Presenting the Co-axial drive, or to give it its full title, the Counter-Rotating Co-axial drive. Ta daa!

Turn the handle on this Essential Mechanism and the inner axle rotates ones way whilst the outer axle rotates the other. Use this as a starting point for your own character based models or as an exercise in pure mechanism. Members and patrons can download the parts for free from the link. Thanks for signing up! Non members can join in the fun for £2.50

Print out the parts onto thin card (230 gsm/67lb). I used coloured card for the moving parts to make then stand out from the box. Score all the dotted and dashed lines and cut out the holes before carefully cutting out the parts.

The gears are made from double thickness card. Fold them over, glue them down then carefully cut them out.

Fit the matching axle stub to each axle.

Roll round and glue down the three axle tubes being careful to line up the edges with the points or the arrows.

Thread the gear with the large axle to the widest tube and glue it into place as shown.

Glue the second axle into place.

Fit the small gear to the final axle as shown

Assemble the handle in three steps.

Fold round and glue the box top and base making right angled triangle tubes.

Fold round and glue down the tabs on the box ends making equilateral triangle tubes.

Assemble the cross piece as shown.

Glue the box ends to the base. Note the flaps on the box base fold downwards. (second picture)

Glue one end of the top into place

Thread the small gear into the cross piece.

Fit the axle roughly into position through the hole in the box end.

Fit together the two other axles, one inside the other as shown. Thread them up through the hole in the box top.

Fold the top and gears down so that they mesh with the pinion gear and the box parts line up.

Close the box and glue the sides into position. Glue the cross piece into place.

Complete the model by fitting the handle.

Once the glue is dry, turn the handle and be amazed as the two shafts turn in opposite directions!