Framebuilders - Is this dropout joint going to fail?

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Six jours
05-29-11, 11:21 PM
http://i10.photobucket.com/albums/a101/Noel3006/dropout.jpg

Paragon sliders for Rohloff hub. Looks to me like the chainstay connection is going to be loaded primarily in torsion, with the seatstay really not adding much strength. The dropouts are stainless, so I used 50n silver and made sure to "fill 'er up", but the whole affair seems pretty marginal to me. What say you folks?


Six jours
05-29-11, 11:27 PM
I mocked up a reinforcement...

http://i10.photobucket.com/albums/a101/Noel3006/reinforced.jpg

...but I suspect it might interfere with the chainrun (I don't have the wheel here yet, so can't verify). Also, it's ugly.

mudboy
05-30-11, 04:38 AM
Do you have any way of bending your support tube (I see a bent piece on your workbench)? Imagine something like a "U" style seatstay bridge, but going from chainstay to seatstay. But, I agree, that looks like an awfully dainty joint to have to deal with brake and internal hub torque. I've seen builders do this, but can't remember who.

Pete


unterhausen
05-30-11, 11:40 AM
you probably need a brake reinforcement on the braking side. Not too hard to find pictures of those, but you want a tube that is more vertical, I believe. I have always wondered about those cantilevered dropouts, but there are tons of them out there on mountain bikes seeing severe service. I wouldn't bother with a drive side reinforcement.

Finally, and a little off topic, you're tall

Six jours
05-30-11, 02:35 PM
Heh heh, yeah, it's a 61 c-c.

FWIW, I won't be using disk brakes. The sliders come with a disk brake tab by default. I just haven't gotten around to cutting it off yet. So there's that, at least.

My concern is simply that the axle is so far behind the seatstay, rather than under it as it is in traditional drops. So rather than loading the seatstay in compression (taking a lot of load off the chainstay connection), both connections are in torsion.

And yeah, I've been going through Flickr and seeing all those bikes built just like this one, so maybe I'm overthinking things. I just don't know. Guess I'll leave the frame unpainted and try riding it down the stairs.

tuz
05-31-11, 11:26 AM
Just a thought. I wonder if the 2 bolts are the weakest part of the assembly. If that is the case they would fail first before the stays would bend?

Six jours
05-31-11, 06:56 PM
The slider actually fits into the slots full depth. That's where the load is transferred from the wheel to the frame. The bolts just keep the slider in the slot, and so aren't under all that much strain.

At any rate, I've semi-convinced myself that I'm worrying about nothing, based on all the photos I've seen of identical builds. We'll see...

Six jours
06-06-11, 08:58 PM
I finally realized I was going to spend the rest of my life worrying about it, so...

http://i10.photobucket.com/albums/a101/Noel3006/reinfordrop.jpg

Not exactly a thing of beauty, but good for peace of mind.

ftwelder
06-19-11, 12:45 PM
problem solved.