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Old 28th March 2011, 15:12   #16
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Default Re: Somvarpet OTR 2010: Escape to Nature

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Originally Posted by SPIKE ARRESTOR View Post
Please explain how measuring with a tape will create parallax error? Does that mean tailors make clothes with parallax error built into it? Nah!

Screw gauge cannot eliminate parallax error, why do you think Screw gauge eliminated parallax error?

Because I thought you did not know that. I guess you are referring to "Zero error" of measuring instruments
Never mind Spike. If you don't understand it already, no amount of explanation will help you. You are probably happier using a measuring tape instead of screw gauge to find the thickness of a pipe, just have to divide the result by Pi.

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Trust me, I am not an illiterate, I did go to school.

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Old 28th March 2011, 16:47   #17
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Unhappy Re: Somvarpet OTR 2010: Escape to Nature

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Never mind Spike. If you don't understand it already, no amount of explanation will help you.
Now you will teach me parallax. I have become the culprit now. Samurai, I think you got me wrong here.

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You are probably happier using a measuring tape instead of screw gauge to find the thickness of a pipe, just have to divide the result by Pi.
Wrong again! The topic of measurement here was "tire". Throughout my life I have never seen anyone measure a tire using a screw gauge, the simplest method is as pointed out by Fazal Saab- measuring tape.

BTW, thickness of a pipe cannot be obtained by dividing the measured value of a pipe by Pi, what you get by doing this ( (2 * Pi * R / Pi) = 2*R) is the diameter / radius. You don't require Pi to calculate the thickness of a pipe.

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Thanks, but you are assuming this is an OE Jeep, Sibi generally mixes that stuff a lot.
Oh, that is surprising, I thought these were stock! Any idea what was done to this one?

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Trust me, I am not an illiterate, I did go to school.
Thanks, I am clear now.

PS- I guess whatever I explain, will never be satisfactory to you. Let me stop here.

Spike

Last edited by Samurai : 28th March 2011 at 17:01.
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Old 28th March 2011, 17:23   #18
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Default Re: Somvarpet OTR 2010: Escape to Nature

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Wrong again! The topic of measurement here was "tire". Throughout my life I have never seen anyone measure a tire using a screw gauge, the simplest method is as pointed out by Fazal Saab- measuring tape.
As I understood, Fazal wanted sidewall to sidewall thickness of a 235mm tyre. I hypothetically mentioned a giant screw gauge since I couldn't imagine how to measure it, I didn't think such giant guage is available. However, Tanveer came up with a neat way to measure it using hi-lift jack, which almost works like a giant screw gauge. Basically, the need is for a U shaped measuring device which accommodates the tyre.

I am still not sure how to use a measuring tape to measure the outer-to-outer diameter of a tyre. A diagram would surely help.

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Originally Posted by SPIKE ARRESTOR View Post
BTW, thickness of a pipe cannot be obtained by dividing the measured value of a pipe by Pi, what you get by doing this ( (2 * Pi * R / Pi) = 2*R) is the diameter / radius. You don't require Pi to calculate the thickness of a pipe.
When I say thickness, I mean the outer-to-outer distance or diameter of the pipe. If I am not totally senile, I remember circumference of a circle = Pi X diameter. You can use a measuring tape to find the circumference and then divide by Pi to get the diameter or thickness. Obviously this method of measuring a pipe can't be used on tyre since the tyre cross-section is not a perfect circle.
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Old 28th March 2011, 17:52   #19
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Default Re: Somvarpet OTR 2010: Escape to Nature

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When I say thickness, I mean the outer-to-outer distance or diameter of the pipe. If I am not totally senile, I remember circumference of a circle = Pi X diameter. You can use a measuring tape to find the circumference and then divide by Pi to get the diameter or thickness. Obviously this method of measuring a pipe can't be used on tyre since the tyre cross-section is not a perfect circle.
That wold be called the Outer Diameter of the pipe (OD).
'Thickness' will always denote 'wall thickness' of the pipe
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Old 28th March 2011, 18:00   #20
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Default Re: Somvarpet OTR 2010: Escape to Nature

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That wold be called the Outer Diameter of the pipe (OD).
'Thickness' will always denote 'wall thickness' of the pipe
The original context of the posts was about outer diameter. Since I am not a mechanical/civil engineer, I tend to use thickness and OD interchangeably.

Most of us technically challenged people say 3 inch thick pipe instead of saying pipe with 3 inch diameter. You experts just have to understand that instead of getting all technical on us.
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Old 28th March 2011, 19:26   #21
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Default Re: Just a thought - Units of measurement

Ha ha, Samurai is right, colloquially 3" thick pipe means 3 " diameter.

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Old 28th March 2011, 20:51   #22
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Default Re: Just a thought - Units of measurement

Pipe are normally referred to by their inside diameter - the nominal bore. Wall thickness will be based on the schedule.

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Old 28th March 2011, 20:55   #23
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Default Re: Just a thought - Units of measurement

Dada, what is your view on "Parallax" discussed above?

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Old 28th March 2011, 21:39   #24
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Default Re: Just a thought - Units of measurement

^^^
(Cautiously coming out of cover)

Both of you are correct. Because you are not addressing the same issue.

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Old 28th March 2011, 21:52   #25
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Default Re: Just a thought - Units of measurement

Wait a minute, are the two issues :- Parallax, Precision (L.C.)? Is that what you meant?

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Old 28th March 2011, 22:06   #26
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Default Re: Just a thought - Units of measurement

^^^
No. If I have understood the posts.

Samurai is talking of the parallax issues if you try to guess the position of the sidewall by holding a scale next to the tread. It will be major.

You are talking of parallax in reading a micrometer. It will be there because the sleeve physically cannot be at the same level as the thimble.

I must add that Samurai's parallax issues will dwarf yours.

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Old 28th March 2011, 22:38   #27
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Default Re: Just a thought - Units of measurement

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Just measuring tape, won't that create parallax error? I am assuming you mean sidewall to sidewall.
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I thought Screw Gauge eliminated parallax error. Please explain how parallax error can happen in screw gauge?
Yeah, got your point. You are right when you say measurement with a scale will lead to major parallax when compared to a micrometer, I fully agree on this.

My point was using a micrometer does not necessarily eliminate the parallax error. The error is still a function of the viewing angle (human factor). Isn't it?

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Old 28th March 2011, 22:53   #28
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Default Re: Just a thought - Units of measurement

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Originally Posted by SPIKE ARRESTOR View Post
My point was using a micrometer does not necessarily eliminate the parallax error. The error is still a function of the viewing angle (human factor). Isn't it?

Spike
Yes. Because the thimble and sleeve are at different distances from the eye. In fact in a micrometer with a vernier, it can lead to an error of a couple of counts. Incidentally, one can design a vernier caliper with no parallax error.

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Old 28th March 2011, 22:59   #29
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Default Re: Just a thought - Units of measurement

Yes, that is what I was looking for. ^^

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Old 29th March 2011, 00:50   #30
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Default Re: Just a thought - Units of measurement

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Originally Posted by Sutripta View Post
Samurai is talking of the parallax issues if you try to guess the position of the sidewall by holding a scale next to the tread. It will be major.

You are talking of parallax in reading a micrometer. It will be there because the sleeve physically cannot be at the same level as the thimble.

I must add that Samurai's parallax issues will dwarf yours.
Thank you, that's exactly what I was trying to say. BTW, it would be Fazal's parallax issues.

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Yeah, got your point. You are right when you say measurement with a scale will lead to major parallax when compared to a micrometer, I fully agree on this.
Thank you for finally accepting my logic.

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My point was using a micrometer does not necessarily eliminate the parallax error. The error is still a function of the viewing angle (human factor). Isn't it?
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Originally Posted by Sutripta View Post
Yes. Because the thimble and sleeve are at different distances from the eye.
That error is so very minute when compared to the width of a tyre. A fraction of a millimeter at the most.
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