Turn the handle in the Cam Box and the push rod protruding from the top of the box moves up and down. Vary the cam profile to vary the movement of the push rod. Use this model to experiment with how cams work or as the starting point for other character based models.

Members can download this model for free at the link.

Print out the parts onto three sheets of thin card. (230gsm / 67lb is ideal) I used coloured card for a colourful model.

Score along the dotted and dashed lines then cut out the holes before carefully cutting out the pieces.

Fold the cam in half and glue it down to make double thickness card. Once the glue is dry cut out the cam.

Roll up the two tubes. Align the edge of the card with the points of the arrows.

Glue the cam to the cam shaft outer using the grey line for alignment.

Fit the cam shaft inner into the outer lining it up with the two grey lines on the inner tube.

Fold up and glue down the cam follower.

Glue the cam follower end into place.

Glue the short tube down and wrap the cam follower end round it gluing the end down o hold the tube ino position.

Wrap a small coin in an off-cut of card. (1p UKP 1c US 1c Euro are all ideal. 20mm diameter, 4g weight) Glue it to the cam follower as shown

Assemble the handle in three steps.

Make up the base and the top of the box. The triangle tubes are all right angle triangles.

Make up the two sides as shown.

Glue the sides to the top with the grey arrows pointing to the top.

Fit the cam into place and glue on the base.

Fold round and complete the box.

Glue the tab on the push rod to the cam follower.

Thread the push rod up through the hole in the box lid.

Glue the cam follower to the centre front of the box. (The front is the side furthest away from the hole in the box lid.)

Complete the model by gluing the handle to the cam shaft.

Turn the handle and watch the push rod jump up and down in lively fashion!

Next I’ll be completing this Dog’s Dinner prototype and showing how you can use the Cam Box to make the dog eat enthusiastically! Nom nom nom!