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Double Eagle M906C - Internal upgrades / tinkering

My DE still isn't quite behaving itself, but in a somewhat unexpected way.

I have successfully chrono'd my gun at 305fps with 0.28g BBs.  Which is peachy, that's actually a little hot (should be 296), but the bit of hop required for accurate long-range shooting brings it nicely down to that.  Or should do... if I could do that.   Because that chrono result is currently only achievable when I have no hop nub / arm in place!
With the arm + Omega nub in place, I can't dial out the hop altogether,  in fact it's over-hopping the 0.28s at 15m... and consequently the hefty amount of friction was bringing it down to ~245fps.

This is what it was looking at with allegedly zero hop...
View attachment 102973

So how can this be?  I've checked the nub is correctly located in the arm, both when fitting and when removing it again (The second attempt I used a smidge of Blu-tack to keep it in place, just to make sure it wasn't moving into a weird position)

I tried changing back to the DE's original (figure of eight, squishy) nub.   A bit less impingement but still there.

Ok, maybe it's the G&G Green hop rubber.... so I swapped out for an ML Macaron 50deg.   
A bit less but still there... I'm up to 275fps but it's still slightly over-hopping at the minimum setting!

There aren't many parts to this equation, what on earth could I be doing wrong?

Or do hop rubbers become less intrusive as they wear-in?   (I'm sort-of tempted to go rooting around in my bin for the old knackered one!)

 

 
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the omega nub isn't designed to be used with anything but the maple leaf rubbers, so i wouldn't be surprised seeing those symptoms with a standard style bucking.

that said, it shouldn't really be doing that with the maple leaf bucking.

these are a rotary style hop aren't they, is it possible the tail end isn't engaging in the wheel in it's correct slot?

also worth looking down the barrel whilst moving the hop through it's range of motion, see if it's actually moving as it should.

 
I'm looking down the barrel to check it... the rotary wheel has a slot that only runs halfway around, it's definitely correctly engaged, and the hop applies just as expected - it's just the starting amount that's wrong.
it's weird it's like this now and affecting the velocity so much, whereas everything was fine up to my previous skirmish.

 
In that case it does really sound like the nub has ended up in an odd position/orientation, but you've already checked for that.....

 
I found the old ML Macaron 50deg hop rubber (tatty and grubby as it is), re-installed it, fps back up to 290fps) at minimum hop with 0.28's.
Looking down the barrel there's still a little bit of impingement at the lowest setting, but it's the least of the three I've tried, and that's with the Omega nub in place.
I'll test it outdoors later, it's a little early to sling BBs now, but I don't expect this setup to over-hop.   Back where I was 4 weeks ago?  Maybe.  The feed lip is slightly shredded, I think it might be adding it's own spin to the BB to spoil my accuracy... except it's been bettter than 'fine' in the last skirmish.

Airsoft... it's as much art / luck as science...

 
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Luke at Negative Airsoft has just published an upgrade video of an M906C

He gives it big love




I think mine has definitely started to run at a lower RoF than it used to, really time to get a replacement motor in, and by the contents of this video I should crack open the gearbox to check the o-ring and piston etc are all ok

I'll need some Brave Pills, nurse

 
There’s a decent chance that your DE will never be the same again if you open it up. Airsoft gnus have strange and inexplicable magic that comes into play, making each and every time you open it create new variables. ?

 
Yeah I've resisted the temptation to do it before, but the guns rate of fire has dropped recently (not by much, but enough to show up when testing using my chrono)... I'll swap the motor first

 
RostokMcSpoons said:
Yeah I've resisted the temptation to do it before, but the guns rate of fire has dropped recently (not by much, but enough to show up when testing using my chrono)... I'll swap the motor first
Click to expand...
That is the best thing to do; stick a decent motor in there and see how it goes.  If you changed the spring to a stronger one, that could explain the reduced ROF.

 
After yesterday's skirmish where the motor got very toasty thanks to a lot of burst-fire and semi-auto spamming, I thought I'd try swapping the motor out of my Scarab (which shoots at an impressive RoF, very smoothly), into my DE, to replace the famously 'ok-ish' Chaoli grey thing.

Here's the motor I took from the Scarab, it's a Classic Army '31000' High Torque motor.  
View attachment 111027

Well, the swap went ahead easily enough in physical terms.   At first I had the motor height set (I think) too high, so the motor wasn't running much faster than the Chaoli.  But I lowered it out and the RoF increased quite impressively. 

It still got hot quite quickly.   I also had problems with multi shots when in semi, and overrun in full-auto too.  Is the 31000 TPA too much for my gnu?  It's got an M105 spring in there and shoots at ~330fps with 0.20g, with some hop applied.
I can try some further experimentation with the motor height, but I won't if that motor is just too much for it. 
Backing off to a 7.4v is definitely an option too (though currently I only have one which will fit in the PTS stock - and I'd rather keep that for my SIG)

 

 
If the "31000" value refers to RPM then I think that's a bit too fast a motor.

DE say that the stock motor is 19k RPM (but not at what voltage), I'm running AK2M4 XT 22 TPA ones that are 22k RPM on 11.1v and get a very snappy trigger (due to the better magnets etc.), so 31k RPM is going waaaaay beyond what the stock RPM is.

 
I just put it all back together and chrono tested the RoF, it's 18rps with the 11.1v. It's plenty snappy enough with the 7.4v for semi auto, but although I didn't test that on my chrono, I'd estimate it at about 12-14rps.

I think the 31000 refers to TPA, turns per armature, and the higher number gives more torque and less rpm.  But this is really my first foray into messing with motors so I'm at the bottom of the leaning curve!

This time when I installed the motor I started with the adjustment screw far in, to the point the EFCU wouldn't let the gun fire, and then loosened it off until it sounded healthy.  A bit more loosening might allow that really high RoF that seemed to cause trouble.  The trade off of having the mechanical resistance is the heat getting generated.  It still gets hot after not many shots

 
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RostokMcSpoons said:
I think the 31000 refers to TPA, turns per armature, and the higher number gives more torque and less rpm.  But this is really my first foray into messing with motors so I'm at the bottom of the leaning curve!
Click to expand...


I'm very happy to be corrected by others but to have 31,000 turns of copper wire on an armature would mean that the wire would be microscopically thin :o  (bending the laws of physics kind of thin). I've not disassembled and serviced an electric motors since I used to race RC cars, but it really can't be TPA.

It has to be RPM, but who knows at what voltage so lets assume 11.1v so they can put a nice high number on their packaging ;)  So, I'm still leaning towards it just being too fast a motor, and we've no idea how efficient the Falcon controller is regarding braking the motor so we only get a single gearbox cycle (but as it's made to a very cheap price point I'm going to assume it's nowhere close to as good as say a GATE Titan). A manufacturer like GATE may even publish figures for how high an RPM is supported, so that active braking can occur effectively, and we could use this as our yardstick for the Falcon as well.

 
it's odd I can't find 31000 Classic Army motors to look at the spec sheet. 

( Edit: I can find a product page, but not many specs : https://www.airsoftgi.com/product/NON-Retail-Package-Classic-Army-Speed-Torque-31K-Motor-Long-34144/ )

But another google turned up this list:
 

  • 16 TPA / 31,000 RPM
  • 18 TPA / 28,000 RPM
  • 22 TPA / 25,000 RPM
  • 28 TPA / 19,000 RPM



So I'm thinking you're right, it must be a 16 TPA motor spinning at 31,000rpm that I've now got in there.

Which I don't want - the 22 TPA is definitely what I should be after - more torque, traded for a little less speed (and heat?) ... so it's this one (as per your recommendation) isn't it?

https://www.ak2m4.co.uk/xt-high-torque-motor-22tpa-long-fan?search=22tpa

Bonus for having a fan that might keep it cool too!

Problem is I shouldn't be spending actual money until I get a new contract, but luckily I won't be playing for another 3 weeks so I've got a bit of time.

 
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RostokMcSpoons said:
... more torque, traded for a little less speed (and heat?)
Click to expand...


Well, the magnets in the Chaoli motor etc. are so crap that the XT motor we're talking about is marginally faster than the stock motor (worth one or two extra RPS) and has substantially more torque. Also I'm finding it quite a lot cooler as well :)  

 
What frustrated me hugely in the past was 99% of motors on a website would give the RPM but never the voltage.  Some older spec pdfs used 8.4v nimh.  In the end I actually purchased a chrono rotation thingy (the name escapes me now) so I could measure motors and find out the rpm.  I switched to the XT motors with the little plastic fan on due to the high number of failures with Rocket and ZCI motors when used with 11.1v.  Heat is indeed a killer.  The brushes on the XT contain a little more silver than normal apparently, not sure if that really affects anything.

Oh ask a Chinese motor factory that you want a "something TPA" motor, they won't have a clue what you're talking about ?

Do DE have vents in the motor grip base plate?

 
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I've recently bought a Titan 7.4v battery off the classifieds here, and trying that in the gun with the high speed motor in place was pretty good.  Yeah, the RoF is 'sensible' rather than 'exciting', but the semi auto response is still good, and most importantly the motor stayed cool after a bit of semi and short burst spamming.  If I don't get around to grabbing the 22tpa motor in time for the next skirmish, I'll run with this configuration.

 
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