M4 single fire issues

[n1ckh]

After today's skirmish day, I noticed a problem. We did some CQB work and was restricted to single fire

 

The piston isn't always returning fully forwards but not a problem on auto

 

I upgraded piston, cylinder head & nozzle with SHS components, high speed motor & AOE is set correctly with sorbo pad on the cylinder head

 

Shall I put 16:1 high speed gears into the box

 

Nick

[Sitting Duck]

what voltage battery ?

up volts and she should go past & cut off lever return ok

you got an Active Braking fet in there ???

 

I presume you are saying it fires ok but switch screws up as it stops too quick on that dead zone of cut off lever

 

rather than trying to double cycle - doubt that coz neodym motors stop real quick over ferrite motors

 

or is she not always firing one cylce on semi ??

[n1ckh]

No MOSFET/AB fet

8.4v NiMH

 

Sometimes it will be fine but then sometimes 3 or 4 bb's roll out so a quick burst on auto and its ok

 

I would say it doesn't cycle properly on single fire sometimes

[Sitting Duck]

not cycle properly on semi might be iffy contacts on switch/selector plate

or selector might not 101% perfect position/contact

 

3 or 4 bb's though rolling out that is strange feed issue but only does this on semi

so it might be "stuttering" and not smooth uninterupted cycle, jittering halfway

and perhaps where more than 1 bb gets loaded

 

normally there are 2 copper strips behind switch that make contact with copper on selector plate

quite a few makes actually have these 2 strips linked but a few do not

 

in a nutshell the "linked" strips could fire on safety in the safety lever arm fails/removed

but as they are linked already the copper on selector plate is doing jack $hit really

 

the unlinked ones can't fire in safety coz selector plate doesn't short them out

but if BOTH of those copper strips do not make perfect contact on selector plate

then you get bad connection and fire problems

 

I don't know if G&G have these linked or not just behind switch assembly

 

http://www.google.co.uk/imgres?imgurl=http://i.imgur.com/UKfir.jpg&imgrefurl=http://www.airsoftforum.com/board/topic/238922-shs-switch-assembly/&h=468&w=781&tbnid=aEvmACnyaiDMmM:&zoom=1&docid=yKhr8K4HP5kzxM&ei=PN3XVLzvF_LQ7QbYg4GAAw&tbm=isch&ved=0CHAQMyhGMEY

 

but deffo seen these wired as seperate contacts which in that case has to have both on a complete circuit to fire

and also

seen these with a link in which means the copper slip on selector is not needed

 

if 2 seperate strips - then it is yet another area for carbon to build up and create an iffy connection

plus both strips need to make good solid connection on semi/auto

and have seen these strips not make great connections on a APS gearbox build that was crap on semi

but was perfect on full auto - will just short them strips next time I have it in bits

[Sitting Duck]

might be other stuff but taking a noobish guess it could be from iffy contacts creating some or most of them problems

[n1ckh]

All that is fine duck, the trigger contacts are fine as I pinched them in a bit to reduce chance of arcing but now is the time to install the MOSFET I've got

 

I'll crack the gearbox and see if anythings shifted, recheck AOE etc

[Sitting Duck]

think it might be more electrical rather than mechanical

them contacts if seperate behind selector plate both have to be perfectly touching the selector copper plate

and making a perfect circuit with all 3 or you get problems - I feel more often on semi

 

edit - HAHAAA found the pic to explain more:

 

http://www.google.co.uk/imgres?imgurl=http://tigertacticalairsoft.com/images/NB0027a.jpg&imgrefurl=http://tigertacticalairsoft.com/trigger-switch-gearbox-blue-p-734.html&h=338&w=450&tbnid=fzsZ8PBaq488HM:&zoom=1&docid=qpBkw3ln7fxbyM&ei=aePXVJnxGuav7AagqoDYBQ&tbm=isch&ved=0CCkQMygKMAo

 

see - them two strips are linked on this one so selector plate copper is doing jack $hit

not safe is safety lever arm fails but bet it fires better coz selector plate don't need contact

[n1ckh]

That's all fine duck but now's the perfect time to stick in a MOSFET so out comes the soldering iron

 

It could also be that I was releasing the trigger a bit to early today it happened 2 maybe 3 times during that one game but fine rest of the time as it was 3 round bursts on auto

 

I'll crack the gearbox anyway

[Sitting Duck]

Just saying if one of them 2 seperate prongs is not completely touching the selector plate it "can" create problems

especially if one of them prongs or strips is higher than other I found.....

 

it "can" push the selector plate copper or bow it a bit and not make great contact on the other prong

it seems more likely to happen on semi than auto coz maybe the selector isn't

in the selector "tracks" so much on side of gearbox on semi

(further back in tracks & less chance of bowing maybe on auto)

 

pinching the switch contacts or making sure they engage switch is great but if them seperate prongs

behind selector plate are not 101% touching then the circuit is not completed = problems

 

Well that is my hunch - very noobish for what it is worth - see what others might say

but might be worth either getting a shs blue switch or do your own link to rule out that problem area on selector plate contacts

 

Finally please note - I not got my G&G box to hand so they might have them contacts "linked" already

but if they are seperate like some are then that could be one area to investigate further

 

the bottom single contact prong - on the other side inside box runs to motor

the top single contact prong - goes to one side of switch contacts

if selector plate doesn't complete circuit 101% perfect then you will have iffy circuit even if switch contacts are soldered together

 

the blue shs type has these linked so they will be making a perfect contact - heck you could remove the copper clip of selector plate on these switch types

UPDATE - Red SHS also has them linked - just colour difference it seems:

http://www.google.co.uk/imgres?imgurl=http://shop.ehobbyasia.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/S/H/SHS-AEGPT-NB0027_1_MARK.jpg&imgrefurl=http://shop.ehobbyasia.com/shs-heat-resistance-switch-for-ver-2-geabox.html&h=600&w=800&tbnid=HkYEfnnMGul4HM:&zoom=1&docid=mwf6ySUsIBBl8M&ei=WG7YVOzTBMSP7AbFpoGAAg&tbm=isch&ved=0CCcQMygGMAY

 

and yes the whole design is poxy and dated but does kinda work - well usually

[n1ckh]

Well the single fire issue has been resolved I was to quick on the trigger, wasn't letting the gears spin round quick enough

 

What difference would putting 16:1 gear set in the GB make

[Sitting Duck]

faster rate of fire (slightly) aprox 10% over 18:1

 

deans + better wire & fet will do same if not more about 15% over stock wiring & small tamiya

(good wire & good fet coz most heat/stress takes place on shotting semi repetatively)

[straffham]

Well the single fire issue has been resolved I was to quick on the trigger, wasn't letting the gears spin round quick enough

 

What difference would putting 16:1 gear set in the GB make

On full auto in theory on a given motor and battery it will give a slightly faster rate of fire yes, BUT it will put slightly greater strain on the motor due to greater torque being required, meaning the motor will probably take longer to spin up, so on semi auto in particular it may slow down trigger response time (unless you already have a high torque motor fitted).