http://www.sonic.net...fferential.html 
Differential bias ratios
Started by
TestaRoasta
, Sep 18 2005 02:45
2 replies to this topic
#1
TestaRoasta
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- 37 posts
- Joined: August 05
Member
Posted 18 September 2005 - 02:45
Does anyone have any formulas for the torque bias ratio of a clutch type limited slip? I found one for the Torsen, but F1 doesn't use these obviously since the ratio is fixed. Any help would be appreciated more than you'd know.
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#2
phantom II
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- 1,784 posts
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Posted 18 September 2005 - 16:42
The only one I know is:
For a mechanical Salisbury type diff according to TPT diffs.
[48/Tangent(Ramp angle)+17*no. of plate surfaces/max. no. of surfaces available=%tage lock.
The above formula gives a good approximation of the locking force as a percentage of a diff that has been set up with a full complement of working plate surfaces, and a set of 30 degree ramps.
It can be seen from the formula that 17 percent of the locking action is not provided by the ramps. This small component is due to the reaction forces of the side bevel gears.
Although the above formula appertains particularly to the TPT diff, it also provides a very good approximation of percentage lock for any other Hewland Powerflow differential.
The Salisbury diff provides ramp angles for the power side and the coast side. These affect the amount of limiting of slippage as torque is applied. The rule is: the steeper the angle, the less limiting effect. These adjustments only impact resistance to slippage when torque is being applied to the rear wheels by the engine or the brakes.
I don't know how GM gets their corvette diff so perfect without electronic input. What do those engineers kow?
As far as F1 is concerned: In Peter Wright's Ferrari Formula 1 book, he doesnt say too much about it. The electronic MAPS and mechanical mecahnisms involved in F1 are a closely guarded secret. RDV is one member who could probably throw some light on the subject. People delve into suspension theory without considering the role of the diff in handeling which to my mind is the most important factor next to tires. There are SAE papers discussing torque split control. Porsche and Audi are not forthcomming with info on their differentials as is the case with rally teams.
All F1 teams are faced with mapping controls who have to consider the same criteria.
IE: Track curvature with the option of adding pressure due to,
· Total brake pressure.
· Filtered longitudinal acceleration.
· Difference in rear wheel spin.
· Under/oversteer.
There will also be the option of tuning based on track position, to allow the flexibility to tune individual corners. There will also be a global, distance dependent, factor on the overall pressure, to allow for the reduction of pressure on long straights.
For a mechanical Salisbury type diff according to TPT diffs.
[48/Tangent(Ramp angle)+17*no. of plate surfaces/max. no. of surfaces available=%tage lock.
The above formula gives a good approximation of the locking force as a percentage of a diff that has been set up with a full complement of working plate surfaces, and a set of 30 degree ramps.
It can be seen from the formula that 17 percent of the locking action is not provided by the ramps. This small component is due to the reaction forces of the side bevel gears.
Although the above formula appertains particularly to the TPT diff, it also provides a very good approximation of percentage lock for any other Hewland Powerflow differential.
The Salisbury diff provides ramp angles for the power side and the coast side. These affect the amount of limiting of slippage as torque is applied. The rule is: the steeper the angle, the less limiting effect. These adjustments only impact resistance to slippage when torque is being applied to the rear wheels by the engine or the brakes.
I don't know how GM gets their corvette diff so perfect without electronic input. What do those engineers kow?
As far as F1 is concerned: In Peter Wright's Ferrari Formula 1 book, he doesnt say too much about it. The electronic MAPS and mechanical mecahnisms involved in F1 are a closely guarded secret. RDV is one member who could probably throw some light on the subject. People delve into suspension theory without considering the role of the diff in handeling which to my mind is the most important factor next to tires. There are SAE papers discussing torque split control. Porsche and Audi are not forthcomming with info on their differentials as is the case with rally teams.
All F1 teams are faced with mapping controls who have to consider the same criteria.
IE: Track curvature with the option of adding pressure due to,
· Total brake pressure.
· Filtered longitudinal acceleration.
· Difference in rear wheel spin.
· Under/oversteer.
There will also be the option of tuning based on track position, to allow the flexibility to tune individual corners. There will also be a global, distance dependent, factor on the overall pressure, to allow for the reduction of pressure on long straights.
Originally posted by TestaRoasta
Does anyone have any formulas for the torque bias ratio of a clutch type limited slip? I found one for the Torsen, but F1 doesn't use these obviously since the ratio is fixed. Any help would be appreciated more than you'd know.
#3
TestaRoasta
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- 37 posts
- Joined: August 05
Member
Posted 21 September 2005 - 21:11
What can anyone tell us about the F430's e diff?
