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Forum - Gear selection

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[#47]
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So far I haven't broken any gears, but I also avoid using 8-toothed and half-width ones. Is it always good to avoid them, or can they be used successfully in some cases?

What about the worm gear? It generates a lot of friction, but also provides a lot of speed reduction. The alternative is using a lot of spur gears (especially when avoiding the 8 tooth gear); is that better?

Posted by Torso on 29 September 2015 at 10:47.
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I haven't had any trouble with 8t gears breaking, but I can offer some thoughts on how to use them.

  1. You can use the newer style, stronger-looking gears
  2. You can use them in places in the geartrain where the torque is low - either using them to drive clutch gears, or having them close to the motor
  3. You can double up on the gears - having two drivers on the same shaft engaging two followers on the same shaft (though, obviously, a different shaft than the other one!) - this halves the stress on each gear

For your worm gear question, consider that worm -> 40t is a 40:1 reduction. If you're avoiding 8t gears, the best you'll get in spur gears is 16 -> 40 = 5:2 reduction. You'd need 4 of them consecutively to get the same reduction (~39:1). Does 1 worm gear generate 4 times the friction as a spur gear pairing? Even if it does, the space and complexity savings would be enormous. I'd suggest that if you need that amount of reduction, then a worm gear is the way to go.

Posted by Captainowie on 1 October 2015 at 13:26.
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I've never broken a 20-tooth half-width gear in a GBC, but I can't think where I've used one in a stressful place. I've broken a fair share of half-width 12-tooth gears. Usually I break them when a gear train jams. I have overloaded them and broken them over time, too, particularly in my Akiyuki train modules.

If you don't overload them there's no particular reason to avoid them.


Posted by ALittleSlow (administrator) on 16 October 2015 at 02:52.

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