Edit: I just posted the below reply only to see that
@emtbeast had been writing up some very similar thoughts at the same time. I'll leave my post as-is though, as it describes a slightly different "dual-gear" method of construction, although that dual-helical setup he shows seems like a likely candidate too...I can't wait to see some cutaways or the first ballsy Youtuber to crack open the casing and show us what's inside the M2S!
@
Zimmerframe said: "I believe the m2S now has some helical gears to reduce the noise whilst the M2 sticks with straight cut."
It would be really nice to see a cutaway image of the new M2 and M2S to confirm, but from the various M2/S articles I've read, it's described as the opposite of what Zimmerframe said. The M2 uses what are described as "new" helical gears (vs. the M1) and the M2S uses "dual-gears". Different media sources describe this a bit differently, and I think they're all just regurgitating what the Avinox press materials said, without having seen the internals themselves, which has lead to different descriptions of this gear situation.
The part that leads to the lack of clarity is that the M1 planetary gears were
already helical, which you can see in the M1 cutaways (see image below). So when we see a media sources talking about the M2 using "new" helical gears, it is unclear if they mean a refined design of the existing helical planetary gears, or if they have truly added new helical cut gears in the locations where the M1 previously used straight cut gears.
View attachment 181748
Regarding the question about the "dual-gears" of the M2S, I have seen that tech variously described in different media sources as being either in place of, or in addition to the helical gears, and I haven't seen it specified if the dual-gears are helical dual-gears, or if they are straight cut dual-gears. Based on my understanding of how "dual-gears" work, I would image that they are using them in place of the old straight cut gears, as it seems like it could be pretty tricky to get them to work in a helical application. The reason being that dual-gears are typically 2 gears functioning as a parallel unit, with either the teeth of the 2 gears slightly offset, or with some sort of springy element that allows a little free movement between the 2 sets of parallel teeth. That allows one set of the dual-gear teeth to tightly mesh with the front side of the opposing gear, and the other set of the dual-gear teeth to tightly mesh with the back side of the opposing gear, eliminating the free play that would normally be required to prevent binding.