Owl Design with Frustums

Thu, 3 Apr 2014

My first draft of a circular bodied owl was based on the Owl Box project. The body was a bit on the skinny side – definitely in need of fattening up!

Rather than using a cylinder for the body, I felt a frustum was more appropriate. Luckily I have just the tool for the job…

<—New section added 5th Apr —>

The owl body is made from a cone shape with the top cut off. The mathematical name for this shape is a frustum.

I made up a rough version of the body shape freehand. Cutting out a curve of card, I rolled it round and trimmed it until it was the size and shape that I was looking for.

I then measured it up ready for transfer to the computer. The important measurements are the radius of the bottom circle (r1), the radius of the top circle (r2) and the height of the model (h). I measured these dimensions and noted them down.

I then downloaded the spreadsheet from an earlier blog post here and opened it in Open Office. (It should also work in excel but I no longer have a copy after Microsoft Word and I fell out.)

I typed in the three measurements into the three arrowed boxes. The circled measurements and the angle are all I need now to construct the net of the owl frustum.

<— end of new section —>

Having decided on the size that I was after, I entered the various numbers into the spread sheet. Using the dimensions given by the spread sheet I constructed the curved part used in the owl’s body.

It all fits together rather neatly. I’ll be making the finished owl available as a download on his own then as part of the rrvs type 2 mechanism.

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Comments (7)

  • nanalee April 3, 2014 at 11:17 pm

    How does inputing


    How does inputing numbers into Excel help with the project?


    My apologies, I’ll expand the post shortly to make it clearer what I mean- RI

    • umehta April 4, 2014 at 11:50 am

      Frustum in head also? The
      Frustum in head also? The body appears and fits just right.

    • nanalee April 4, 2014 at 7:38 pm

      Great! I watch for more


      Great! I watch for more information. 


      • robives April 5, 2014 at 2:03 pm

        Updated as promised. I hope
        Updated as promised. I hope that helps 🙂

        • nanalee April 6, 2014 at 2:11 am

          I’m not that well versed


          I'm not that well versed on your Excel setup. I'm glad it helps you create some fantastic designs.


          It could that it doesn’t work properly in excel. I’m afraid I haven’t been able to test it. I’ve only used Open Office – RI

    • Smelter April 5, 2014 at 8:46 am

      nanalee, check out the links
      nanalee, check out the links to Robs other pages.

      Excel is a spreadsheet program that does the number crunching.
      With Robs formula set-up, you put in the finished dimensions you want the model to be, and Excel tells you the size of the lines and angles to make it.

  • Shelley April 4, 2014 at 5:48 pm

    Once again, I love seeing
    Once again, I love seeing into your design development process, Rob. It still looks like magic to my. Even lifting back the wizard’s curtain doesn’t make what you do any less astounding to me.

Comments are closed.