- #1
vinay ks
- 8
- 0
what is the approx brake pedal force that a person applies while braking on the brake pedal?
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Discussion Overview
The discussion revolves around the approximate force applied to the brake pedal while braking, specifically focusing on disc brakes. Participants explore various factors influencing this force, including mechanical advantages, the role of brake boosters, and the physical capabilities of drivers.
Discussion Character
- Debate/contested
- Technical explanation
- Conceptual clarification
Main Points Raised
- Some participants suggest that with manual brakes, a pedal force of up to 100 lb per g of deceleration is typical, while others question the practicality of applying such force, especially for average drivers.
- One participant notes that typical race car brake pedals can have mechanical advantages ranging from 3:1 to 8:1, translating a small input force into a much larger force at the master cylinder.
- Another participant cites NASA's claim that a properly positioned person can exert forces as high as 2500 N (approximately 560 lb), but this is challenged by others who argue that such force is unrealistic for average drivers in standard vehicles.
- Some participants emphasize that the leg muscles are capable of generating significant force, while others argue that 100 lb is not representative of normal braking in modern passenger cars.
- There is a contention regarding the definition of "normal" braking, with some asserting that the question lacks clarity due to the variability in brake types and assistance systems.
Areas of Agreement / Disagreement
Participants express disagreement regarding the typical force applied to the brake pedal, with some asserting that 100 lb is a reasonable estimate while others contest its applicability to average drivers. The discussion remains unresolved with multiple competing views on the topic.
Contextual Notes
The discussion highlights limitations in defining "normal" braking force due to variations in brake systems, mechanical advantages, and the physical capabilities of drivers. The lack of a clear, universally applicable question contributes to the complexity of the discussion.
- #2
Ranger Mike
Science Advisor
- 2,461
- 446
drum brakes or disc brakes which have power booster?
- #3
jack action
Science Advisor
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Usually, with manual brakes, you set up the brake system such that you need a pedal force no more than a 100 lb per g of deceleration.
A booster may divide easily the pedal effort needed by a factor of 2. (more info here)
A booster may divide easily the pedal effort needed by a factor of 2. (more info here)
- #4
vinay ks
- 8
- 0
disc brakes
i want to know for disc brakes. 100 lbs is a large force! can a person apply that much of force while he is seated on the pedal? i want to know how a person who is about 130 to 150 lbs apply that amount force??
i want to know for disc brakes. 100 lbs is a large force! can a person apply that much of force while he is seated on the pedal? i want to know how a person who is about 130 to 150 lbs apply that amount force??
- #5
Ranger Mike
Science Advisor
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Typical race car brake pedals have 3:1 mechanical advantage and some production automobiles have up to 8:1 mechanical advantage.
The most common pedal IS 6:1 so if you apply 100 pounds force to the pedal the input force to the master cylinder is 600 pounds.
So you see a slight amount of input force will be translated into a huge amount by the linkage to the master cylinder. I had a brake pressure gage on an old race car one time and it read up to 1500 PSI for the hydraulic brake fluid pressure. More than enough to stop a passenger car.
The most common pedal IS 6:1 so if you apply 100 pounds force to the pedal the input force to the master cylinder is 600 pounds.
So you see a slight amount of input force will be translated into a huge amount by the linkage to the master cylinder. I had a brake pressure gage on an old race car one time and it read up to 1500 PSI for the hydraulic brake fluid pressure. More than enough to stop a passenger car.
- #6
jack action
Science Advisor
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vinay ks said:
According to NASA, with the proper position, you can go as high as 2500 N or around 560 lb (a 100 lb is 445 N):
- #7
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
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The leg muscles are some of the largest in the body. It is quite easy to generate 100 lb of force with one leg. After all, your legs keep you from falling down.
- #8
Kozy
- 140
- 7
Go and put some bathroom scales against the wall in a corridor, sit on against the opposite wall and push on the scales with your right foot. That'll give you some idea of what is reasonable. I can assure you, 100lbs is not 'normal' braking in a modern passenger car!
I challenege anyone to generate 560lbs too. Maybe an F1 driver in an F1 car capable of braking at 3g (additive force from decelleration), but not an average driver in a normal road vehicle. Not a chance.
I challenege anyone to generate 560lbs too. Maybe an F1 driver in an F1 car capable of braking at 3g (additive force from decelleration), but not an average driver in a normal road vehicle. Not a chance.
- #9
xxChrisxx
- 2,056
- 85
Is there any reason you've taken two posts out of context?
One might also say that 1g is not 'normal' braking. It's a rough rule of thumb of a limit of input force.
Everyone should be able to apply that force, and passenger cars will lock the wheels before 1g.
So in essence the rule is saying that the 'average' person should be able to apply a force sufficient to lock the wheels.
That is a capability of 'a leg' at certain angles. The practicality of doing so is neither here not there.
The whole thread is off to a bad start because the question isn't defined properly. With such a range of servo assistance and pedal ratios and brake types, you can pick almost any figure you want. It's like asking "what is the average amount of steering lock to go round a corner".
It's such a ill defined question that it borders on meaningless.
Kozy said:
One might also say that 1g is not 'normal' braking. It's a rough rule of thumb of a limit of input force.
Everyone should be able to apply that force, and passenger cars will lock the wheels before 1g.
So in essence the rule is saying that the 'average' person should be able to apply a force sufficient to lock the wheels.
That is a capability of 'a leg' at certain angles. The practicality of doing so is neither here not there.
The whole thread is off to a bad start because the question isn't defined properly. With such a range of servo assistance and pedal ratios and brake types, you can pick almost any figure you want. It's like asking "what is the average amount of steering lock to go round a corner".
It's such a ill defined question that it borders on meaningless.
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