system. But this problem seems to have been largely solved in newer designs. For example, the Saleen S7 employs large engine-compartment vents on the sides and rear of the bodywork to help dissipate heat from its very high-output engine.
[edit] Variations
Traditionally, the term mid-engine has been applied to cars having the engine located between the driver and the rear drive axles. This layout is referred to here as RMR layout. Sports and racing cars typically have this mid-engine layout, as these vehicle's handling characteristics are more important than other features, such as practicality. Additionally the mechanical layout and packaging of a RMR car is substantially different than that of a front engine or rear engine car.
A subset of Front-Rear when the engine is in front of the driver, but fully behind the front axle line, the layout is sometimes called Front Mid engine Rear FMR layout instead of the less-specific term front-engine. In handling and vehicle layout FMR is substantially the same as FR. Some vehicles could be classified as FR or FMR depending on the factory installed engine (I4 vs I6). Historically most classical FR cars such as the Ford Models T and A would qualify as a FMR engine car/ Additionally, the difference between FR and FMR may be as little as a few millimeters of engine protrusion in front of the front axle line. Not all manufactures will use the Front-Mid designation.
07-16-2008, 10:54 AM
#12
F1's weight bias is not at all comparable, simply because they're limited so much by tire sizes & aerodynamics. I believe that right now they're actually running a bit of a front weight bias as the rear tires are too small and already overworked.
The cars have an obvious front end drop when hoisted by the cranes, but this is probably more due to the rearward location of the crane hooks.
The cars have an obvious front end drop when hoisted by the cranes, but this is probably more due to the rearward location of the crane hooks.
07-16-2008, 11:06 AM
#13
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Open wheel race cars are rear heavy. In laying out these cars from a design standpoint its always a game of how much weight can one move forward. Weight splits F to R are generally around 42-44%F.
More important is aero center of pressure and how stable it is at various attitudes since this pressure is much greater than static.
An Atlantic chassis corner weight example from a set down (not set up
) some time ago:
258 / 273
386 / 379
More important is aero center of pressure and how stable it is at various attitudes since this pressure is much greater than static.
An Atlantic chassis corner weight example from a set down (not set up
) some time ago: 258 / 273
386 / 379
07-16-2008, 11:06 AM
#14
Burning Brakes
The amount of front drop on an F1 car being hoisted is heavily dependent on the location of the roll hoop. An inch or two change would show a significant differential in angle...