I noticed that the High Strength 84 teeth gear using PA6. But all the other gears are using Acetal.
Someone told me that Acetal is stronger than PA6, and would be better using to regular 84 teeth gears rather than HS gear.
I wonder if anyone have tested of have a special knowlege in this area?
In materials science there is a distinction made between the “hardness” of a material and its “toughness”. I’m guessing in this case the material might be less hard but more tough, so that the teeth don’t chip as easily. Often, very hard materials are also brittle, as in the case of high carbon steel.
I’d say my kids have abused the heck out of the new 84 tooth gears this year and so far they haven’t chipped a tooth. They did, however, reinforce them on the sides a little to make sure they wouldn’t bend sideways under load. I’m not sure that reinforcement was really necessary but I guess it didn’t hurt.
Most teams actually avoid running 12 tooth gears into other 12 tooth gears because the metal gears have significantly more friction when meshing with other metal gears. Seeing as how teams aren’t breaking the gears I can’t see a reason to increase the strength especially when taking into account more energy loss.
As a former team mentor, I am opposed to metal gears. When we were building FTC robots we had someone get a finger or hand cut on the metal gears nearly every build session. The cuts were not bad, for the most part, but we spent a lot more on Band-Aids and Neosporin than we ever did with VEX.
Metal gears, especially machined gears, are way more expensive, too.