How to draw 2:1 Elliptical Head 3

[ColinPearson]

Hello folks. I want to see if anyone has a good reference for drawing a 2:1 elliptical head. I always draw them in CAD and get the volume to calculate the weight, but it's kind of a pain. I've got two xeroxs out of old layout books and they offer slightly differently rounded versions of the same approximation. Sometimes that's close enough but other times I'm left having trouble b/c my polylines won't join to make a revolution solid, or I can't make a region out of the shape, etc. That's AutoCAD specific problems as I don't have Solidworks and I still suck at Inventor.

So, good folks of the internet, does anyone have any older style ways to draw these suckers i.e. laying the thing out with arcs and bisecting etc? Or do I stick with my approximations that I've got. I'm not interested in gaining a potential tiny tiny tiny bit better approximation, I just want to find a way that makes the drawing easy.

THANKS!

 

[ColinPearson]

abuanaselmasry , I would appreaciate a dwg if you don't mind. I've done them myself, but never had the option to check it against someone else's. Thanks!

 

[abuanaselmasry]

Of course. This is ID 1000 mm internal head profile that I use to make any diameter of head by scaling the geometry, and offset the thickness and SF.

https://www.dropbox.com/s/0to5vjb6vmn95pa/Ellip Head.zip?dl=0

Please check as well. Your feedback is most welcome.

Regards,
M.Salaheldin
Static Equipment Mechanical Design Engineer

 

[ColinPearson]

I see glaring differences between the two... we are an ENTIRE 1/256" off! Kidding, of course, looks essentially the same as what I have. Thank you.

 

[JStephen]

I just got an email back on my request for interpretation above, thus- note the second question asked in particular:

Dear Sir,

Thank you for request for interpretation. After review, it appears that a previously issued interpretation may address this:

Interpretation: VIII-1-01-57
Subject: Section VIII, Division 1 (1998 Edition, 2000 Addenda); UG-32(d) and UCS-79
Date Issued: 06/11/2001
File: BC01-288

Question (1): A 2:1 ellipsoidal head is being fabricated from flat plate having a thickness t with a spherical radius of 0.90D and knuckle radius of 0.17D, where D = inside diameter of the head, based on UG-32(d) of Section VIII, Division 1. When applying UCS-79, where there is not an intermediate heat treatment performed during the forming operation, is the original center line radius equal to infinity and the final line radius equal to 0.17D + t/2?
Reply (1): Yes.

Question (2): Does the head described in Question (1), which is manufactured as a flange and dished head, and a head formed having the exact dimensions of a 2:1 ellipsoidal shape both meet the requirements of UG-32(d)?

Reply (2): Yes.

 

[pennpiper]

Look here;

https://www.google.com/#q=ellipse+template+set&tbm=shop

Sometimes its possible to do all the right things and still get bad results

 

[pennpiper]

or here;

https://www.google.com/search?q=ell...X&ved=0ahUKEwiZ2fGvpuHJAhVFOz4KHTbUAyEQsAQIUA

Sometimes its possible to do all the right things and still get bad results

 

[jte]

JStephen-

Thanks for closing the loop on this one!

 

[pperlich]

I just wanted to add to this discussion that of the manufactures that we buy heads from, they all produce 2:1 heads as 90/17 heads.

Also, to the OP I would suggest contacting your head supplier to see how they handle 2:1 head manufacture. Then make your CAD model match what they do. We have found considerable differences between the two shapes in the "knuckle" area, which can impact the size and location of clips and other minor details.

 

[ColinPearson]

Thank you pperlich. That was kind of what I was thinking. We rarely use heads in items that we manufacture as our scope ususally is demo of old and installation of new (prefabricated) equipment. That usually involves welding on lifting lugs which brings up the issue you highlighted.