0 items in the shopping cart
  • No products in the cart.



T.Rex with Interchangeable Cams to Download and Make



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 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.

The project parts come as a downloadable file. Members of can download the file for free. Non-members can download the file for a payment of just £2.50.

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.

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

Glue together the four parts of the body.

Assemble the lower jaw.

Glue together the head.

Fold round and glue together the head inner.

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

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

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

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.

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.

Thread the jaw push rod up through the body and glue the tab to the grey area on the underside of the jaw.

Thread the head push rod up through the body and glue it to the head support piece as shown.

Glue on the feet and glue the feet to the box top so that they are one on either side of the hole with the back of the foot just touching the back of the box top.

Fold up and glue together the two cam followers. Notice that the triangular section at the end of the cam follower use valley folds.

Glue the cam followers to the grey areas on the front of the box top.

Glue the end of the push rods to the cam followers.

Assemble the two parts of the box.

Glue the box body to the base. Make sure that it is straight and square.

Glue the top to the box again making sure that it is straight and square.

Glue together the drive shaft tube. Glue the washer to the end.

Thread the drive shaft through the holes in the box and fix the second washer into place. the drive shaft must be free to turn.

Assemble the handle in three steps. Fold over the two sections and glue to make square section tubes.

Fold on section into the other and glue them at right angles.

Roll round the long tab and glue it down.

Glue the handle to the drive shaft.

Making the interchangeable cams.

This project features easily interchangeable cams. Make a set for each story you want to tell. There are two cam sets already included in the pack as a well as a blank set of cams for you to design your own.

Fold round and glue together the cam shaft. Line up the stop with the grey line and glue it into place.

Thread the head cam into place on the shaft. If you are experimenting with cam profiles, don’t glue them on yet. Thread the lower jaw cam onto the shaft. Make sure that the read line on both are lined up so that the parts are in sync with each other.

Once you are happy with your cam design glue them to the shaft.

Lift the cam followers out of the way and thread the cam shaft into the drive shaft so that the stop butts up with the box.

This cam pack makes the T.Rex eat. Nom nom nom!

Don’t forget to complete the model by gluing the eyes into place otherwise it won’t be able to track down its prey!

8 reviews for T.Rex Cam

  • the model looks great and the

    the model looks great and the interchangeable cams is a great idea.but one quick question i had no trouble downloading it, but when i did it said it expires  on 03/07/12 and just wasn't sure what that meant

    It is only the download link that is set to expire, once you have downloaded the file it is yours. – RI

  • This is a nice idea to create

    This is a nice idea to create different stories with the cams. I hope that we get different variations of the members and builders to see.


  • just finished my

    just finished my model letting the glue dry on the cam shaft but i slide it in to the drive shaft to make sure everything was lined up.but everything seems lined up so im pretty sure it will work.i was going to give my model pose able arms using tabs and circles like the other t-rex model  but i cut the holes too high so just glued the arms on.also the box could use a little decoration maybe a little color and a tree on top by the the t-rex. i haven't tried to make my own cams and play around with them either but its a great concept.

  • Rob I love your models I’m a

    Rob I love your models I'm a ten year old and my favorite thing to do is make your models but i sort of have no money so i would suggest you make more free or cheap because all my friends want to make your models but have enough money and to be honest you would make more money if you did.but it would beyond awesome if you could oh ya i do have one suggestion to make models that are older and don't make much sales anymore you should make free because it may make more people stay more interested in your site and to be honest it would boost sales because then people get sucked in to wanting to do more automata so they get a membership and thus boost sales of memberships so just giving you some sales advice from a consumer because my friends like your models but there aren't enough models to suck people in to papercraft automata if you had more free models you'd have all my friends buying memberships ok thanks.

    Thanks for your interest. I’d like to be able to give all the projects away for free but this is how I make my living so I’m not sure. Your suggestion of making the older stuff free is interesting but I’m not totally convinced it would help. You say that if there was more free stuff you would be tempted to sign up but you also say that you can’t afford to sign up. I’ve deliberately set the price really low. A full year of membership is only £10, less than a quarter the price of a new video game or about the same as a paperback book. What does everyone else think? – RI

    • i understand what you are

      i understand what you are saying thats why i suggested that you make ones that dont sell much anymore free and because you asked my friends agree with me that you whell should what i suggested above

      • Rob has made lots of his

        Rob has made lots of his models free on the "Projects" pages.
        The first page alone has 4 there including the excellent Agreeable Sheep.
        Some models are available to buy individually but if you look at the number available to members, then for the price of Membership they are great value for money, compared to the cost of a cut-out book.

        So you are happy to pay for a Computer, Internet connection, Printer, Inks and Card; but not the creative guy that makes it worth having all that stuff. That is sad.

        Good point Smelter. The last pack of printer ink I bought was much more expensive than an annual membership. – RI

  • ;D


  • I have finally completed

    I have finally completed the"Camosaurus".When designing for other cams I had the idea for a third movement. Particular pleasure is the design of the cams for a particular movement.

    A videoclip on youtube :


    Another brilliant creation! – RI

  • great


    • how do you get the follower

      how do you get the follower to move so freely?

  • GooD!!!


    • I just finished making this

      I just finished making this one the other night. Seeing how smoothly it moves is so satisfying. After making a few models now I have discovered that it is amazingly important that you don`t get glue near any paper hinges. Even the slightest bit will stiffen up the whole movement.

      This model was an absolute joy to make! The design is just incredible.

      Thank you! 

      • Good tip Ross! Any glue on a

        Good tip Ross! Any glue on a hinge really does stiffen them up.

Add Review

Add Review

Add a review