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Just found out about these, kind of like a rivnut but with less potential to do damage. They seem to be used on motorbikes.
It's to go in a tube with 2.5mm wall thickness. Good idea?
What potential damage are you worried about? I've seen rivnuts damage stuff when they've pulled through things or been installed cack handedly but these won't solve either of those issues.
Conjecture, if anything won't the softer body and linear placement of the nuts will allow the cage to move more as the rubber flexes but the bolt and insert won't, potentially causing more not less of a problem?
Good point. It's cack handedness of installation I'm worried about, having never done it.
The well nuts need a larger hole though, is the other thing. I'll go with rivnuts if deemed best. OD of tube is 35mm.
Are you drilling the tube or is the hole preformed?
Drilling. Seatpost slot went well, drilled then cut with a dremel.
I'd personally be much more concerned about drilling a carbon frame than using a rivnut in one.
Noted. Went with extra thickness (most carbon frames seem to be very thin indeed).
The frame in question.
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I'd maybe look for options to bond a captive nut/insert on the outside of the tube so you don't need to drill a hole through or introduce any extra stresses from an expanded rivnut/rubbed mount pulling through the laminate.
Have you already drilled the bamboo down tube?
Edit:
It's worth watching some.of the cut-up videos on the LuescherTeknik YT channel most of the bottle bosses on there seem to be bonded in (Aluminium?) With a fibreglass barrier ply not expanding type inserts.
Went with extra thickness (most carbon frames seem to be very thin indeed).
Doesn't that just negate the point of using carbon in the first place i.e. thinner/lighter tubes for a given strength. It's a stupid material for bikes.
Luescher Teknik has a video on rivnuts, I'd just do what he says -
Not about weight. It's to replace the cracked bamboo seat tube. Strength is more of a priority,and it's plenty strong as a frame having been battered and heavily modified already 🙂
I just mean if you're going to put in a thick carbon tube and mess about with drilling it etc. I'd have just put in a regular metal tube and saved myself the headache.
I don't care, it's your bike, it'll be fine.
Don't know if it's a viable alternative for you, but after reading another thread on here from a week or two ago I ordered this kit.
https://r2-bike.com/ARUNDEL-Bottle-Cage-Adapter-El-Jefe
My replica 1910's Pathracer doesn't have any bottle bosses, but this wee kit is fairly unobtrusive (even more so if mounted on a black tube), and seems very secure. The adapter is stuck to the frame with a big patch of 3M adhesive tape, then further secured in place with a couple of zip-ties. All going well, I should be properly hydrated for the Velo Retro Festival ride in Ulverston next month....the day after the Keswick Beer Festival. The company I bought the kit from were great. It only took 3-4 days to get to Central Scotland from Germany and they chucked in a mini pack of Haribo!
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Luescher Teknik has a video on rivnuts, I’d just do what he says –
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Thanks for that.
Why not just use a broom handle witch would have saved you a fortune.
Sure it'll look cack[le] but no worries about cat-astprophic failures.
Can't help feeling that would spell trouble down the line.
To the original question, has anyone got experience of using rubber well nuts? I've got some on order, and rivnuts. At the moment I'm thinking of trying the rivnuts first, and if that doesn't work drill a slightly larger hole for the wellnuts. The tube isn't glued in place yet. I can drill the holes before fitting.
Strapping on an external mount is an option, but where's the fun in that?
Strapping on an external mount is an option, but where’s the fun in that?
Where? About twenty miles from anywhere when it doesn't snap and stab you in the bum. 😉
If you're set in drilling and inserting, My suggestion would be bonding a stainless insert, ideally with a local wrap of fibreglas to minimise the odds of galvanic action/corrosion...
That's what I'm thinking - stainless steel rivnut, presented in an araldite jus. Or y'know, rubber. Bit of further reading says they're used for fairings on motorbikes. Not sure how the forces compare to a litre of water being bounced around, but I think they'd be up to it. I am not a mechanical engineer.