slipping gear sound when the finger covers the air nozzle 220 FPS ???

[Willyg1981]

Ok guys , so after getting the gun working perfectly and I thought I’d got it perfect for game day it was actually quite hot around 365-370 FPS 

i was pretty sure it was close to 350 it fires 340 , 337, then a few 351, 355, but majority was under so I was quite happy that it would settle ,...well I ended up stripping 3 times at the site on game day practically losing most of the day but eventually getting down to 345,348,347,348,355,351,349 but when doing the strip downs I noticed the shims got a bit mixed up so me being me I didced to do another strip down a few weeks later to put the shims back in correct order and switch out the stock bucking to a pinky’ish maple leaf bucking and also some nice ball bearing bushing and now it’s firing 220 FPS  booooo

when I did the home strip down and fitted the new bucking and bearings and sorted out the shims I did the compression test with the cylinder and it seemed pretty good but when I hooked the battery up to make sure it cycled correctly with a few semi auto shots I hear a gear slipping noise when my finger is pressed over the air nozzle , Iv also noticed the Tappet plate doesn’t want to move freely when the gear box is assembled??? Is that normal ?? 

I’m going to strip it back down again and re-do the cylinder and piston air seal with silicone oil , oh and Iv just fitted a new spring which was a 105 which I thought I wouldn’t need to cut anything and possibly give a more consistent FPS ,which was fitted today with the new bearing and bucking as I’m typing this I’m wondering if it had to of been the piston seal what does everyone else think ? Could it be a case of the motor needing to be wound in a hair giving a bit more torque ? 

[Iceni]

For the TL:DR crowd

Rebuild gun - hot 370fps
Stripped and rebuilt on site. 350fps

Stripped again at home, Added upgrades:
Maple leaf 75!!!! degree.
Bearings
Badly shimmed.

Compression test seemed O.K

FPS low 220fps.

Tappet now binding.

Going to open it again I got some special lube to smear on.

Upgrades to go in:

M105
Going to dog up the motor to see if it makes the gun a bit more special.






O.K....Alrighty then!


Firstly let us have a look at that list I made.


Maple leaf pink rubber... It's 75 degree. For 450+fps guns. In yours, @ 350fps it's going to act more like a stopper than a bucking. It needs swapping for a soft bucking. Maple leaf 50 degree (Green) or Prometheus purple.


Bearings are good provided you seated them correctly.

The bad shim job is responsible for the tappet plate binding in a lot of cases. Chances are the sector gear is too high and it's trapping the tappet between the sector and the gearbox shell.

The bearings may also have changed the shimming requirements of the gearbox. Thicker or thinner walls on the bearings compared to what was removed will mean more or less shims are needed. When you do the bearings you have to do a shim reset and start again from scratch with a motor height reset, then the gears to suit.

 

Fps low 220fps. This is probably due to a compound set of problems. The binding tappet plate, and the hop rubber acting as a stopper. Re-shim correctly, and put in the correct rubber and it should come back up again without needing the new spring.


Dogging to motor up isn't going to give it more of anything. There is a point where the motor pinion meshes correctly with the bevel gear. Too far in all you are doing is mashing the gears together, too far apart they sound very loud or start jumping over each other. It's a balance and there are countless threads and videos about setting up motor height. 


Since you are obviously willing to learn and are the sort of person that will do it anyway I can't tell you to send it out!

So what you need to do is slow down, and start watching shimming video's. Watch what others do and learn.

 

Also, do some research before you buy your parts. The Maple Leaf bucking you picked up is so far off spec it's useless.  Even in a 400fps DMR it's not much use. It's one of those learning curves. Prommy purple is the easy way. It requires the least amount of messing with to get working.

https://eagle6.co.uk/shop/catalog/product/view/id/318/s/laylax-prometheus-hop-up-rubber-nub-soft-purple/


Gears don't slip. The sounds you are having might be poor motor height, the binding tappet plate or something else! It's impossible to tell without the gearbox in front of me.

 

[Willyg1981]

Hahaha yep , I can’t help myself , I have done a lot of research ,but I didn’t do any on the bucking to be honest ,..I bought it in a shop and the owner said it would be fine for a aeg so I just trusted him , obviously a bad move , 

since making the initial post this evening I stripped it back down and got the sector gear down and the taper plate now moves freely , and the gears spin freely ,...

absolutly no pissing chance in hell am I sending it off,  I enjoy it too much lol and I will fix it eventually with the help of you Iceni 😁

what do you mean by “dog up the motor “ ?

sorry to be a bit lame with all this and I really appreciate you taking the time to help me 👍

 

 

Also what does TL:DR crowd mean ? 

[Iceni]

There are 2 motor adjustments.

The most complicated is the pinion to bevel height mesh done with the shims.

The second is the pinion to bevel engagement mesh done with the middle screw on the pistol grip. Dogging up is the action of tightening something to near destruction. As physically tight as your dirty dick beaters can make it. This is the one I mean by dogging up.


TL:DR is a common forum abbreviation. Too Long Didn't Read.

It's used in a few instances, Posts that are more like essays.
Posts that fail to use forum grammar. This is what your original post falls into.

Forum grammar is the way you space your sentences. You use blocks of information for each point to make it easier to read.

 

Ok guys , so after getting the gun working perfectly and I thought I’d got it perfect for game day it was actually quite hot around 365-370 FPS 

 

I was pretty sure it was close to 350 it fires 340 , 337, then a few 351, 355, but majority was under so I was quite happy that it would settle,...well I ended up stripping 3 times at the site on game day, practically losing most of the day but eventually getting down to 350 ish.

 

When doing the strip downs I noticed the shims got a bit mixed up so me being me I decided to do another strip down a few weeks later to put the shims back in correct order and switch out the stock bucking to a pinky’ish maple leaf bucking and also some nice ball bearing bushing and now it’s firing 220 FPS

 

when I got I home stripped down and fitted the new bucking and bearings and sorted out the shims I did the compression test with the cylinder and it seemed pretty good but when I hooked the battery up to make sure it cycled correctly with a few semi-auto shots I hear a gear slipping noise when my finger is pressed over the air nozzle, I've also noticed the Tappet plate doesn’t want to move freely when the gearbox is assembled??? Is that normal ?? 

 

I’m going to strip it back down again and re-do the cylinder and piston air seal with silicone FPS , which was fitted today with the new bearing and bucking as I’m typing this I’m wondering if it had to of been the piston seal what does everyone else think? oil , I've just fitted a new spring which was a 105 which I thought I wouldn’t need to cut anything and possibly give a more consistent

 

Could it be a case of the motor needing to be wound in a hair giving a bit more torque?

[Willyg1981]

Yep ok , the mesh between motor to pinion is fine , I haven’t touched the motor adjustment , all Iv done it switched a few shims round mainly on the sector and spur not much on the bevel gear , Iv just woken up so I’m gonna feed my son then make a coffee then change the bucking back to the previous stock bucking fingers crossed that’ll be all that’s been messing it up god I hope your right Iceni and I’m not even religious 👍

[Willyg1981]

Ahhh ok I see your not only correcting my Airsoft mistakes but also correcting my grammar 😂 . 

Thank you sir 👌

[Iceni]

22 minutes ago, Willyg1981 said:

Yep ok , the mesh between motor to pinion is fine , I haven’t touched the motor adjustment , all Iv done it switched a few shims round mainly on the sector and spur not much on the bevel gear , Iv just woken up so I’m gonna feed my son then make a coffee then change the bucking back to the previous stock bucking fingers crossed that’ll be all that’s been messing it up god I hope your right Iceni and I’m not even religious 👍

Spot on.

If you don't own a chrono - buy one. It's one of the most useful tools if you are rebuilding your own gearboxes. Even a cheap one that isn't perfectly calibrated is far better than trying to guess. 

 

Once you get the gearbox basics down you'll be fine until you come up against your first real problems. Electrical problems are the most common and a multimeter and soldering iron are the most exotic tools you will need. A good supply of heatskrink (ebay assortment packs) and some wire are also good stock items if you tinker. 

Get some basic greases. Silicone and soft moly. It doesn't need to be expensive, just functional.

Get some O-rings. There are multipacks out there, and some will recommend them. I don't because I buy specific rings for specific jobs.

Piston 19x2.5mm in nitrile (buna-N).
Cylinder heads it depends on how wide the grooves are as to what ring is needed.

Going to a store like simply bearings will let you buy 50 rings for about £6. So it's cheap and gives you enough rings to never have to buy them again.

 

[Willyg1981]

Awesome yeah I have quite a bit of the tool list already as I was quite hooked on rc crawling for a while ,

iv just switched the bucking and it was in actual fact a maple leaf blue god knows why I thought it was pink !!!???

anyhow it been changed back to stock and it’s now firing 245 FPS so an increase of 25 approx,...

iv just ordered the promy purple though ,..

 

I did notice a tiny lean in the post that receives trigger spring and attaches in the same manner as the Tappet plate spring , it hooks onto the top of trigger contacts and pulls the fire contact back to the non firing position ,

 

Here’s a straight forward question when I reposition the sector gear I always place all the sector teeth from about 3-9 o’clock this is right isn’t it ? 

 

I have pirchased the xort chrono mk3 I think about £50 which I use and it’s ok 

[Iceni]

Blue would be fine for a 400fps DMR at a push. So it's not a total waste for the future.

For the minute, however, it's still way out there for an AEG. Blue is 70 degree.

Get the old one back in for the minute and see if the work you have done and the old bucking solve your problems. 

Sector gear placement isn't critical. Most put it in so there is no pressure on the tappet plate. Provided there is no engagement on the piston it'll be fine.  You can always hold in the air nozzle if the sector gear is causing rebuild problems.

The low fps at this stage could be a number of things.

The bucking is correct but might be torn (you are on this already)

The air nozzle might have an air leak on the back edge (easy to test)

The piston head o-ring might be damaged or worn. 19(id)x2.5mm nitrile o-ring will fix it.

It might also be worth dropping in the new spring. You have it already so there is no harm in using it.

The cylinder head might have an airseal problem. It's normally o-rings that cause the problem but I have seen warped cylinders and heads also cause problems. 

So before you continue do a full compression test.

Cylinder, Cylinder head, Piston, Piston head. All in the hand and pushed into each other with a finger over the air pipe. See how far you can push the piston into the cylinder before it overpowers your grip and the cylinder head pops off. A good seal is 2-3 teeth, average 4-7, Poor most of the piston or all of the piston. Use the front of the Piston body to the back of the cylinder as your starting position. If you have a ported cylinder this doesn't work.

Once you know the main assembly compression, add the air nozzle and try again. A fast leak is bad, A slow leak is acceptable on a non-O-ring variant. With an Oring nozzle, it should be almost perfect and show the same compression as the test without the nozzle or very close to.

Also double check your BB weight. .2's will want to be close to 350fps, but if you have loaded .25's then the numbers change quite dramatically and 310fps becomes the target.


 

[Willyg1981]

Cool I’ll do another stripdown later this evening and check the air seal again Iv just watched a you tube vids that discusses the point of having the air nozzle set forward which is something I haven’t taken into account at all thanks again Iceni 👍

[Willyg1981]

Update : The air seal is good , so good in fact that it pops the cylinder head off as I compress the piston and so is the air nozzle .

 

I think I can feel a tiny little uneven bump on the o ring of piston though but it seems to be ok ,

 Iv re done the shimming totally and feeling pretty confident and also set the bevel to pinion again ,

 

Iv attached a video of my piston compression test this is without the air nozzle attached ,...see what you think .

[Willyg1981]

2nd update : the tiny post that retracts the firing contacts has now snapped off ,so now it fires on full auto when I pull the trigger ,...

 

 I want to drill and tap a 2.5 x10 mm counter sunk screw but I’m wondering if I’m trying to polish a turd here ,

 

iv just looked online and theres there’s a full g and g gearbox that I could slip straight in there .

 

i like modding but I’m not a sadomasochist lol and wished I’d chucked another £150 into the pot and got the KRYTAC trident  ,.. live and learn I suppose !!! 

 

Just for the record aswell it’s still not working , just before it went into full auto the chrono was saying it was at 245 FPS  

[Iceni]

The little post will be the cut off lever.

https://www.fire-support.co.uk/product/ultimate-version-2-cut-off-lever

 

49 minutes ago, Willyg1981 said:

I want to drill and tap a 2.5 x10 mm counter sunk screw but I’m wondering if I’m trying to polish a turd here ,

You stripped a shell thread as well then.

If the airseal is right, and the hopping is right, then the only thing left is the mainspring and airseal nozzle.

One random question, when you took the hop unit out, did you remove the small spring? And did the small spring go back in place?

The spring is actually quite important. It pushes the hop unit back in towards the gearbox. Without it the hop unit will be sat slightly further forwards and the airseal between the bucking lips and the air nozzle will leak like a sieve. 

 

If the spring is missing rob one out of a ball point pen.

[Willyg1981]

No the spring is on there nice and tight,..

it’s stuck on with a red silicon glue of some sort and has never been taken off , 

 

this is the part part that has snapped , no stripping of screws in shell I was thinking of how to fix the snapped off post and it shouldn’t be a massive job to grind flat ,

 

drill through and then countersink from

the outside Iv got loads of good quality high tensile small screws from

the rc hobby .

 

this is an old picture before the piston change but it serves the purpose of showing the post in question.

 

Could you see the video I posted it’s not showing on my feed ????

[Iceni]

Never seen one of those pins break!

You are right about the drilling of a new hole, I wouldn't bother tapping it. I'd drop a small nut on the inside of the shell with some red threadlock. You should have enough space on the internal shell wall that nothing interacts.

 

6 minutes ago, Willyg1981 said:

before the piston change

You didn't mention you had changed the piston. Did you check it moves freely in the gearbox shells when clamped closed? A small amount of resistance can significantly slow down a piston, and that will affect the FPS. 


Outside of that, you are near to exhausting what I can do for you.

Airseals are good.
Gearbox is running.
Potential bucking problems resolved.
New spring has been added.

There isn't a lot more I can add without having the gearbox in front of me to look at it.

[Willyg1981]

The other thing I have noticed is that the new Tappet plate that I got from ak2m4 that’s in there now isn’t a perfect right angle from the “back bone “up to the air nozzle “bridle/yolk “ section it’s not a huge amount but I’m desperate to fathom this out .

excuse the crap drawing but you get the gist hopefully , im

thinking this might cause the air nozzle to twist and leak it’s all Iv got now lol 😆 

Cool , I’ll do that then as I can’t find my tapping kit at the moment lol 

 

yeah the new piston it was fitted prior to my game day when it was firing hot , I have not done the piston slide check though which is a good point !!! 

[Iceni]

You replaced the tappet plate as well.....

Dude! You need to mention this.

All upgrades have to be mentioned. Have you Changed the airseal nozzle as well?

I can't be helpful if you don't mention the modifications you have made. Gearboxes are designed for fixed tolerances. And swapping components in bulk leads to all sorts of crazy happening.

The tappet plate might need an adjustment for the hop, The airseal nozzle might be a touch too short for the hop, or fit the air tube badly. You can't just swap both at the same time without knowing how one will affect the other. And if you do you have to know exactly what to look at to make sure you get the engagement of those components correct. This is where gearbox techs make the money.

Put the original tappet plate and air nozzle back on the open shell with the sector gear. Make a note of the maximum extension distance. You need to be accurate with this measurement.

Now drop in the new tappet plate and nozzle. Measure again. If the new set is a shorter distance you need to modify the tappet plate flag to correct the distance.

0.25mm is enough to create a significant air leak at the hop, You can't just go taking off 1mm at a time however as if you take too much and push the nozzle too far forwards you will eat hop rubbers or create a feeding issue. Like I say it's where techs make the money as most people are incapable of making the adjustments correctly.

 

[Willyg1981]

Yeah I bought it along with the other parts you suggested I buy from ak2m4 in my previous posts (huge loss of FPS ) 

 

iv only just switched it because I noticed it needed slight adjustment in terms of chop outs on either side of it just before the air nozzle connection which I did with my makita cordless angle grinder and slitting disc then tided up with a nice flat file , 

 

This is something which I thought was a simple “fit and forget” part but it’s probably the cause of it all now you mention it I recon ,

even when I’d got the gears perfect and would check the movement of it the air nozzle and it doesn’t move as freely as say my sons arp9 .

 

im going to take it all back apart fix the snapped screw and check the width of the Tappet with some callipers and I might aswell check the movement of the piston even though I have used it and it has been firing fine ,...until now ,...

 

However ,..i have noticed small shiny patches of polished aluminium along the piston wings which I put down to the spring bouncing round .

 

 

And no I haven’t changed the air nozzle just the Tappet plate .

[Iceni]

Tappets are normally just a drop in part. It's the combination of tappet and airseal nozzle that can provide problems, I had totally forgotten I'd already advised you on parts in another thread.

The Tappet plate should be O.K. It's the one I normally buy for myself. And I've not had any issues with them. You should still check the distances to just be sure.

Aluminium on the piston is interesting. There is a good chance the piston is binding in the slides. Have you checked the piston slides well in the shells and there are no tight spots when it's all bolted together. You might have to just do some sanding to get it running without resistance.

I'd also totally missed the fact I'd advised you before on the same gearbox! A few of these threads pop up, and it's best not to assume anything even if the same user is posting. It's easy to ask a question and it be another gearbox or gun, so each thread is taken at face value and not linked to anything else.

If you lived locally I'd sit down with you and that gearbox and go through it with you. Chances are it's a really basic problem that you just can't see for looking.

[Willyg1981]

Sorry for the confusion buddy , when I made the the initial install of those parts advised everything fitted fine except the Tappet plate ,

 

I just chucked the original one back in as it didn’t seem to bad and allowed me to check the other parts and low and behold it fired awesome 

 

on the first home tear down after the site fix I decided to get the problem Tappet plate fitted , 

this is when I noticed the chop outs needed ,

 

fitted the new bucking and new spring and this is where the problem started 

 

Iv found a lovely little countersunk screw and nut perfect for the repair so I’m going to do no. 2,00056 tear down lol and check the movement of the Tappet plate get that perfect and then check the piston movement but I’m pretty sure it’s all down to the Tappet plate .

 

thats very kind to offer sitting down with me mate im in pontnewynydd in southwales where are you ? 

 

[Iceni]

Coventry lol! It would be a bit of a drive for you!

 

[Willyg1981]

Tis but a stones throw lol ,....if only ,...thanks for the offer though buddy 👊