Please help me with the Scale of Chrods -_-'

@eranushka-4BgWe8 • Oct 27, 2024

Oct 27, 2024

1.2K

Hi ^_^ I thought Engineering graphics would be easy but actually it's not! I've exams within 2 days! -_-'

Anyone can explain me how to construct scale of chords? It's too difficult to understand the concept from the Book. 😔
Please help me if you know about it 😀

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Ramani Aswath

@ramani-VR4O43 • Jan 20, 2013

I thought that scale of chords relates to music. I have not heard of this term in engineering graphics.
ErAnushka

@eranushka-4BgWe8 • Jan 20, 2013

bioramani
I thought that scale of chords relates to music. I have not heard of this term in engineering graphics.

No, it's a method to measure and construct angles without using the protractor 😀

And I got it. My problem solved 😀
Jeffrey Arulraj

@jeffrey-xA7lUP • Jan 20, 2013

Do post how you mastered it in simple terms here May be it will be of help to some one in the future
Ramani Aswath

@ramani-VR4O43 • Jan 20, 2013

The length of the chord of a circle with a given radius has a direct relationship with the angle that the chord subtends at the centre.
If l = chord length, r = radius of the circle and A the angle subtended by the chord at the centre then,

l = r x sin(A/2)

After I read the last post of #-Link-Snipped-# I went back to my old trusted Perry's handbook to check.
Sure enough the Scale of Chords is very much there, though not called that.

The main point is that since length measurement is more accurate than angular measurement with a protractor, the scale of chords can give very accurate measurement of angles.
ErAnushka

@eranushka-4BgWe8 • Jan 21, 2013

Conqueror
Do post how you mastered it in simple terms here May be it will be of help to some one in the future
#-Link-Snipped-# already did 😀 but if you've any questions, feel free to ask me 😀
ErAnushka

@eranushka-4BgWe8 • Jan 21, 2013

bioramani
The length of the chord of a circle with a given radius has a direct relationship with the angle that the chord subtends at the centre.
If l = chord length, r = radius of the circle and A the angle subtended by the chord at the centre then,

l = r x sin(A/2)

After I read the last post of #-Link-Snipped-# I went back to my old trusted Perry's handbook to check.
Sure enough the Scale of Chords is very much there, though not called that.

The main point is that since length measurement is more accurate than angular measurement with a protractor, the scale of chords can give very accurate measurement of angles.

True ^_^

And do you know how to draw Rhombus of 100 mm and 70mm diagonal?

Correct me if I'm wrong:

1. Draw x-axis of 100 mm
2. Draw y axis of 70mm at centre of x axis. -_-
3. Now join all four points.

Is that correct? I've exams, please reply ASAP 😕
Saiwal

@saiwal-NOzuWb • Jan 21, 2013

ErAnushka
True ^_^

And do you know how to draw Rhombus of 100 mm and 70mm diagonal?

Correct me if I'm wrong:

1. Draw x-axis of 100 mm
2. Draw y axis of 70mm at centre of x axis. -_-
3. Now join all four points.

Is that correct? I've exams, please reply ASAP 😕
😀 correct
Ramani Aswath

@ramani-VR4O43 • Jan 21, 2013

Apologies, the formula I gave has a Typo.
The chord length is l =2 x r x sin(A/2),
I missed the important 2.
Check: The chord for a 60 degree angle is equal to the radius.
l = 2 x r x sin(60/2) = 2 x r x sin(30) = 2 x r x (1/2) = r.

Both of you are right about the rhombus. Diagonals bisect each other at right angles.
ErAnushka

@eranushka-4BgWe8 • Jan 23, 2013

bioramani
Apologies, the formula I gave has a Typo.
The chord length is l =2 x r x sin(A/2),
I missed the important 2.
Check: The chord for a 60 degree angle is equal to the radius.
l = 2 x r x sin(60/2) = 2 x r x sin(30) = 2 x r x (1/2) = r.

Both of you are right about the rhombus. Diagonals bisect each other at right angles.
Oh! Thanks 👍