Finding tube dead center for rivnut install,,,

[MikeD]

Originally Posted by AngryScientist

the FD mount would have been riveted on, not rivnuts. similar concept but different product.

the rivets have a smaller diameter and much moire stress on them than bottle cage mounts would.

the problem with rivnuts is they may come loose eventually, but i have never heard of a failure at the hole. they would not be my first choice for bottle mounts, but in the case if this frame, they are by far the best choice.

No, it was rivnuts. Positive on that. The derailleur mount was bolted to the rivnuts.

I had a Cannondale mountain bike that used rivnuts for the bottle cage mounts. However, I have no idea if the tubing was thicker walled to provide strength for the hole. Butted tubes are very thin walled except at the ends of the tube.

Curious to see if Dave Kirk can comment on this subject.

[David Kirk]

Originally Posted by MikeD

No, it was rivnuts. Positive on that. The derailleur mount was bolted to the rivnuts.

I had a Cannondale mountain bike that used rivnuts for the bottle cage mounts. However, I have no idea if the tubing was thicker walled to provide strength for the hole. Butted tubes are very thin walled except at the ends of the tube.

Curious to see if Dave Kirk can comment on this subject.

Holes on the side of the seat tube are going to be MUCH more prone to cracking over time than holes that are on the front/rear of the tube. This is one of the reasons we don't see too many frames made today with bolt on FD bosses. We used to see this type of failure back in the day with bolt-through shifter bosses on the down tube - same deal.

If the frame is metal and the bottle bosses are brazed or welded in there is very little chance of seeing a failure at the hole. The boss acts as a gusset or sorts and once welded or brazed in place the whole thing acts as one single piece. A rivnut does not have the benefit of acting as one piece. The rivnut is not "one" with the tube it's grabbing a hold off and the hole is not in any way reinforced. That said of the hole is clean and free of burrs then it's pretty rare to see failures of bottle boss holes with rivnuts.

Tubing is not typically reinforced in the area where bosses might be located so one can't count on the butting saving the day.

dave

[NHAero]

Assuming you get the two holes in the right locations….and drilled…is it nutz to epoxy in short bolts, from the inside of the tube, with the result that you have male threaded bosses instead of female ones?

I'm imagining double sticky tape on the end of a stick/rod that you stick the bolt head to. Then, slather the bolt with five minute epoxy, and carefully insert the stick into the seat tube and get the bolt through the hole from the inside. while holding it there, wipe excess epoxy off the visible bolt threads. Maybe tape them first so epoxy doesn't get on the threads?

[prototoast]

Originally Posted by NHAero

Assuming you get the two holes in the right locations….and drilled…is it nutz to epoxy in short bolts, from the inside of the tube, with the result that you have male threaded bosses instead of female ones?

I'm imagining double sticky tape on the end of a stick/rod that you stick the bolt head to. Then, slather the bolt with five minute epoxy, and carefully insert the stick into the seat tube and get the bolt through the hole from the inside. while holding it there, wipe excess epoxy off the visible bolt threads. Maybe tape them first so epoxy doesn't get on the threads?

Paragon makes a part that's similar to what you're describing with a male threaded boss, that's designed to be welded on the outside of the tube: https://www.paragonmachineworks.com/...oose-material/

If you're going to rely solely on epoxy, you could just go with these, which are actually made for it: https://calfeedesign.com/store/Water...air-p429231486

[NHAero]

Originally Posted by prototoast

Paragon makes a part that's similar to what you're describing with a male threaded boss, that's designed to be welded on the outside of the tube: https://www.paragonmachineworks.com/...oose-material/

If you're going to rely solely on epoxy, you could just go with these, which are actually made for it: https://calfeedesign.com/store/Water...air-p429231486

I'd no idea these existed, cool! Thanks

[koldobrew]

Thanks for the information.

[Nomadmax]

I'm lazy. Do this

https://www.universalcycles.com/shop...hoCeTcQAvD_BwE

and call it good.

[charliedid]

I bet you could eyeball it well enough just using a bottle cage and a zip tie as a guide.

[AngryScientist]

closing the loop.

Done.

In the end I used a combination of David Kirk's advice and a final check with the bottle cage electrical taped to the frame. Center punch and drill bit with pilot tip got it done in one shot. Is it perfect? Probably not, but certainly good enough for me

[fellowpicker]

Good job, you're hired!!

[David Kirk]

you have a bright future in the rivnut industry!

dave

[AngryScientist]

Originally Posted by David Kirk

you have a bright future in the rivnut industry!

dave

ha! thanks for your advice here Dave.

[robt57]

I want a WB cage on the seatube of my SLX 1985 Nago so bad... But it is original Saronni/white panel paint in still fairly decent condition. I can't bear the thought of taking a drill to the seat tube, but I should just do it...

[AngryScientist]

Originally Posted by robt57

I want a WB cage on the seatube of my SLX 1985 Nago so bad... But it is original Saronni/white panel paint in still fairly decent condition. I can't bear the thought of taking a drill to the seat tube, but I should just do it...

C’mon over - the shop is open!

[robt57]

Originally Posted by AngryScientist

C’mon over - the shop is open!

I am over due for a trip back home...