| Making Nylon Threaded Rod Worm Gears |
| Concept: Take two threaded rods, lay them side-by-side, and intermesh their teeth together. A third threaded rod will also intermesh with the first two rods. If the first two rods are bend to form a circle, they form the teeth of a worm gear. The third rod becomes the worm. I used Nylon threaded rod because they are flexible yet tough. |
| Construction: I used a 1/2-inch plywood between two sheets of 1/4-inch plywood. I used my router and a circle maker attachment. The two 1/4-inch sheet are 1/2 inch larger in diameter than the 1/2-inch sheet. This forms a natural groove for the threaded rods. I use #8-32 bolts to clamp the boards together in case I need to replace the Nylon threaded rods some day. |
| How to attach the rods to the boards: First, I tried using Hot Glue gun and gluing the rods the boards. The glue did not hold to well. So I use my backup plan. I went a hobby store to pick 1/16-inch steel rod to use as pins. I drilled 1/16-inch holes across the groove to hold the rods together. The pin idea works well. I made one mistake. On one drill hole, the drill bit went side ways. It destroyed a thread on one rod and partly destroyed the opposing thread on the other rod. I don't think this will be a problem since the worm engages about twenty threads on each rod. Missing one thread should not be a problem. |
| Recommendations: If I would do it over again, I would use 3/8-16 threaded rods with 3/4-inch plywood. To make the groove, I would use 1/4 thick strips of wood and attached them near the outer edge. (See Picture) |
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| FAQs: Where can I get Nylon Threaded Rods? McMaster-Carr & MSC Direct. How is my Az gear and is its gear ratio? The gear is just over 22-1/2 inches in diameter. The gear ratio is 1409:1. How about accuracy? I did the laser pointer test. This test is simple. Take a laser point and attached it to the gear. Mark the spot at where the laser beam is pointing. I use a sheet paper taped to my garage door which was 19 feet from the gear. I use Mel's software to command the motor to move the gear 120 degrees. I repeated the command two more times to get a total of 360 degrees. The laser beam returned to the pencil mark on my garage door. I then repeated the commands but in the opposite direction. Again, the laser point returned to the pencil mark. I think the test was a total success! |
| Questions/ Comments? |
| Drill bit went sideways. Results: Two damage teeth. |
| The Hot Glue Test |
| Using a Steel Rod as a pin. |
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| This page was updated on 05/28/2004 |
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| Below are more pictures for your convenience. |
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