RCCrawler Forums

Tzicul

I remember, when I first started to build this rig, that I tried to do the third bearing mod and it seems it was a complete BS because of the amount of shims needed to make a correct play between pinion and ring, so I just went with a standard self made copper pipe spacer instead of that original crappy plastic one. But a few days ago BHB caught my attention saying the third bearing is not used only as a spacer, but also as reducing the stress on the other two bearings. Obvious, right? But never thought about it this way
You know my opinion about this problem, it not a pinion/ring issue, but mainly a bearing issue being THAT undersized. Here are the original straight cut pinion after 100+ runs. As you can see, they look more than reasonable after all this time, both on 4S and 6S. The only two chipped teeth are like this exactly because bearings failure. Otherwise I would have absolutely no reason to change them




Remembering that stupid amount of shims needed to do the third bearing mod, it strikes me that Axial might have partially resolved this problem by making that edge at the end of the pinion. That almost 1 extra mm might help, considering that the width difference between the spacer and the bearing is 0.9mm. Exactly the length difference between the old pinion and the new one.

So, here is my mod

Shims in order from left (pinion side) to right (drive shaft side). You can use, of course, the standard 0.1mm shims provided by Axial, except you have to use more of them. In total I had to use 0.7mm worth of shims.




In addition to the original 0.1mm shims I also use a 0.5mm shim I bought some time ago. I also used an 0.1mm shim near the pinion which I had to dremel inside in order to have the inner ring of the bearing move freely. But this shim is not mandatory. However, if you use it, you do have to increase the inner diameter to more than 17.5-18.00mm. If you don't install this shim you will have a gap of about 0.1mm between the front bearing and the screw fixing it in place. Not a big deal, but that's me, perfectionist




I have to admit, not being very sure if this mod will work I even make a shaft just to be sure I can make BHB's mod. But after a few runs with my mod I'm pretty sure I don't need to cut down that edge.



Advantages over BHB's mod:
- you now have one extra bearing to keep up with the stress on that poor bearings
- you don't necessarily need a Dremel or a BHB , especially when you don't live in the US.

Disadvantages:
- I don't see any. Maybe you, guys, can find any