Two Step Ratchet
A Paper Engineering project to download and make. Members can download the project file for free, thanks for signing up!
Pulling the paper tab back and forth is converted into intermittent rotary motion.
Download the parts file and print it onto thin card. I used coloured card for a more colourful model.
Score along the dotted and dashed lines, cut out the holes then carefully cut out the parts.
Fold over and glue the ratchets and wheel to make double thickness card.
Fit the long axle tube to one of the ratchet pieces. The short axles fit in the remaining two parts.
Roll the axle tube and glue it down as accurately as possible.
Assemble the pawl housing as shown.
Glue the pull tab to the grey area on the pawl.
Locate the ratchet gear with the long axle inside the pawl housing and push the axle tube into place. Make sure it is free to turn. It should only turn one way as the pawl and ratchet will stop it turning the other way.
Assemble the box side as shown so that the second pawl is ready to go!
Glue the two sides together.
Fold up the base and glue down one side as shown.
Fold and assemble the guide as shown.
Glue the guide inside the box.
Fit the pawl assemble into the box as shown.
Glue up the bottom flap.
Fit the second ratchet to the outside to that it lines up with the inside ratchet. Optionally fit the wheel on the other side.
Pull the tab back and forth to rotate the ratchet! How will you use this mechanism in your own paper machines?
…let me know what you come up with!