High Speed v3 setup and previous failed attempt

[Kalzakov]

Hello,

So i'm making a custom Bizon PP-19 set up for mainly trigger response and high rate of fire, my first build had a catastrophic failure and im trying to pin point where i went wrong so i don't repeat the mistake.
here are the part involved:
SHS 16:1 gears
SHS 15 tooth lightened piston
SHS light piston head
7mm steel bushing
Stock CYMA cylinder (1 port) and cylinder head
Stock Tappet plate
ASCU gen 3+ v3 mosfet trigger board
m95 spring
ASG Ultimate infinity u-45000 motor
11.1v 25c electro river battery

So what happened is during the test it went through one mid cap mag of 170rnds and i noticed the BB's velocity was getting weaker and the BB's where no longer getting through the cardboard, so i chrono'd it and in semi it was shooting 290 -300fps but in auto it was 205fps however thing went from bad to worse the lipo which was brand new and been charged less than a 5 hours before burst into flames and fried the ASCU unit so in a flash £100 down the drain. i'm completely baffled by this whether it was my fault or maybe a lemon battery or something else?

Anyways round 2, i've bought a chimera mk2 v3 this time as it has higher tolerances, but definitely dont want a repeat.

Other things to note, the gearbox had been shimmed by Gunfire's techs in poland when i purchased the gun.

Any help would be greatly appreciated and if i've missed any details please feel free to ask.

Cheers.

[Sitting Duck]

Re: High Speed v3 setup and previous failed attempt

if it has a 250mm barrel then possible options are:

DSG on GOOD 18:1 or the recent 16:1 gears and a mofo m150/60 spring
(sector gear has same teeth on shs dsg gear as 18/16:1 sector)

13:1 gear set, Short stroke a couple/few steel teeth off a swiss cheese lightened piston, M120 sping

gearbox should be running with solid bushings for the above setup btw
(only ceramic bearings should be used - even then solid bushing under bevel/spur gears)

The above setup should get you to near 30 on SSG or 40 on DSG
Well actually over this if using 11.1v and an insane motor
(those figures can be achieved on 7.4v lipo but that is really going some with ultra thick wire and very fast and torquey motor)

Running above 25rps with a m95/100 using 11.1v is just pushing it for Pre Engagement
Which could of started to take place or got extremely close to happening imho

As for catching fire - wiring or gearbox failure causing lockup - but would of thought even with a sticky trigger finger the fet would of had some cut out - so guessing a wiring fault perhaps.....

Me personally I'd forget the ascu at least for a moment, get a basic 3034 non-ab fet
m120 then SS 3 teeth and she won't PE or double cycle at 30+, probably ok for high 30's
(motor won't really need AB, it can give out a little bit more heat than non ab fets when spamming on semi)

Then see how she goes, if and when she runs well then look at ascu option if you still wish

no offense but there is a lot more to getting a gun to run faster than just chucking in a list of expensive bits
I'm no expert but have made LOADS of mistakes & failures, snapping pistons coz didn't do AoE etc.....
All I'm trying to say is you can get very good results quite cheaply if you do homework & plan/fit most "normal" bits with care

Google: Legacy's Guide to Building a High Speed AEG
is a good starting point - but so is taking extreme care when building a high speed box

best of luck

[Kalzakov]

Re: High Speed v3 setup and previous failed attempt

Thanks for the reply, well i got a v3 chimera mk2 now and i'm in the process of SS and using a tap washer to correct the AoE.
as for the ascu, ive check all the external wiring and found no signs of shorting, so must be an internal fault, just my luck i'm a lemon magnet...

will keep you posted on how the m120 + SS + AoE goes!

side note: im out off money this month for parts like bushings and another gear set so i have to make do until next month.

[sparrowhawk]

Re: High Speed v3 setup and previous failed attempt

As soon as I saw ascu, I thought "should of used a BTC " so well done for that

[Kalzakov]

Re: High Speed v3 setup and previous failed attempt

Lesson learned, haha.

so update, gun lives been through 6 180round mid caps,
32rps at 360fps on .2's(haven't short stroked yet) i've been informed there's most likely a air leak somewhere as i should be getting around 400 with a prom ms120.
i't did drop to 330fps in full auto but i have 3 weeks before my next game and a very welcome payday to put the final touches on the Bizon

[Sitting Duck]

Re: High Speed v3 setup and previous failed attempt

well yeah you "should" be at about 400fps in a normal m4 of 363mm
but as you got a short barrel you do lose a bit off that figure

so with your current 360fps in mind do only 1 tooth at a time
you can't put them teeth back so go in small stages

you don't HAVE to remove the metal teeth off the piston's LAST tooth or two
but ensure you remove 1 tooth off the sector at the START not the end of sector gear
if you remove 2 teeth off the sector at the end then you screw up tappet plate timing etc...

So using a dremmel or something you grind off the very first tooth on sector that engages the pick up tooth on piston

reckon dropping one tooth will be perfect to get just under 350fps maybe 345

also if you are not 101% sure, I am quite sure if you compare old sector gear with shs 16:1
then I reckon it will be the exact same as most 18:1's (16 & 18:1 sets usually have just slightly different spur gears)
Soz to break it to you but 18.65:1 are 18:1 stock gears
but worse is getting mugged on 16:1 sets are not 16.65:1 but in fact 17.25:1 ratio's
great eh - 16:1 set owners get mugged over

anyway reckon you can test out stuff on ya old 18:1 sector I reckon - but remember take off first tooth off sector

you may not need to SS to avoid PE at higher speed
but you need to bring down the fps a smidge and hence it will slightly lessen the spring compression
you could replace bearing spring guide with a normal spring guide as it will be about the same adding or reducing 15fps aprox I've found
Or if you add a spring guide over a normal one then you may need to remove one more tooth etc.....
Oh well you get the idea etc.....
best of luck

[Kalzakov]

Re: High Speed v3 setup and previous failed attempt

ok, so next month ill be getting a 13:1 gear set and to try and get a 9 toothed bevel, would i need to shave a tooth off that to keep the fps under 350?

[Sitting Duck]

Re: High Speed v3 setup and previous failed attempt

ok, so next month ill be getting a 13:1 gear set and to try and get a 9 toothed bevel, would i need to shave a tooth off that to keep the fps under 350?

bloody hell - how fast ya wanna go ???

first off a 13:1 will not give you as much increase as you first might think coz there is a tiny bit more work on the motor turning them gears especially from still
also a 9 tooth bevel actually slows you down 10% than a normal 10 tooth bevel
(absolute mental speed freaks go for 11 teeth but seriously stick with 10 tooth bevels)
they also do a 8 tooth but that is lame for pulling mega strong gears

1 full turn of bevel clicks 10 teeth on spur on normal sets
but 9 or 8 teeth onlu click 9 or 8 teeth on spur gear so it all turns at a higher ratio/slower speed

also as you go faster n faster some mags struggle to feed though yours may be fine
but often quite a few cheap hi caps don't work well above 25-30rps
mid caps feed well but crazy dsg mofo's often have to experiment a bit to get things feeding well at crazy speeds

Finally your box will crap out quicker at higher speed, higher wear, more heat friction etc.....
so decide on a reasonable limit to ya mofo gun is my advice unless you like rebuilding boxes more than using them

The short stoke of 1 tooth is two fold when using m120 etc...
it returns piston faster using a faster higher spring to clear in time and avoid PE
but as you are over to bring down fps and also reduce the stoke length - you start to remove a tooth or two
thus bringing down fps and a slightly shorter stroke to return spring a smidge quicker from having a stroke 3mm less

keep a 10 tooth bevel setup if possible as most gear sets seem to use them
if at anytime the bevel gear loses a tooth or two you can use almost any spare 10 tooth bevel

I had a 13:1 set go crunch when bearings crapped out on me but only thing I lost was bevel gear
luckily a good spare bevel in the spares box came in handy and got her going again
this time with solid bushings in there - a little slower but working and hopefully won't crap out so quickly like it did on stock bearings

seriously - 32rps is enough for me but it is up to you
just remember going more nutz will promote more wear n tear like thrashing a car more n more

[Kalzakov]

Re: High Speed v3 setup and previous failed attempt

My plan is to get as fast trigger as possible and the reason i after the fast rof is for burst mode, i want the burst to be as fast as possible. much like the an94 2 shot burst function.

[Sitting Duck]

Re: High Speed v3 setup and previous failed attempt

As I said it is your gun and totally up to you how fast you go

I'm happy with 25 to 33rps on just 7.4v

you can go nutz with 13:1 or 12:1 or nutz with Riot's 10:1 gears
chuck in 14.8v or stay on 16:1 and pop in a DSG sector is another option with a m160+ spring (fun getting that mofo in)

Just remember it WILL crap out quicker

If I get a 28rps feeding well, shooting straight & consistent that does me tbh
I've got a HC05 but 40rps on 7.4v is just overkill so it hardly ever gets out much
big difference in say 20 & 30rps, but to me not much going from 30 to 40rps - just a crazy hose of bb's

if you decide to take it further say 40rps then you may have to SS more with a m130
see how you go, but it is totally up to you what you do with your gun

[sparrowhawk]

Re: High Speed v3 setup and previous failed attempt

Other things you can do is Polish your gearbox shell where the piston rails sit, and tappet plate runs, also radial your corners of the gearbox especially the front, it will spread the stress of the piston hitting the front and stop the shell from splitting, and finally what is the weight of your piston and head combo, a lot of people drill holes in the piston to remove excess baggage, a lighter piston is a faster piston

[Sitting Duck]

Re: High Speed v3 setup and previous failed attempt

Indeed if you really go nutz and get into this speed malarky & tuning freak like some....

Buy a cheapy set of scales from fleabay or somewhere - £4 type like drug dealers use
get the .01gms not 0.1gms if possible
yeah the 0.1gms will do for piston work but 0.01gms comes in handy if say you got a mag of unknown bb's
(then you will know if mag contains 0.20's or 0.25's etc...... - just a tip if buying drug scales)

Forget the piston bearing full stop for high rof setup's
The bearings add weight and often if you don't use red permanent threadlock they can undo and bone cylinder
The bearing assemblt can add up to 5gms with 2xraces + bearing & collar
Drop bearing and 1 race and you can add a 5mm x 20mm plastic washer like what G&G use in CM's
that setup equates to about 2.75gms - so over 2gms saved - don't sound much but it is trust me

Then swiss cheese piston but I avoid lightening below the rails especially on full metal rack
coz they can weaken around that area holding in the steel rack - so just swiss on top of piston
usually around 1.5gms to 2gms saved in weight but takes a little bit of time to make a clean neat job

Hopefully this will end up saving about 5gms on a FULLY assembled piston

Piston's can really vary in weight - a shs plastic piston with 3 teeth is about 12.5gms
a strong Lonex piston with say 7or8 steel teeth is about 18gms !!!
That is about the weight of some full steel rack pistons - these weights are bare pistons btw
(and the blue ultra light shs 3 or 7 steel teeth are too soft for high speed setups - 2 have stripped and now don't use them unless it is gonna be a slower stock setup but even then doubt if I'd bother with them coz found they just strip easily)

After all that messing about you should be able to get a FULLY assembled piston with a poly piston head:
18gms for a 3 or 7 steel teeth piston - couple of steel teeth removed for SS
22gms for a strong full rack with a couple of teeth removed if SS

pistons can weigh as little as 15gms for an ultra light full piston
or up to 30gms for a steel rack with alli piston head - ok for dmr's but not for hi speed setups

as long as you use a bearing spring guide it will still allow for some spring twist but with a much faster returning piston

Phew - well that is what I do but like so much else it takes work and time when building
rather than just chucking in parts and slapping it back together

And I'm still breaking and learning stuff all the time with every boned box I try to fix
great fun

[sparrowhawk]

Re: High Speed v3 setup and previous failed attempt

Pom piston heads are reputed to be strong and light weight, I Swiss cheesed a blue shs piston and it flexed itself out of the rails