To create the hammer action, we'll need to build a lightweight, yet sturdy hammer -- a perfect time to use corrugated cardboard! The hammer will have a pivot running through its handle so that the motor-driven striker can whack the back of the handle, raising up the hammer. Gravity will cause it to drop back down.

Since the TT motor doesn't have a huge amount of torque, we need to help it along so that it doesn't stall out. That's what the slinky rainbow spring is for! We'll use it to assist with raising the hammer, plus it's highly adjustable, and looks awesome!!

Hammer Head

  • Cut a rectangle of corrugated cardboard roughly 8" x 4" with the flutes of the corrugation running parallel to the short (4") side -- working with the grain this way will make it easier to roll the cardboard into a cylinder
  • Roll the cardboard into a cylinder
  • Place a strip of packing tape on one of the ends as shown, then tape the ends together
  • Trace then ends and cut out two circles from paper or chipboard (cereal boxes are a good source)
  • Glue the ends onto the hammer head


  • Cut a strip of cardboard about 11" x 3/4", making sure the grain runs parallel to the long edge
  • If you can, use 5-ply, double thickness cardboard, or cut two strips and laminate them together with glue for added strength
  • Cut a small notch in the hammer head to insert the handle
  • Place some glue on the head end of the handle, then insert it all the way in, pressing it in place while the glue dries
  • If needed, add a dab of glue at the insertion point as well

Hammer Stand

  • Bend a strip of cardboard as shown into a bracket to support the hammer's handle pivot, again using either 5-ply or double up two strips for extra thickness
  • Glue the strip down to a piece of chipboard
  • Poke a hole through the handle and the stand for the pivot
  • Use a length of bamboo skewer or a toothpick for the pivot

Striker Assembly

The striker assembly is made with a gearbox motor and a paddlewheel with a popsicle stick attached to it. This will strike the hammer handle once per revolution when it is spinning.

First, we'll build the striker wheel, and then attache the motor to a small box to act as a stand.

Striker Wheel

  • Secure the popsicle stick to the paddle wheel with two zip ties as shown, with one end protruding from the wheel and the other end flush with the wheel
  • Be sure the stick clears above the axle mounting hole on the paddle wheel
  • Pull the zip ties tight
  • Trim the excess zip tie ends

Motor Mount

  • Place the strike wheel on one shaft of the TT motor, no need to screw it in just yet
  • Find and mark a the position of the opposite shaft when the assembly is positioned so that the end of the popsicle stick will reach approximately the middle of the box horizontally, and clear the bottom without hitting the ground vertically
  • Poke a hole through this point large enough to fit the shaft
  • With the motor shaft in the hole you just made, use a paper clip or safety pin to mark two points on the box where the motor's screw mounts will be positioned as shown
  • Poke the holes out a bit larger so they will fit the twist tie
  • Mount the motor inside the box with the shaft protruding as shown, using the twist tie to secure it
  • Place the paddle wheel on the motor shaft, then secure it in place with a small screw

Make sure the motor wires are outside the box, then close its flaps. Depending on the style of box, you may be able to leave two flaps open to help secure the striker assembly to the putting green later.

Move the hammer stand in place and you can see how the full striker assembly will work. However, the hammer is a bit heavy for the motor, so we'll add a spring assist!

Add the Spring

  • Use a piece of packing tape to secure the first coil to the top of the hammer as shown
  • Press the tape down firmly, then test pulling up on the hammer with the spring

This guide was first published on Jul 05, 2018. It was last updated on Mar 08, 2024.

This page (Build the Hammer Hazard) was last updated on Mar 08, 2024.

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