Shimming Gearbox, have questions. DONE.

[MuPPeT_ON_TouR]

Hi,

I've stripped and cleaned me gear box and I'm fitting a new set of SHS 16:1 gears.

Not doing motor so only going for a small upgrade from 18:1 to 16:1.   Pointless to many, and I would agree, but gears that were in it were rusty.. long story (see my very first post in the AEG section).  I wanted to do a shim job to both learn and clean/maintain the gearbox.  Anyhow, the reason I've said the above is so this doesn't stray off topic for what I would like help with.

First gear..   the motor pinion, setting the height.   I've set it so it's aligned with the bevel drive gear, not to high, the outer edges are alinged, I believe this is correct. 

Now setting the height of the bevel drive gear to the pinion, this seems to need a lot of shims to me to get the right height...  But I don't know.

Can anybody confirm?

Motor pinion, this is the first pic.  I moved it up from this original position to remove the slight overhang of pinion to bevel if that makes sense.

View attachment 113052

Below shows the height needed to make contact between pinion and bevel (I know full contact is bad, I will leave a baw hair of play)

Is this too much shimming? Will it cause me issues with the next 2 gears?

View attachment 113053View attachment 113054

Thanks for any help.

 

[Leo Greer]

Take the motor and bevel in hand, and spin them together to find the optimal motor height--the easiest most proper fitment will feel right. You then need to fully close up your gearbox with the bevel in it and screw the motor grip on. From there, adjust the motor height until it reaches the height your hand test showed.

Next, add very small shims beneath the bevel until there is about 0.1-0.3mm of play in the bevel gear. It's important to do all testing with the gearbox tightly screwed shut.

Full contact is good. You want the bevel gear to have a hair of play between it and the pinion, but it looks like your bevel is rather low to my eyes.

After you shim the bevel to pinion, you can add shims to the top until you hopefully end up with just a hair of play. The way I personally measure if I've done it right is by tilting the gearbox side to side, when screwed fully shut. If the bevel gear rotates on its own, yet has maybe 0.1mm of up and down play, I know it's right.

 

[MuPPeT_ON_TouR]

Thank you Leo.

Fitted motor pinion to bevel gear by hand and it's tightest with the motor pinion at an angle to the drive gear.  Can you get better pinion gears with an angle more matching the bevel gear?

View attachment 113060

As this isn't achievable right now the next best thing was pushing the motor further in, there is now a tiny bit of play in the bevel drive and pinion gear but putting an extra 0.1 shim in removed all play to the point I think it is pushing the pinion gear up.

Your advise has made me more comfortable it is as good as it can be, at least for me and has to be better than stock.

Rocking the box back and forth the bevel gear does move but adding 0.1 shim stops it so again your tips have helped.

Thanks again.

 

[MuPPeT_ON_TouR]

All done.  definitely sounding better, on closer inspection of the pinion I could see a shiny spot on the edge, so pretty sure it wasn't making good contact from the factory setup.

Anybody know if new pinion gears with a better fit to HSS gears are available?   Not going to redo just for that but next time gearbox is open I might as well. 

Now getting 13.4 RPS up from the 11.8 I was getting.  No change on the FPS, I wasn't expecting any.

 

[Leo Greer]

All done.  definitely sounding better, on closer inspection of the pinion I could see a shiny spot on the edge, so pretty sure it wasn't making good contact from the factory setup.

Anybody know if new pinion gears with a better fit to HSS gears are available?   Not going to redo just for that but next time gearbox is open I might as well. 

Now getting 13.4 RPS up from the 11.8 I was getting.  No change on the FPS, I wasn't expecting any.

HSS gears? Never heard of them... Where'd you get them from?

Different pinion gears absolutely effect sound and fitment--you can switch pinions with a pinion puller relatively easily as long as your motor has an o-type shaft.

 

[MuPPeT_ON_TouR]

HSS gears? Never heard of them... Where'd you get them from?

Sorry my bad, SHS gears.

Moved onto doing my sons V3 gearbox, just a shim job and a check.   Good job too, a nice surprise from the factory......

View attachment 113107View attachment 113108View attachment 113109

No major sign of damage on any gears, I guess he got lucky....   But...  I have the gearbox open so seems silly not to upgrade, his cylinder head leaks air as well, it slowly loses compression when being compressed coincidently it has the same cylinder head as mine and mine had the same issue.  There also wasn't a drop of grease/silicon lube on the cylinder rails. 

£350 each and nothing but piss poor quality control right out of the box.

 

[Leo Greer]

SHS gears usually match up well with SHS pinions—what’s your motor?

A lot of guns actually have good shimming jobs from the factory nowadays. Truly bad shimming is relatively rare.

 

[MuPPeT_ON_TouR]

SHS gears usually match up well with SHS pinions—what’s your motor?

 I couldn't say who makes the motor, it's a standard stock one, no identifying marks on it at all.  Will not play with the motors on these till they go bad, or I get bored and want a gate titan.

Found the pinion and pinion puller....  new gears and pinion on way for son's gun and mine. 

The shiming job done was probably ok, it was the extra sprinkle of lose shims that over did it.