alex90 Posted March 13, 2017 Share Posted March 13, 2017 so iv built gearbox myself and shimmed and got the engament angle so picks up piston in the 12oclock position and fitted it fired few test shots and making a funny noise from what sounds like the main spring after the piston have slammed forward this is the spec 18.1 gears and shimmed perfectly g&g etu dream army high torque motor tomtac metal rack piston pom piston head WII tech cylinder SHS cylinder head and nozzle ASG ultimate tappet ASG ultimate gearbox shell modify 8mm ceramic bearings standard spring guide (non bearing) guarder SP 95 spring and im using 11.1 25c lipo any idea what the noise could be or if I need to worry about it the gun cycles fine and sound good until it twangs thanks alex Link to comment Share on other sites More sharing options...
Supporters Sitting Duck Posted March 13, 2017 Supporters Share Posted March 13, 2017 the twang can sometimes be down to the spring & the metal spring guides the coils of the spring resonate against the metal spring guide doesn't happen it every build but this twang happens usually now & then on some builds saw a post on airsoft mechanics and they suggested if it drove you nutz a heatshrink sleeve over the guide though this can start to fray or break up in use - however somebody posted about a special h/s tube that was self adhesive I have lived with it on the odd gun myself as it happens say once in 3 or 4 shots only on the odd build to avoid this - just SHOOT MORE Some - very few guns come with a robust plastic bearing spring guide - D-Boys do and the guide is nice (box is ok but spring guide & even stock piston head is quite good) Suppose you might be able to find a very very thin walled pipe and epoxy/glue a short length on that might be a better option but would really need to thin walled for it to function with spring slipping past on compression There was a post on a Krytac doing this but we tend to think it might also be the AR latch not functioning 101% Meaning it didn't catch correctly everytime on the 4 lugs of the bevel gear - quite lame having just 4 lugs Plus this is a Krytac so you'd expect it to be 101% (ish) pukka for the price I mean check the AR latch & its spring is operating correctly but I feel it might be the metal spring guide & spring causing the twanging Link to comment Share on other sites More sharing options...
alex90 Posted March 14, 2017 Author Share Posted March 14, 2017 was playing around last night and it definitely coming from spring/guide area and its almost very shot/cycle of the box it happens but this is running without the top receiver on so might try it with that on or maybe just live with it and the AR latch is a 5 lug style but the spring not 100% but does function but not to worried about that as the motor is pretty torquey and the etu SHOULD finish every rotation Link to comment Share on other sites More sharing options...
alex90 Posted March 14, 2017 Author Share Posted March 14, 2017 do you think a bearing spring guide would have any effect on the sound Link to comment Share on other sites More sharing options...
Supporters Sitting Duck Posted March 14, 2017 Supporters Share Posted March 14, 2017 19 minutes ago, alex90 said: do you think a bearing spring guide would have any effect on the sound only to change it to more a TWOOOONNNNNNGGGG than a TWAAAANNNNNGGGGG - lol Seriously - it "might" but same time it "might not" However depending on what your gun shoots at a bearing spring guide will compress spring a smidge more The bearings will add about 4mm compression - or just over a tooth - this will be about 15fps So DON'T just chuck in bearing spring guide coz it could place you over site limit if you are close to it already if you are at 320fps & site is 350 yeah nowt to lose if you feel it is driving you nutz. The sound in my mind is the metal on metal that might resonate a little as spring settles Think also we in UK might suffer this more than US as they have a higher fps so stronger spring may settle quickly but this resonate theory crap of mine is just that..... You could try a bearing spring guide if fps is a bit low & safe to proceed but could still do it in the end However with old spring guide you could look into plastic or heatshrink or tape to just take off the metal resonance sound Sorry I can't give you a full final solution, I haven't found a complete cure/answer to this myself if I'm honest... Oooh edit - just had a thought in desperation... Could also try turning the spring round the other way too - might help or make it worse Yes irregular springs usually go with tighter coils at the back have found that if you fit an irregular spring it can vary by about 10fps - depending on the direction (some have said the difference is greater but I have chucked in various springs in a quick change APS UAR gun and these are my general findings on many occasions) this might also alter the resonance risk factor too some guns use regular springs - spring looks the exact same at both ends Irregular springs are supposed to be fitted tight coils on spring guide to assist it easier piston retraction But tbh a m100 or so spring isn't going to bust a gut/gun if fitted the other way around Might be worth a try perhaps either before or after if twang/twong still exists Link to comment Share on other sites More sharing options...
alex90 Posted March 14, 2017 Author Share Posted March 14, 2017 was never sure what way the spring went round so could well be the wrong way round and im unsure of fps yet as not tested but I think in this case might be worth just sucking it up and leave alone for a bit and maybe in time might settle down once everything had a chance to bed in but thanks for help Link to comment Share on other sites More sharing options...
Supporters Sitting Duck Posted March 14, 2017 Supporters Share Posted March 14, 2017 1 hour ago, alex90 said: was never sure what way the spring went round so could well be the wrong way round and im unsure of fps yet as not tested but I think in this case might be worth just sucking it up and leave alone for a bit and maybe in time might settle down once everything had a chance to bed in but thanks for help see how it goes, maybe order a bearing spring guide as/when the fps drops a bit swap the spring and bearing spring guide around if it still drives you nutz in a while obviously if the fps really drops over time sub 300fps then you need a new spring The bearing spring guide Vs std guide is only about 15-20fps max I'm still kind of stabbing at stuff - if I was that good I would know for sure how to eliminate it completely in every build I'm 90% certain twanging is from the spring/guide resonance and it "might" be more common on diameter of spring/guide clearance and/or the orientation or how the damn spring is fitted plus other crap BUT - this is still me guessing/stabbing at crap if I'm honest Springs do fade a bit over time but so do the seals - so yup best live with it for a while if possible then have another go at it when it really needs it re-doing spring/guide seals n stuff like AoE Leave it a while - read up some stuff especially the horror stories & disasters/mistakes others make Then hopefully after that you will have gained more insight from other people's failures Your own work benefits from gaining wisdom from others screw ups than your own (wish I had done this a little bit more. Our screw ups are the best way but the most costly) Hey - at least your box went back together - my first one didn't well in my defense it was a crap plastic box with metal gears (SRC Dragon- horrible thing) But didn't help it exploding across the room and never found the AR spring - WTF was that thing ??? plastic threads all stripped - yup learned you DO need the AR latch that I couldn't find the spring to sounded $hite and ran hot blowing fuse from my first attempt at shimming - yeah that will do I thought A real work of art - yeah think we will buy a new box son... That iffy gun that was playing up - yeah it is totally f*cked now boy I'll shut up & yeah - just see how it goes for now sounds about right Link to comment Share on other sites More sharing options...
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