You read in Chapter 11 (Working with Roller Chain and Sprockets) about how roller chain and sprockets can be used to transfer power between rotating shafts. In this project, you'll do exactly that for the project robot. First, you'll make and install the tensioner blocks. Then, you'll size the chain and install it. Finally, you'll add any spacers, if necessary, to tweak the chain tension. Note: It's likely that the chains will be super oily, so you may want to get some latex gloves from the hardware store, or have lots of clean rags handy.
|Caution: Eye protection is required for all of these operations. Review all of the general power-tool safety protocols described in Chapter 5 of Kickin' Bot, as well as the sections that correspond to the specific tools used below.|
The chain tensioner blocks will push the chain up and take up some of
the slack, so that the chain is a bit tighter. The material selected for this job is Delrin, which is naturally
slippery, and can be used in applications where you need low friction. The blocks will be cut into half-rounds
out of a full rod.
click on an image to enlarge it
|Take the 1" diameter Delrin rod and place it on and 3/4" L-channel. Mark a 4" long line down the length of the rod.|
|Feed the rod straight into the bandsaw keeping the blade centered on the line. When you reach the end of the line, withdraw the rod, carefully pulling straight backwards, so that you leave a slot in the rod. Make sure to use water or WD-40 for lubrication.|
|Mark off two 1-3/4" lengths on the shaft. With the slot parallel to the bandsaw table, feed the shaft into the bandsaw blade on the first line. This should produce two half-round shapes. Feed the rod into the blade on the second line to produce two more half-round shapes for a total of four blocks. (Two for each side of the robot.)|
|Clean up the sides of the block on the disc sander, being careful to keep your fingertips away from the abrasive surface.|
|Also clean up the bottom of the block on the disc sander, being careful to keep your fingertips away from the abrasive surface.|
|Flip all the blocks over so that the flat side is facing up and apply the hole pattern with spray adhesive. Mark the holes with an automatic center punch. The half-round may be difficult to clamp in the drill press vise, but if your vise is equipped with a horizontal notch as shown, you can get one side of the half-round in there. Drill the two 1/4" holes in each block.|
|Install the blocks on the baseplate using 1/4"-20 x 3/4" long button head screws.|