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dsg setup , porting cylinder?

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hi guys, so doing a dual sector gear setup on my cyma ak 74u , got really good rate of fire but it seems like i have an air seal problem , fps is terrible and i had some inconsistant misfeeds , that could be the mag tho {delayer chip is fitted} , could my fps issue be down to barrel length/needing to port the cylinder further down? barrel length is like 290mm ,cheers

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The dual sector gear only compresses the spring halfway. Certainly the spring only half compressed has much less power than it fully compressed. You will need a much stronger spring to get higher fps.

I'm not sure the delayer helps here or not. Since it fires twice with one cycle, maybe with the delayer the nozzle can't close fast enough.

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the fps/range is totally unusable , like 10m and totally inconsistant  {to where i think theres a problem } ,  i understand like you say its ony bringing it back halfway so fps will be lower but that much on stock spring? ,  i do have the spring spacer to put in but i just wanted everything to work although at a lower fps perfectly first as its pretty hard splitting the shell with the spacer installed and the spring compressed , i think you might be on to something with the chip though so ill remove it and see whats up ,  one of them new fangled quick change spring gearbox shells would be an absolute treat here!  cheers.....

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No clip is ever used, just a trimmed tappet fin

The only delay you can use to draw back tappet/nozzle a smidge more is a busted inner race of a bearing

(or a metal tube/pipe 3mm ID x 4.5/5mm OD or there abouts to retract it just under 1mm more but watch for nozzle hitting the cylinder head at full retraction. New or newish tappet plate without wear and perhaps a SHS tappet plate as they do seem to retract a smidge more than others without any delay clips imho)

You can't use the regular delay clips coz you simply don't have the time or timings

The nozzle needs to retract back enough for a split second, the bb feeds by slipping in front of nozzle

without catching on any bucking lips and chamber asap within a time frame half that of a regular setup

 

People think delay clips are the be all & end all of feeding issues.....

In fact they are not and in some cases - not just DSG's but also SSG's they can make it worse

fit the delayer the wrong way, full tappet fin in a DMR with powerful spring & piston can be building compression before bb is properly chambered is one example. The DSG setup without a mofo delay cycling at higher speeds proves that delay clips are not the miracle cure for misfeeds that many think they are. They keep the tappet/nozzle retracted longer and perhaps a wafer further to assist in feeding but really if all worked correctly the delay clip would not be needed in most cases. Yes in certain builds I may use a delayer, but more for a simdge more possible retraction than duration as I often part trim the fin to ensure the tappet isn't held open too long. Also I check/file very slightly the fin after paying very close attention if I suspect it may catch or impede on either the sector's axle or spur's axle in operation. (Some gears/axles are thicker than others and in some builds this can all make slight differences restricting the tappet/nozzle's smooth effective operation)

Phew - soz but people do think slap stuff together and it just works like Lego or Meccano

(ergh often TM compatible is not quite 100% TM compatible)

 

 

Shave/sand front of tappet plate, use correct nozzle, strong tappet spring etc....

hop/bucking spot on without big lips and bloody good mags to feed at speed

 

Cylinder - might as well use a full or 3/4 cylinder or whatever if you haven't got a correct one to hand

The piston only comes back about 55-60% of the way anyway

(8 teeth plus pickup & slip = 9/9.5 retraction compared to 16 being 17/17.5 retraction/stroke)

If you have a port just at the end of half stroke great but if not go with anything that is decent

(you can always make your own ports at the final half stroke to help filling cylinder)

The main thing is a good steel polished cylinder and a great piston head + o-ring to seal sweet asap 

(the way the o-ring falls allowing air to quickly fill the cylinder & re-seal on release etc...)

 

DSG tbh is over rated, a good short stroked SSG setup comes fairly close

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Sector delay chips don't work with DSG sectors. Trim the tappet plate and ensure everything is moving smoothly.

If you're using a stock spring and a heavy stock piston then you could actually be getting pre engagement. That could explain the inconsistent performance as the sector would be picking the piston up from a different place each cycle. You need the heavy spring to ensure the piston has completed its cycle, not just to push the fps up. Likewise the light piston.

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cheers for the info guys, this is going to sound funny but i thought i had fitted a delay chip, turns out i didnt lol ,would of needed two anyway, {its been atleast 6 months since i actually had this box apart}  i had it in my head that i fitted one but that must of been when i played with my spetznaz gearbox again that was ages ago, anyway i split the box open before and found the cylinder head to be a real weak seal so just ordered a shs cnc double sealed one.. i did shave off a tooth and abit of the next tooth on the piston iirc so the sector gear allways picks up the first tooth on the piston and sg clears the teeth but ill use the spring spacer once the new cylinder head arrives , didnt know pre engagment could happen because of a weak spring, i am using an alloy shs piston aswelll as i wanted a decent metal tooth for the sector to pickup , but then again if pre engagment was happening would the shots/gearbox sound different ?. dry firing it sounded really good! and the cycle's sounded consistent/complete  , which leads me to then think air seal problem ? , ill look further into the tappet plate/nozzle/hop ... cheers guys

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The SHS alloy pistons aren't light. Get yourself one of the pre lightened SHS ones with the full metal rack, epoxy the rack in and run it with a light plastic spacer instead of a bearing.

If it's a DSG  with a fairly modest ROF (motor/gears /battery?) then the sector gear isn't actually rotating all that fast. That combined with the alloy piston and the weak spring could mean that the sector will pick up the piston just fine without it sounding bad, regardless of whether the piston has completed its stroke. Have you measured fps on semi auto?

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on semi auto i dont remember what it was like , pretty sure it was just the same tho , i'll check out the pistons , had no idea weight was an issue with these . cheers...

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It sounds like you could do with some more research into DSG builds. They're not as difficult as can be made out by some, but they do have a very specific set of requirements that need to be met or they'll either just not work, break bits and usually both. Perhaps if you give us a complete list of what you've got, and what you're trying to achieve we can point you in the right direction, because at the moment you seem to be struggling somewhat.

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well put everything back together the other day with new cylinder head and light weight piston and the spring spacer also had to replace the trigger as part of that broke off , Had a chance to test it out tonight and what ever the issue was is long gone!! :)   R.O.F using a 9.6v nimh battery is pretty decent,  consistency is there and no miss feeds, i would guess the fps is around the 250-300 area ,i'll know more when i chrono it at the next game, i can deffinatly use it as it stands but going to upgrade the wiring , new hop rubber and polish the hell out the barrel  , thanks for the help....

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