wally
Nominated Tester
Posts: 139
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Post by wally on Dec 23, 2010 0:53:28 GMT
But you are talking about diameter at this stage. If you had a washer 6mm outer dia and 4mm inside dia then each side would be 1mm.
Wally PS Can you not sleep either?
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Post by Admin on Dec 23, 2010 10:38:39 GMT
Kunifer has wall thickness of 0.71mm...
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hayden
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Post by hayden on Dec 23, 2010 11:48:52 GMT
(Cu),Nickel,(ni),ferrous,(iron,Fe) cunifer/kunifer. dave, surfed my head not the net for this one hope it's right. LMHO ;D
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Daveg
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Post by Daveg on Dec 23, 2010 11:52:53 GMT
But you are talking about diameter at this stage. If you had a washer 6mm outer dia and 4mm inside dia then each side would be 1mm. Wally PS Can you not sleep either? Not been too good with health over the last week lol ;D, just recovering from an infection, boss already been on phone to get me back to work, but told him no no next week I will be back Looking at your example of inside and outside diameters Wally, I am not sure where you are coming from or what you are trying to explain But if I explain this would it make things any easier for us to get on a level playing field? Diameter = The distance through a circle's centre from the outer circumference, so the line drawn through the centre must touch each point at the circumference. If this circle was now a bar of 30mm diameter and we fixed it into the vice, then filed off a flat on the outer circumference of say 04mm, if we then measure the diameter at two different points, i.e. the original diameter of 30mm, and then the diameter at the point were we have filed 04mm off it, would the diameter of the bar be the same at both points of measure??? If 30mm = 30mm, then 30mm - 04mm = 26mm, which surely is a different diameter??? But you cannot divide by two because you have only filed off one flat at one part of the diameter, so the wall at one point is weaker and the diameter of the bar is less, if you see what I am getting at Dave Edited to say; Mathematical techniques used can and do cause some confusion, however in my calculations previously the only data I used was the outside diameter of the brake pipe. The results of my calculations shown can be converted again which work out very close to Admins post of 0.71, but again it depends on which pipes used and the quality of manufacturer, it is not an exact science but is very close, i.e. 0.62
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Post by aylesburyjock on Dec 24, 2010 9:37:57 GMT
Surely Dave we are not talking about diameter, merely wall thickness. As Admin has already given us the figures for that and VOSA have given us a rounded off figure for a third of the wall thickness we don't need to try and complicate everything. The only difficulty is in measuring the depth of pitting with a visual inspection. But a visual inspection is what is called for in the manual, not the withstanding of braking pressures incurred during the roller brake test.
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hayden
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Post by hayden on Dec 24, 2010 11:46:55 GMT
as we can only use the tools VOSA allow us eg. cat tool for scraping and eyes for visual inspection it will never be a 100 % definite pass or fail to the figures in the manual, all we can do as testers is to use our experience and training to make the best judgment we can at the time as to the level of corrosion and wall thickness, and it will differ between testers.
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Daveg
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Post by Daveg on Dec 24, 2010 15:41:06 GMT
Surely Dave we are not talking about diameter, merely wall thickness. As Admin has already given us the figures for that and VOSA have given us a rounded off figure for a third of the wall thickness we don't need to try and complicate everything. The only difficulty is in measuring the depth of pitting with a visual inspection. But a visual inspection is what is called for in the manual, not the withstanding of braking pressures incurred during the roller brake test. The manual makes mention to "Wall Thickness" as you say and not the "Diameter" as I mentioned, however look at this scenario;- Looking at one of the faces of your internal room doors you can see a large surface area, but you cannot guage how thick that door actually is can you based on what you see? Suposing then you open the door and take a side view, now you can see how thick the door material is? How can any mot tester look at a length of brake pipe and advise how thick the wall actually is? This thread had pictures on it of brake pipes and every mot tester failed them based on visual appearance, but nowhere on those pictures could you see any section of pipe that had "necked" clearly indicating that the pipe wall thickness had reduced by either (1/3) 33%, or the (0.25mm) 25%, both examples clearly asking for a lot of deterioration before an NT fails the pipe(s)? Looking at any brake pipe along it's length on a vehicle after surface cleaning any NT with reasonable eye sight can assess if the brake pipe(s) diameters have reduced in comparison along the length. In my mathematical example above I calculated the internal diameter of the "fluid area" of the brake pipe from the CSA of the pipe, the diameter 2.0mm was based on this calculation using the CSA, which is kind of like comparing a 9" pizza to a 12" pizza, only 03" different, but the area is "significant"? Dave
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Post by Admin on Dec 24, 2010 17:53:34 GMT
The above extract from the testers manual clearly states 'reduced by 1/3 (approx. 0.25mm)'. There is no mention of 25%. Introducing this figure into the replies is confusing the subject.
If a pipewall is reduced by 1/3 (approx. 0.25mm) then this implies that the pipewall thickness is approximately 0.75mm to start with. (Close to the 0.71mm in my Kunifer post above).
Reduction of pipewall thickness of 0.25mm is not easy to confirm with a basic visual check as per the MOT test.
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Daveg
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Post by Daveg on Dec 24, 2010 20:53:20 GMT
The above extract from the testers manual clearly states 'reduced by 1/3 (approx. 0.25mm)'. There is no mention of 25%. Introducing this figure into the replies is confusing the subject. If a pipewall is reduced by 1/3 (approx. 0.25mm) then this implies that the pipewall thickness is approximately 0.75mm to start with. (Close to the 0.71mm in my Kunifer post above). Reduction of pipewall thickness of 0.25mm is not easy to confirm with a basic visual check as per the MOT test. Admin wrote;- If a pipewall is reduced by 1/3 (approx. 0.25mm) then this implies that the pipewall thickness is approximately 0.75mm to start with. (Close to the 0.71mm in my Kunifer post above).I agree with you Admin, in respect to VOSA's (1/3) and (0.25mm) for me mathematically they are not the same, and all brake pipes diameters although similar are not an exact science. As I wrote previously with my pipe wall thickness;- Wall Thickness = 2.25mm using the CSA, therefore;- 2.25 = sqrt 2.25 - 4/3.141 = 0.79mm Wall thinkness very close to kunifer as you pointed out. Dave
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Post by aylesburyjock on Dec 26, 2010 15:38:25 GMT
I think we can all agree that what we are trying to do with a visual inspection is pretty near impossible. My point being that is what we have to do to the best of our ability.The manual requires a jugement based on a visual inspection. I failed a brake pipe recently for what I judged to be excessive corrosion. When it came back for retest, the customer brought the old pipe back with him. It was so corroded from inside it was paper thin. This could have happened without any outward sign, so even the best judgrment of the most experienced tester is no better than a guess. Whether you fail, or pass and advise, the presenter is informed and knows he has a problem. Job done.
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chris
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Post by chris on Dec 27, 2010 20:12:19 GMT
Hi all. Looking at the pictures it is not as if the pipes have reduced by 1/3 but have swollen due to corrosion. The assessment tool may have picked this up but very tricky and a visual judgment may have been taken. Common problem is when this surface corrosion is removed (generally with sand-paper) it can also take good metal with it and reduce pipe thickness. It is then down to the tester to asses the pipe.
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Daveg
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Post by Daveg on Jan 8, 2011 17:59:25 GMT
Just issued a VT30 to a Renault Clio for a excessively corroded steel brake pipe, looks like a really good example, so as soon as we cut it off next week I will photograph it and upload for you to see. In my opinion it is a much better example to base a decision than the previous pipes shown.
Dave
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hayden
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Post by hayden on Jan 18, 2011 18:13:46 GMT
Dave,have you got the pics for us to see yet .
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Daveg
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Post by Daveg on Jan 18, 2011 21:02:04 GMT
Dave,have you got the pics for us to see yet . The mechanic who changed the pipe destroyed the evidence even though I asked for it to be preserved by cutting the pipe off a good distance back each side, just can't trust people Will get another good example as soon as I can Dave
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hayden
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Post by hayden on Jan 19, 2011 8:22:54 GMT
i should have a couple of nasty pipes coming off a Ford probe soon and i will try and post some pics of them for us to asses.
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Post by aylesburyjock on Feb 8, 2011 19:51:21 GMT
Just another quick question on brake pipes. I tested a grand cherokee today and the flexible brake hoses on them have large lengths of steel pipe as part of the unit. This steel pipe has a much larger diameter than standard brake pipe. Anyone know if the pipe wall of these is the same thickness as standard pipe? Obviously if it is different we would have to test for a different level of pitting due to corrosion, but I personally have never removed one and looked to see.
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Daveg
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Post by Daveg on Feb 8, 2011 22:24:08 GMT
Brake pipe ferrules I think you might be talking about? These are normally quite dense in their manufacture and I have often wondered how far one should let them deteriorate before saying they are "excessively deteriorated", as worded in the manual at (3.6B.4e). I have seen them thinned out on a few vehicle models over the years and passed and advised mostly, except for the odd ones where they were so far gone that the rubber was almost visible through the ferrule itself , then I failed them Dave
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nitros44
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Post by nitros44 on Feb 8, 2011 22:24:14 GMT
I would have to examine the pipe using the rfr and method of inspection as its laid down in the manual irrespective of the diameter of the pipe,i would presume that car makers use the same wall thickness on brake pipes throughout the car manufacturing industry ..if however they are thicker.would we have to test for a different level of pitting?i would have to say no as you would be testing for the 1/3 criteria no matter what the diameter pipe is .After all the manual only says rigid pipes so i would believe it covers different size pipes .might be good one to ask at the seminars
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nitros44
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Post by nitros44 on Feb 8, 2011 22:44:41 GMT
ARE THE PIPES 3/8" AND NOT 3/16"
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Daveg
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Post by Daveg on Feb 8, 2011 23:11:18 GMT
If we are talking about brake pipe and not hoses with ferrules, then not all brake pipes are the same diameter. On some models of vehicles with ABS brakes, if you look at the ABS unit the pipes are of a different diameter inlet to outlet. Energy is very important but not always recognised, vehicles which are of a greater mass will generate more Kinetic energy when they move, therefore will require more energy to stop them. A braking system off a mini one would be no good on a Range Rover? Dave
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