# -Penn Foster? HVAC transition piece

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Hi,

I think I followed the text correctly to find the true lengths. It's what to do next that I am stuck at. I think I have what you said correct now.

Thank you so much for helping me and everyone on these forums out especially on a Saturday.

Edited by chloe2012

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#### Posted Images

Oops, I just noticed that the circle is offset from center so B-10' is not equal to A-10'

Your circles don't look like perfect radius.

Don't type in the radius - use snap points.

Your next step will be to determine the length of arc from 10-9.

Not the cord length (many books miss this) you need the arc length.

Once you find this it is the same for all (9-8 is the same as 10-9).

Tip- you can find the arc length by

copy and paste pie shape away from the drawing.

trim the pie

list the arc

Draw circle of R 10-9 arc length at point 10' in your flat development..

Draw circle of R A-9' at point A

Where these two circle intersect is point 9' you now have line A-9

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No, its not centered. Do I have this first stage correct?

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Ok, I have done that step, hopefully correct

Project 7 - PLATE 3.dwg

Edited by chloe2012
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I'm not at my CAD computer thus the reason for my question. Are you working on the Penn-Foster HVAC project?

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Yes I am. I have seen the pictures of Plate 3 posted. It shows that the end result is supposed to be but not how to get there. I attached a picture of where I have reached. I assume I do the same thing on the left side but not sure what to do next on the right.

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This is what I have come up with following instructions that I found online, though they were for a symmetrical piece. I know something is wrong as my arc on the inside isn't correctly meeting the lines for each point. However, I do not know what. Please help when able.

Project 7 - PLATE 3.dwg

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It should be a spline curve - not an arc.

But you have point D in the wrong location.

Draw circle R A-D at A.

Draw circle R A-7 with center at 7 (A-7 and 7-D are same length).

Where these two circles intersect is the actual location of point D.

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HI,

Think I have it all correct now...hopefully

Project 7 - PLATE 3.dwg

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• 2 years later...

hello,

please i need hel for

DRAFTING THE 14X16X6 HVAC patterns.

thank you!

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Just what is it that you need help with specifically? Did you look at some of the similar HVAC threads to this one? A number of images are available.

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• 2 months later...

Hello, after reading through this thread, and others, I still do not know how to find the "true lengths". Once I understand something, then I know it forever, unfortunately I just don't get it. Please someone, spell it out in simple terms. Keep in mind I am an ex-framer, so not too bright

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J-stone: Which HVAC project are you doing? The regular one or the elective?

True lengths are needed when a side is slanted. For an example of what I am talking about see this...

http://www.achrnews.com/articles/laying-out-rectangular-duct-transitions

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It's the regular one, project 7 HVAC.

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I guess my question is; how do I project the true length lines, how do I figure out what the radius is to project the lines out and down from my top view to my front view?

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So how does one go about finding what the true length's are?

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I have not worked on the HVAC project personally but I have posted images from it that were handed over to me by a former Penn-Foster student. Have you looked at any of the other threads regarding this project as I know there are at least two that have images of some if not all of the plates.

I have copies of the drawings done by Car5858 that he included as images in the thread.

Are you working on Plate 3?

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Ya I've read through all the threads that have HVAC anywhere mentioned in conversation. Here is a screenshot.

I just need to know the process that one does to figure out the projection lines to find the true length's. Without just looking or copying, I am trying to figure out how to figure out what the true length's are. If that makes sense.

On a side not, I am obviously almost done with this program, but I do have a 98% average. I got dinged on two drawings for following the directions to the letter. So, for the last few drawings, I am utilizing this wealth of knowledge that you guys have.

I would preffer to not have my grade drop anymore than it already has. But, honestly, I am tempted to just blow through it and leave this horribly compiled course behind.

On a side note, would anyone reading this know of a GOOD course for structural drafting?

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I am not well versed in HVAC re: sheetmetal fabrication so I would have to defer to forum members JD Mather and/or Tanner Frampton when it comes to advising you on the proper procedure.

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I guess my question is; how do I project the true length lines, how do I figure out what the radius is to project the lines out and down from my top view to my front view?

After looking at Car5858's drawing (in the thread I provided the link to) I think I know how the arcs are created. Draw circles using corner 'B' as the center through points 10, 11, 12 and 1 of the cylinder; trim as required. Like this...

If I am wrong JDM will be sure to castigate me and Tanner Frampton will most likely want to castrate me. Either way, you'll get a more definitive answer.

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