Hobbies And Interests
Things You'll Need
Instructions
Purchase a plastic miniature rack from a model retailer. One that is about 2 inches long is ideal for a mini rack and pinion. Use a ruler to measure both the width and the length of your rack, so you can make good housing for it, and note down the dimensions.
Cut a length of 1/2-inch by 1/2-inch balsa wood strip to twice the length of your plastic rack using a hacksaw. Now make a second strip of exactly the same size. Position them side by side on top of a sheet of 1/8-inch thick balsa wood that is of a suitable size. Make sure the two strips are flat on the sheet, parallel to one another and with their ends in line.
Push the two balsa strips towards each other so that the distance they are apart is the width of your miniature plastic rack. A good way to do this is to set the rack between the two strips. Hold the balsa in place by gently pushing down with one hand and slide the rack from side to side to ensure that it can move freely.
Fix one of the two balsa wood strips that you have cut to the base sheet with wood glue. Allow it to dry before continuing.
Set your plastic rack next to the strip you have glued in place such that it sits midway between both ends. Make sure the teeth of the rack face upwards. Place a plastic pinion gear on top of the rack right at the half way point. Check that the pinion's teeth interlock with those on the rack and that it sits in a parallel position to the balsa wood strip. Mount the pinion in place to the strip with a small nail. Carefully hammer through the center of the pinion into the balsa wood strip.
Prevent the mechanism from sliding around without control when you turn the pinion by gluing the second balsa wood strip into place on the other side of the rack, in the way that you lined it up before. Turn the pinion both clockwise and counterclockwise to demonstrate the rack moving back and forth.