Ring gear wobble with SSD axle and FI Spool

[Antsiranean]

I have just assembled the rear axle of an upcoming Bomber build, and it should be top notch. SSD centered diamond axle, SSD HD axle shafts, 43 tooth ring gear and LockedUp RC FI Spool. However, the ring gear wobbles. I ordered three spools at the same time, one for my Yeti and two for my Bomber, and after testing have found that they all have a wobble to them. For lack of ability to explain better, the sound when spinning the assembled axle with pinion and all goes rrrRRRrrrRRRrrrRRRrrrRRR. Does it make sense? And if I eyeball the ring gear, I'd say there's 0,5 mm wobble to it. If the axle is the Y-axis, then the X-axle is not perfectly perpendicular to it, but slightly off.

Now, since all three spools are the same, it makes me wonder if it should be this way, or if I have just been unlucky and have three coming from a faulty bunch. I have contacted LockedUpRC regarding the issue, but input from the forum would be appreciated as well.

[JSterrett]

Did you use the same ring gear each time? Maybe it's machined weird or has something super small stuck to the mounting surface? Surface imperfection maybe?

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[Antsiranean]

I have used two different ring gears, both have wobbled, so I believe it's the spools that are imperfect.

[JSterrett]

Have you tried different bearings also? Extremely unlikely to be the issue, but you might as well check everything. An inner bearing race machined off-center could (technically) cause it also...

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[Antsiranean]

Originally Posted by JSterrett

Have you tried different bearings also? Extremely unlikely to be the issue, but you might as well check everything. An inner bearing race machined off-center could (technically) cause it also...

Will do, but the ring gear is not off center, it's off angle. It's not 90 degrees to the axle, but more like 87 degrees (well, I haven't measured, but it is a noticable difference)

[Jboucher]

I had a similar issue, after 3 rebuild I couldn't get rid of the little grindy spot in my gears so I left it as is.

Bomber housing, axial HD gears, Axial shafts and FI Spools

I think it's either normal and wears out or it has to do with the little metal spacer from the FI spools, I think I didn't need them and will remove them next rebuild.

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[Antsiranean]

Thanks Jboucher, good to know I am not the only one with this combination of brands and this issue. After a couple of rebuilds and some testing with an axial spool, I am pretty sure that the problem lies with the Axial ring gear, not with the FI Spool. The spool is straight, the gear is slightly skewed, causing a periodic grinding.

I have shimmed the output shaft on the outside, so that it can't go to far into the axle and cause bind issues.

But is this the right thing to do? Should I shim the pinion on the outside, so that I have a slightly loose fit, but very little grinding? Or should I shim it slightly on the inside, and get a bit more grinding (but no binding) and just let it wear out?

Or should I contact Amainhobbies and ask for a replacement or refund?

Edit: I have contacted Amain and am hoping for an Incision replacement.

[Jboucher]

I put shims inside and outside the pinion so it can't move much
My mesh isn't too bad, I drove all summer on 21T 3s with it.
I'll see if there is any damage in my winter maintenance.

If I need replacement gears, I might go for double underdrive axials or the locked up RC gears.

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[Antsiranean]

I managed to catch the wiggle on film, and Amain will send me a 20$ voucher that I can use for an Incision gear set. They offered me an Axial replacement, but I'd rather try my luck with another brand. And rebuild my axle for the umptieth time... Great customer service!

[Derr429]

I have the incision spools and gears and they are great. No wobble or strange sound from them.

[Antsiranean]

I got the Incision gear set, installed it, and guess what? It wobbled!

If I just put the spool in the axle, hold on to the bearing with my finger and spin it, it doesn't wobble.

If I just put the ring gear in the axle, hold onto the bearing with my finger and spin it, it doesn't wobble.

If I put them together - and they mate perfectly - and put them in, it wobbles. Really, really weird. That should mean that the area contact area on either the spool or the gear was tilted, but if the spool was tilted I would have seen it when I spun it. And if the flat, central area of the gear was tilted, I would see that by eyeballing it against the ridges of the gear.

So, after having tried two different ring gears and two different spools, and still having a wobble, I've decided not to care about it. Gear mesh is a tad tight now, but it will just have to wear down. And when I ruin the Incision gear, I'll just replace it with the Axial spare I now have on hand.

[NitroBugg]

Could one of the bearing "seats" on the axle itself be milled out of spec? Could spin ok holding it with your finger, but when you tighten it down, it pulls one side down further than the other? (just guessing here)