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Hi all,

Since the B4 top shafts have become unicorns and the whole industry has gone metric I was wondering on how you guys would try to ream the Ø 3/8 inch (= 9.525mm) bearings seats of the gearbox top shaft bearing location to Ø 10mm. That is an increase of 0.5mm in diameter. So only 0.25mm of Material would be emoved.

That way a hole lot of current top shafts would become usable.

Herer are a few examples:

STRC shaft for Traxxas Bandit / Rustler in combination with a 20t gear (Axial makes one)
B5 top shaft
Durango DEX210 top shaft and slipper (If you can find one Durango has gone out of business)
B6 top shaft and slipper if you remove the flange
.........

How would you proceed to keep everything centered?

I just like the modern slipper setup so much more.

Thanks for your input.

Tony

just use a 10 mm reamer. you could use it in a drill press and it will center just fine. you might have to modify the reamer though, to remove much of the leading chamfer, because the bearing bores are pretty narrow. how wide is the 10mm bearing vs the 3/8" bearing? narrower or wider? that could be a bit of a sticking point if you can't get the reamer in far enough.

Thanks for the suggestion. Drill press and reamer are no problem, I just want to avoid ruining a perfectly fine gearbox.

I was afraid the reamer might bite into the plastic.

In this case I wand to modify a GT gearbox for a GT-E conversion.

The 5 x10 or 6x10mm bearings are available in 3mm or 4mm thickness. I will have to measure the current ones.

I am pretty sure the 3mm will be thinner, the 4mm I don't know.

Yeah you will want to fixture the case to a block of wood or something to hold it in position. You could actually just spin the drill quill by hand once you have it centered to make the cut. Basically you use the drill press to keep things aligned

I just came up with a plan B. At least for 5mm shafts.

There are 5x9x3mm bearings available, I couldn't find 6x9mm (yet).

So I can buy 0.25mm feeler gauge stripes and make a shim to fil the 9mm bearing into the 3/8 inch hole.

At least I won't be destroying anything that way.

For testing I have both the Durango and the Traxxas STRC shaft.

projects projects....

Yes, that works too. I'd throw in a dab of CA to keep things honest.

Are these an option?

https://www.avidrc.com/product/5/accessories/3506/Associated-Aluminum-Topshaft-B4-Stealth-AV10062-accessories.html

Seems preferable.

i was going to suggest that but not sure regarding shipping to Germany.

juicedcoupe wrote: ↑Tue Jun 29, 2021 11:35 am Are these an option?

https://www.avidrc.com/product/5/accessories/3506/Associated-Aluminum-Topshaft-B4-Stealth-AV10062-accessories.html

Seems preferable.

I just grabbed one and it's a perfect fit. there is no reason for a topshaft to go for more than $25 at this point

Actually I could order one. I also like unorthodox approaches.

We’ll see

So, instead of harming a stealth case I first tried some electrical tape around the 9mm bearings.

The dry run works perfectly fine