This technique is included to illustrate how to correct a positioning error. What if you find the need to move a component after everything is already mounted? Do you have to remove everything from the base to do this? No, that would be very time consuming. Instead, you'll make a template that you apply to the outside bottom of the robot, and drill it with a cordless drill. The trick is that your template will include two through-holes for the existing tapped holes, and guide holes for the new positions. You will bolt the template to the robot with the through-holes and existing tapped holes. This guarantees correct alignment. [Note: I have already corrected this positioning error in the pattern provided to you, so you don't need to do it. Hey, it wouldn't be realistic if didn't make any errors, right?]
click on an image to enlarge it
|When I went to install this speed control in my original parts layout, I found that the motor terminals were a little too close to the chain for comfort. I wanted to add extra space between those terminals and the chain, but most of the parts were already installed. By using a template and drilling on the bottom of the robot, I was able to avoid disassembling everything.|
|You'll make the templates out of spare 3/16" plate. You're only interested in the holes, so you can rough-cut the plates on the bandsaw. It doesn't have to be really precise. Apply a drill pattern to the rough-cut plates that includes through-holes for the old tapped hole positions as well as tap drill holes for new hole positions. Remember that the drill sizes for through-holes and tapped holes are different.|
|Remove all electronics (speed controls, receiver) and put them in a plastic bag before doing any drilling. The chains and all mechanical components can remain as long as you vacuum out the robot after you're done.|
|Flip the robot over and bolt the templates on, as shown. Make sure that the plate is flat and tightened securely to the robot's base. The holes provide a guide for the drill bit. For this operation, you'll be using the small drill size to create the holes to be tapped (threaded).|
|Caution: Make sure to wear eye protection when drilling the holes.
After drilling, the template can also double as a tapping block. Loosen it from the base and hold it in place so that the through-holes in the template are directly over the new holes that you're about to tap. Make sure that it doesn't ride up on any of the screws poking out of the bottom of the robot, and that it sits flat on the surface.
|After the operation is complete, you can see that the speed control terminals are farther away from the chain, giving me a bigger safety margin.|