Happy Feet

I have a fat bike with a tapered top tube that I am considering putting a bottle cage on.
The tube is tapered so hose clamps won't hold over time and I am thinking of either rubber straps (not sure how well they will hold either) or drilling for riv nuts.
My concern is whether adding three holes will weaken the frame. It's pretty wide but the bike also does a lot of off road trails.
Any frame builders have experience with this or a different solution. The mounting system needs to keep 1.5L of water on the frame while withstanding torsion from turns bumps etc...

I want to add this cargo cage



To the frame where the current gas tank bag is

bwilli88 

Why not mount it on the rear rack?
Not sure about rivnuts in the top tube.

AnkleWork

On the seat post with hose clamps?

dsbrantjr

https://recklesscognition.wordpress....ws-and-bosses/
Adding Water Bottle Cages to Bicycles without Braze

Litespud

In your situation, I would have no hesitation drilling and mounting the bracket. If three little holes compromise the structural integrity of your top tube, it was pretty marginal to begin with, and it’s not like they’re going to be unsupported voids in the tube - they’re going to be filled with riv-nut. I would suggest, however, that you do what you can to avoid stress risers by drilling the holes slightly small and finishing them out with a Dremel.

fietsbob

There are nice seat post double water bottle cages from the Tri race set,

and Wolf tooth offers a dual bottle cage adapter, to have a couple bottles on either side of your frame bag,

using the single bottle cage mounts , your frame bag may be covering up..

jadocs

Since it is supposed to replace the tank bag. Why don’t you just get a small water bladder and put it inside instead.

Happy Feet

Well, after trying a few ideas today I discovered a great solution that did not involve drilling the frame. It seems my Blackburn cargo cage has three slots that line up with three loops in my Blackburn frame bag, allowing me to secure both with the frame bag velcro loops. I'm going to get some 3M double sided tape (like the stuff used to mount GoPros) and then it will be stuck fast but still removable without altering the frame.




My 1.5L Nalgene bottle with SS cup/cook pot just fits and allows the stem to rotate.
There is a second bottle cage mounted to the handle bar as one of several other ideas I tried but I took it off.




One reason I wanted a cargo cage here is that it is also good real estate for other things to carry in a cage. Now I will get a second Blackburn cage for the downtube.
Unfortunately my Al fork is tapered and has no barnacles so cage mounts there won't work.
Other people mentioned mounting to the seat post or seat stays but I have a rack and panniers so that wouldn't work either.