Saturday, July 16, 2011
Friday, July 15, 2011
Monday, July 11, 2011
Variety, the spice of life.
I am amazed by this Gawler club, so much variety. Fair enough for the Sporting Car Club, it's in a big city, but this is out of town a bit. Lots of really nice Vintage cars, a huge variety of sports cars and the Sunday sparrow fart runs usually provide the opportunity for a decent squirt to the breakfast spot and a good reason to drag out the Pommie bikes plus a bit of muscle like this.
Sunday, July 10, 2011
Tech session from Grant - How a braking system works.
Hello John
How are all you obp Motorsport Tech Session hard core fans?
Thank you for all the feed back you give us, with out you we are nothing.
If you are new to the obp Motorsport Tech Session then I am sure you will enjoy this article.
How a Braking System Works?
The Master Cylinder is one of the key elements of a brake system. This article will inform you how the Master Cylinder / Pump forces brake fluid through the system.
The way this happens is a basic lesson in hydraulics.
It all starts with the actuating force that is fed into the master cylinder. This force is provided by the driver’s foot on the brake pedal. The maximum force that is exerted on the brake pedal is approximately between 150 to 200 pounds of pressure, the average pressure on the brake pedal in a race condition is 100 pounds of force.
The driver is normally limited to a maximum of approx six inches of pedal travel that can be applied to the brake pedal. This is determined by the pilot leg length, closeness to the pedal and leg angle. The ability the driver has to apply the force to the pedal will be influenced on the driver body restraints like the seat belts and shoulder harness, the angle of the hip and the angle of the knee joints. Having a straighter knee joint will allow an easier operation of the pedals, and more force can be applied to the brake pedal.
The force that is exerted by the leg and foot to the brake pedal is then multiplied by the leverage that is in the pedal ratio. Most production cars are 3 to 1 or 4 to 1 this is enough of a ratio when a servo is used, however with out a servo this ratio is a little low. Most race car pedal boxes that do not use a servo and will have a ratio between 5 to 1 and 6 to 1.
6 to 1 Ratio obp BMW E46 Race Car Pedal Box
To give you an example of the ratio increase here are a couple of examples:
100 pounds of pressure created by the driver to a 5 to 1 ratio pedal will deliver 500 pounds of pressure to the master cylinder push rod. (100 lbs x 5 = 500 lbs)
100 pounds of pressure created by the driver to a 6 to 1 ratio pedal will deliver 600 pounds of pressure to the master cylinder push rod. (100 lbs x 6 = 600 lbs)
However always remember if the pedal ratio is increased, the pressure will increase and also the movement of the pedal will increase.
The next consideration with a race car brake pedal system is the master cylinder bore size. The most common bore sizes used are:
.75 - Internal piston bore size O/D
.7 - Internal piston bore size O/D
.625 - Internal piston bore size O/D
obp Branded .625 Master Cylinder
.75 Cyl Bore is .44 Sq. in. of area
.7 Cyl Bore is .38 Sq. in. of area
.625 Cyl Bore is .30 Sq. in. of area
For example:
300 pounds of pressure created by the driver with the pedal ratio increase is applied to a .75 bore master cylinder (Force supplied into the master cylinder is divided by Square inches of the piston) 300 pounds divided by .44 = 681 pounds per square inch line pressure
300 pounds of pressure created by the driver with the pedal ratio increase is applied to a .625 bore master cylinder (Force supplied into the master cylinder is divided by Square inches of the piston) 300 pounds divided by .30 = 1000 pounds per square inch line pressure
It is easier with this knowledge to understand that a smaller bore master cylinder will deliver more pressure into the brake lines and to the brake calipers.
So why not use smaller bore master cylinders all the time? There are two reasons why this is not the perfect solution.
Thank you for all the feed back you give us, with out you we are nothing.
If you are new to the obp Motorsport Tech Session then I am sure you will enjoy this article.
How a Braking System Works?
The Master Cylinder is one of the key elements of a brake system. This article will inform you how the Master Cylinder / Pump forces brake fluid through the system.
The way this happens is a basic lesson in hydraulics.
It all starts with the actuating force that is fed into the master cylinder. This force is provided by the driver’s foot on the brake pedal. The maximum force that is exerted on the brake pedal is approximately between 150 to 200 pounds of pressure, the average pressure on the brake pedal in a race condition is 100 pounds of force.
The driver is normally limited to a maximum of approx six inches of pedal travel that can be applied to the brake pedal. This is determined by the pilot leg length, closeness to the pedal and leg angle. The ability the driver has to apply the force to the pedal will be influenced on the driver body restraints like the seat belts and shoulder harness, the angle of the hip and the angle of the knee joints. Having a straighter knee joint will allow an easier operation of the pedals, and more force can be applied to the brake pedal.
The force that is exerted by the leg and foot to the brake pedal is then multiplied by the leverage that is in the pedal ratio. Most production cars are 3 to 1 or 4 to 1 this is enough of a ratio when a servo is used, however with out a servo this ratio is a little low. Most race car pedal boxes that do not use a servo and will have a ratio between 5 to 1 and 6 to 1.
6 to 1 Ratio obp BMW E46 Race Car Pedal Box
To give you an example of the ratio increase here are a couple of examples:
100 pounds of pressure created by the driver to a 5 to 1 ratio pedal will deliver 500 pounds of pressure to the master cylinder push rod. (100 lbs x 5 = 500 lbs)
100 pounds of pressure created by the driver to a 6 to 1 ratio pedal will deliver 600 pounds of pressure to the master cylinder push rod. (100 lbs x 6 = 600 lbs)
However always remember if the pedal ratio is increased, the pressure will increase and also the movement of the pedal will increase.
The next consideration with a race car brake pedal system is the master cylinder bore size. The most common bore sizes used are:
.75 - Internal piston bore size O/D
.7 - Internal piston bore size O/D
.625 - Internal piston bore size O/D
obp Branded .625 Master Cylinder
The force supplied into the master cylinder is divided by the square inches of the piston, and the output of the master cylinder is pressure in pounds per square inch.
.75 Cyl Bore is .44 Sq. in. of area
.7 Cyl Bore is .38 Sq. in. of area
.625 Cyl Bore is .30 Sq. in. of area
For example:
300 pounds of pressure created by the driver with the pedal ratio increase is applied to a .75 bore master cylinder (Force supplied into the master cylinder is divided by Square inches of the piston) 300 pounds divided by .44 = 681 pounds per square inch line pressure
300 pounds of pressure created by the driver with the pedal ratio increase is applied to a .625 bore master cylinder (Force supplied into the master cylinder is divided by Square inches of the piston) 300 pounds divided by .30 = 1000 pounds per square inch line pressure
It is easier with this knowledge to understand that a smaller bore master cylinder will deliver more pressure into the brake lines and to the brake calipers.
So why not use smaller bore master cylinders all the time? There are two reasons why this is not the perfect solution.
1) With a smaller bore master cylinder the pedal will require more travel to displace the given fluid needed.
2) Higher line pressure aggravates line and calliper expansions and thus uses up more fluid.
If a system is so stiff (meaning no or little line expansion or calliper deflection) that the driver is only using a small part of the total pedal travel, then using a smaller bore master cylinder will reduce the pedal force, or effort required by the driver to stop the car.
Once the pressure leaves the master cylinder there is not a great deal of movement in the brake lines, what does happen is a pressure build up and pressure transmittal.
To understand this theory in a practical way, please imagine you are blowing down a straw. Place a finger two inches from the base of the straw and blow you will feel the air passing over your finger.
Now block the straw with your finger. There is still the volume of air in the straw and you are still generating force by blowing down the straw. However your finger only feels the force against it.
This is a very simple example of the principle of pressure transmittal, as used in a sealed brake system.
I hope you have found this tech session interesting and thank you for your time.
2) Higher line pressure aggravates line and calliper expansions and thus uses up more fluid.
If a system is so stiff (meaning no or little line expansion or calliper deflection) that the driver is only using a small part of the total pedal travel, then using a smaller bore master cylinder will reduce the pedal force, or effort required by the driver to stop the car.
Once the pressure leaves the master cylinder there is not a great deal of movement in the brake lines, what does happen is a pressure build up and pressure transmittal.
To understand this theory in a practical way, please imagine you are blowing down a straw. Place a finger two inches from the base of the straw and blow you will feel the air passing over your finger.
Now block the straw with your finger. There is still the volume of air in the straw and you are still generating force by blowing down the straw. However your finger only feels the force against it.
This is a very simple example of the principle of pressure transmittal, as used in a sealed brake system.
I hope you have found this tech session interesting and thank you for your time.
Saturday, July 9, 2011
Why Bizzarrini?
That was a question I was asked recently. In other words - what's so good about the Bizzarrini? I'm not sure really but I think they're OK. I'm no authority, I'm only familiar one model, the 5300GT. I've only seen one in the flesh, the yellow one that came to the Classic Adelaide.
But I liked what I saw and it sounded good. In a way they're a bit funny looking, they're so low and so wide but the concept is good, a decent V8 set way back.
Doesn't this look mean though.
Vents all over the place.
There were two running at the LeMans Legends race this year, a blue one and a red one.
But what about a Bizzarrini Bizza? Powered by a Lamborghini 400GT V12, which is fitting as Giotto Bizzarrini designed the V12 engine for Ferruccio Lamborghini in the first place.
Yet another Perentti on eBay.
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Friday, July 8, 2011
Clemente's new wheels
Norm calls it the new car, I call it the new Clemente. Anyway, they've specifically designed and had made the first batch of 60 wheels. Very impressive.
Zeta grille
This is the early Zeta runabout grille.
It's actually the 6-cyl Morris Marshall grille turned upside down.
This is a Morris Marshall, for sale on the What's in your paddock? site.
Maybe it's not upside down.
I only mentioned it because Immanuel Hansen was looking for a Morris Marshall grille. It turned out he needed it for his Zeta. When asked which model Zeta he had he said "the ugly one". Luckily I knew he had the early model. By the way, has anybody found a wheel yet?
Now here's something that could make or break a marriage.
A honeymoon in a Zeta.
This is a Morris Marshall, for sale on the What's in your paddock? site.
Maybe it's not upside down.
I only mentioned it because Immanuel Hansen was looking for a Morris Marshall grille. It turned out he needed it for his Zeta. When asked which model Zeta he had he said "the ugly one". Luckily I knew he had the early model. By the way, has anybody found a wheel yet?
Now here's something that could make or break a marriage.
Wednesday, July 6, 2011
Nothing is new No. 3.
Covini C6W
Too late, Ken Tyrrell thought of that yearts ago.
But Tyrrell weren't the only ones in Formula One with 6-wheelers. Williams and March had a dabble too.
Two JWF Milanos on Carpoint at the same time.
Here's the first.
http://ninemsn.carpoint.com.
And the other.
http://ninemsn.carpoint.com.
While my preference would have to be for a Zephyr powered one, look at the pedigree of John Scott's MG Milano - first owner Bruce Leer, followed by Moss Angliss.
http://ninemsn.carpoint.com.
And the other.
http://ninemsn.carpoint.com.
While my preference would have to be for a Zephyr powered one, look at the pedigree of John Scott's MG Milano - first owner Bruce Leer, followed by Moss Angliss.
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