Removing teeth from Supercore piston

[RSM]

No, thats short stroking which releases the piston earlier than normal - it does lower FPS because the piston doesn't acheive full stroke but thats not what we are talking about here.

 

Angle of Engagement is all to do with the piston pick up tooth (big one at the open end) and the first tooth on the sector gear. These parts effectively slam into each other during gearbox operation. Normally they meet at an angle which is fine in a stock set up, in high demand set ups you need to minimise the angle so both teeth faces are flat against each other at the point of contact. How to do this has already been discussed.

 

The removal of the two teeth after the pick up tooth (still at the open end of the piston here) is necessary because more often than not, once you have adjusted your angle of engagement those two teeth will be where the pick up tooth will be, so they need to go to remove interference between piston and first sector tooth.

 

 

[[BS]_MARS]

So with the shimming process between the piston and piston head, is their a set amount or do you need to mod the gear and piston teeth first then shim it for the best engagement?

[ertgunner]

no you remove the second one near the spring guide end

 

 

[[BS]_MARS]

What about the other 2 teeth and the Sector gear tooth you have to remove?

[Utty]

So with the shimming process between the piston and piston head, is their a set amount or do you need to mod the gear and piston teeth first then shim it for the best engagement?

No. You measure how far back the piston has to be seated for its pickup tooth to be optimally engaged by the sector gear. Then you shim the piston head that amount.

 

You will then need to remove the 2nd to last piston tooth (the last is the fat pickup tooth), and maybe some/all of the 3rd to last, maybe even some of the 4th to last, to prevent these teeth from conflicting with the sector gear after shimming the piston head.

 

You do not remove any teeth from the sector gear.

[[BS]_MARS]

That makes sense now. So, how do you know if you need to remove the 3rd and 4th teeth and if not entirely, how do you know how much to remove?

[Corvid]

That makes sense now. So, how do you know if you need to remove the 3rd and 4th teeth and if not entirely, how do you know how much to remove?

You almost certainly won't need to remove the 4th tooth. It would probably be easier to totally remove the 2nd and 3rd teeth straight away. If you are running a high-speed set-up this should be done as standard. That makes it FAR easier to see what the "correct" angle is, and leaves the 4th tooth intact to show up any premature engagement. I personally don't remove any more teeth than that, although you could remove most of the 4th if you wanted to. I leave it intact because quite simply, if you are seeing wear on the 4th tooth, you are pushing the limits of premature engagement and need to get things sorted. You may only need to space a few millimetres, but some AEGs (like the ICS M4 for example) need almost 10mm of spacers. This is what the AoE looks like on a stock ICS M4 with a TM piston:

 

 

As you can see, there would be just enough space for the sector to clear the 2nd and 3rd teeth. When adjusted properly, the AoE looks like this:

 

 

As you can see, there is no way in hell you'd manage that without taking off the 2nd tooth and the vast majority of the 3rd. The 4th tooth is just fine.

[aznriptide859]

Wait, so you cut off the 2nd and 3rd tooth BEFORE you do the AOE mod?

[Utty]

Wait, so you cut off the 2nd and 3rd tooth BEFORE you do the AOE mod?

You don't have to, but you might as well. Whatever you do, the 2nd and 3rd teeth aren't really needed anyway, so you may as well start with lopping them off.

It doesn't matter which order you do the things in, as long's you end up with a correctly shimmed piston head and the correct missing piston teeth.

[[BS]_MARS]

It seems like gearbox parts are in need of a redesign...

 

So, in closing, you should do this when running high FPS (around 400 or above?) or high speed setups, correct?

[FaRKle]

So, in closing, you should do this when running high FPS (around 400 or above?) or high speed setups, correct?

 

High ROF. Although it's a wise idea to just automatically do this to all your setups as it will still add to durability.

[Utty]

It seems like gearbox parts are in need of a redesign...

Indeed. The fact that upgrade pistons come with all teeth in place is ludicrous. Of course, it's no problem to remove teeth yourself - if you know you're supposed to.

 

It's also silly that AEGs outputting above-average fps and being 12V/lipo-ready out of the box still come with all teeth in place and bad AOE.

 

However, dboys AKs come with a missing 2nd to last tooth on the piston.

[[BS]_MARS]

Odd...