about regular&HS gear material

[dereksc]

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?

Thanks

Alex

[Kevin_Boenisch]

https://vexforum.com/t/are-the-new-84-tooth-gears-more-flexible-than-you-might-expect/26799/1

And there was a thread where VEX explained why they are using a different material, but I can’t find it.

[dereksc]

Well, as far as I searched on internet, the HS 84 gear is softer, but in a good way, to protect itself…

[FullMetalMentor]

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.

[Kevin_Boenisch]

I am stupid, the post from VEX I was talking about was not in another thread, but in the thread I linked to.

Are the new 84-tooth gears more flexible than you might expect?

The material was changed from POM (AKA acetal or Delrin) to PA6 (Nylon) to increase the strength of the gear. Switching to PA6 increased the yield strength of the gear material by around 50%. In the past POM was chosen for most VEX motion components because it has a very low coefficient of friction and can even be self-lubricating in certain circumstances. Due to the higher torques that the 84t gear will see when used on robots, the VEX engineering staff elected to use Nylon, which also has a low coefficient of friction, for the gear.

The gear may seem less stiff than the existing high strength gears, but this is due to a difference in geometry, not material strength - the large size of the 84t gear makes it naturally less rigid than the smaller high strength gears. However due to the increase in material strength, it is capable of carrying more torque without failing.

Let me know if there are any further questions,

Charlie

[blatwell]

I would like to see more metal gears. Certain applications would do better with metal while synthetics are better for other applications.

[tabor473]

I would like to see more metal gears. Certain applications would do better with metal while synthetics are better for other applications.

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.

[Rick_TYler]

I would like to see more metal gears. Certain applications would do better with metal while synthetics are better for other applications.

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.

[OscarMNOVA12]

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.

Second this as a former FTC and VEX Participant. We also generated a good bit of heat with the Tetrix DC motors and metal gears.

I know for my VEX teams when using the metal pinion gears we applied a tiny amount of grease and just ran them connected to motors to lubricate them.