Specna Edge/Orion Gearbox Stripped Gears Twice in 2 Months - 11.1v lipo

[Will (Bad Boy) Smith]

My Specna Arms Edge SA-E11 has chewed TWO gearboxes. It's firing around 22fps on auto with 11.1v lipo - is this likely because the gear is meeting the piston on the way back? Is it a spring problem or a battery problem?

TLDR;

I had a brand new Specna Arms Edge SA-E11 from SoftairGames.net but within a month, the gearbox chewed itself up. I'd played with it 2 or 3 times only. The Orion gearbox that comes in these is supposed to be uprated with metal piston teeth, o-ring nozzle etc. and it was a nice replica. The gearbox is specified to handle springs up to 150. Evike.com recommend 11.1v lipo. Patrolbase suggest 7.4. Softairgames gave a choice, but said, "less trouble with the 7.4 without being specific about what that meant". So I decided to get the 11.v - as I'm a noob and more is better right?

Gun Sucks - seems you *don't* get what you pay for

The first trouble was, when it arrived with a weak 270fps, nowhere near the promised 340fps and not terribly accurate. Shots would go left and right. I spoke to SoftairGames and they reluctantly admitted that they may have swapped out the spring for a non-EU spec one and finally, reluctantly agreed to send out the correct spring. I'm not impressed with Softairgames by the way. Their customer service doesn't put the customer first. They try to avoid liability and against EU law they'll expect you to pay shipping charges in both directions, even under Warranty, which they also shorten.

Spring upgrade (to correct?, stock Specna spring)

They are quick-change springs inserted from the back. They are also shorter than standard springs - I don't know if anyone else has seen those before or whether it matters. I put in the new spring, and corrected some barrel wobble using rubber grommets which appeared to be a culprit of the wayward shots.

Broke on first test

Test firing no problem on semi, but almost as soon as I put the gun on auto, there was a clunk, followed by an awful noise and screeching. Looking inside the gearbox from the back I could see the stripped gears. 

View attachment 49247

I won't buy from SoftairGames.net again

I didn't trust SoftairGames to repair or replace FoC and were likely to hold my gun to ransom in Italy (shipped at cost from me in the UK) and say that I'd somehow not replaced the spring (which they swapped first) properly (which I had). I wasn't getting any joy from the EU consumer advice department so I figured since I was into about £60 worth of shipping alone I might as well write off SoftairGames and chalk it down to a bad experience and repair it myself. Warranty more or less unusable.

View attachment 49245View attachment 49246View attachment 49243

I repaired the gearbox myself.

Now those of you who remember doing this for the first time know this isn't a quick job, but to cut a long story short, I repaired and slightly upgraded the gearbox with Nuprol 16:1 gears, 8mm Ceramic bearings from Patrolbase and nicely shimmed it. Imperceptible lateral movement, gears spinning freely, gun grease (ptfe grease on the spring so as not to corrode the plastic piston) and a little silicone oil on other parts like the nozzle.

View attachment 49244

Looks good so far

All good again on Semi but now 370fps on 0.2 so unfortunately, I had to downgrade it. So I replaced the weedy original spring. Find on Semi. Fine on full auto. And now firing at 22fps. So I took it to out to play yesterday.

View attachment 49249View attachment 49248

2 Minutes on Auto and it failed again.

I had a game on semi, mainly to zero the sights, and the barrel wobble I stopped seemed to make it fire much more straight. But in the second game I started to fire three round bursts in full auto mode. Within a couple of minutes, the gun was spinning gears like the cogs weren't engaged. Upon inspection later that night, I can't see any stripped gears looking through the inspection holes, and they're all inline in the right places, but the motor is clearly engaging and spinning the first gear but it's not making contact with the second two. So I'm guessing that when I open the gearbox up I'll find a few teeth missing again.

Might as well upgrade to HPA?

I'm not sure where to go from here. I don't what to throw good money after bad. Am I just unlucky with the 11.v Lipo? The rate of fire doesn't seem that high. Although I'm now an accomplished gearbox mender, it takes time and the parts aren't cheap. I'm confident I took my time to get it right. Would I be better investing in upgrading to HPA instead, for a simpler device?

From what I can tell, the only reason I wouldn't want to do that is the airpipe coming out of the bottom. Although most guns are large enough, I can't work out why they can't hide a compressed air cylinder in the design.

Help, advice please?

 

[Davegolf]

AEGs are one of those things, when everything works together they work for an eternity,

If you did get the gearbox rebuilt spot on last time and you were at 22 RPS then you shouldn't have any pre-engagement issues provided the spring is powerful enough and the piston is unimpeded in its movement.

The only other thing that wild cause pre engagement is if there was a blockage in the hop/barrel.

If piston / sector failure is not the culprit as before then you have other mechanical issues.

Take it apart and inspect / report, also list all the parts.

I know it's frustrating but I wouldn't jump ship, the grass isn't always greener.

 

[Will (Bad Boy) Smith]

Could I have used the wrong oil/grease and slowed down the piston? But as you say, if it's doing 22rps it must have been moving ok. I cleaned out the barrel etc and all the previous gunk in the gearbox. 

My concern is that I could stick another set of gears in there and be in exactly the same boat in a few shots time again. 7.4v battery would be safer but I'm still really surprised that it seems so vulnerable. I'm tempted to get stronger/expensive gears - but I could still be throwing good money after bad.

I'm only speculating on the cause of the failures. Can you think of any ways to confirm?

 

[Davegolf]

The only way is to inspect it, there's always a reason and more expensive parts doesn't necessarily fix anything.

As of now you don't actually now what has failed, correct?

Looking at your original pics did it strip the piston 1st time round?

 

[Will (Bad Boy) Smith]

Nope, I'm not sure, but I'm over 98% confident it's gears again. The motor is freely turning the first gear but the other two aren't engaging with it. They're all in alignment though and move freely on their own. If I turn the two piston gears they again move freely and start to drag the piston back. When I spin the motor again, they nudge, as if just touched, but then presumably fall back into the 'clean' section where there are no teeth to engage the gears.

I will strip down later tonight and report back.

However, something else I noticed; when I move the two piston gears [can't remember the proper names for the three] the piston starts to move back but then settles back again. There's no main spring in the gearbox at the moment, but I suspect that's the spring attached to the long plastic actuator thing? It's presumably supposed to do that?

I guess I could also gently push the piston slightly forward so it disengages with it's rotary gear, allowing me to turn them 180 - likely then I'll see if there are missing teeth.

It never did damage the piston btw. That's all metal teeth and in great condition.

 

[Davegolf]

That's what I was wondering, I don't really like full metal pistons because it's nice to have a sacrificial part... EG the piston, much easier to swap a piston than re shim a gear set if SHTF!

Cool yeh have a look, it's all speculation other wise ?

 

[Will (Bad Boy) Smith]

Yep. As I suspected, although more than I'd guessed. Every tooth has been shaved off the bevel gear where it connects to the spur gear, which looks intact.

View attachment 49282View attachment 49285View attachment 49281

The piston appears to move freely and all the gears spin as they should. There are just no teeth on that gear above. Strangely, there's no damage on the spur gear. Perhaps that's the harder metal.

One thing has occurred to me though, as I remember from the build. The nozzle return spring (pictured below) is a fraction shorter, approx 1/12th shorter. I recall the spring loop at one end broke off somehow, or straightened, so I bent one of the coils 90degrees to make a new one, effectively shortening the spring by just a fraction.

I don't know what effect that would have, but it's worth replacing whilst I'm inside. Other than that, I'm not sure what would cause that gear to completely strip?

View attachment 49284

 

[Davegolf]

The tappet plate spring will have no effect, actually a lot of DSG builds do that so it keeps up.

Assuming the box was built perfectly both times I would have to say that pre engagement is the cause, it's just that being a full steel piston the next weakest part is going to be the the one to fail - hence you breaking a gear axle and teeth 1sf time round and stripping the bevel this time.

Is there not any witness marks on the first few teeth from slippage on the piston rack?

Get yourself an ICS Orange POM, CYMA white or SHS blue piston - NON FULL STEEL RACK!

Remember to check the piston move freely... I.E. will fall end to end in the gearbox casing without a piston head or cylinder fitted, then recheck with the piston head and cylinder fitted (should slide easily, it won't fall because of the piston head O ring)

If you want to be really safe then short stroke it 1 tooth and you'll be sound as a pound on 11.1V

Also if you're running 18:1 gear ratio the ICS gearset is really nice, quiet and very strong.

https://www.fire-support.co.uk/product/ics-standard-gear-set-for-version-2--version-3

PS you'd prob want a delay chip to go with those gears.

SOZ FOR THE BRAIN DUMP

Does this have the silly double seal piston head?

What power spring are you running for what FPS?

What length inner barrel?

 

[MrInfernal]

What is the rating fo the spring that you were using when the problems occur?

I have Specna Arms Edge SA-E06 and it does about 377 fps with 0.2g BBs on M110 spring. But I want to upgrade it to M130 spring, I don't mind to shorten the life expectancy of stock internals since I planned to replace them for something better anyway. But  I don't want it to chew itself up after two games, that would be too bad.

Also I hope that M130 spirng will help to lessen the problem I have now with 11.1V batter and M110 spring when the gun sometimes does more that one cycle on semi, just runs too fast.

 

[Will (Bad Boy) Smith]

@MrInfernal I don't know which two springs they ship in the box to the vendor before they ready for customer shipping, but mine came with the spring that's installed now, which yields a pretty weak 270fps. I can't tell you for sure what Mnnn that is. The *other* spring they subsequently supplied as you can see from the chrono pic my first post yields around 370fps so I'm guessing that's the M110 that you have in yours. It broke on both. The first time on a factory built gearbox with the stronger spring you have, and the second time around with the weaker spring after I rebuilt it with the 16:1 gears. It failed much more quickly.

Unfortunately, 340fps +/-10% is the limit for most UK CQB sites AFAICT and certainly where I play. So 370 is a non-starter on 0.20s.

Interestingly, I've had mine fire more than once on semi. In fact after the rebuild I was getting two shots for every single trigger pull on semi. But a momentary burst on auto seemed to fix that. 

 

[Davegolf]

Yeh 16:1 with 11.1 is a tad fast, hence the pre engagement most likely. Double shot due to overspin because the mosfet cannot brake enough. If it does at all???

 

[MrInfernal]

@Will (Bad Boy) Smith I must say that at first I was worried a lot, I thought that it stripped after some minor spring change, but now it seems that the whole box/insides are just weird whatever you do. Hope that I will have more luck thank you. I will try the M130 since the M110 goes just fine only tad too fast on rps with 11.1V battery.

 

[Will (Bad Boy) Smith]

@Davegolf thanks for the braindump. I'll take all your pointers. I'm curious as to the cause of pre-engagement if that's what we think. You don't think the 11.1 lipo is too much then? I'm tempted to move down to a 7.4, but of course, this particular gun is supposed to manage, and @MrInfernal sounds like he's running his on 11.1v which is frustrating. Exact same gearbox, hop up, bucking etc.

If it is the speed/rof then surely it's not *that* fast. The chrono looks like it's clocking around 17fps in fact (I may have misread previously). However, and I'm speculating here since I'm only new to the engineering aspects here, that barrel length and hop up must make a difference on how fast the piston can return. @MrInfernal says he has a SA-E06 which if anything appears to have at least the same length barrel, perhaps longer, @MrInfernal would have to report back. The SA-E06 is longer by 5.5cm but in my SA-E11 the inner barrel goes all the way to the end of the 10cm mock silencer, so it's hard to tell which is longer for sure. @Davegolf my 6.03mm inner barrel measures @ 300mm since you asked.

There was a bb sitting on the hop when I looked through the barrel, but that's probably just waiting to fire when it trashed itself. The bb didn't appear to be damaged at all and wasn't blocked. The barrel itself is flawlessly shiny and clean as a whistle.

I was trying to get my fps spot on 340fps +/- as advertised (but I didn't buy from Patrolbase unfortunately - as they were out of stock and I was impatient). I have a selection of springs now, but the two Specna springs I have around about 4cm shorter than the other standard springs I have. 

The gearbox has failed twice, once with a higher spring (M110 I believe) on a factory build, and then again recently with the weaker spring, but with 16:1 gears as well. Have I made the pre-engagement with the 11.1v even more likely with the 16:1 gears - and how's it best to fix it? Would shorter stroking by one tooth make that much difference? It might also allow me to use the M110 and get it nearer to 340fps instead of the 370 do you think?

I get the logic of making the piston weaker so it's fails faster, but I don't really want any of it to fail. I know there are much faster AEGs than mine which originally was stock. I'm pretty disappointed with this so-called uprated gearbox's inability to survive what seems pretty standard. To me it seems that with today's RoF AEGs are surely inferior to far simpler systems with less moving parts like HPA. If I was designing something electric from scratch today I'd probably look at electromagnetic, but HPA is surely still simpler.

@Davegolf, you mentioned a 'delay chip' - are you talking about some programmable mosfet? I wouldn't know what delay to use before it broke again, but it sounds like due to a combination of the 11.1v (even on stock) plus 16:1 gears, 30cm barrel my RoF would need to be reduced to avoid pre-enagement. Is that what we're saying? I'm nervous about throwing more good money after bad. Another gear set, a new piston and a Gate Titan I'd be into £150 to £200 in parts alone. For £140 I could cut my losses and just get a brand new Krytak Nautilus gearbox. Or from what I can tell, £300 I could drop in a mid-range HPA engine. Plus tank, regs, connectors & hose of course, but there are bundles and even complete HPA M4s for £400 to £500.

Or could I keep the setup I have (16:1 gears, 11.1v lipo) and just lose a tooth on the piston, maybe upgrade the bucking and hop then choose the right spring to get me back to 340fps.

Here's the piston removed. As Specna already have a gap between teeth 1 and 3 it normally engages really nicely, when I rotate the gears by hand, which of course assumes the piston is fully returned. I suspect for short stroking you're talking about removing a tooth near the other end? And yes, there are TWO O-Rings. 

View attachment 49290

Yeh 16:1 with 11.1 is a tad fast, hence the pre engagement most likely. Double shot due to overspin because the mosfet cannot brake enough. If it does at all???

@Davegolf It's supposed to take 11.1 stock - which originally it was. It broke within a month originally after I tried installing the stronger Specna spring it was supposed to have originally shipped with that @MrInfernal has. The mosfet that comes standard on the Edge is for power only, it has no programmable microcontroller, so no braking, no.

@Will (Bad Boy) Smith I must say that at first I was worried a lot, I thought that it stripped after some minor spring change, but now it seems that the whole box/insides are just weird whatever you do. Hope that I will have more luck thank you. I will try the M130 since the M110 goes just fine only tad too fast on rps with 11.1V battery.

So to be clear, you're running the same gearbox (and gun basically) with 11.v lipo and M110 spring with auto burst mode?

Where are you getting your new springs from? Have you noticed they are longer than the Specna springs?

How long have you run it? has it ever failed?

@MrInfernal Do you know your RoF - have you any idea what inner barrel length the SA-E06 has?

 

[MrInfernal]

@Will (Bad Boy) Smith Yeah I know, because that was one thing why I bought the gun, they stated it has an inner barrel measuring 390mm but in reality, it has 340mm, see a picture that I took yesterday. Little bit saddening but nothing holds me back of using silencer and buying a longer barrel if I need to.

ps. I dont know the rof unfortunately.

View attachment 49293

 

[Davegolf]

You don't need longer barrels.

Built properly an AEG with a 300-400mm barrel should put out 350 FPS with an M100 short stroked 1 tooth. 360 with full teeth.

If not you have incorrect cylinder and poor air seal.

Back to the main problem.

The standard internals running 18:1 with an M100 or higher should be perfectly safe on 11.1

Fitting a faster gearset or weaker spring will make it less safe - you did both when you rebuilt it.

I suspect the original gearbox failed due to a quality control / assembly defect / possible BB jam etc

I suspect the rebuilt gearbox failed due to faster gearset / possible assembly defect.

I would say your options are:

1: Put it back perfectly as stock with a 7.4 - no braking on 11.1 is iffy.

2: Build it up nice right ?‍

 

[Will (Bad Boy) Smith]

Thanks @Davegolf, so that's a good summary of my options.

So @MrInfernal is running stock 11.v with a longer barrel than me. Seemingly defect free.

As I understand it, I need a stronger spring with 11.1v which makes sense now. So it sounds like my most economic option now would be to go back to 18:1 and shim it right again. I should be in the same territory as @MrInfernal. Of course this all comes back to SoftairGames customer service screwing me over. They put the wrong (weaker) spring in to begin with, despite me asking specifically for the 350fps spring *and* a recommendation for 11.1v lipo.

Alternatively, I guess could try 7.4v with 16:1? but that seems pointless, and I might just as well get the 18:1 standard set than risk changing both.

It sounds like 270fps I currently have(had) is indicative of the weaker spring, but I need to get it to around 340 not 370 as it was shooting after my first build with what I'm now reliably guessing is M110.

I also have M105 and M100 from various manufacturers, but as I say, they're longer than the Specna springs - I don't know if that's relevant, or maybe better?

OK. So I'll get a standard gear set and work down carefully, testing on Semi from M110. You think I should be OK on 11.1v even without a brake?

BUT, If I wanted to stick with 16:1 and 11.1v which tooth would I need to lose - and how reliable would that make the avoidance of pre-engagement? I'm aware that I'd need to go slightly higher on the spring, perhaps M110 because of the shorter stroke, but that might be nearer to perfection? Should I avoid the 16:1 unless I have micro-controller braking?

I guess I'm talking about going on and up (spend more) or throttle back.

Should I get a brake anyway? Is that option 2, "Build it up nice right" ?

 

[Davegolf]

Speaking from experience the standard setup with 11.1 should be safe, but it's close - by that I mean it has a full cylinder not a ported one, and a heavy piston/head both of which are not conducive but work.

The problem is the slightest resistance internally mechanically or air blockage will cause it to trip up at 22RPS.

THATS BONE STOCK.

Built up nice the world is your oyster but if your set on 11.1 cos you already have the batteries etc then I would do the following for reliability and your sub 350 UK LEGAL FPS goal;

Type C cylinder

Piston as above

POM piston head

M100 / M110 spring

Sorbo AOE

Everything else stock

Built correctly this would last an eternity.

 

[Will (Bad Boy) Smith]

So the 11.1 is pushing it. Can active braking or a pulled tooth make me safer or do I still have to go lighter on the piston as you suggest above?

Tighter springs are faster I guess?

 

[Davegolf]

Yes

Yes

Yes

No you don't HAVE too

Yes faster returning

 

[MrInfernal]

Just quick question is it possible to install on this(his/mine) gun (with x-asr gate mosfet) additional active brake? If yes, where and how.