Bevel gear getting pressed against pinion too hard with no shims?

[DropTheBomb]

So I have a very strange problem occur to me when I attempted to shim my CTAC AK74 which is a JG rebrand. Now it seems that with the original JG gears the bevel and pinion gears grind like crazy, and this is with NO shims on the bottom? (wide part) of the bevel.
I adjusted the motor to be perfect as well.

I managed to improve the noise level drastically by using a KWA bevel (once again no shim on the bottom). I noticed the difference between the two bevels is that the KWA has much deeper groves then the JG one.

Although the KWA bevel does fix the noise I found the rest of the gears kinda become out of wack just to be shimmed properly with the bevel. IE stand much higher then they should, so for example the Anti-reversal latch is actually only 3/4 on the bevel gear.

SO this makes me think that either A) Pinion positioning of the side to side position is somehow messed up or B) gearbox shell is a lemon or C) this is normal for some gearboxes?

To give you some reference of shimming i had to do these are my numbers:

Bevel: Top (narrow end) 0.7mm Bottom(Fat end): 0.00mm

Spur: Top(narrow end) .8mm Bottom(Fat end) 0.7mm

Sector Top(Where sector chip sits) .1mm Bottom(Spur-Sector connection) .8mm

Any Ideas?

[ThunderCactus]

Could be the bevel is too close to the pinion causing it to grind all the time. Try shimming it further away from the pinion

[DropTheBomb]

No thats the point I cant there is literally no space to left to push the bevel away from the pinion, as stated I was only able to fix the grinding by getting a "deeper" groove bevel

[ThunderCactus]

see how it looks with the motor in
attach the motor cage on the open half of the mechbox shell and check. Could be the angular alignment is off, but that's pretty rare. Could be a malformed pinion though.

[DropTheBomb]

Dont think its exactly the pinion since I just upgraded to a new motor and same problem exists, mind you it does mesh better then the previous motor.

An attaching the motor it looks pretty good to me, looks straight.

[ThunderCactus]

Try it without the spur gear, maybe it's another gear you're hearing?
If the engagement angle was off, you wouldn't necessarily see it, doesn't take much to be off

[DropTheBomb]

I know this is the bevel for sure since I have put only the bevel in and it is the bevel causing the difference in noise. I know for a fact that it is simply the bevel being pushed on by the pinion. Problem Is of all the gearboxes Ive ever shimmed Ive never come across a gearbox where I didnt have to raise the bevel gear towards the pinion some how, let alone for the pinion to put this much pressure on the bevel from the get go.

To give some idea I put a 0.1mm shim underneath the KWA bevel to raise it towards the pinion and that changed the bevel from running near perfect to grinding.

Now my question is, is it normal for the bevel to be this low sometimes? The gun still functions fine, but im worried about the effect this may have on the gearbox.

As stated because I shim from the bevel it makes the other gears kinda "raised up" so to speak. Im worried this might affect the performance of the Sector on the cut off lever and the Anti-reversal latch on the bevel since they are not perfectly lined up.

[ThunderCactus]

I've had the bevel that low before, but usually in mechboxes that were really wide and needed like 1.3mm of shims

[Dynamo]

is the base of the bevel gear (wide side) rubbing on the gearbox shell? you said it's already too tight for shimming. if it's not touching the gearbox shell, then it's likely that either the bearing/bushing for the bevel gear is not fully seated in its hole. or if it is fully seated, then the shoulder depth of the hole is off spec (poorly made gearbox).

being that you tried a different make of bevel gear and still have the same problem, then it's pointing to a problem with the bushing/bearing sitting too far into the gearbox. a fully seated bearing/bushing, should be either flush or just a hair over the inside wall of the gearbox shell. if the bearing/bushing is sitting more than the thickness of two pieces of paper over the gearbox inside wall surface, then there's your problem.

i had a similar problem with an ares made gearbox for the PTS ACR.
this is how i fixed it.

[lurkingknight]

some bushings sit very proud over the side of the gearbox(SHS), take a pic of the gearbox and show us, dynamo is probably on to something here.

There might be room to sand the bushing to narrow it.

[DropTheBomb]

Alrighty took a good number of pics for you guys. And to answer you Dynamo, no the bevel does not rub at all against the shell. I took a picture of the Anti reversal and sector gears to show you what this pretty much causes in terms of shimming for the other gears. If any other pics are needed just say so.

[Dynamo]

well that confirms it. quite obvious really.

[DropTheBomb]

Hmmmm ok well thats good to know, by chance could you tell me what is that bit you used is called? Or would getting a new gear box shell be more worth it?

And If I do lower it then wont that cause more skewed off gears? as stated the ARL is already only sitting 3/4 on the bevel.

EDIT: Also judging from the pic the sector gear bushing also is sitting a little high, should i lower that one too?

[ThunderCactus]

it's an end mill, and it's a cutting tool.
A "bit" is something you stick in a 1/4" drive impact drill.
it's a better idea to get a new one than have an amateur try to fix the old one. But it's scrap anyway.

[DropTheBomb]

Fair enough, what are some shells that are recommended? Ive done a little bit of google searching and looks like the Lonex shell is recommended quite often.