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VCU Archaeology

Cardboard 3-D Slice Model: Megalonyx Femur

Guest blog by Ryan J. Wheeler rwheeler@andover.edu
Robert S. Peabody Institute of Archaeology https://www.andover.edu/learning/peabody

May 16, 2020

I was excited when Bernard Means of the Virtual Curation Lab posted 3D slice models of artifacts and fossils. The models reminded me of the topographic models we made in the Boy Scouts. We cut out and stacked cardboard pieces, replicating the elevation contours of a topographic map. A two dimensional image was transformed into 3D! Lock down means most of us are away from 3D scanners and printers, so the cardboard patterns are a fun way to make 3D models. Plus, I LOVE building stuff out of cardboard, often with my eight-year old son Leo. Leo and I have made a Corinthian helmet, the TARDIS and K-9 from Doctor Who, a wearable sea turtle carapace, a model of our house, and much more.

Choosing a 3D Slice Model

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Initially I wanted to build the Virtual Curation Lab 3D slice model of a dire wolf skull. I downloaded the plans and watched the video loop showing a virtual assembly. Ultimately, I opted for the Megalonyx femur. I decided that it was a little simpler, and might make a better first build. Each set of plans includes numbered pieces with registration marks that indicate how all the pieces stack. I like Megalonyx too, since these giant ground sloths existed in my home state, and some Florida rivers occasionally reveal fossilized bones. Megalonyx existed across much of North America for over 10 million years, ultimately becoming extinct around 11,000 years ago!

Assembling Materials

I started by downloading and printing a set of the plans from the Virtual Curation Lab. There are five pages with approximately 26 pieces for the Megalonyx femur. I printed two sets of plans, keeping one for reference as I cut each piece out to make patterns. As I worked on creating the patterns for each piece, I assembled my other materials, including:

  • pieces of thick, corrugated cardboard from a shipping box (thin cardboard, like a cereal box, won’t work well),
  • an X-acto knife with a supply of #11 blades,
  • a cutting mat,
  • an envelope to store the paper patterns,
  • adhesive glue,
  • and some black spray paint and some brown and tan acrylic modeling paint.

Creating the Model

As I began making paper patterns for each piece, I noticed that some of the pieces are rather small or have narrow sections when printed on an 8.5 x 11-inch piece of paper. I decided to scale things up by adding about 1/8-inch on each side of each pattern. One could also use a program like Photoshop to scale up the pattern. I traced the patterns onto the cardboard, making sure to keep the long axis of each piece against the “grain” of the cardboard. This produced pieces that showed the honeycomb structure of the corrugate cardboard along their long side. I was a little worried that my cardboard might be too thick (2/8-inch), but the Megalonyx femur is a big, thick, flattish piece of bone, so I decided to keep going. Next time I will use some 1/8-inch corrugated cardboard. Change the X-acto blades with some regularity—they get dull quickly! I also made sure to transfer over the piece number and registration marks as I went. I saved all the pattern pieces in an envelope for future use.

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Once all the cardboard pieces were cut out I made a few test stacks and cleaned up edges as needed. I used some silicon glue left over from another project to adhere all the pieces. This provided for easy cleanup, allowed me to reposition pieces as needed, and made for a nice, solid bond after 35 minutes. White glue should work fine too. Dr. Means suggests on the Virtual Curation Lab blog assembling the models from the center moving outward. This worked well, and I made two large sections of the model that I then joined. I also had the virtual assembly loop playing to make sure the pieces were going together correctly. Following the registration marks is important too!

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Painting and Decorating

When the cardboard was well bonded, I went to the garage to spray paint the model in a well-ventilated space. I used some leftover black spray paint to give a quick base coat.

After the paint dried, I added some details with brown and tan acrylic paint. Minerals and tannins have heavily stained fossils from Florida rivers and quarries blackish-brown. Once I achieved the desired effect, I left the Megalonyx model to dry. My son produced a background drawing for display.

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Final Thoughts

Building these cardboard 3D slice models is a fun and low-tech way to learn about fossils and artifacts. During each stage of the build, my son and I looked up facts about the Megalonyx. The name Megalonyx is Greek for “large claw,” referring to the large, curved claws used for grabbing branches and foliage, their main food. We learned that our model, measuring about 9-inches long is about one-half scale. Megalonyx femurs measured by paleontologists are as much as 20-inches long! This was an impressive animal, measuring around 10-feet tall and weighing over 2,000 pounds. Their closest living relatives are the three-toed sloths of Central and South America, though these are much, much smaller! There are indications, too, that Native Americans hunted Megalonyx during the late Pleistocene.

I’ve also made a Youtube video illustrating the build: https://youtu.be/pcJ9zGAdNFU

Discussion

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  1. Pingback: Cardboard 3D Slice Model: Megalonyx Femur – The Peabody - May 18, 2020

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