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Building a Powered Wheel for a Robot

June 15, 2016
Building a Powered Wheel for a Robot

I chose the 32 pitch .500 bore aluminum hub gears in the following sizes: 48, 64, 72 & 76 teeth.  I also selected a pinion with 11 teeth for the motor shaft.

To begin, I turned some 6061 aluminum down on the lathe to an outside diameter of 3.270 x .500 thick; I also bored a .500 hole in the center

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I knew there would be several different operations for the CNC so I machined out a set of soft jaws for the vise so the stock could be clamped easily without having to find the center each time I load a different part.  For the 14mm holes, I chose a .250 end mill cutter.  A rough cut is made then a cleanup cut completes each hole.  The CNC interpolates each hole so using the same cutter; I can make almost any size hole I need.

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With the stock mounted, I ran a basic pocket program to hollow out the hub.  Once again a rough cut followed by a cleanup cut leaves a nice finish.

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Once the piece was pocketed, I was ready for some details.  Below is a screen grab of the CAD program on the left and the CAM G-code on the right.  The CNC will use the G-code to machine the part.

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I double checked the tool path and then let the first program run.  The 14mm hole at the top is closer to the sidewall so I machined deeper to allow clearance for the pinion.

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An additional program drilled all the holes I would need.

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The completed piece turned out almost perfect the first time.  I also ran a program to machine ServoCity’s .770 mount pattern so the hub would be easy to attach.

Using the 64 tooth gear, I attached the gear to the wheel and assembled the pieces.

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Using the same 11 tooth motor pinion and moving the motor to different positions on the hub, I can run the ratio that works best for any projects I want to build using this wheel.  Numerous motor ratios are available from 26 RPM to 2,737 RPM.  These particular motors have the encoders already attached for feedback.  Here’s a picture of the finished unit:

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I had to add small spacers to each motor to adjust the depth of the motor shaft.  I don’t like cutting the shafts of motors so the spacer is a good choice.  Here’s another picture of the finished units along with a set of prototype units with brushless motors just for fun.

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Stay tuned for more from David Nyman.