I got a cheapo fat bike for riding in the crappy weather...it doesnt have sealed bearings...what if i drilled a hole on the bottom bracket and put in a grease fitting and filled it to keep water out ??

There are often holes between the BB shell and at least some of the other frame tubes. You'll just end up filling the whole frame with grease. If it really is an unsealed BB, either learn to disassemble, clean and repack. Or ride until trouble develops, then have a lbs install a sealed unit as a replacement.

if you braze up the holes in the bb shell first

Or put one of these in there. With a hole that you can hopefully push onto the back of the grease fitting.

Suntour/wtb used to make a bottom bracket like that. If the bike is cup and cone and square taper, just buy a cheap shimano square taper BB.

Just drill a hole in the bottom of the bottom bracket shell to allow water to drain out. you don't need to pump the shell full of grease; you just need to provide a means for whatever water gets in there to come out again.

Cut a liner from a pop can.Lots of overlap. Figure some way to anchor it, Perhaps a fitting with an extra long thread. Ed

Pack the bearings in water-proof grease (like that found in auto parts stores for boat trailers) .

+1, traditional cup/cone bottom brackets handle water very well. Even without a weep hole the venting between the spindle and cup allows the water to evaporate. The irony here is that weep holes weren't necessary, until the advent of sealed BBs or the use of liners, which eliminated the venting past the spindle.

Years ago I made water "seals" by cutting donuts out of sheets of open cell foam, coating them in grease and trapping them between the crank and cup face. My road/touring bike went over 50,000 miles of mixed weather riding, including plenty of rain, with minimal maintenance --- teardown once per year (about 5k mikes) in the Spring to make sure all road salt deposits were removed --- and was still on all the original bearings (except the headset) when I retired it.

I did the exact same thing in the 1980s with my square taper cranks. I would open it up many miles later and it was as clean as the day I overhauled it. I still have them on my old mtn bike.

Wow, how clever! I'd expect it to be a more common practice!

Used to wrap a greasy pipecleaner around the spindle to cover the gap around the spindle-BB Cups.
then
There was a Zirk Kit , a stiff thick plastic tube went between the bearing cups , and the zirk tapped into it after passing thru the BB shell .
It also had a stack of O rings and a seal with it to go against the outside face of the cup, to keep crud from getting in..

later
I First got the Higher end Campag cartridge BB with my 'race triple' (internal spline, same as the hub lock ring)
then seeing the lower cost ones let me trap an O ring on the spindle , before I put the arms on [ external spline, ring wrench fixed]
single O ring fits tight between the arm, and BB face.

in addition..
A custom touring bike, building around a '90's Burly Tandem stoker's BB shell, we left the shell solid , TIG'd on the other tubes.

so it being a larger volume, and the oversize bearings were held in with Loctite and a snap ring, the Zirk
let me put in a lot of grease between the bearings , seals on the outside , none on the inside..
so it became fit and forget.


more recently UNxx went rough rather quickly winter commuting so I tossed it , already has a NOS GreaseGuard BB
for my Bike Friday-Rohloff bike .. they fit seals inside so grease is put in the inside , pushing the old out around the spindle .

Too bad no external bearing BB is made to do that..