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

Replies

• 

  Ramani Aswath

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

  ErAnushka

  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

  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

  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

  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

  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

  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

  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

  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 👍