Sector gear seems too far away from the piston head...

Discussion in 'Gun Building, Modifications & Repairs' started by guitarmaniak, Aug 7, 2012.

  1. guitarmaniak

    guitarmaniak New Member

    35
    0
    Ok, so this is the second piston I've gone through, with about 2000 rounds through the gun. The first time it broke because of a jam when I tried out a 6.02 barrel (bad idea...:mad:). I've talked with several techs and seen several tutorials on creating the right AoE, so I shaved down my piston teeth and shimmed my sector gear up so that it was flush.

    I opened up my gearbox and noticed that A) the back of the piston was ripped right off, and B) the sector gear seemed way to far away from the piston. The following pictures show what it looks like (sorry for the crappy quality pics):
    [​IMG]
    [​IMG]

    I do realize that the piston is too far back in that first pic, but it's hard to make my point when it's all the way in since there aren't any teeth left on the piston..

    It's hard to judge how the piston and gear mesh after the gearbox is shut, so I'm not sure if the bearing and piston grooves on the other half pull the two pieces together.

    Any thoughts on how to fix this?
     
  2. Mystery43_4

    Mystery43_4 New Member

    1,307
    2
    Santa Barbara
    Why are you running a half toothed Piston? You don't seem to need them, but then again I can't see your sector too well.

    I've had the 2 of those SHS half tooth pistons pick up teeth break exactly the same.

    What are you using to correct AOE? If Sorbo, what Durometer and how thick?
     

  3. guitarmaniak

    guitarmaniak New Member

    35
    0
    The guy at my local airsoft store gave me two little washers which I glued in between the piston and the piston head. What is the reasoning behind a half or whole tooth piston? My sector gear's top teeth aren't wide enough to have full contact on a full-tooth.
     
  4. CoppertopNeasg

    CoppertopNeasg New Member

    1,440
    2
    Boston
    A half tooth piston is for when you are running 32:1 gears.
     
  5. Adman234

    Adman234 Active Member

    3,022
    9
    Wildwood
    If the teeth are too wide for a full tooth, that is fine, because as long as any other teeth don't make contact, full tooth is better.

    Also, you need to glue on the metal rack of the piston, so that it doesn't seperate like that.

    Finally, please take a picture of the piston all the way forward, with the sector gear contacting the first tooth, as if it is picking up the piston.
     
  6. guitarmaniak

    guitarmaniak New Member

    35
    0
    Glue on the metal rack? The piston I have in the pictures is the one I blew out. And since the back metal tooth got ripped out, it won't look right pushed all the way in. I'll put one up anyways when iger off of work.
    Obviously something's either wrong with my AoE or these shs pistons are garbage... Lol. A piston blowing out after 2000 rounds is not cool.
     
  7. EDI1st

    EDI1st New Member

    2,062
    3
    Fountain Valley
    Washers......Jesus Christ who the hell are these techs?
    Adding weight to the piston only adds stress to the system....
    Even plastic/polymer washers.....
    You are suppose to add "sorbo pad" on the cylinder head to move the piston back....

    For AoE, you are not suppose to shave 2 teeth off completely....
    Just the first after the pick-up and some of the 2nd.
    SHS pistons are nice....run in 570fps setup....run in 60rps setup...
     
  8. Lefse

    Lefse Well-Known Member Supporting Member

    6,228
    1,842
    In the first photo the piston is not in the guide rails, if it was in the guide rails, it would be closer to the sector gear. It's true that you should not run a half tooth piston for this setup. It's also true that your tech is not a good tech, I would never correct AOE with that method, I always add rubber washers to the cylinder head. Not quite as good as sorbo pads, but a hell of alot better than adding washers to the piston. A regular sector gear will have full contact with a full teeth piston if the gears are shimmed right.

    I can't really confirm or deny how good SHS pistons are. I did instastrip a regular SHS piston in my P90, but that was most likely due to a jam, the piston seemed ot be of good quality, and SHS pistons have a very good reputation. Just buy a new piston and do a complete overhaul of the gearbox, using the correct mehtods. Shim from the bevel gear, add sorbo pad or rubber washer to the cylinder head to correct AOE, glue the bushings in place and so on. Even a mediocre polycarb piston will take some punishment if the gearbox has been tuned right.
     
  9. guitarmaniak

    guitarmaniak New Member

    35
    0
    Well it was a plastic washer and what looked like a copper washer. I heard that Sorbo pads decrease the fps though. Is that true?
     
    Last edited: Aug 8, 2012
  10. teamAggressivefoxxtrot

    teamAggressivefoxxtrot New Member

    16
    0
    Yes it decreases fps but not by much
     
  11. Lefse

    Lefse Well-Known Member Supporting Member

    6,228
    1,842
    Won't washers on the piston actually have the same effect, because they will make the piston stroke shorter, making it compress less air?
     
  12. CoppertopNeasg

    CoppertopNeasg New Member

    1,440
    2
    Boston
    If you are referring to copper washers those would add weight to the piston and increase the amount of force applied to the front of the gearbox. This will decrease the amount of times that the gun can be fired substantially if you use a lot of washers or a high power spring. Also if you want to decrease the length of your pistons stroke why don't you short stroke teeth off the piston and sector gear and add a sector delay chip.