Frame progress — finished up the rear triangle
I had planned on doing this in 2 or 3 blog entries, but I’m running behind. That means you get one mega entry.
The frame is pretty much done. It just needs cable routing brazeons and rear canti posts. This is what it looks like in profile:
A set of photos for making the seatstays (mostly the caps). Ifound this to be more challenging than I expected. Things that I learned for the next time are to cut the seatstay a little shorter than I did, and make the cap longer. I also should have used thicker caps, I used .4mm thick tubing. That didn’t leave me a lot of room for error. At the end of the series you’ll see a pool of brass on top of the cap, that was to thicken it up a bit.
I made an M5 seatpost binder on the lathe and made this cantilever brake cable hanger too. I like the twin wire design, but enhanced it a bit by wrapping the wire around the seatpost binder. It is very strong, but light and delicate looking.
I was a little worried about tire clearance when I wrote my last blog entry. In response I made a tool for denting the chainstays and went at them. The dents aren’t too elegant, but they gave me a couple of extra mm of clearance and that was all that I needed.
I want a good fenderline on this bike, so I carefully measured tire height with three different tires and a test wheel. I set the bridge 18mm above the tread of the tire that I expect to use with fenders. That still left me pretty good clearance with a knobby (for riding without fenders). The fixture holding the bridge in place is called a “bridge jack”. There was a blurry photo of one in the Patarek manual and I couldn’t find one anywhere else, so I just made what I thought would work. I can adjust it’s length then lock it into place. It worked well for getting the chainstay and seatstay bridges equidistant.
This bike is being designed for a Rohloff internal hub. The Rohloff has three different options for a reaction arm to keep the hub from rotating. Lee Williams described how R&E used the OEM2 one (normally designed for disk brakes) with a hidden bolt inside the seatstay. My seatstays are very thin, so I added this bridge instead. I like how it looks, it is a lot more elegant than the normal Rohloff reaction arm (photo from an old bike at the bottom). The boss for the bolt head was made on the lathe. It is like a blind water bottle boss, but sized for an M6 bolt. The boss goes all the way through the bridge for extra strength.
The ugly black arm with holes is the normal alternative. I’d say that mysolution looks nicer.
.JPG)
A detail shot of how the eccentric works. I think that this is a little nicer than the normally fully slotted bottom bracket, and much nicer than using set screws:
A couple of blog entries ago I talked about alignment. Brandon Ives saw my photos and suggested making this tool instead of using a square. I call it a vertical dummy axle, and have to agree with him that it works well. The dummy axle just threads into the base. Right now I just have a dummy axle that is 10mm for rear dropouts, but when I make my fork I’ll also make a 9mm dummy axle for front dropouts.
i like that dummy axle idea, much more elegant than using a square (like i have also). now that i have a lathe/mill i can make fun things like that!!
Great creative problem solving! The Rohloff mount and bottom bracket are really clever and just seem perfect for the job. The rear brake cable hanger is really nice looking, but I wonder about flex unless the cable run is close to perfectly straight to the straddle cable yoke. I would also worry about a loaded saddlebag bending those long, skinny wire arms. But, it will probably be a non-issue, and there’’s nothing stopping you from using a conventional hanger from the binder bolt later.
What size are those knobbies, and how long are the chainstays? Thanks as always for sharing your work! It’’s inspirational for sure!!
Hi,
Information about Rohloff axle plate (attempts to rotate under load) : position of bolt is good for eyes but bad for maintain of wheel.
Position in front of rear wheel axle is forbiddden with these type of dropout = dangerous.
See this document, page 30 : http://www.rohloff.de/uploads/media/Benutzerinfo_en.pdf
Best regards.
Thanks, I hadn”t seen that detail before in their manual, I must have looked at an older version.
It doesn”t hurt the hub to have the anti-rotation in the wrong angle, but it can push the hub out of the dropouts in low gears under high torque. With my wheel position that can be a problem if I don”t use a good QR (sharp serrations on the nut and a strong steel QR mechanism are a must), but with one it isn”t an issue. It is a tradeoff that I”d make again if I were building the bike again today.