Theoritical problem: gears, tapper plate, stripped teeth

[etd]

Problem with a friend's mechbox and from wha he was telling me this is what happened.

He has xyz (the brand) standard ratio gears
I replaced (what he thinks was) a m100 spring to (what I know to have been) an m115 spring.

Now I didn't check his shim job. He says it was perfect and I was in the room when he spent 2-3 hours on it and he tends to be a perfectionist.
Next I installed a better tapper plate spring as I was concerned his was to worn out (the spring was really really weak). We test fired the gun and we both heard the distinct noise of his gears grinding. Now I never touched his gears or his shim job. I told him that he should change his shim job where the sector gear and tapper plate meet as he had different diameter shims everywhere. I explained this may lead to major tappet plate issues as there was a possible catching problem. So he changed everything to be uniform.


So what he states has happened shocked me. Now if what he is saying is true I have a few problems with the logic behind his theories. He went home started trouble shooting. Btw If I'm wrong that's fine I'd rather have a few questions answered and learn a bit more. I find his statements rather impossible:

If you have properly shimmed gears and while closing the mechbox back up.. Let's say the tappet plate got above the shims and was caught between the bushings/shims on the sector gear (this I know is possible). Now "somehow" one of the posts (on the sector gear) pops out of the bushing and goes on an angle and the other post stays in properly with full contact on the bushing. Would you be able to close the mechbox without a fight? Also when you test fired the gun would all of the gear teeth strip before the mechbox seized?

The piston teeth where damaged. Prior to installing anythig he had placed a sorbo pad on the cylinder head and he removed the second piston tooth. He also state she trimmed part of the 3rd tooth down as the engagement was still sketchy.

My theory for the issue is that it's almost impossible to close a properly shimmed gearbox with a gear post all of the way out of the bushing. I find it more likely the xyz gears couldn't handle the new spring or that the shim job enabled to much play causing the bushing to not make snug contact with the gear post/mechbox shell. Both would of my theories would explain the gear shreading. Regaurdless if the gearbox somehow closed without a fight, and a gear post was out of the bushing, this could only happen due to a lack of shims to contain the gears within the bushings correct?

[Kos-Mos]

No.

The shim job was incorrect. The gears where too close to each other and they bound. Once one of the teeth was broken, the fragments probably helped in damaging the other gears.

Shimming takes place in 3D. You have to shim each gear vs the width of the mechbox, then each gear vs each other to make sure they don't bind and finally the whole gear set vs the center of the mechbox to make sure the piston does not get stripped (the pistons usually have weaker sides than the center of the teeth rack).

You would not be able to close the mechbox with something out of alignment.

[etd]

I'm going to back peddle here for a minute so please forgive me. I forgot to mention that the gearbox is slightly warped. If the shimm job was 100% correct, could the tappet plate going over the shims cause the post to somehow pop out if the bushing? Or even the warped mechbox alone? I don't have much experience with warped mechbox shells. I'm using one right now but it has a drop in smooth gearset in there so shimming really isn't a factor.

[VooDooPeteK]

I am not sure how a tappet plate would make a gear pop out of the bushing. Warped or not if its shimmed proper the tappet plate should not cause this

[Jackarutu]

etd,

Could you please supply us a picture of a warped gear box. I've seen a lot of gear boxes from JG to G&P, G&G, Modify, etc. $38 - $200 but never one that was cast of such thin material that it would warp rather then break when stressed. Pehaps I have had one before and just didn't snap to the fact it was warped. A picture would realy help to show better what you are speaking of. Thanks you.

[Amos]

I've seen several warped gearboxes.

Dboys/Boyi is HORRIBLE for that... and that's one of the largest reasons why I refuse to work on DBOY's products

[etd]

At this time im not in possession of said gearbox. I can say (from memory) the bend appeared to be slightly noticible on the upper/middle section of the shell and it's (by eye) around a 5% incline. It doesn't seem like much but when you reach the front end of the upper it's you simply cant overlook it when placed on a level surface.

I've been thinking about the tappet plate/post issue and I can't replicate it with my spare gearbox shell either to the point where a post pops out without some missing shims. Right now I'm wondering if maybe one of us forgot to put in the readjusted shim job before closing it up. Less shims = more movement = possible post falling out of the bushing = teeth misalignment. Ive had tappet plates jump over the shims but it's never done anything more serve than snapping the tapper plate... Never enough to jam up a gearbox or break teeth (unless the broken off/ free floating piece of plastic wedge between some gears). Still the tappet plate is apparently intact.

[ThunderCactus]

Well if you did the shimming with a different tappet plate, then put the new one in there, reassemble the mechbox and make sure the air nozzle moves back and forth freely. I've noticed myself, some tappets are thicker than others. If the sector gear isn't shimmed far enough away from the right side of the mechbox shell, then it can wedge the tappet plate in place, as well as cause serious resistance on the sector gear.
But it sounds more like a motor height problem to me, the only three times I've ever heard gears grind were 1) improper shimming 2)motor set too high or too low 3)piston jammed, broke teeth and stripped gears.

And if your buddy is spending 2-3 hours shimming a mechbox, I'm sorry but he has no idea what he's doing lol
Takes me 5 minutes (fluke perfection on the first try), to 45 minutes (on the worst guns) to get it right.
You do actually want some play in all the gears, .05-.1 on the spur, .1-.2 on the bevel, and .1-.2 on the sector gear. The purpose is to have minimal side to side movement, while still being able to freely spin the gears. So give it a good spin while the mechbox is close and tightened without the anti-reversal latch or cylinder assembly in, and you should get atleast a good 4 full rotations out of the sector gear.

[damage]

Precisely shimmed gearset is quiet, be it flat or helical. I shim gearset a different way. Spins freely and no axle wobble. Here is a 7yr old Prometheus Gearset. Its been into a different Aeg's in the past. Under the grease is in immaculate condition. Only wear is the discoloration of the gear teeth from meshing. It looks like I just installed it yesterday when its brand new.

[OMGWTF]

I'll come out and say it, I was pulling your leg.. just didn't think it would go this far, sorry buddy <3 LOL it'll teach yah not to open other people GBs :P .

There was no misalignment, and the Shim job was flawless for a warped gear box (realistically took 15-20 miuntes, the rest of the 2-3 hours was spent playing xbox and smoking twisty ended cigarettes , while socializing)
The axle was in the both Bushings...

as for shims, different Outside diameter shims were used, but very little, when they were used, the Max thickness was no greater than .005 and were used as the closest shim to the bushings..

It's a simple case of the spring tension being far to great for stock gears (spring was swapped out).. no more no less...

Everyone can Sleep well on ASC tonight