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 Posted: Sat Aug 16th, 2008 09:21 pm
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KevG
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David wrote: Hi Kev

Not sure I agree with you regards the brake test weight being the same as the vehicle weight, + driver and fuel, when you go back to work, look at your car brake test weight on the wall chart, then compare it to your vehicle gross weight on the VIN plate, you will find a difference. There is a method and formula for working out the vehicles brake test weight.

David:D


Its the Kerb weight we want  not the gross weight. (Class 123 &4 are all i'm familiar with.)

eg. the gross weight for my bike is 450Kg. its kerb weight is 225 kg.

I agree there is a method, one would be to weigh it , like we do on the class one and two tests.

Kev

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 Posted: Sat Aug 16th, 2008 07:52 pm
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David
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Hi Kev

Not sure I agree with you regards the brake test weight being the same as the vehicle weight, + driver and fuel, when you go back to work, look at your car brake test weight on the wall chart, then compare it to your vehicle gross weight on the VIN plate, you will find a difference. There is a method and formula for working out the vehicles brake test weight.

David:D

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 Posted: Sat Aug 16th, 2008 06:39 pm
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KevG
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Wesley wrote: KevG wrote: Thanks Rebel, I didnt know that. I've always put the weight in, I only do 1 or 2 decelerometer tests a year though. Ive got one of those new fangled digital ones!

 

Kev

and theres a "loophole" if you require one.


Loophole? Tell me more. Theoretically of course!

Kev

 

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 Posted: Sat Aug 16th, 2008 05:20 am
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Wesley
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KevG wrote: Thanks Rebel, I didnt know that. I've always put the weight in, I only do 1 or 2 decelerometer tests a year though. Ive got one of those new fangled digital ones!

 

Kev

and theres a "loophole" if you require one.

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 Posted: Sat Aug 16th, 2008 05:17 am
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Wesley
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KevG wrote: I simply red the chart it takes a good 3 or 4 seconds, then I RBT the car. You still input the weight on a Decelerometer test Don't you? My machine always asks the weight.

Anyway as we have the info we dont have to do a decelerometer test, so save time.

The charts are a few quid?

What do you do if the device is down and you need an ABS light sequence?

I look on my wall chart. It takes 2 seconds.

 Anyway the point was the extra weight of fuel and driver is included in the quoted weight wherever you get it from be it a Chart or the device.

Kev

 



 

 


the correct answer is in Section 3.8 page one.;)

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 Posted: Sat Aug 16th, 2008 12:56 am
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Rebel
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KevG wrote: Thanks Rebel, I didnt know that. I've always put the weight in, I only do 1 or 2 decelerometer tests a year though. Ive got one of those new fangled digital ones!

 

Kev

No probs mate.

None of us know it all, but if we learn from each other then we're hopefully going in the right direction!

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 Posted: Sat Aug 16th, 2008 12:16 am
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KevG
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Thanks Rebel, I didnt know that. I've always put the weight in, I only do 1 or 2 decelerometer tests a year though. Ive got one of those new fangled digital ones!

 

Kev

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 Posted: Sat Aug 16th, 2008 12:00 am
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Rebel
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"You still input the weight on a Decelerometer test Don't you?"


No, you don't.
When entering results for a decel test the testing weight goes in as something along the lines as N/A or not required - it's in a drop down thingy.

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 Posted: Fri Aug 15th, 2008 11:48 pm
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KevG
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Mana: 
I simply red the chart it takes a good 3 or 4 seconds, then I RBT the car. You still input the weight on a Decelerometer test Don't you? My machine always asks the weight.

Anyway as we have the info we dont have to do a decelerometer test, so save time.

The charts are a few quid?

What do you do if the device is down and you need an ABS light sequence?

I look on my wall chart. It takes 2 seconds.

 Anyway the point was the extra weight of fuel and driver is included in the quoted weight wherever you get it from be it a Chart or the device.

Kev

 



 

 

Last edited on Fri Aug 15th, 2008 11:51 pm by KevG

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 Posted: Fri Aug 15th, 2008 01:00 pm
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David
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Hi Kev

No Brake test data is not a refusal you do a decelerometer test and issue VT32

David:D

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 Posted: Fri Aug 15th, 2008 04:52 am
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Wesley
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KevG wrote: Wesley wrote: What Charts?

Where since Computerisation was introduced is the requirement? Check your SN`s,

My Battery is tied in with a piece of baler twine, Is it secure?

I know my SN's thank you Wesley, I am the AE, and the director of Three MOT businesses.


The brake testing weight is the vehicle weight plus a driver and fuel.

What do you use to get the weight of say, a 1976 Vauxhall Chevette, for your brake test if you dont have wall charts?

You surely have a some references as older cars are not on the computer?

What if the computer goes down?(completely)

You can't test!

This would cost me thousands of pounds a day!

 

Kev

 

 


 So Where is "The Requirement"?

 Why can`t "you" test?

Last edited on Fri Aug 15th, 2008 05:06 am by Wesley

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 Posted: Fri Aug 15th, 2008 04:46 am
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KevG
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Wesley wrote: What Charts?

Where since Computerisation was introduced is the requirement? Check your SN`s,

My Battery is tied in with a piece of baler twine, Is it secure?

I know my SN's thank you Wesley, I am the AE, and the director of Three MOT businesses.


The brake testing weight is the vehicle weight plus a driver and fuel.

What do you use to get the weight of say, a 1976 Vauxhall Chevette, for your brake test if you dont have wall charts?

You surely have a some references as older cars are not on the computer?

What if the computer goes down?(completely)

You can't test!

This would cost me thousands of pounds a day!

 

Kev

 

 

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 Posted: Fri Aug 15th, 2008 03:24 am
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Wesley
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What Charts?

Where since Computerisation was introduced is the requirement? Check your SN`s,

My Battery is tied in with a piece of baler twine, Is it secure?

Last edited on Fri Aug 15th, 2008 04:08 am by Wesley

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 Posted: Thu Aug 14th, 2008 10:22 pm
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KevG
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Wesley wrote: David wrote: Hi Dubsy



Just imagine what VOSA senior Engineers could do with your brake test readings entered into computerisation, you say three wheels locked out, they/I could work out the readings you have given would not justify the forces involved, therefore could say that the minimum brake efficiency had not been met, allowing for an average additional 140Kg?

David:D




Where "In The Manual" Does It State, An Average "Additional" Testers Weight (140kg) Included in "Your Calculations", Should Be Taken Into Consideration?;)

Laters, Wes.:D

ps; The RFR for Insufficient Screenwash Delivery, Is a Very "Grey" Area? No Defined mention of the actual description is printed in "The RFR" for the said RFR?;)

pps; All of what You are Stating, Is not really an "Issue" With Us Testers? But An Issue with Siemmens and VOSA?  

 
zzzzzzzzzzz:D
 




The 140kg is included in the VSI weights, read the bottom of your brake weight chart.

Kev

 

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 Posted: Thu Aug 14th, 2008 05:54 am
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Wesley
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David wrote: Hi Dubsy



Just imagine what VOSA senior Engineers could do with your brake test readings entered into computerisation, you say three wheels locked out, they/I could work out the readings you have given would not justify the forces involved, therefore could say that the minimum brake efficiency had not been met, allowing for an average additional 140Kg?

David:D




Where "In The Manual" Does It State, An Average "Additional" Testers Weight (140kg) Included in "Your Calculations", Should Be Taken Into Consideration?;)

Laters, Wes.:D

ps; The RFR for Insufficient Screenwash Delivery, Is a Very "Grey" Area? No Defined mention of the actual description is printed in "The RFR" for the said RFR?;)

pps; All of what You are Stating, Is not really an "Issue" With Us Testers? But An Issue with Siemmens and VOSA?  

 
zzzzzzzzzzz:D
 


Last edited on Thu Aug 14th, 2008 06:00 am by Wesley

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 Posted: Thu Aug 14th, 2008 05:23 am
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Wesley
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big..E. wrote: KevG wrote: Is the answer;

"Name a car thats made today that has drums on the front?"

Kev

 

 

Anyone viewing this site that works for CITROEN TECHNICAL DEVELOPEMENT DEPT.Please avert your eyes to the previous post......NoBody wants the CHALLENGE....;)lol lol lol...

Is that the C3 disguised as a retro 2CV? LOL!:D

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 Posted: Thu Aug 14th, 2008 04:54 am
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David
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Hi Dubsy

That's the problem with VOSA, they have not passed the old age Mini with twin leading front brake shoes and drums, they still think in the sixties and seventies, like most of us now who only see brake discs and calipers at the front, so naturally I misread the post skimping over it and assumed brake discs and calipers, but the physics is right, which clearly illustrated which way the brakes would pull over. I used larger diameters for a reason. Anybody can disagree with it, but its right and VOSA would agree.:D and the next part from that I could use the results gained to prove how much effort a tester applies to the brake pedal to get your roller brake test readings, not just assuming, and don't need to be there?

So just imagine what VOSA senior Engineers could do with your brake test readings entered into computerisation, you say three wheels locked out, they/I could work out the readings you have given would not justify the forces involved, therefore could say that the minimum brake efficiency had not been met, allowing for an average additional 140Kg?

David:D

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 Posted: Thu Aug 14th, 2008 04:31 am
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big..E.
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KevG wrote: Is the answer;

"Name a car thats made today that has drums on the front?"

Kev

 

 

Anyone viewing this site that works for CITROEN TECHNICAL DEVELOPEMENT DEPT.Please avert your eyes to the previous post......NoBody wants the CHALLENGE....;)lol lol lol...

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 Posted: Thu Aug 14th, 2008 04:31 am
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Wesley
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Dubsy wrote: Hello I was just checking the answers to the test and noticed you put:

3. A car is accidentally fitted with O/S/F wheel cylinders that have pistons 2.0mm GREATER in DIAMETER than the N/S/F wheel cylinders pistons. This is likely to cause ?
C = the brakes to pull to the N/S


How do the brakes pull to the N/S, if the diameter is greater then the force applied will be greater which will result in the brakes pulling to the O/S.


so with your recently gained knowlege,

Answer = C the brakes to pull to the N/S

I Wish avocco Had replied! to the post.;)

Regards, Wes.:D

Last edited on Thu Aug 14th, 2008 04:36 am by Wesley

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 Posted: Thu Aug 14th, 2008 04:23 am
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Dubsy
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David wrote: Hi Dudsy

you ask for my answer, so here it is;

OK you asked what my answer is; well before I do answer I think a little explanation of some key facts would be beneficial first.

Before we get into the hydraulics, let’s recap on some circle geometry, we do agree the brake pistons will be round don’t we?

Somebody has previously said that the “area” is not counted but the “diameter” is, so let’s start at this point. You can’t calculate brake force from a diameter, so you need the area of the cylinder in question.

There is a relationship between the diameter and circumference of a circle, which is;

The diameter increases proportionally to the circumference, so if C = kd, then C/d = k, which is the constant of proportionality.  Now we now that C/d = , which is usually remembered as C = d or C = 2r.

Now when the service brake pedal is depressed, the force applied to the brake fluid creates a pressure which is constant throughout, undiminished.

Let’s now say that the brake piston diameter is 50mm, to find the force applied we now need to find the area, so we can use the formula C = d or  ï€†d/4;

Find the circumference C = d

C = 3.142•50 = 157  now if you divide 157/4 = 39.3 to 3sf. Or you can use the following formula;

A = d/4        3.142•50/4 = 39.3mm2  which gives the same answer which is the area of the cylinder. Now to find the pressure acting in the brake caliper, you need to find the area of the master cylinder, so let’s say its 400mm2

You now apply your foot to the service brake, and let’s say 100N force as a guide, to find the pressure acting in the master cylinder, you divide;

100/400 = 0.25 N/mm2 multiply this by 10 gives 2.5Bar of pressure, this pressure is undiminished throughout the hydraulic system, so to find the force at the brake caliper;

0.25•39.3 = 9.83N or 98.3 Bar. Let’s say that this brake is the nearside front.

Now we can do the same for the offside front, but this time we will change the diameter, let’s say 05mm less.

A = d/4 = 3.142•34.3/4 = 26.94 4sf.

0.25•26.94 = 6.73N or 67.3 Bar. So as can be seen the offside front brake efficiency is less when the diameter and the area are less, therefore the brakes would pull to the nearside when applied.

Nearside front working pressure = 98.3 Bar

Offside front working pressure    = 67.3 Bar

Hope this clears up any misunderstanding

David:D

 


:D 

Hi dalid, just for the record it's Dubsy as in VW's :P .

Now to the question. Techically, you gave the wrong answer but a perfectly good explanation, had it been an exam question you would have got it wrong.

The question was:

3. A car is accidentally fitted with O/S/F wheel cylinders that have pistons 2.0mm GREATER in DIAMETER than the N/S/F wheel cylinders pistons. This is likely to cause ?

;)

Yes i am bored and have nothing better to do with my time.

 

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