The art of DOWNGRADING???

Ghost4893

Downgrading is something I don't want to do but have to meet 1 Jule for competitions I have to. IT shoots about 410fps wit standard spring! I've put a M90 in it but the ROF is way up and cut the piston to bits in 500 rounds! What do I need t do t sort it? thanks to any1 that can help me!

Witcher

Ghost4893 wrote: »

Downgrading is something I don't want to do but have to meet 1 Jule for competitions I have to. IT shoots about 410fps wit standard spring! I've put a M90 in it but the ROF is way up and cut the piston to bits in 500 rounds! What do I need t do t sort it? thanks to any1 that can help me!

Buy another piston:pac::pac:

But seriously that's the answer, a prometheus hard piston might hold up better to the increased rof.:)

Puding

Downgrading is something I don't want to do but have to meet 1 Jule for competitions I have to.

you have to do its because its the law not just because you want to go to a competition

anyway to help you will need a little more information as you getting premature engagement of the piston by the sounds of things, what model is the aeg? what battery are you using?

Ghost4893

A new piston is where I'll start but don't want to mangle it as quick as the last 1. And wiv a quick look on the net it looks like it might be a standard problem wiv them? Every 1 is sold out of the long piston which has 19 teeth instead of the 16 teeth found on all other guns. The batt is a standard 9.6v 1200 (passable 1500??? can't remember without going to look!) Its A&K SR-25 about 5 months old with 20,000 ish rounds fired through it wiv no stoppages till now! :mad:

Firekitten

9.6volt is NOT standard.... you ought to be running an 8.4 volt battery with the gun un upgraded THAT is why it ate the piston... a 9.6 and a downgrade would have made it empty mags faster than turnming it upside down and shaking...

Drop to an 8.4 volt battery, grab a new piston, like the one bellow....

http://shop.ehobbyasia.com/upgrade-part/parts-upgrade-aeg/pistons/guarder-piston-psg-1-econ.html <-- One Long type Piston for your blatting pleasure....

And The gun should be fine... The gun isnt designed for 400 fps. It will run just as well at 1J...

Ghost4893

Firekitten thank you very much for that post, I'm going rite now to try that out. Your a star, no mater what anyone else says :P As for the batt 9.6v is what came in the box when it was new!

Firekitten

That is.... curious... and no problem Ghostie

Masada

That gun should be perfectly fine on a 9.6, as far as i remember it actually comes with one as standard,
This above piston is also one designed for use with a helical gear set and has very little surface area for the sector gear to contact, it'll wear faster and its not suitable for what you need. you'll get much better reliability from a G&P SR25 piston in there.
http://www.airsoftgi.com/product_info.php?cPath=31_148&products_id=4340

You could also do the AOE (Angle of engagment) mod which is basically placing a spacer between the piston head and the piston itself, then remove the number 2 tooth altogether from the piston, this means the piston will sit slightly further back into the gearbox and when the gear comes around to meet it, it will do so with a full face contact as opposed to pulling the piston into position by the leading edge of the first tooth. this mod alone will greatly increase the life of your piston. The size of the spacer depends on the application but its usually around 3mm.

TheDoc

There is very few brands that wont run a 9.6 as standard without causing mega problems.

From experience with a small amount of AK SR25's, they seemed ok with 9.6v, and that is what they came supplied with. They had awful problems with bent barells though, and the actual inner barrel is shorter then a pistol which gave me some serious lols.

Then again that was a first batch I think, but have a nosey and see what inner barell is in it. If it is infact a very small bronzey coloured barell, You might want to upgrade the barell length asap, and whilst your at it get a tightbore, you'll notice a big improvement
Check ehobby out for an m16 length 6.03/6.04 tighbore barell.

That should be sufficent length, you could even go bigger and run it through the silencer.

Firekitten

considering his of fire... a downgrade on the battery front to 8.4 cant do any harm... Infact it will slow down the wear on his gearbox too... cheers for the info on the long type gearboxes richie... I wasnt as up to speed as you there... (only dealt with one, and it was already 'modded' as you mentioned.

Masada

the problem is though with those long stroke gearboxes, if you run them on lower voltage there prone to locking up a lot. i wouldn't use anything less than a 9.6v in there.

Firekitten

:cool:swap his motor to a high tourque not a high speed? Anyway... I thought you were the short stroke expert, not long stroke :D

Masada

I know all the strokes baby...

Firekitten

two stroke? :rolleyes:

Stercus Accidit

Firekitten wrote: »

two stroke? :rolleyes:

They call him two stroke because thats how long he manages to last...


Oh no he went there, woo woo woo, jerry!

mafiaboy

iv the same prob when i was down in g-tac 2 one of my stubys was firing at 360fps (all new gear box just put into it) and one of the lads where saying to drop back from using a 9.6v to a 8.4v and this would bring it down to 1j
is that right just dont wont to spend the money to find out it wont work???

Firekitten

oh dear... someone doesnt have a clue... I'd not listen to his advice mafiaboy... changing the voltage has NO effect on fps what so ever... just rate of fire... If its a new gearbox, where did you buy it from? if it was abroad, its most likely hot... and will require a downgrade to 1J with a spring swap to an... m95 or m90 work best...

mafiaboy

i got two stubys for fec all and had one of the lads make one good one out of them it needed a new spring and it we cronoed it at 325fps but g-tac says it was 360fps and when i used the same crono as the frist time it did come in at 360fps...

TheDoc

Higher voltage batteries dont do anything to fps readings as far as Im aware. They merely increase the speed at which your gearbox will turn over, there for increasing your rate of fire.



As i now realise has already being posted above..whoops

Ghost4893

Thanks for all the help. I've got a G&P piston and explosive piston head on its way to me, when it comes I'll get back into action! The removal of the second teeth seems a common thing to do? Do you need to do any adjustment to the gear to match it? Or just cut out the second tooth on the piston? If any1 had a pic of it done that would rock as its not something I've seen done before. (I take it is the second tooth at the end the spring goes in? lol like I say I've only been airsoft'n since February this year so I've got lots to learn!)

Masada

yeah the second tooth as in the second one to come i contact with the gears, not the piston head end.

you dont need to anything other than add a spacer to the piston head and cut out that tooth. the spacer size depends on the individual setup but you want the piston to sit back enough to make a full face contact with the sector gear when it comes around.

Phractal

Recently I realized a great way of downgrading is to stick a bloody massive barrel on it! A LOOOOONG barrel will take your FPS RIGHT down. I will say no more... just reduce your pistons efficiency

Puding

Recently I realized a great way of downgrading is to stick a bloody massive barrel on it! A LOOOOONG barrel will take your FPS RIGHT down. I will say no more... just reduce your pistons efficiency

your piston does not have enough volume to push the bb out of the barrel, in my opinion not a great idea, your aeg is not functioning as intended as in effect has a fault,

i think its worth taking your time downgrade your spring if only for the fact it will take pressure of your gear box internals,

Leftyflip

Ah be nice, maybe he didn't know the effects off a longer barrel that didn't have a suitable cylinder.

Puding

Ah be nice, maybe he didn't know the effects off a longer barrel that didn't have a suitable cylinder.

sorry the comments where not ment to be agressive towards Phractal the guy seems to clearly be aware of the principles with the comment on pistons efficiency but maybe im reading to much into things re typed my original post

my comments where more direct at the air of improvised downgrading that seems to be going around of late

Phractal

*grin* sorry if I came off as an idiot... I was having a laugh. I actually know a ****load about piston/barrel relationships and sacrificed two AEG and one spring rifle to experiments on barrel length to piston volume. I found that in theory a ten yard barrel would make a real stable BB... That would be goin at 1fps :P.

Us engineers are allowed to make a small joke, no?

Puding

Us engineers are allowed to make a small joke, no?

no not when im too tired to catch on :P

Phractal

Its ok, I made a fool out of myself tonight several times - not good for my continued online existance! I am cutting my VSR's barrel to optimum once I chrono it at stock, then chrono it again once the cut upgrade is done. Hopefully a noticable difference will be visible! I shall be reporting on that ASAP.

TNTQ

You can easy afect performance of you replica by combining barrel and cylinder. Depending on barrel lenght, different cylinder is recomended. E.g Systema Type ''3'' for 110mm-170mm barrel.

Phractal

TNTQ - you hit it in one. The piston volume must be equal to, or greater than, the barrel volume. Basic pneumatics! Otherwise vaccum formation, suckback phenomenon, and loss in velocity. Also even if you port the barrel the rest of barrel is friction, lowering velocity!

Dread-Lock

I wouldn't cut the barrel as you'll lose the crowning (which would be hard to do yourself). AFAIK it needs to be crowned properly otherwise it will screw up your accuracy alot (open to correction on this).

TNTQ

Phractal wrote: »

TNTQ - you hit it in one. The piston volume must be equal to, or greater than, the barrel volume. Basic pneumatics! Otherwise vaccum formation, suckback phenomenon, and loss in velocity. Also even if you port the barrel the rest of barrel is friction, lowering velocity!

It's common knowledge for some:) Piston cylinder corelation. Regarding The friction in the barrel. I recommend KM Head Barrels teflon coated. In my humble oppinion best barrels on the market. It's not always about the inner diameter, but also finish of barrel inner surface.

@Dread-Lock: I wouldn't cut barrel. If something I would CNC machine it, but as far as I'm concern would be cheaper to get different barrel.

Firekitten

Um guys... this is why they invented 'vented' cylinders.... Dont vent your barrel ffs *facepalm*

Tbh, anything over 500mm barrel length is unneeded in airsoft, and wont make a blind bit of difference unless you wish to poke your opponent into submission...

I recommend KM Head Barrels teflon coated. In my humble oppinion best barrels on the market.

Planning on stocking those?

Its also perfectly simple to cut your barrel... Tape (electrical around the cut site, mark on the line in the tape, and cut.... ) Then, use a craft knife (it does work) and a sharp blade to crown the barrel yourself. Done. Obviously dont do this when it's IN the gun.... and clean it afterwards to make sure no warf is left inside the barrel.

thermo

i like the mad bull barels, they have a great finnish and make your aeg very consistant! iv used them in 5/6 aegs with good results,,,,,,,

Head_Hunter

thermo wrote: »

i like the mad bull barels, they have a great finnish and make your aeg very consistant! iv used them in 5/6 aegs with good results,,,,,,,

Where did you get the madbull barrels?

TNTQ

Firekitten wrote: »

Um guys... this is why they invented 'vented' cylinders.... Dont vent your barrel ffs *facepalm*

Tbh, anything over 500mm barrel length is unneeded in airsoft, and wont make a blind bit of difference unless you wish to poke your opponent into submission...

Planning on stocking those?

Its also perfectly simple to cut your barrel... Tape (electrical around the cut site, mark on the line in the tape, and cut.... ) Then, use a craft knife (it does work) and a sharp blade to crown the barrel yourself. Done. Obviously dont do this when it's IN the gun.... and clean it afterwards to make sure no warf is left inside the barrel.

We acctually stock them, and I recommend them not be cause we have them in offer, but those are simply outstanding. (we are in the process of adding products to the web)

And I've to dissagree regarding the lenght of the barrel. It have massive impact on performance of replica, but have to be combined with proper cylinder to most of it.

BR,

thermo

Head_Hunter wrote: »

Where did you get the madbull barrels?

i got them in MIA they usually have a good selection of barel lengths in

Head_Hunter

thermo wrote: »

i got them in MIA they usually have a good selection of barel lengths in

I can't find them on their website, are they just availabe in the walk in shop?

Inari

You can order Madbull barrels off of http://www.actionhobbies.co.uk, or ask any of the irish retailers if they have them available (either in stock, or to order in).

I'm currently getting a madbull tightbore installed in my JG M4 through Eirsoft, so I'll let you know how it fares:)

Beast ASI

TNTQ wrote: »

And I've to dissagree regarding the lenght of the barrel. It have massive impact on performance of replica, but have to be combined with proper cylinder to most of it.

In all honesty, your not going to see any significant increases at all over 363mm onwards.

thermo

Head_Hunter wrote: »

I can't find them on their website, are they just availabe in the walk in shop?

yeah just in the shop, you could ring them and find out???

Head_Hunter

thermo wrote: »

yeah just in the shop, you could ring them and find out???

Will do just that, tomorrow .

Masada

Beast ASI wrote: »

In all honesty, your not going to see any significant increases at all over 363mm onwards.

Yeah i agree,
in around the 360-400mmish mark the advantages of longer barrels get less and less noticeable., Id concentrate on having a good smooth, clean barrel and a decent hopup over longer barrels.,

Phractal

A vented cylinder merely seems to lower the pressure in the barrel if I understand it correctly, and this will still leave the friction bit. I reckon a long stroke piston, perfectly matched barrel length and piston cylinder volume, good crowning (actually crowning is an interesting subject - no crown WOULD be the best but is not practical according to many ballistics technicians, the crowning is only out of necessity.) a teflon coated barrel seems like a good idea but wear would reduce its life, so maybe just a normal tight barrel and perhaps a teflon coating to the BB's? Or one of them twist barrels. A good hopup seems like a neseccity to me, and after that just apply the laws of physics .

The less friction in the barrel the better, and the higher pneumatic efficiency of the system is of great importance. putting good backspin via good hopup seems to be a key point - I think the 'rifling' effect of the twist barrel gives good horizontal stability - or am I completely on the wrong track?

Oh, I may add that this is the subject of LONG and protracted discussion on many Finnish airsoft forums according to my friends there, and often they come to same conclusions as us.