Picture of T.Rex with Interchangeable Cams.
This project is a cam powered T.Rex automata. The head and lower jaw are driven by separate cams which can be interchanged to change the way the T.Rex moves and so tell a different mini-story. The file of parts is available here.

The T.Rex is a fascinating project to make with students aged twelve and up. By building this model, students will be improve their skills in accurate cutting and scoring. Students will also learn how cam profiles can be used to create movement and how these movements can be used to act out a story.

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Step 1:

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The project parts come as a file which can be downloaded here

Print out the parts onto thin card. (230 micron 67lb). Score along the dotted lines and cut out the holes before carefully cutting out the pieces.

Step 2:

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Make up the base and the top in the same way as shown in the picture. Make sure that all the edges are at right angles.

Step 3:

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Glue together the four parts of the body.

Step 4:

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Assemble the lower jaw.

Step 5:

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Glue together the head.

Fold round and glue together the triangular head inner.

Glue the head inner into place so that it is lined up with the crease across the top of the head.

Step 6:

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Glue the two lower jaw tabs to the top back of the body. Make sure that the lower jaw is free to move up and down.

Step 7:

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Glue the head tab into place on top of the lower jaw tabs.

Step 8:

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Fold the legs and arms into half and glue them together to make double thickness card. Once the glue is dry carefully cut out the pieces.

Step 9:

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Glue the lower legs to the grey areas on the body. Note that the legs bend forwards at the joint, use this to get the right leg on the right side.

Glue the two arms into position as in the picture above.

Step 10:

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Thread the jaw push rod up through the body and glue the tab to the grey area on the underside of the jaw.
tocsik3 years ago
I was inspired by this so I went out o my shed and found a scrap piece of ply-wood. Then, I slapped this together. It only has a single cam. I'm super happy with this a a first effort at anything cam driven like this. Thanks for the inspiration.

robives (author)  tocsik3 years ago
Wow! That is fantastic!
dwhite01 year ago
Too bad we have to buy the plans. This is just like an ad.
chubawabu2 years ago
Amazing instructable! But sad that anyone who wants to make it has to pay on your website for the template. But still an amazing instructable! thanx
Bonfi962 years ago
Amazing papercraft! One of the best I've ever seen on the web!
Can I ask you how do you design them? What software do you use?
robives (author)  Bonfi962 years ago
Hi Bonfi96, I use mainly Adobe Illustrator witha bit of Photoshop thrown in. I talk a lot about the design process on my website at
Bonfi96 robives2 years ago
i think I'll use inkscape and Gimp :) Thanks!
robives (author)  Bonfi962 years ago
Yep, that should do the trick!
keraiwailjs2 years ago
Nice (both wooden and paper models)
Thats cool. Maybe you could 3d print/laser cut the cams so there sturdier, they looked kinda flimsy. Good job
Jakwiebus3 years ago
I always wanted to make something like this, but I don't have fancy woodworking skills, now I can with paper ;-)
very clear and complete instructable! thumbs up!