Occasional double-shot on semi?

[SSPKali]

I have recently fitted some 13:1 Solink helical gears to my M733 build. Everything else stayed the same - warhead motor (mid speed one?) 7.4v via a Perun AB++ Totally flawless with the SHS 13:1 gears but a bit noisy, hence the helicals.

 

Now it has started double tapping every 20-40 shots. Tried turning off precocking, turning on “sniper delay” or using AB to no avail.

 

Stripped it down the check trigger trolly and cut off lever - apart from a little greasy gunk I dug out all working fine and shimming spot on.

 

Took one tooth off the pick up side to drop power a smidge (right on site limits with an M95!) and it is still doing it.

 

Any ideas?

[Galvatron]

It may be worth recalibrating your trigger.

[Colin Allen]

6 hours ago, Galvatron said:

It may be worth recalibrating your trigger.

The Perun AB++ uses a traditional trigger switch.

Edited 7 hours ago by Colin Allen

[agors]

it means everything is butter smooth in the gearbox, so well done lol.

 

up the spring and short stroke the sector to meet fps. what barrel and bb weight do you use? 

[Skara]

Does the sector gear properly activate the cut-off lever? Is there enough contact?

Edited 6 hours ago by Skara

[Rogerborg]

2 hours ago, agors said:

up the spring and short stroke the sector to meet fps. 

 

I'd be minded to agree, except that active braking isn't sorting it.  Is there anything sorcerous about brushless motors that might be in play there?

[agors]

I mean, brushless motors have loads of torque and the setup is not great to start with.

there's lots of torque and lots of inertia due to the low ratio Gearset. 

 

I really don't get why people use 7.4v with 13.1 gears.

just use 11.1 and 18:1 gears. same semi time and way less strain on the Gearset and motor (building torque with gears, NOT with motor!)

 

but again, if changing gears and battery is not a possibility then yeah the only solution is to short stroke and use a heavier spring.

 

at some point based on BBs used and barrel length the cylinder to barrel volume ratio will be affected so short stroking won't be the best solution

[Skara]

3 minutes ago, agors said:

at some point based on BBs used and barrel length the cylinder to barrel volume ratio will be affected so short stroking won't be the best solution

We're talking silly long barrels though, 400mm +

Your average 360mm-and-below barreled AEG can take some short stroking. My 7" SSG is short stroked by 4 teeth and I'm pretty sure I can knock five more off without worrying in the slightest about running into voluming issues.

[agors]

well yes because your barrel on a 7inch is only 20cm or so. definitely you're nowhere near that situation but that's a terrible comparison lol. 

 

if the OP has a 363mm+ barrel and using .32 or heavier bbs with -5 on sector then definitely it is to be considered. 

 

in any case case that is a corner case, without knowing OP setup it's difficult to help;

 

independently it is a terrible setup (7.4v+13.1+brushless) IMO. 

[SSPKali]

Thanks all, I am running a 300mm x 6.01mm barrel and 0.28g BBs. 

 

Cut off lever is working fine and being tripped by the sector gear.

 

I am starting to think I will sell the Warhead motor and fit an XT or SHS one as this is only a back up gun and spends more time being used as a test bench than actual use 😁

[Fatboy40]

3 hours ago, Rogerborg said:

 

I'd be minded to agree, except that active braking isn't sorting it.  Is there anything sorcerous about brushless motors that might be in play there?

 

They really don't like active braking, they can stutter etc., and pretty much handle stopping themselves using their own circuitry / speed controller.

 

As the Perun AB++ is an inline MOSFET, it's not an optical controller, it's not smart enough to monitor the cycle of the sector gear. I'd bet an "optical controller" would immediately resolve this, telling the motor to stop at exactly the right time to prevent overspin.

 

I'd try a slower / brushed motor first if one's available, and if all is then good consider your options.

[Zarrin]

I'll occasionally get these kind of issues in a build I throw together. There are two things I can usually do to get the system running smoothly.

- what I usually do to correct it is try different switch blocks (the part of the switch assembly with the single contact that pushes into the two leaf plate contacts) The little molded L shape groove that engages with the end of the cut off lever can come in quite different shapes and thickness from switch block to switch block. Finding one that works well with your setup can help - note that over time that molded piece can get worn down and squished resulting in slipping and sliding that could just cause the effect you are talking about of a double shot - after all it is a very abrupt mechanical / kinetic flick that occurs when the switch block is pushed out of the channel. 

- The other side of the same problem is the cut off lever - It's possible that your new sector gear does not bump the cut off lever quite as consistently as your old gears resulting in a slightly tamer (though usually efficient enough) tug on the switch block, resulting in that almost perfect engagement but just bad enough to give you issues once every 20-40 shots.

@ak2m4 posted on FB not too long ago about some precisely machined switch blocks with a nice big square contact - as someone who still has old school switch assemblies in all but one of my AEGs, that's the kind of thing I would love to get my hands on 😅

I'm guessing if you put something like that in your M733 it might well sort you out.

Edited 1 hour ago by Zarrin