Umarex ARX 160 Project: Done... For now...

[Asomodai]

Hello gents. 

Tonight I took on a project with my beloved and oddly trustworthy ARX160. Simply put, I wanted to tighten up the bolt lever which had gotten loose when I fell on the rifle and to replace the air seal components and piston with decent quality FPS Ergal stuff (Made in Italy). Basically standard preventative maintenance/upgrade to make it as efficient as possible. With a M105 spring it was hitting at 337FPS, which is pretty good, though the consistency was a bit off. 

The ARX has a custom V3 gearbox, from what I heard it was very tightly packed together and could be an arse to put back together. 

The initial taking out the barrel and hop was easy as I had done it before to do a barrel and hop rubber upgrade. I removed the back panel and took out the old spring using the quick release. I had to enlarge the window in the back of the stock to thread the Deans connector through. 

Once that was done, I pressed the upper release button at the back and hinged open the body. 

View attachment 46280

Cheap plastic, but nice how they have made it easy to take apart. 

View attachment 46278

View attachment 46279

I accessed the bolt lever, unscrewed the bolt, covered in Loctite and screwed it back in. Solid as a rock. 

View attachment 46281

Half pushed out one small body pin to rip out the gearbox and motor, very easy! 

View attachment 46282

Taking note of the gearbox selector mechanism, I started stripping away to the base shell. 

View attachment 46283

The original motor is a high torque one, likely a ferrite, but its a pretty good motor for stock and will be keeping this for now. 

View attachment 46284

Cracked open the gearbox, only a few screws. 

View attachment 46287

Standard crappy piston, a little eaten away. Standard cylinder head and plastic nozzle. Quick release spring guide is ok, but not great. 

View attachment 46288

Gears look a bit flimsy, quite a narrow spur gear, but not the worst. Wiped out the current grease and reshimmed the gears. Installed a spare delayer chip which fits snugly. 

View attachment 46289

Assembled my new air seal components, SHS 4/5 Cylinder to replace the full one, the barrel length is 400mm, so its just about matched. FPS Ergal Piston head, Cylinder Head and nozzle. All made of lightweight aluminium. The Piston is a 14 tooth SHS all metal piston. Topped it off with a new FPS Ergal Spring guide, also quick release. 

View attachment 46286

Cracking airseal once assembled.

 View attachment 46290

There was a problem, the new piston combo would get caught on the last tooth as the rear of the piston hits the gearbox casing. Sanded down the back of the piston to alleviate this and seemed to work. I didn't want to short stroke a gear as I hadn't done it before. 

View attachment 46291

Putting together the gearbox again, the trigger spring being very difficult par for the course with V3 boxes. The micro switch as standard is a lovely touch!

Put the gearbox back together and tried to fire it a few times. Nozzle does not have the full range of movement, wont move back forward after going back. 

Opened up the box, the tappet is at fault as the nozzle wont fit correctly which necessitates sanding on the mount. Not wanting to ruin the original tappet, got an SRC one from my spares box and sanded it to fit the Nozzle. 

Reassembled and the nozzle now retracts correctly. 

Ran a test, the gearbox seizes up, piston head comes right off inside the cylinder! Couldn't open the gearbox back up easily as I couldn't use the quick release mechanism and had to force it open.

Result was a broken spur gear tooth and sector gear tooth...

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Got a set of new Golden Bow (JG) gears that I grabbed out of a G36 recently. The bevel is a bit thicker on this one. The delayer chip only fits on the sector gear loosely, will need to replace this at somepoint. 

Unfortunately the piston was hitting the back of the gearbox again, so decided to attempt a short stroke. Took two teeth out of the sector gear with my trust Dremel, not the tidiest job, but it will do. 

View attachment 46294

Ran another test and the gearbox was firing nicely, with decent ROF from a almost dead 9.9v LiFE. 

I wanted to install a Mosfet but I was running out of time, so reassembled the rest of the rifle to perform chrono and feeding test. 

Chronoed at just over 300FPS with +/- 1 FPS, very high ROF with a half charged LiFE battery. 

Looked for a spare higher powered spring and found an M115, chronoed at 344 FPS, also very consistent FPS reading. Feeding was fairly good, though it would occasionally drop a shot due to a poor mag. Will test other mags soon. 

So there we have it for now! What was supposed to be an upgrade for reliability, turned into an upgrade for ROF! I really hope this thing will be as consistent as it was before! The trigger response and rate of the fire is really impressive in its current state. I will be installing a mosfet sometime this week to protect the microswitch. 

 

[Sitting Duck]

Wow - very nice post - full of info and detail

(I got an ARX160 so this post will come in very handy)

Good to see you will chuck a mosfet soon as the microswitch do tend to burn out

Just a tiny note on piston & Short Stroking......

(pmsl - since when did my posts ever become tiny or concise ffs ???)

Some piston's or piston upgrades/replacements can hit the back of boxes

it is a question of tolerances and where the rack/teeth sit slightly slightly differently

plus some boxes have slightly bespoke/shorter piston etc......

The piston hitting the box was very likely just about 1mm or 1.5mm extra travel

Some sectors have an ultra thick last tooth - but most don't

What you could have done to the last tooth is just filed/ground it down a smidge

(say take off a third of it's height, to release the piston a whisker earlier and not hit back of box)

Just a smidge on last tooth would have sufficed most likely

Or - just removed one tooth

Also - me thinks or it is recommended to remove teeth for short stroking

on the PICK UP side rather than the RELEASE side like you did

but I did the wrong side too when I first Short Stroked a sector

(must be a bad tutorial out there somewhere)

should really be on pick up side, if taking off one or two teeth

and maybe a third tooth still on pickup side,

though some start to remove one on the release side to "balance" the weight

(nah - I still take 3 off pickup side, but maybe 4th tooth if I was ever SS that much, though only done 3 teeth myself)

Anyway - waffle waffle & all that, reason they recommend you take off pickup side than release

is to do with tappet timings, if you take off the release side too much, the piston now releases

a little bit earlier than the tappet/nozzle returns - so throws out the tappet plate timing

So the general rule is to SS teeth from the pickup side/first tooth on two on sector

rather than the last tooth or two on the sector gear like you did.....

View attachment 46294

Now this may not be too much of a problem in a stock/moderate gun

but higher rof guns this altered tappet timing can effect stuff - eg: piston/releases before nozzle seals

so compression is lost as it builds & leaks before the nozzle seals on bucking at higher speeds etc.....

Plus you added a delay clip so the tappet remains retracted a little more than usual on top of piston releasing earlier

One of these things may not be too much of an issue on their own

but combined the piston & tappet timing is thrown a bit more out of whack - hence my war & peace post

So IF you notice weird stuff happening

then locate another sector and file down:

last tooth slightly if a gun needs max stroke like 455mm AK47

(if you can't find a piston that doesn't hit/lock up at back of box)

or

grind down just one tooth or only what is needed on the PICKUP side

you don't need to remove any teeth on rack unless you got jumbo last tooth sector (fairly rare)

if you had a jumbo release tooth like pic and SS say 2 teeth off the pickup side then yes you need to remove the teeth on rack

but in general you don't need to remove teeth off the metal rack as most teeth are evenly pitched/size etc.....

If tappet timing becomes a real issue then it will need to be addressed

another possible thing is to trim the tappet fin so the tappet plate releases earlier and comes back into sync

on much higher speed setups the tappet fin is trimmed down with a strong spring to ensure tappet returns asap etc...

or this trimming of the fin is performed to compensate for ultra long delay clips

Whoa - ultra long post, my bad

but maybe next time take off the teeth on the other side, removing the first tooth/teeth that contacts the piston.....

other than that - brilliant teardown on the ARX box

 

[Asomodai]

Wow - very nice post - full of info and detail

(I got an ARX160 so this post will come in very handy)

Good to see you will chuck a mosfet soon as the microswitch do tend to burn out

Just a tiny note on piston & Short Stroking......

(pmsl - since when did my posts ever become tiny or concise ffs ???)

Some piston's or piston upgrades/replacements can hit the back of boxes

it is a question of tolerances and where the rack/teeth sit slightly slightly differently

plus some boxes have slightly bespoke/shorter piston etc......

The piston hitting the box was very likely just about 1mm or 1.5mm extra travel

Some sectors have an ultra thick last tooth - but most don't

What you could have done to the last tooth is just filed/ground it down a smidge

(say take off a third of it's height, to release the piston a whisker earlier and not hit back of box)

Just a smidge on last tooth would have sufficed most likely

Or - just removed one tooth

Also - me thinks or it is recommended to remove teeth for short stroking

on the PICK UP side rather than the RELEASE side like you did

but I did the wrong side too when I first Short Stroked a sector

(must be a bad tutorial out there somewhere)

should really be on pick up side, if taking off one or two teeth

and maybe a third tooth still on pickup side,

though some start to remove one on the release side to "balance" the weight

(nah - I still take 3 off pickup side, but maybe 4th tooth if I was ever SS that much, though only done 3 teeth myself)

Anyway - waffle waffle & all that, reason they recommend you take off pickup side than release

is to do with tappet timings, if you take off the release side too much, the piston now releases

a little bit earlier than the tappet/nozzle returns - so throws out the tappet plate timing

So the general rule is to SS teeth from the pickup side/first tooth on two on sector

rather than the last tooth or two on the sector gear like you did.....

Now this may not be too much of a problem in a stock/moderate gun

but higher rof guns this altered tappet timing can effect stuff - eg: piston/releases before nozzle seals

so compression is lost as it builds & leaks before the nozzle seals on bucking at higher speeds etc.....

Plus you added a delay clip so the tappet remains retracted a little more than usual on top of piston releasing earlier

One of these things may not be too much of an issue on their own

but combined the piston & tappet timing is thrown a bit more out of whack - hence my war & peace post

So IF you notice weird stuff happening

then locate another sector and file down:

last tooth slightly if a gun needs max stroke like 455mm AK47

(if you can't find a piston that doesn't hit/lock up at back of box)

or

grind down just one tooth or only what is needed on the PICKUP side

you don't need to remove any teeth on rack unless you got jumbo last tooth sector (fairly rare)

if you had a jumbo release tooth like pic and SS say 2 teeth off the pickup side then yes you need to remove the teeth on rack

but in general you don't need to remove teeth off the metal rack as most teeth are evenly pitched/size etc.....

If tappet timing becomes a real issue then it will need to be addressed

another possible thing is to trim the tappet fin so the tappet plate releases earlier and comes back into sync

on much higher speed setups the tappet fin is trimmed down with a strong spring to ensure tappet returns asap etc...

or this trimming of the fin is performed to compensate for ultra long delay clips

Whoa - ultra long post, my bad

but maybe next time take off the teeth on the other side, removing the first tooth/teeth that contacts the piston.....



other than that - brilliant teardown on the ARX box

Thanks for the post. 

The piston is the same length and teeth are the same position as the stock piston, the issue here is that the replacement Piston Head is deeper then the stock one by about 1/2mm. Which I felt necessitated either dremeling the gearbox or sanding the back of the piston. Obviously I felt the need to short stroke anyway so it becomes a moot issue. 

I actually looked at the same Patrol base photo but in my knackered state still removed the teeth from the release side. Everything seems fine with regards to timing and compression is not affected. But I have another Gear set I can use, though hopefully I will just replace the sector and it will mesh fine with the strong bevel gear already installed. 

I am not going for ultra high speed ROF as I prefer reliability, so maybe on the next sector gear I will just take off one tooth, but I do like the trigger response with two teeth removed! When I go to install the mosfet I will open the box up again and do another gear change. 

---

EDIT: Of course I can always just keep sanding the back of the piston so I can get the gears to turn all the way around. Is there any detrimental to doing it this way?

 

[Sitting Duck]

I'm 99% certain or think the piston head itself won't affect the piston's final retraction point

For example you can place washers between the piston & the piston head to correct AoE

effectively pushing the piston head further forward or rather setting the piston's position

slightly further back - a bit of bodge or alternative way to correct AoE but some do this

(personally I'd only use this to very slightly tune or adjust AoE a smidge but to each their own)

However - even if place a 3mm spacer between a piston & piston head to correct AoE

it alters the piston & the rack/pickup tooth's initial position

BUT  it does not alter the final retraction point of the rear of the piston - it doesn't

It might alter the point of rest where the rack sits to engage with sector

but the final point of travel for the rear of the piston has not been altered at all

But different pistons can be very ergh uhm "different" and issues can arise

For example - they can bind in one box but glide smoothly in another box

There are pics and studies on say Airsoft ociety of various pistons & lengths

they can vary in say 1mm - maybe only 0.5mm but that is not just the full picture

but the exact position of the pack/teeth on the position

specifically how much material is behind the initial pickup tooth = more/longer material at rear to bottom out

Doesn't matter if the piston has a large lump of plastic pickup tooth like stock pistons

or less material like some metal racks have behind them, but more as to the position of the rack at full retraction

This is checked by placing the piston - complete of bare piston in the box and rolling the sector back

Best method to check stuff is test in the top/other side of box without the switch/tappet etc....

(just seems to operate better as the sector-piston teeth are on that side anyway)

if you suspect at the final point of retraction just as the teeth slip past to release themselves....

if you feel that it might just be a possible risk of bottoming out then review the situation.....

try another piston or look to file down the last tooth on sector just 0.5mm max so it slips without hitting the box

now under spring tension that piston will be very pressed up against the sector gear's teeth

but as I said if you test it in the other half of box and feel it could strike the box or a risk of it bottoming out

then if no alternative piston is available then modify the teeth slightly to reduce this

In a medium length gun - sod it I'll just SS 1 tooth, but in a AK you need full stroke

so in that case just a very mild smidge - just 0.5mm max filed off sector release tooth should suffice

It is the variation(s) or different tolerances in different pistons that can cause this bottoming out in some builds

not the piston head used or if you pack/space the piston head & piston method of correct AoE

I think it was MadBull Alien pistons were known to bottom out in many boxes at full retraction

but other pistons operated perfectly at full retraction coz they had the rack/final tooth position slightly differently

or the material at back of piston wasn't so thick

yeah basically - it is recommended to check the piston & sector's operation to check for bottoming out

in the other half of gearbox, observe closely the operation and clearance at point of release

and decide if it fully passes this check or if alternatives or slight modifications might be needed

But it is the piston or different pistons used not the piston head that can cause these issues I feel

 

[Asomodai]

I'm 99% certain or think the piston head itself won't affect the piston's final retraction point

For example you can place washers between the piston & the piston head to correct AoE

effectively pushing the piston head further forward or rather setting the piston's position

slightly further back - a bit of bodge or alternative way to correct AoE but some do this

(personally I'd only use this to very slightly tune or adjust AoE a smidge but to each their own)

However - even if place a 3mm spacer between a piston & piston head to correct AoE

it alters the piston & the rack/pickup tooth's initial position

BUT  it does not alter the final retraction point of the rear of the piston - it doesn't

It might alter the point of rest where the rack sits to engage with sector

but the final point of travel for the rear of the piston has not been altered at all

But different pistons can be very ergh uhm "different" and issues can arise

For example - they can bind in one box but glide smoothly in another box

There are pics and studies on say Airsoft ociety of various pistons & lengths

they can vary in say 1mm - maybe only 0.5mm but that is not just the full picture

but the exact position of the pack/teeth on the position

specifically how much material is behind the initial pickup tooth = more/longer material at rear to bottom out

Doesn't matter if the piston has a large lump of plastic pickup tooth like stock pistons

or less material like some metal racks have behind them, but more as to the position of the rack at full retraction

This is checked by placing the piston - complete of bare piston in the box and rolling the sector back

Best method to check stuff is test in the top/other side of box without the switch/tappet etc....

(just seems to operate better as the sector-piston teeth are on that side anyway)

if you suspect at the final point of retraction just as the teeth slip past to release themselves....

if you feel that it might just be a possible risk of bottoming out then review the situation.....

try another piston or look to file down the last tooth on sector just 0.5mm max so it slips without hitting the box

now under spring tension that piston will be very pressed up against the sector gear's teeth

but as I said if you test it in the other half of box and feel it could strike the box or a risk of it bottoming out

then if no alternative piston is available then modify the teeth slightly to reduce this

In a medium length gun - sod it I'll just SS 1 tooth, but in a AK you need full stroke

so in that case just a very mild smidge - just 0.5mm max filed off sector release tooth should suffice

It is the variation(s) or different tolerances in different pistons that can cause this bottoming out in some builds

not the piston head used or if you pack/space the piston head & piston method of correct AoE

I think it was MadBull Alien pistons were known to bottom out in many boxes at full retraction

but other pistons operated perfectly at full retraction coz they had the rack/final tooth position slightly differently

or the material at back of piston wasn't so thick

yeah basically - it is recommended to check the piston & sector's operation to check for bottoming out

in the other half of gearbox, observe closely the operation and clearance at point of release

and decide if it fully passes this check or if alternatives or slight modifications might be needed

But it is the piston or different pistons used not the piston head that can cause these issues I feel

Interesting. 

I would like to keep the same Piston, I have spare gear sets which I don't mind mucking around with. 

So if I want to keep full stroke it would be best to grind down the last release tooth a smidgen, will that not affect tappet timing much like the short stroke? 

Or I could short stroke the pickup teeth, but I wont have full stroke... The current barrel length is 400mm, with a 4/5 Cylinder, would you try to keep the full stroke or do you think I can get away with a single tooth short stroke? I do have a spare full cylinder if that makes a difference. 

 

[Sitting Duck]

EDIT: Of course I can always just keep sanding the back of the piston so I can get the gears to turn all the way around. Is there any detrimental to doing it this way?

I wouldn't really advise sanding the back of piston too much if at all possible

as you might loose strength or material require to retain a metal rack's pickup tooth etc.....

Best thing is to test stuff in the top half of box,

from tappet plate retraction bottoming out on cylinder head if using a mofo jumbo delayer

to piston bottoming out at the back of box, tested with sector (remember to include the spring guide of course in test)

The top half od a gear box is a good way to test anything sector related as it is more stable in rotation

than the wibbly wobbly in the lower half upon assembly

The top half of box is where you can quickly test for smooth operation of stuff and reduce a number of issues arising

So easy to drop that in there add that have a looksey and go ooooh erghh looks a bit iffy, just sand that or try that instead

And some spring guides might be a bit more lumpy that others etc...., different pistons blah blah blah

yeah always worth giving it all a once over using the top half of box if going for full stroke setup

or fuck it if you are removing a tooth for a SS setup then no worries (well still need to check other stuff etc...)

Interesting. 

I would like to keep the same Piston, I have spare gear sets which I don't mind mucking around with. 

So if I want to keep full stroke it would be best to grind down the last release tooth a smidgen, will that not affect tappet timing much like the short stroke? 

Or I could short stroke the pickup teeth, but I wont have full stroke... The current barrel length is 400mm, with a 4/5 Cylinder, would you try to keep the full stroke or do you think I can get away with a single tooth short stroke? I do have a spare full cylinder if that makes a difference. 

I think you would probably want a full stroke setup with maybe the sector's last tooth filed down just a smidge

I mean you you probably be ok with a slightly vented cylinder but tiny slits at back....

as a full cylinder is for a 455mm AK or 510mm at a push

but if lifting .25's or .28 especially a full cylinder would be wise - especially as you lose say 3mm stroke

or effectively one tooth as the teeth are 3mm pitch when you corrected AoE

so the stroke has reduced 3mm from stock setup after correcting AoE

I mean yes you could SS one tooth - no more off the pickup side

but I'd be tempted to go full stroke or nigh on & very very slightly over volume a whisker

than be bang on what all the graphs/books/maths say

which once the o-ring wears a smidge the efficiency of compression may reduce slightly & under volume

I think on a 407 barrel I'd be happy with correcting the AoE, which reduces the stroke by say 3mm

then mod the release tooth very slightly to get it to just slip/release without bottoming out

- yeah that is what I'd do for an AK ' 455mm not much more than your barrel

and use the full cylinder if the piston head operates sweetly and the o-ring falls forward

and allows the piston to retract quickly and seals promptly etc....

yeah nigh on full stroke and full cylinder, just slightly reduce the last tooth on sector a tiny bit

keep checking the operation on other half of box until satisfied and go with that

 

[Asomodai]

I wouldn't really advise sanding the back of piston too much if at all possible

as you might loose strength or material require to retain a metal rack's pickup tooth etc.....

Best thing is to test stuff in the top half of box,

from tappet plate retraction bottoming out on cylinder head if using a mofo jumbo delayer

to piston bottoming out at the back of box, tested with sector (remember to include the spring guide of course in test)

The top half od a gear box is a good way to test anything sector related as it is more stable in rotation

than the wibbly wobbly in the lower half upon assembly

The top half of box is where you can quickly test for smooth operation of stuff and reduce a number of issues arising

So easy to drop that in there add that have a looksey and go ooooh erghh looks a bit iffy, just sand that or try that instead

And some spring guides might be a bit more lumpy that others etc...., different pistons blah blah blah

yeah always worth giving it all a once over using the top half of box if going for full stroke setup

or fuck it if you are removing a tooth for a SS setup then no worries (well still need to check other stuff etc...)

Technically I already tested for this before putting it together and that last tooth would just not get through as the piston is bottoming out on the gearbox. You mention "looks a bit iffy, just sand that instead", Do you mean the back of the piston or something else?

I was thinking of getting a slightly better gear set locally today and came across an original guarder one which has that thicker reinforced last tooth. Obviously the gear set will be quality, but will likely be forced to short stroke by one tooth from the pickup side due to that last tooth.

Damn cheap gearset mind! 

https://wolfarmouries.co.uk/browse-products/parts/electric-parts/gears/guarder-steel-gear-set-for-tm-aeg-ii-iii-original-type.html

as a full cylinder is for a 455mm AK or 510mm at a push

but if lifting .25's or .28 especially a full cylinder would be wise - especially as you lose say 3mm stroke

or effectively one tooth as the teeth are 3mm pitch when you corrected AoE

so the stroke has reduced 3mm from stock setup after correcting AoE

I mean yes you could SS one tooth - no more off the pickup side

but I'd be tempted to go full stroke or nigh on & very very slightly over volume a whisker

than be bang on what all the graphs/books/maths say

which once the o-ring wears a smidge the efficiency of compression may reduce slightly & under volume

I think on a 407 barrel I'd be happy with correcting the AoE, which reduces the stroke by say 3mm

then mod the release tooth very slightly to get it to just slip/release without bottoming out

- yeah that is what I'd do for an AK ' 455mm not much more than your barrel

and use the full cylinder if the piston head operates sweetly and the o-ring falls forward

and allows the piston to retract quickly and seals promptly etc....

yeah nigh on full stroke and full cylinder, just slightly reduce the last tooth on sector a tiny bit

keep checking the operation on other half of box until satisfied and go with that

Gotcha, I'll not purchase the Guarder gears due to that last tooth being thicker and a pain. I will buy a set of 18:1 from AK2M4. Probably the ZCI Advanced (Which has a small delayer built into the gearset.) Thinking either 18:1 or 16:1 and will flatten out the last release tooth. 

https://www.ak2m4.co.uk/internal-parts/gears/zci-gear-set-advanced-18-1

I have two spare full cylinders so will use one of them. I haven't been able to find a cylinder within easy reach that has the half holes at the end. 

 

[Sitting Duck]

Technically I already tested for this before putting it together and that last tooth would just not get through as the piston is bottoming out on the gearbox. You mention "looks a bit iffy, just sand that instead", Do you mean the back of the piston or something else?

I was thinking of getting a slightly better gear set locally today and came across an original guarder one which has that thicker reinforced last tooth. Obviously the gear set will be quality, but will likely be forced to short stroke by one tooth from the pickup side due to that last tooth.

Damn cheap gearset mind! 

https://wolfarmouries.co.uk/browse-products/parts/electric-parts/gears/guarder-steel-gear-set-for-tm-aeg-ii-iii-original-type.html

Gotcha, I'll not purchase the Guarder gears due to that last tooth being thicker and a pain. I will buy a set of 18:1 from AK2M4. Probably the ZCI Advanced (Which has a small delayer built into the gearset.) and will flatten out the last tooth. 

https://www.ak2m4.co.uk/internal-parts/gears/zci-gear-set-advanced-18-1

I have two spare full cylinders so will use one of them. I haven't been able to find a cylinder within easy reach that has the half holes at the end. 

The I'll sand that or mod that was in general terms rather than sand the back of piston

for example an some reinforced v2's long tappet fins can also bottom out with all that extra metal material they chuck in at back of box

you look at the runners of tappet plate in the box and where they end and what takes place at full tappet retraction etc......

SOME tappet fins "can" in "some" boxes hit on parts of box or on the thick axles of "some" spur gears for example...

but it was just a general term of checking & deciding to to sand/file/mod or try other combinations/parts etc.....

I mean you don't have to nutz ordering more gears though

any or almost any std sector in a junk box will do as 18:1's are same sectors as 16:1's etc...

what meshes fine with present gears are in there and if another JG sector is about then shimming should be fine most likely

You can file the sector's last tooth down to say 75% height, it is likely 3mm in height so take off up to 0.75mm absolute max

you check and see that the last tooth clears the piston's rack as it slams back etc.....

but feel if you reduce the last tooth any more to half its height it might risk not quite clearing fully as piston is released

hence you need to make this judgement yourself

but if it still doesn't allow clearance then you could simply go with SS one tooth off the pickup side

If you have another JG sector gear, then taking your incorrectly SS 2 sector, file down that a bit, the last available tooth

(which was originally the 3rd to last tooth)

align that tooth on that the last tooth, now filed down a smidge, align this with last tooth of the piston rack

check if the piston still bottoms out & experiement to decide if that will work with a filed down last tooth

if it does then apply this minor modification to the other full JG sector, test again - viola max stroke & no bottoming out

if you old sector won't work with a shaved tooth then mod the other JG sector to a SS 1 tooth off the pick up side - job done

ps - for delay clips I love these.....

https://www.ak2m4.co.uk/internal-parts/gears/zci-gear-delayer

they have a slither extra material just above tappet lug on sector

that retracts tappet/nozzle a whisker more than most other clips

and they fit quite snuggly onto sectors too - sometimes a minor mod coz so damn tight

however you do need to check it doesn't retract too much and bottom out on cylinder heads

this needs to be checked as SHS tappets retract a smidge more than others imho

so combined with these brass delayers with extra whisker of material

the nozzle retracts a bit more to assist feeding - even with so-so mags

long duration delay clips are not always the answer if the nozzle doesn't retract enough

if you only got a 5.75mm gap in front of nozzle then a bb may not slip past & feed no matter how long it is retracted for

but on an insane dsg which doesn't have a delay clip as such, it will feed if there is enough nozzle clearance to slip past

 

[Enid_Puceflange]

I Must say Asomodai , your posts are quite inspirational to me

I'm on the hunt for a FAMAS of some description to have a tinker about with and upgrade if possible

Just need to find one first ?

 

[Asomodai]

Stuff

I opened the gearbox back up. I got a spare SRC 18:1 Sector gear (My last one) that seemed to mesh quite well with the JG spur and bevel. With the original gear I did the test you mentioned about grinding down the third tooth, unfortunately I couldn't get the piston to release even grinding down the third tooth to over half its height. To the point where it really wasn't doing much, so I decided to do a one tooth short stroke with the last remaining sector gear. 

I installed the full cylinder I had, thinner walls then the 4/5ths one, but same diameter, so in theory a bit of extra volume. I dremeled off the first tooth of the new sector gear, accidently knicked the second tooth a little bit (Dammit! Should be ok?) This sector gear had a small built in delay mound, not the type to install an aftermarket delayer. 

Put it all back together using the spring that was giving me 342 FPS on the two tooth short stroke and even though I was only one tooth down, I ended up with the same FPS. I may have lost a bit of compression somewhere, probably the Cylinder head is a little looser in the new Cylinder, but its not a massive problem, at least it has kept me under the 350 FPS limit! 2FPS variance and quite consistent Nozzle/tappet/piston sync.

Its a bit sluggish on Full auto in storage mode 7.4V Lipo compared to the two tooth SS, but it really comes to life on the 9.9V LiFE, I need some more of these batteries! Planning to use .28's and .30's so hopefully even if there is a smidgen of undervoluming, it wouldn't matter anyway. 

So not quite there, but with the piston and piston head making the assembly longer inside a very tight tolerance gearbox, it was always going to be a challenge. 

Next up is the Mosfet install! Basic 2 trigger point Acefet. Hopefully will increase responsiveness when using 7.4's 

I Must say Asomodai , your posts are quite inspirational to me

I'm on the hunt for a FAMAS of some description to have a tinker about with and upgrade if possible

Just need to find one first ?

Thank you sir! Go for the Cybergun, The TM's are great, but needed a lot of work to get going by my tech. 

 

[Sitting Duck]

Some SRC's sectors are shite

the cheap SRC sector is made of alloy - not ferrous/attracted to magnets

plus not only it is not as hard wearing as a steel/ferrous/magnetic sector

but the teeth at back of sector that meshes with spur gear are much thinner too

So much so I will never bother using a SRC sector ever again, the alloy thin tooth type

the moment a bit of stress, even just in general use, the thin weak teeth at back of sector just wrecks....

see here... 







View attachment 15912

If you got a better SRC sector then no worries, but if it was an alloy looking SRC stamp sector

with real narrow teeth on the rear, watch out coz there is little strength/contact in that shite sector

(only thing decent-ish in the whole cheap SRC gear set is the bevel as it is 5 arl lug bevel - rest is crap)

 

[Asomodai]

Some SRC's sectors are shite

the cheap SRC sector is made of alloy - not ferrous/attracted to magnets

plus not only it is not as hard wearing as a steel/ferrous/magnetic sector

but the teeth at back of sector that meshes with spur gear are much thinner too

So much so I will never bother using a SRC sector ever again, the alloy thin tooth type

the moment a bit of stress, even just in general use, the thin weak teeth at back of sector just wrecks....

see here... 







View attachment 15912

If you got a better SRC sector then no worries, but if it was an alloy looking SRC stamp sector

with real narrow teeth on the rear, watch out coz there is little strength/contact in that shite sector

(only thing decent-ish in the whole cheap SRC gear set is the bevel as it is 5 arl lug bevel - rest is crap)

Luckily mine is from a Gen 2 G36, pretty robust. Mine was not stamped SRC either. 

I think the project has been finished. I had an absolute nightmare trying to rewire this with thick 16AWG wire. Trying to get the gearbox to fit back into the pistol grip I managed to shear off the positive motor tab so had to chuck the pretty decent stock Ferrite motor. Luckily I had a spare unused SHS Green 16TPA Neo. There was no room to put the mosfet anywhere in the body so had to extend the wiring out into the stock, which because the way the holes in the back of the body and front of the stock piece line up, meant I had to melt my way into making a bigger hole to allow a mosfet through as well as the wires needed. This means I can no longer fit my decent high power LiFE batteries. Will need to invest in some smaller ones with a lower C rating. Admittedly using the storage charged LiFE meant the ARX was very very close to double fire on Semi, so probably best to for a lower C rated LiFE anyway. 

Put it all back together and had a quick test fire. FPS has settled around 348 on .2's with zero hop. 

I have put about 300 rounds through it, I hope it lasts awhile as I really don't to have to deal with the wiring again! Its my most hated job. 

View attachment 46364

View attachment 46365

View attachment 46366

Here is a quick test with a fully charged 7.4 Lipo. Seems pretty swift! Not sure about motor height at the moment, sounds very different from yesterdays test, but could be because of a different motor and less powerful battery. It's firing faster then my P90 with a 14:1 gearset. 

What do you guys think?

 

[Sitting Duck]

Very nice sir, yeah 16awg is a thick bitch at about 3mm diameter

Alpha eco wire is quite a bit thinner but stiff as f*ck

If a Gate nano mosfet was used, one with deans at both ends

then you could run Alpha 14awg stiff as f*ck mofo wire in the box

& silicone for the battery, as silicone is nice and bendy/flexible to tuck in stock etc...

(but that is me being a tart but pointing out pro's n con's of the popular wire types)

A tiny bit shrilly on the start of the cycle - but I have heard & done a LOT worse at times

half a turn either way on motor height screw should help a smidge

and/or as it is a v3 with motor cage, loosen the cage very slightly

you should have a minor bit of play, see if you can alter the angle a smidge

retest and see how it sounds

reckon with a whisper of adjustment the shrill should quieten down

throwing the motor cage angle a smidge should work & hold to improve the angle of pinion to bevel

on some boxes though there was a little bit of a wobble where the cage doesn't bite/clamp

you don't want to go ultra nutz tightening the motor cage to box or risk stripping M3 threads

so if still a smidge loose/wobbly, work out if cage tilts forward/back a smidge

then place a bit of paper/card on one side below box where it meets the motor cage

That should just swing the motor angle a smidge & hold it there

a bit of a pull to one side should get the motor inline better and reduce that slight shrill

TBH, I've never been a fan of LiFe's, they do seem to have a bit more juice

but I think real raw grunt they are not quite on par with LiPo's

I know they add some zest to stock guns over a 7.4v

BUT when I've tested them in tweaked guns there was not such a difference

leading to suspect they might lack as much raw brute power as the punch from mofo LiPo's

So I've tended to get a gun tweaked up a bit and just run with 7.4v 25c

(cheap & easy to source in a variety of sizes/specs)

But that is just my opinion - but I know others love their LiFe's, just I feel LiPo's still rock