Airsoft Canada - View Single Post - What caused this failure? (Piston stripped)

ThunderCactus · February 17th, 2016, 21:17

TLDR: AOE matters, but it's a short range of engagement, not one specific point.

Weaker nylon pistons tend to get more wear on the pickup tooth when engaged at an angle than when they're engaged flat.
Ultimately though, perfect AOE DOESN'T make any difference on POM and metal rack pickups since they're harder and don't deform nearly as much.
I've had incorrect AOE on my system supercore piston for over 300k rounds and it's got next to no wear on it.
Pretty sure the AOE on every systema M4 ever made is off, clearly hasn't made any difference since those racks last forever when they're MADE right.
Basically it just makes people feel better lol
Although shaving the second tooth does help reduce pre engagement and wear. Sometimes the sector comes around a bit too quick and DOES actually clip the bottom profile of tooth #2 off, which later leads to failure of that tooth. And although that isn't particularly damaging since we shave it anyway, the bit of plastic circling around in the gears IS, and does jam up gear trains.

That being said, the angle of engagement still does need to be within a certain range to reduce wear. As you said, the gear profile is involute, so they're designed to work at a certain range of angles. And I've seen some people be WAY the fuck out.
If the piston is too far forward, the pickup tooth tends to be impacted on the bottom which affects the distance to tooth #3, if you shaved tooth #2.
If the piston is too far back, you can clip tooth #2 if it's still there, or apply all the gear's force at the bottom edge of the pickup tooth which may or may not contribute to breaking off the back end of the piston.

But shaving the 3rd tooth is just plain bonkers. By the time the sector has crossed the gap of TWO missing teeth, the profile is no longer lined up properly with tooth #4, and that causes serious problems very quickly. The teeth are designed to engage tooth to tooth smoothly, with a profile close enough to skip one tooth reliably, but not two.

What I really miss is helical gears. Not for torque transmission or anything (They're kind shitty for torque transmission when paired with radial bearings without being double helical), but just because they were nice and quiet.

February 17th, 2016, 21:17	#20
ThunderCactus Not Eye Safe, Pretty Boy Maximus on the field take his picture! Trader rating Join Date: Feb 2007	TLDR: AOE matters, but it's a short range of engagement, not one specific point. Weaker nylon pistons tend to get more wear on the pickup tooth when engaged at an angle than when they're engaged flat. Ultimately though, perfect AOE DOESN'T make any difference on POM and metal rack pickups since they're harder and don't deform nearly as much. I've had incorrect AOE on my system supercore piston for over 300k rounds and it's got next to no wear on it. Pretty sure the AOE on every systema M4 ever made is off, clearly hasn't made any difference since those racks last forever when they're MADE right. Basically it just makes people feel better lol Although shaving the second tooth does help reduce pre engagement and wear. Sometimes the sector comes around a bit too quick and DOES actually clip the bottom profile of tooth #2 off, which later leads to failure of that tooth. And although that isn't particularly damaging since we shave it anyway, the bit of plastic circling around in the gears IS, and does jam up gear trains. That being said, the angle of engagement still does need to be within a certain range to reduce wear. As you said, the gear profile is involute, so they're designed to work at a certain range of angles. And I've seen some people be WAY the fuck out. If the piston is too far forward, the pickup tooth tends to be impacted on the bottom which affects the distance to tooth #3, if you shaved tooth #2. If the piston is too far back, you can clip tooth #2 if it's still there, or apply all the gear's force at the bottom edge of the pickup tooth which may or may not contribute to breaking off the back end of the piston. But shaving the 3rd tooth is just plain bonkers. By the time the sector has crossed the gap of TWO missing teeth, the profile is no longer lined up properly with tooth #4, and that causes serious problems very quickly. The teeth are designed to engage tooth to tooth smoothly, with a profile close enough to skip one tooth reliably, but not two. What I really miss is helical gears. Not for torque transmission or anything (They're kind shitty for torque transmission when paired with radial bearings without being double helical), but just because they were nice and quiet.