Q on shimming

[T6e9a]

Just a quick question on shimming; when you change your motor, should you re shim your gearbox? Or should the shimming stay true to being shimmed?

In my thoughts, it might depend on the motor a little bit, but in other thoughts, it seems like a good shimming should be decently universal.

Just wanted to hear a few other opinions or facts on the matter.

[MayhemXXXFrosty (AndrewMp5k)]

If you shimmed your gearbox to your previous motor, your bevel might be too tight on the motor (for instance if you changed brands; like a G&P to a Lonex or something). Not all brands keep the same tolerances, and even QC within the same brand may be off a tad. When you're dealing with fractions of a millimeter, you can never be too safe.

If you're running a decent setup, I wouldn't worry unless you experience issues. If you're running a precision setup, I would be inclined to re shimming it to be sure.

[T6e9a]

Thanks, that makes sense and clears some things up.

[ctres]

I'd tend to agree with mayhem. The "correct" way to do it would be to shim it via motor every time, but in an average setup it probably won't make much of a difference. I'm pretty positive that stock guns are never shimmed that way and they can last a long time. I am a perfectionist and I shim via pinion to bevel every time. Aside from noise and wear, shiming has a lot to do with efficiency of the drivetrain, which is especially relevant when you start pushing more performance from the gearbox.

[drewroud]

The shimming will remain the same except for bevel to pinion. The length of the axle that the pinion gear goes on varies, as well as the dimensions of the pinion gear.

[T6e9a]

Also, should there be any noticeable give in the gears when the box is locked together? Or should it be closer to unnoticeable?

[ctres]

It will depend. You should shim your gears as tight as they will go while still allowing them to spin completely freely. Sometimes, depending on your shell, bushings, gears, an shim sizes, you will be able to shim it until there is pretty much no detectable movement but the gear will still spin freely. Generally I end up with a tiny bit of play, but so little that another .1 mm shim would be too tight. If you are dealing with bearings that may have some wobble within their races then take that into account. You don't want to shim the gears so they push out on the inner races of the bearings.

I always put the motor in with bevel, adjust motor height, then shim the bevel until there is just an ever so slight play when the pinion is in. I then shim the other side of the bevel (left side of the gun) to fill in the gap. After that, don't touch your motor height. If you do, do only quarter turns and keep track. I shim the other gears each individually to figure out how many shims I need total, then install them one at a time and move shims around as needed for maximum tooth contact without the faces of the gears touching.

[T6e9a]

Ok, thanks. That's what I thought that was exactly what I was doing.

[ctres]

You should have no issues then. That is the way I'd recommend to do it every time, but I realize that it is not always practical if you are crunched for time for whatever reason, hence my first comment. I should note also, that it won't always give the absolute quietest shim job. I tried forever to shim my lonex gears with three different grips all with alignment corrected, three different pinions, and hours upon hours of fiddling over the course of several months. I never got it as nice as I wanted. I switched to Seigetek gears about a week ago and literally got it perfect on the first go.

Also, if it is a v2 and you want to give it the best job possible, you have to make sure your receiver isn't messing up alignment. It almost always is, and will require removal of material from the grip so that the pinion contact is the same whether you are testing with just the grip on the gearbox, or the whole gun assembled. This will definitely add a lot of time to the process, but if you have a dremel it will be much quicker.