AEG's double firing when a weaker spring is installed..
 

This seems to be a REALLY common problem but I can't find much info on it because I'm not really sure what to search for. I've tried terms like 'double fire weak spring' and 'semi auto problem' but not having much luck.


So I have a P90 with the v6 gearbox and an AK with the v3. My friend has an F2000 with a v6. All 3 of the guns are doing this thing where it fires 2-3 round bursts when in semi auto mode.

The P90 came with an M90 spring but both the AK and F2000 came with stronger springs, and only started double/triple firing AFTER they had an M90 put in them for indoor. The AK and F2000 are both brand new.

If anyone could shed some light on the matter I'd really appreciate it. Why does this happen? Since it's only with a weaker spring I'm thinking it has something to do with the motor having too much inertia and not stopping fast enough. I should also mention I'm using 11.1 lipos in the P90 and AK, and my friend's F2000 uses a nimh nunchuck battery.

The only thing I've been told so far is "buy a triggermaster". :banghead:

it's the battery, use a weaker battery.

The problem is that the spring doesn't slow down the gears enough for them to stop after one shot thus they are retaining their momentum for another shot or two even after the power has bee cut off when the first shot was complete.

yup, it's the battery. It too strong for your setup and it's cycling 2-3 times. I had the exact problem with one of my gun, and I just down graded to a weaker battery and it solved it.

active braking is another solution

Your sector gear and the cut off lever may need to be shimmed such that the gear will strike the cut off and stop. I had a similar problem before I installed a trigger master on the P90. The switch was getting stuck and wasn't returning to battery on semi auto. I sanded the rails that the switch rode on, and removed the excess material with silicon gel.

Supposedly active braking is hard on the motor or something like that (was it something about overheating maybe?) but I'd use a weaker battery (if you're keen on using LiPo then 7.2V should do the trick, otherwise a 8.4V NiMh/NiCd will do the trick).

However yes a MOSFET with active braking (such as the TriggerMaster) will do the trick. Or maybe a 6.6V LiFePo4 (Lithium Ferrite Phosphor I think the proper name is). Note that the nominal voltage is 3.3V so either you get it in 6.6V or 9.9V flavours, also it's supposedly a "safer" alternative to LiPo which are prone to "exploding" (but that is if you abuse it and don't take care of it) But still it's probably a good idea to charge LFP batteries in a non flammable "battery bag" like most RC'ers do.

LiFe batteries are even more stable than NiMh... we charged one at 50A (no joke) and it was not even warm. Also shot one with a 3" nail and nail gun... a tiny puff of smoke and nothing... not even warm again.

Hmm, well the thing is that my friend's F2000 does it even with the stock nimh battery.

Well, let me ask this then.. is there a way to make it work on the battery I have? I guess you're saying a triggermaster will.. Is there anything else?


Close, Lithium Ferrite Phosphate.

I did actually try using some 18650 size LiFe cells I had laying around from an old laptop battery, but they can't put enough current out and the gun wouldn't fire at all with them. :(

Oh, question though.. How does the triggermaster know that the gun has fired a full cycle? I'm assuming if the cutoff lever is working properly it just starts braking as soon as the trigger circuit is opened?