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The Big Gears on my camera rigs are always driven by a smaller gear, not the other way around. That way the servo that rotates the smaller gear works less, and the rotation produced is slow and smooth. Click on the thumbnail to see a larger image. |
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For the Video Rig I used the Traxxas #4472, 72 tooth-32 pitch gear. I bought this at the local hobby RC store. I like 32 pitch because the teeth are large and there's plenty of room to adjust the mesh for gear wobble. 48 pitch gears have smaller teeth and therefore the gears must rotate that much more concentrically on their shafts. |
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I used an 8-32 bolt for the shaft. In order for that to work for the Traxxas gear I needed to do some modifications. A small bronze spacer purchased at the same time as the gear has a 0.250 inch ID and a 0.375 inch OD. Oddly enough the center hole of the big gear has a diameter of only 0.370 inch. I used telescoping brass tubing in the center of the bronze spacer to create a new ID that the 8-32 bolt would fit snugly through. |
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Three pieces of brass tubing were cut and fit into the ID of the bronze spacer. Then the spacer was fit over the 8-32 bolt and held in place with double nuts. By chucking this assembly into the vertical lathe (drill press) I was able to turn the OD down to .370 inch with fine grit sandpaper glued to a flat wooden block. |
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The lighter colored ring in the center of the bronze spacer are actually 3 pieces of brass tubing glued in place. Turning the OD of the spacer down by .005 inch enabled it to fit into the center hole of The Big Gear. |
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A fender washer and nut with lock washer on each side complete the gear/shaft assembly. |