L85A1 - Gearbox/motor fault (maybe)

[thebamsco]

Hi folks,

Got a new spring today (m100) for my AA l85a1 (good times)

Fitted it, reassemblled, fired it a few times..... great!

Then.....................

Went to take a few shots.... heard an almighty screech...gun fired.. then... it done the same thing again... then rather than stopping... went to fire again....got the terrible screeching.

On disassembly, i had a look at the piston (really should have replaced it at the time...but money and all that)... first few teeth, werent in best of nick and reckoned perhaps the gear was slipping on it.

However...

On test firing while apart, it turns out the piston is getting cocked 3/4 the way back, to approx tooth 10 or 11 on the piston - the piston teeth after about tooth 4 or 5 are perfect.

So came to the conclusion that on cocking, inside the gearbox seems to jam, ie it keeps the piston coked back two thirds of the way, then just screeches.

So, what ya reckon guys... is my gearbox chanked? Or is the motor chanked and not supplying enough power to get the gears to pull the piston the last bit back... or indeed something else?

Maybe looks like I will go with the semi auto fix, when I get this repaired (new piston/spacer/selector gear) when I have the funds right enough.


Whats your thoughts guys... the help as usual appreciated

J

[thebamsco]

Re: L85A1 - Gearbox/motor fault (maybe)

Does this fault sound like the motor pinion gear to you guys?

Have took the motor out and the gear looks like it is not in top nick.

[Destroyer]

Re: L85A1 - Gearbox/motor fault (maybe)

could be motor depth.......... or any of the gears

or the actual motor itself..... get a tm motor

[thebamsco]

Re: L85A1 - Gearbox/motor fault (maybe)

Not took the gearbox apart (.....yet...) But without load, ie piston it, it turned freely and strong .... the problems only occur under load and then only when it gets to a certain point... ie 2/3 way through stroke.

Motor seems to tun strong and gears, after motor pulled out, turn nice, without any grinding.

Defo thinking its this motor pinion gear... check out the following pic, how curved the gear is, pretty sure there supposed to be nice and staright.

http://vqexzw.bay.livefilestore.com/...hHDrw/gear.jpg

[Destroyer]

Re: L85A1 - Gearbox/motor fault (maybe)

that pinion gear dont look to happy to me....

[thebamsco]

Re: L85A1 - Gearbox/motor fault (maybe)

Definatelly the pinion gear - found the following article

http://reviews.ebay.com/AEG-Motor-ad...00000000112221

Adjusted the hieght - ie moved the pinion about 3mm forward - everything worked good - unfortunatelly the little hex key looks like it is indeed 1.5mm and i dont have the proper key - tightened as much as I could with an imperial equivilent, but kept slipping.

gear looks pretty gubbed anyways, so shopping list for this week....

1 pinion gear(hardened systema one from zero one if it fits) and a 1,5mm allen key

[Oli]

Re: L85A1 - Gearbox/motor fault (maybe)

please note that the AA l85 gearboxes aren't always shimmed correctly (gears loose laterally) under higher loads of stress they can move and touch each other (bad noise)
this then could have caused the wear on your pinion gear.

worth examining.

Oli

[thebamsco]

Re: L85A1 - Gearbox/motor fault (maybe)

Thanks oli.... there was indeed a fair bit of play on the gear that the pinion gear goes too - have ordered up a shim set....

Now to take apart the gearbox - was trying to avoid that, but hey

Thanks again, and big shout out to Zero One for top customer service

[thebamsco]

Re: L85A1 - Gearbox/motor fault (maybe)

Update - Reshimmed (pure pain in the ar$e that was ) And new pinion gear in.

Full degrease and relube while i was at it.

Before problem I re-sprung with a systema m100.

Gun now shoots, really quiet, just a thud from the piston, gearbox is pretty darned quiet, and a good sight better than before the work.

Chrono results from a 6 shot string were between 308 and 310 fps = 309 average +/- 1

Not shabby. Note this was with the hop up set so most likelly a little quicker with it off.

Word on the spring - was expecting 330-340fps with the m100 - reckon perhaps a sfae bet would be for future a m105 to keep within site limits or a m110 - which maybe a bit too close.

NOTE - Don't know if perhaps there is other things wrong, keeping the fps that little bit lower, but everything seems well and the gun is quiet and consistent..so who knows?

Now fingers crossed my novice forays into airsoft tuning don't feck up on me :D