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abugroza

fps loss due defect parts?

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hi guys, I'm new in this hobby and I just trying to tinkering around my AEG until found fatal fault several days back

so, I got second hand unit dboys casv which with my ignorant I just put a stronger spring (M120) to fill my ego after put m120 G&P custom hi-speed motor (I was stupid back then)

several days after I'm about to replace nozzle, I realize original dboys piston teeth in horrible condition, still able to works but heavy worn

so I get shs piston 14 t full metal rack and put back original dboys spring, it caused lock up several times but cleared by firing it in burst (the 3rd gear haven't filed down) and it caused catastrophic result with bevel teeth broke down

now the gun been reassemble after getting new bevel gear, put back m120 spring and still having lock up even tho it's rare occasion which required me to reach AR latch to reset it, and when I chrono'ed it, it result just 320fps (380fps when I haven't mess with GB with anything on stock)

is it pre-enggagement so I having fps loss that much? or anything else I messed up, or should I file down the last piston teeth?

my unit spec:
inbar stock
gnp bucking
military action nozzle (got good compression with this cheap nozzle but not tight either to move)
prowin chamber
dboys casv gear set stock (except the bevel one) assume 18:1
shs 14t piston
m120 supershooter spring
g&p hi-speed m120 motor

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In this day and age of Western Consumerism. It does not apply for Airsoft parts. In the last 4 years parts have become less compatible. Not all parts are upgrades. Many are just stock parts in a bag and in some cases a downgrade.

 

First off an unprepared Full Rack Piston is very weak. Weaker than 1/2 rack pistons. If you do not know why...you should not be upgrading.

 

If you are running a double bearing system. This could be a factor on the binding issue. You do NOT need bearings at all. This is a legacy solution for a problem that no longer exists.

 

Pre-engagement is not your issue. This is a pre-engagement issue. Piston teeth that have been stripped. This happens when the piston does not move forward fast enough as the sector gear comes around again to try and pull the piston back.
maxresdefault.jpg

 

So, are you running double bearings. If you are...lose one set. As for your compression issue. Have you tested the compression between nozzle and hop-up chamber with a the paper/tissue test?

Edited by Guges Mk3
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thanks for respond

I doesn't get what is double bearing system, but if it mean 2 bearing as one in spring guide and one in the piston head, yeah I got that

and I change piston not for upgrading but, because the stock piston teeth are heavily worn, as I knew I'm just taking risk using a steel rack againts sector gear


just check paper over chamber hole and it didn't flew away, just shaken by gearbox vibration, but I did it in semi and put another bb one by one, am I doing it right?

 


post-94812-0-92902400-1508162930_thumb.jpg

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No offense, but your gun is a hodgepodge of various brands so it's no wonder you're having issues. One potential failure point would be the Prowin hop-up chamber, time and time again people post threads everywhere about issues with these chambers, I don't understand why people still buy them. In the photo of the stock piston there's definitely signs of premature engagement, probably because you installed a faster motor in the gun without taking measures to prevent this. You're also using a Supershooter (SHS) spring, it's not unlikely that it's incorrectly rated and isn't actually an M120 spring.

 

The lockup issue is probably because of the G&G M120 motor that has very little torque and a meh battery. It's also possible that it can be cause by poor shimming.

 

How consistent is the FPS? If it's very inconsistent you probably have a major leak somewhere, if it's consistent it's either the spring or possibly un-optimal cylinder to barrel volume ratio.

 

Guges Mk3 speaks the truth, the tolerances in the airsoft industry would cause lawsuits in other industries, that's how poor tolerances they're operating with.

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none taken,

I've change the motor because the stock one start smoking even running without load, at first I'm gonna put it back at first but it getting worst, so I keep using G&P one

and prowin, my stock chamber c-clip broke and I like prowin for it's nub placement compared to stock, and last time I checked chrono before I messed everything up it reach 380-379 with 0.2 stock spring, I just reseat the bucking last night and found uneven seating in chamber, but haven't chronoed it since

and for piston, I used it with stock spring with g&p motor for one game, so I dunno if it because stock spring or the shs is the culprit

the last chrono is result between 317 - 320 (after changing piston), before messing around with piston, I shot with m120 and found it leave marks more deeper in target paper

I'm gonna experiment again this weekend with stock spring, and if the shs is proven a lemon, it's looks like time to get another M120

and btw... is 110+ from modify enough to avoid PE??? but my motor still able to push it and not put my MB in stress too much?

my battery is GE power 2200v 20C lipo 3S

Edited by abugroza

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Guarder or Prometheus are the brands you wanna use for springs, higher quality and consistent spring rating. I presume you haven't changed the cylinder or inner barrel? As for the PME question, that depends on ROF and piston weight. With a piston assembly lighter than 20 grams you can do at least 35 rps safely with an M120 spring, a Guarder SP110 is equivalent to an M120 by the way.

Edited by Lefse

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11.1V...sigh.

 

I hear you LEFSE...but new player need to start with 2S instead of 3S...3S can exascerbate minor issues into big ones.

 

The piston damage could come from PE and it can also be caused by a bound piston that was over torqued by a motor that has access to high voltage.

 

I have seen stupid kids strip pistons in the field. Abbreviated case in point.

 

"My gun is bound up. Loan me your 3S battery...." Connects battery....click...hmmmrrrr...click...hmmrrrr...click...scratzes-crackeld...vreeeee...chata...scractly....vizzztatatatatatat < the last part is the sector gear bouncing over the partially stripped gears of the piston..

Me "If your gun is jammed...don't up the power!" Wishing I could strike this idiot on the head.

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I actually always recommend 7.4V li-po for stock AEG's, even for AEG's that's supposedly factory built to run an 11.1V li-po. Where did I talk about an 11.1V li-po in this case? Yes, I did say "meh battery", that didn't necessarily refer to lower battery voltage, I was referring to power output.

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11.1V...sigh.

 

I hear you LEFSE...but new player need to start with 2S instead of 3S...3S can exascerbate minor issues into big ones.

 

The piston damage could come from PE and it can also be caused by a bound piston that was over torqued by a motor that has access to high voltage.

 

I have seen stupid kids strip pistons in the field. Abbreviated case in point.

 

"My gun is bound up. Loan me your 3S battery...." Connects battery....click...hmmmrrrr...click...hmmrrrr...click...scratzes-crackeld...vreeeee...chata...scractly....vizzztatatatatatat < the last part is the sector gear bouncing over the partially stripped gears of the piston..

 

Me "If your gun is jammed...don't up the power!" Wishing I could strike this idiot on the head.

I learn it with bitter way but the bevel one that got hit, I read the forum too late and they says alot PE culprit is 3s battery and 3s is what I got with secondhand unit, gonna save up to get 2s as I haven't even got mosfet for 3s

 

I actually always recommend 7.4V li-po for stock AEG's, even for AEG's that's supposedly factory built to run an 11.1V li-po. Where did I talk about an 11.1V li-po in this case? Yes, I did say "meh battery", that didn't necessarily refer to lower battery voltage, I was referring to power output.

yeah I suspect it too, but is it still sufficient for 120-class spring?

 

and *sigh* I forgot to open forum as last night I just open my gearbox to check compression and didn't measure the piston weight

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You could pull an M170 spring with a 7.4V li-po with the right setup. You don't seem to know Ohm's law, it's the power output in watts that determines how much load the motor and battery can handle. The downside to using a lower voltage battery is that current goes up, but I doubt the current will be too high if you stick to standard ratio gears. A neodymium magnet motor would definitely be beneficial as it'll have more torque and won't require as much power to pull the same load.

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I actually always recommend 7.4V li-po for stock AEG's, even for AEG's that's supposedly factory built to run an 11.1V li-po. Where did I talk about an 11.1V li-po in this case? Yes, I did say "meh battery", that didn't necessarily refer to lower battery voltage, I was referring to power output.

In times when you talk about trigger response.

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found the problem with the fps loss, haven't chrono it tho, but I test with poor man's one and it cannot even gone through the side wall, but I found the chamber forward spring doesn't play and the chamber gone too forward and I suspect the huge leak going through there, after I reposition the spring , it sit right on the front of gearbox and can shoot through the can flawlessly (maybe I should make poor nerd's chrono with dust-catching-arduino)

and I've taken apart the gearbox, and measure the weight of the piston with head on it, it's SHS 14t piston (that I suspect to be fake) which I short stroke 1 teeth, file down 3rd and weight exactly 20gr , change back the motor to stock due the GnP pinion is sheet, and I cannot replace it yet

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In times when you talk about trigger response.

Yes, but not in this thread, I have primarily focused on the compression issue in this thread. I do favor 11.1V li-po's for my own builds because I prefer to use lower ratio gears and higher TPA motors to not just get better trigger response, but to reduce gear and motor noise. With a higher voltage battery the motor will have the RPM of a lower TPA motor without sacrificing torque so it will accelerate to the working RPM more quickly.

 

 

OT: No wonder you were having compression issues if the hop-up chamber wasn't seated properly.

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maybe I should put shim on the back of gearbox to make it need less to be tighten as what I see it feel about going upward for forward part and I'm afraid it make the nozzle punching upper wall of chamber and push the chamber forward

and thanks everyone, but one more question, what else you do to keep your chamber pushed against gearbox

and I will reconsider to change the gearset, or the motor for torque one, but my tech said my v2 reinforced gearbox is having limit option for gear set

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Your tech is not very experienced.

 

You can put "any" gear set in a V2 box. Why would there be a limited option? You can go 10:1 for HS or 64:1 for HT. We did this in the old days 14 years ago when motors were weak (especially ICS), unlike modern motors.

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Use shims on the rear of the gearbox to prevent the front of the gearbox tipping up as you tighten the buffer tube screw. If you remove the barrel and hop then look down the outer barrel with the bolt cover open, you should see the air nozzle exactly central with the outer barrel.

Find an O ring that fits over the barrel and push it right up to the hop up. Use a razor blade to cut it to about half thickness. This will push the hop against the gearbox. It might take a couple of attempts to get just right, but it's much better than the little spring that's supposed to do the job.

 

If your gearbox is 'reinforced' with the pointless lump of metal around the spur gear you won't be able to fit low ratio gears. But this is nothing that can't be fixed in five minutes with a Dremel.

Edited by Hangtight

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Your tech is not very experienced.

 

You can put "any" gear set in a V2 box. Why would there be a limited option? You can go 10:1 for HS or 64:1 for HT. We did this in the old days 14 years ago when motors were weak (especially ICS), unlike modern motors.

he doesn't said impossible tho, but he said he got to filed down some part, he showed me a guarder shell for example he fit modify modular gear set, and I think I should find another shell instead grinding it

 

my bad, for word of choice

 

Use shims on the rear of the gearbox to prevent the front of the gearbox tipping up as you tighten the buffer tube screw. If you remove the barrel and hop then look down the outer barrel with the bolt cover open, you should see the air nozzle exactly central with the outer barrel.

Find an O ring that fits over the barrel and push it right up to the hop up. Use a razor blade to cut it to about half thickness. This will push the hop against the gearbox. It might take a couple of attempts to get just right, but it's much better than the little spring that's supposed to do the job.

 

If your gearbox is 'reinforced' with the pointless lump of metal around the spur gear you won't be able to fit low ratio gears. But this is nothing that can't be fixed in five minutes with a Dremel.

thanks for chamber fitting tips, and gearbox back shimming ones, gotta try that one, for gearbox, maybe I'll pass, don't wanna mess with this one any further hehehe, I still feel bad for messing it before

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Oh...he is using Modify Modular Gear Set...

 

There are issues with those sets:

 

Old models the sector gear teeth is to narrow and should not be used with heavy springs.

Bearing retention nut is not secured. Can vibrate off and then gear falls out along with bearing set.

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I'm sorry for my rudeness for not replying, my unit works flawlessly last game so I'm exhausted and haven't replied, haven't chrono but my friend said it working well when he borrow it

and thanks guges, just dodge a bullet back then, maybe I should stock on SHS or some rational priced gear set for spare

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