PROJECT 4: Assembling the Parts

So far, you've cut out all the armor plates and drilled all the holes for your project robot. You're almost ready to bolt everything together. In this project, you will prepare the polycarbonate plates, axles, motors, and other drive system components for assembly and fasten them to the base. You'll get practice in preparing Lexan (no sharp edges, as mentioned in Chapter 4), as well as your first taste of soldering with the motor leads, and cutting steel for the axles.

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.

Part 4: Cutting Down the Axles

This series of steps focuses on cutting down the axle material into usable lengths for the project robot. Although the hacksaw will make it through the material just fine, a reciprocating saw can save you a lot of time (and effort).


click on an image to enlarge it

Tip: A pair of soft jaws made from aluminum L-channel will prevent the vise from marring the shaft. A shaft that's been marred (has divots or burrs on the surface) may be one reason why it won't fit through a bearing. As mentioned in Chapter 10 (Mechanical Building Blocks), if a shaft won't fit through a bearing, it's usually not the bearing's fault.

Use a hacksaw or reciprocating saw to cut down the axles using the techniques described in Chapter 5 (Cutting Metal). The plain keyed shafts should be cut to 5-1/2" long, while the splined motor shafts should be cut to 6-1/4" long, including the spline.

The reciprocating saw will cut through the steel much faster and with less effort than the hacksaw. However, it may take a bit more practice to get a straight cut. Make sure to observe all safety precautions in Chapter 5.

Lightly clean up the edge on the disc sander. Make sure to hold the shaft perpendicular to the abrasive surface. Next, use the deburring wheel to put a slight chamfer on the end by turning the axle slowly while holding it into the wheel.

If you've got any burrs on the surface of the shaft from clamping it in the vise, you can remove them by filing the surface with a flat file until it's smooth.

The splined motor shafts had some residue on them from the heat treating process that interfered with the fit. I had to sand them a bit to remove the coating before attempting to insert them in the bearing blocks. You can tighten the shaft in the chuck of a drill press and use sandpaper to quickly remove this coating. I used 100-grit sandpaper. Keep moving your piece of sandpaper up and down the shaft to prevent wearing a thinner point in one place.



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