Framebuilders - Is this dropout joint going to fail?
Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.
05-30-11, 12:21 AM
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?
05-30-11, 12:27 AM
I mocked up a reinforcement...
...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.
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.
05-30-11, 12:40 PM
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
05-30-11, 03:35 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.
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?
05-31-11, 07:56 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...
06-06-11, 09:58 PM
I finally realized I was going to spend the rest of my life worrying about it, so...
Not exactly a thing of beauty, but good for peace of mind.
06-19-11, 01:45 PM
Powered by vBulletin® Version 4.1.12 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.