how to shim a gearbox

[natethegreat32]

So, you are wondering on how to shim your gearbox huh? First off I bet you are wondering what shimming is? well shimming is changing the position of your gears, so that they have the best transfer of energy possible. shimming usually takes 2 hours for a beginner, and 20-30 minutes for the experienced. There are some thing that you will need to shim your gearbox. This includes: shims, epoxy, your gearbox with NOTHING inside except for your bushings and I also suggest some sort of pick or long screwdriver. Now before you start whipping shims everywhere, you will need to glue down your bushings. The purpose behind this is to make sure that your gears do not rotate the bushings in the gearbox while cycling. Add some epoxy to the flanges on the inner hole of your bushings. Press the bushings firmly in place, and wipe off the extra. Good bushings that i recommend are: lonex, shs, zci, vfc etc. As long as your bushings are completely flat, your'e fine. If you are using bearings, you do not need to glue them down, but if they repeatedly fall out, it doesn't hurt. Good bearings that I recommend are: modify ceramics, g&p, and if you have to use lonex go ahead. 

now for the fun part, shimming your bevel gear. We will be using the bevel to pinion method. A method favored by almost every tech. The pinion gear is the gear that cannot be shimmed (besides motor height) so we want to shim the rest of your gears based off of this master gear. The first step you need to do, is set motor height. Setting your motor height is one of the most important things that you can do. If your motor height is not perfect, you will find your self re-shimming constantly trying to get your gears to shut up. Take your bevel gear and insert it face down in the upper half of the gearbox, screw on your grip (or motor cage) and put in the motor and heatsink *like shown in picture. Now adjust the set screw at the bottom of your motor mount to get the bottom of the pinion gear parallel with the bottom of the bevel gear.




After you can visually see your pinion and bevel meshing perfectly, we can move on to achieving perfect b to p. Take the bevel gear and put it in your gearbox, I like to start out with a .1 mm shim on top of the bevel because you generally need at least .1 anyways. Close the gearbox shell and lock it down with every screw, yes you will fail if not every screw is in. Attach the grip, motor, and heatsink. Flip your apparatus so that the bevel gear is flat side down. You can reach down the cylinder head with a screwdriver, or reach in the window next to the bevel gear. Move your bevel back and forth side to side. Basically this is the meshing of the pinion to the bevel. You want the bevel gear to be low enough so that is makes good contact, but not to low to where it is mashed up to the pinion. Odds are that the bevel gear can probably move a bit side to side. Add shims to the TOP of the bevel gear to bring this side to side movement to as low as possible. if you add one more .1 mm shim, it would be too tight and not wiggle at all.     





Now your bevel gear is shimmed to the pinion gear. Your bevel gear can probably move up and down in your gearbox shell, so add shims to the BOTTOM of the bevel gear so that it just barely moves up and down. Again, if you added one more shim, it would be too tight and not move freely. Now we can shim the spur or "step" gear to the bevel gear. Add shims to the bottom of the spur gear so that the spur and bevel mesh perfectly. You want between 50-95% meshing between the two.
*Bad spur to bevel meshing*        

*Good spur to bevel meshing*



Now you can add shims to the top of the spur gear to remove that access movement. You want the spur gear to just barely move up and down just like the other gears. while the gb is locked down with every screw that is. 
Shimming the sector gear is the last step and also the easiest. I like to add one shim at a time to the bottom of the sector gear to raise it up so that it doesn't grind on the spur gear. Once it doesn't grind, I like to add one more shim to account for factory defects (sometimes the gears will be cut differently towards the top of them) Now just like the other two gears, add shims to the top of the sector to shim out the remaining up and down movement to its lowest as possible state..

Now you can put in all of the gears, and close the gearbox shell. Spin the gears with your finger and make sure that there is no wierd grinding noise. And also that there is no added friction. If there is a grinding noise, check each gear meshing with its counterpart(s) and make sure that they have good contact, and are not grinding. If you have added friction, you probably shimmed a gear too tight. Remember, you want each gear to move just a little. You want .09-.03 of approximate up and down movement. If you hear a very strange squeak noise or something that we refer to as "zipping" add some grease to the gear axles and test them again. If it still has that terrible noise, you need to look into new bushings.


There you have it fellas, a method on how to shim your gearbox properly. Remember to take your time and don't be afraid to ask questions. -nathan

[Stinger]

Preferably, you want no up/down movement on the axles of the gears, but still freedom to spin easily.

[T6e9a]

The gap Should be like 0.05mm max(Optimally). Loose enough to spin freely. The less resistance the better. Different people shim slightly differently. All up to your personal preference.

[Stinger]

Sept 20, 2014 22:07:22 GMT -5 T6e9a said:

The gap Should be like 0.05mm max. Loose enough to spin freely. The less resistance the better. Different people shim slightly differently. All up to your personal preference.

What I meant was, it should be as tight as it can be, but still be absolutely free.
If you have a setup where there is a little bit of axle play, but you add a 0.1mm shim and the gear is too tight (can't spin freely) then would have to allow that axle play to remain for the sake of free-spinning gears.

[Deacon]

One thing to mention is to check the position of the Pinion gear against the Bevel gear. Adjusting the motor height at this point before shimming the other gears is recommended.

This will impact your shim adjustments. If you shim it too low and push the pinion gear in later on you're going to get a very nice grinding noise as the pinion gear will push up on the now too low Bevel. (similar to figure 2.)



Easier to just show what I mean.

[Stinger]

Sept 20, 2014 23:55:53 GMT -5 Deacon said:

One thing to mention is to check the position of the Pinion gear against the Bevel gear.

He mentioned setting motor height towards the beginning of his writeup.

[Pagan]

Sept 21, 2014 8:57:43 GMT -5 Stinger said:

Sept 20, 2014 23:55:53 GMT -5 Deacon said:

One thing to mention is to check the position of the Pinion gear against the Bevel gear.

He mentioned setting motor height towards the beginning of his writeup.

Sept 20, 2014 23:55:53 GMT -5 Deacon said:

One thing to mention is to check the position of the Pinion gear against the Bevel gear. Adjusting the motor height at this point before shimming the other gears is recommended.

This will impact your shim adjustments. If you shim it too low and push the pinion gear in later on you're going to get a very nice grinding noise as the pinion gear will push up on the now too low Bevel. (similar to figure 2.)

If you fully read what Deacon mentioned, he is stating that the motor height is important at this early stage. He didn't say the OP left it out, he's stating why it's important.

Your post came off very defensive and frankly a little bit condescending. Deacon added a helpful image to help illustrate what was being described, and wasn't knocking the OPs post, but helping add to it.

[Stinger]

Sept 21, 2014 9:08:32 GMT -5 Pagan said:

Sept 21, 2014 8:57:43 GMT -5 Stinger said:

He mentioned setting motor height towards the beginning of his writeup.

Sept 20, 2014 23:55:53 GMT -5 Deacon said:

One thing to mention is to check the position of the Pinion gear against the Bevel gear. Adjusting the motor height at this point before shimming the other gears is recommended.

This will impact your shim adjustments. If you shim it too low and push the pinion gear in later on you're going to get a very nice grinding noise as the pinion gear will push up on the now too low Bevel. (similar to figure 2.)

If you fully read what Deacon mentioned, he is stating that the motor height is important at this early stage. He didn't say the OP left it out, he's stating why it's important.

Your post came off very defensive and frankly a little bit condescending. Deacon added a helpful image to help illustrate what was being described, and wasn't knocking the OPs post, but helping add to it.

Jeez
Sorry I offended you
I did not intend to condescend, but Deacon made it sound like the OP missed that. He did, after all, say "one thing to mention," as if the OP hadn't mentioned it.

[Deacon]

He mentioned motor height after an edit to include what I suggested.

/end of argument.

[airborn]

Sept 20, 2014 22:16:39 GMT -5 Stinger said:

Sept 20, 2014 22:07:22 GMT -5 T6e9a said:

The gap Should be like 0.05mm max. Loose enough to spin freely. The less resistance the better. Different people shim slightly differently. All up to your personal preference.

What I meant was, it should be as tight as it can be, but still be absolutely free.
If you have a setup where there is a little bit of axle play, but you add a 0.1mm shim and the gear is too tight (can't spin freely) then would have to allow that axle play to remain for the sake of free-spinning gears.

I believe you're stating what OP said in a different way. He did state that you want your gears shimmed as tight as possible while still being able to spin freely, thus eluding that if you put a 0.1 shim on the gears wouldn't spin freely.

[Stinger]

Sept 21, 2014 17:17:30 GMT -5 airborn said:

Sept 20, 2014 22:16:39 GMT -5 Stinger said:

What I meant was, it should be as tight as it can be, but still be absolutely free.
If you have a setup where there is a little bit of axle play, but you add a 0.1mm shim and the gear is too tight (can't spin freely) then would have to allow that axle play to remain for the sake of free-spinning gears.

I believe you're stating what OP said in a different way. He did state that you want your gears shimmed as tight as possible while still being able to spin freely, thus eluding that if you put a 0.1 shim on the gears wouldn't spin freely.

I was referring to when the OP said that you want AT LEAST 0.1mm of movement. However, as I said, it would be better to have free-spinning gears and NO movement. I just wanted to clarify that for other people. The OP may have meant it, but the way he said it was a bit misleading.

[natethegreat32]

Precisely airborn. You would optimally want the gears to not move up and down, however even a .1 mm shim will add more friction thus adding more amps. I did not however say that you want at least .1 mm of movement. I said that you want between .09-.03 mm of movement. If the gears did not move up and down, there will obviously be added friction. This is why we leave that slightest bit of movement. 

[airborn]

Sept 21, 2014 17:30:17 GMT -5 natethegreat32 said:

Precisely airborn. You would optimally want the gears to not move up and down, however even a .1 mm shim will add more friction thus adding more amps. I did not however say that you want at least .1 mm of movement. I said that you want between .09-.03 mm of movement. If the gears did not move up and down, there will obviously be added friction. This is why we leave that slightest bit of movement. 

My mistake. I did mean at least .01 mm of movement. I'm better at doing than discussing. To truly critique one's work or posts you have to be experienced enough to know that what you do is the right way and works. If not, read and learn or ask questions. Connotation is key through text everyone. I know most techs will stand behind the steps in this guide 100%, even if he didn't state it exactly how you would've. If you do it this way you would know what he meant by it. If not, ask questions! But be willing to learn. No tech knows everything. Just remember when you think you know everything that HS5 learns about his products from other techs.