Help on Finding Centers

[Behemothrex]

Hey guys,

 

Well its been a while since I posted, but that's a good thing, as I have been progressing in my AutoCad adventure without to many problems. But this semester I have run into a problem that I have yet to overcome. So assistance would be appreciated.

 

The trouble I am having is finding the centers of some of the circles I need to place to create the different curves that I need to complete the drawing. I have highlighted the area in question in yellow.

 

Now a few of the circles are dimensioned on the drawing and they are easy to plot out, but for the life of me I cannot figure out how they are placing the other circles. Specifically the circles with the radii of 1.63, 1.98, 1.13 and the one on the outside of 1.25.

 

Any thoughts would be appreciated.

 

I have included the original and what I have completed so far.

 

Thanks

DGM - Problem 5-11.dwg

[JD Mather]

TTR will be your best friend.

[rkent]

You will want to use the FILLET command on this, establish the center lines where you can, draw arcs and finally fillet them together.

[JD Mather]

This is how I started out.

 

[JD Mather]

Trim it up

 

[JD Mather]

Add the fillet

 

[JD Mather]

Add the R1.63 (and R.25)

[nestly]

Either CIRCLE>TTR with a radius of 1.13 or FILLET with 1.13 radius between the 4.18 dia arc and the 0.75 circle will establish the centerpoint in question

 

[JD Mather]

Add the 1.25

 

[JD Mather]

Next step

 

[JD Mather]

Trim and add another fillet

 

 

So on and so on.... step-by-step...

[Behemothrex]

As always you guys are fast and on the ball, but the main issue I am having is the placement of the initial circle with the radius of 1.13. How did you find that center? Am I missing a dimension someplace?

 

Thanks

[nestly]

Since you know the center of the 1.13 circle is 1.13 from the 0.75 circle and you also know that it's 1.13 from the 4.18 circle, some of the options to establish the center are:

 

1) Use the FILLET command to create a 1.13 fillet between the 0.75 circle and the 4.18 circle. The center of the FILLET is the point you are trying to establish.

 

or

 

2) Use the CIRCLE command with the TTR (Tangent/Tangent/Radius) option to create 1.13R circle that is tangent to the 0.75 circle and the 4.18 circle (as shown in the animation in post #8 )

 

or

 

3) OFFSET the 0.75 circle 1.13 units toward the outside, and OFFSET the 4.18 circle 1.13 units towards the inside. The intersection of the offsets is the center.

[Behemothrex]

Hey thanks nestly, guess I sort of overlooked that animation, duh. I have used the TTR many times before but I guess I was just baffled by all the circles I had drawn that still needed trimming, it was making things way too complicated. Its great to see other peoples thought processes to the same problem. The way JD started the drawing is completely different than the way I did and made the curves much easier to visualize. Once again its great to have the input of people that have been doing this for a while. That's the one downfall of Online school, its very hard to see how others would do the same problem.

 

Thanks again!