Aoshi Shinomori

I searched the forum and found nothing. Could someone explain exactly what it is? I know it's supposed to help strengthen gears and the like, but how is this accomplished? Anyone considered having it done? I've heard a lot of complaints about the Aisin 6 speed on the RX8, would shot peening gears make any significant differences on strength? Thanks in advance everyone.

draco067

shot peening introduces residual compressive stresses into the surface of the metal, introducing dislocations and effectively strain hardening it

trophymaker

Simply compacting it?

Aoshi Shinomori

I think I sort of understand, but the more important question is, will it help the RX8s transmission handle more power? Say how effective would it be with forced induction? I don't know if these questions can be answered without someone actually having this done, but I got curious.

shaunv74

It really depends on where the weak link in the tranny is. I don' t know much about transmissions but I understand shotpeening. Draco067 was right on. You shoot the components with tiny metal ***** at high speed with an air gun "shot-peen". This is essentially like cold hammering the components all over very hard and very fast. The result is you reduce the possibility of having surface imperfections that can cause stress rupture points and hardening the surface giving it more uniform wear properties. It will give you more stress margin in the material and you can assume yield stresses closer to your theoretical limit but you're not going to drastically change the abilities of the material. It's a good idea to strengthen your gears and components but what you really want to know is what is going to break first and how much extra stress you are going to put on it. At that point you can see if shot peening will help or if you need to upgrade the material.

There are some threads out here about broken transmissions and rear diffs. See what they said broke first.

Aoshi Shinomori

Thanks man, that's a bit more clear. I'm gonna go check out some of the broken transmission threads and figure some things out. Later.

oi812

Shot Peening can't be used on gears that are already manufactured. The shot peening process as described above is correct, and the strength increase is caused by the compressive stress at the surface caused by the steel shot hammering the surface. It also leaves a pretty rough surface finish (think thousands of little dents). Gear teeth have to and very smooth almost polished surface finish since the teeth of one gear has to rub and slide on the mating gear (with a little film of oil between). You could shot peen a gear before grinding the teeth, but the benefit you got from the peening would be lost once the teeth were put on, so it doesn't make sense.

The only way I know of to strengthen a gear that is already manufactured is to cryogenicly treat it. http://www.metal-wear.com/Cryogenics_heattreat.htm and many others like them... That being said, like someone said above, I'm not sure the gears are the weak link.

I have not seen the actual failed parts of any RX8 transmissions, but from reading about the failures on this board (and seeing a few broken transmissions in the past) I can take a guess. I think that people are bending shift forks first, then causing incomplete gear engagement, then causing gear failures due to the fact they are not completely engaged before getting back on the power. The reason I think this is happening is that most people say they have trouble getting into one or more gears prior to "total" failure. It could be that using too much force on the shift lever, or trying to shift too quickly.

Gomez

I'm hoping to sort to the first to second notchiness with Richard Paul's short throw shifter. Although I am not a demon shifter, I figure the less time I am spending on the gear change will reduce the mismatch in gear speed and allow the synchros to do their job better. The other thought though is that I may graunch more shifts by being a little too fast for the box.

I think most people are bending forks on this gearchange....

Gomez.