Alex Wetmore is always busy with something…

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.

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.

The next step in building my frame is attaching the seatstays. Before doing that I needed to make sure that the chainstays were properly aligned. It will be much more difficult to correct axle alignment issues once my seatstays are attached to the frame.

Whenever I have the bike on the alignment table I double check the head tube and seat tube alignment. This is how I setup the bike:

The frame is connected to the table at the bottom bracket. The bottom bracket post is machined to be exactly perpendicular to the table, and the table is a flat reference surface. If the frame is aligned then it should all lie in a plane exactly parallel to the alignment table.

The first check that I’m doing here is comparing the plane of the head tube to the plane of the seat tube (I’ve already checked that the seat tube is square to the bottom bracket shell).To do that I’ve rotated the frame so that the head tube is over the alignment table and the bottom of the seat tube is also over it. My head tube is 33mm in diameter, while the seat tube is 28.6mm. To make alignment checks easier I put a dummy steerer inside the head tube (that has a 1″ or 25.4mm diameter) and then put a sleeve over the steerer which makes it 28.6mm in diameter. That looks like this:

The pointy thing coming down from the top is a scratch gauge. I set it’s height so it just barely touches the sleeve. When you draw it across the sleeve you can just hear it make a scratching noise. It is important to check both sides of the steerer to make sure that it isn’t twisted with respect to the seat tube. At this point in the build it would be very difficult to correct that, but when the frame was just tacked (before final brazing) it was easier.

Then I slide the scratch gauge over to the seat tube and compare it. In this case it is perfect, I also get just a very light scratching noise:

Now that we’ve double checked the front triangle alignment it is time to take a look at the chainstays. First I check to make sure that they are centered with respects to the seat tube. To do that I use this alignment gauge that I had made (I copied the design from Martin Tweedy) and a height gauge to hold it. In this photo I’m aligning the height gauge with the seat tube. Notice that the frame has been rotated on the alignment table to put the chainstays over the table.

This is what the chainstays look like when I slide the alignment gauge over. Clearly they aren’t centered:

The alignment gauge has steps for dropout spacings of 100mm, 120mm, 130mm, 135mm, and 145mm. This bike will have a 135mm Rohloff hub, so I cold-set (bend) the stays to make them work with the second largest steps:

Now we know that the stays have the right spacing and are centered on the seat tube. We haven’t checked to see if they are in line with each other. To do that I use a square placed on the table. This is how the setup looks:

This angle doesn’t tell us too much, but looking from above we can see that they aren’t properly aligned:

It just takes a little push to eliminate that gap.

On a final alignment I’d also use the Park dropout alignment tools to make the dropouts square with each other. I don’t need to do that at this point though.

The whole process is iterative. After every change I need to go and double check anything connected to what was changed. In the process of cold setting the rear dropout spacing I could easily bend the chainstay up so that the dropout is a millimeter or two out.

This is obviously only showing a little bit of the alignment process, but it covers the basics of how I use the alignment table. You can also see why a larger table would be nice. I have to rotate my frame many times to compare everything. A 2×3′ table allows you to check the whole front triangle or the whole rear triangle without rotating the frame. A 3×4′ table is enough to check alignment of the whole frame without rotating it. My table is 8″ wide by 32″ long.

Administravia first: A couple of weeks ago I blogged about the Ibex Vim jacket. I actually raved mostly about the Dash Hybrid, which is an awesome jacket. I thought that the Vim would be very similar, but I’ve been using one for a couple of weeks (thanks to John Speare for loaning it to me) and I can report that it isn’t. The Vim is a much lighter jacket and nice in 50ish degree weather, but I don’t think I could wear it all winter long as I do with the Dash Hybrid. It also isn’t cut for cycling (the back doesn’t extend as far) and has no rear pocket.

Now onto the real news. I didn’t do much work on my bike frame this summer, deciding to spend weekends outside instead. I’m finally back at it, and got past what I expect is the most challenging part of the build. That was putting on the chainstays.

One minor note is that I fully rebuilt the front triangle for this bike early in the summer. I had some issues with the first one, but this new one has better brazing (thanks to a few key members of the framebuilders list who gave me good advice) and the geometry is right on.

This is what it looks like today:

I’d say it is starting to look a lot like a bicycle.

What follows is a photo essay of the chainstay work.

Checking the bends against BG101 to mark where I needed to cut the stays:

Using a slot cutting wheel on the milling machine to make slots for the rear dropouts:

Rear dropouts brazed:

Mitering the chainstay on the milling machine. This doesn’t look that sturdy, but the setup worked pretty well:

Testing the fit. It was critical that both chainstays were exactly the same length.

All brazed up. I used Fillet Pro from Freddy Parr to braze this. It is silver based (instead of brass), so the brazing took place at a lower temperature. This made it easier to use Alistair’s heat sink and resulted in less bottom bracket distortion.

A 50mm wide Pacenti Quasi-Moto tire fits with 6mm of clearance. I was hoping for a little more, but this is still pretty good. Most of the time this bike will run with ~40mm wide slick tires and fenders, but I wanted the option to fit 50mm knobbies for offroad riding.

I’ll do one thing differently with my next fillet brazed bottom bracket. Instead of fully brazing the dropouts into the chainstays first I’ll just tack them. Then I don’t need to worry about the chainstay length quite as much, because I could move one of the dropouts a little bit to tweak the alignment.

Remaining items before I have a bike:

• Fillet cleanup
• Seatstays
• Brazeons (canti bosses,cable routing,water bottle bosses, etc)
• Fork
• Rack

I’m hoping to push through in the next couple of months and wrap this one up by the holidays.

I brazed the front triangle of my first frame this weekend.

Things went pretty well. I did have one mistake which has made a fairly minor change to the geometry. My brazing order around the downtube, seattube, bottom bracket area should have brazed the front of the downtube and the back of the seat tube first before any of the crotch in between them. The fillet in the crotch pulled them them together, which made the seat tube angle a bit tighter. I think that this is all okay, I’ll just build the bike with a 72.5 HTA and a 73 STA instead of the opposite as I had planned. The seat tube is 56cm C-T and the top tube is 56cm C-C (giving me a virtual of around 57cm because it has a sloping top tube). The top tube slopes at roughly 4 degrees. This is a learning frame, so I’m okay with a few little mistakes.

The seat tube to top tube junction was one that I spent a lot of time thinking about. I wanted to put a sleeve here to keep heat distortion down and I don’t like brass brazing long sleeves. Mark Bulgier had the best suggestion for handling this area, but I didn’t have the right materials on hand. My solution (a pretty common one) was to sleeve out of 1 1/4″ x 0.058″ (which sleeves perfectly over a 1 1/8″ seat tube). The top tube was brazed to the sleeve first with brass, then the sleeve was brazed to the seat tube using silver. The silver inside the joint will melt a bit when I braze on the seat stays, but the sleeve is so long that the top and bottom will stay solid and the silver won’t be able to go anywhere. That is the theory anyway, we’ll see if it is true in a few weeks. My biggest concern is that I probably don’t have good silver penetration between the sleeve and seat tube behind the top tube fillet. I’m not worried about the lack of strength there, but I hope that it doesn’t create a good area for rust.

I used a pin through the sleeve to align the vent hole in the top tube with the one in the sleeve.

Everything came out fairly straight when I checked it on my alignment setup. The head tube has a very slight twist when compared to the seat tube. I might try to cold set it out of there, but I’m not too worried about it.

I mitered everything on my milling machine. My setup for this was really simple,but seemed pretty effective. I used two of Alex Meade’s clamping blocks and clamped the tube into the milling machine. I set the angle using the machine’s head (I don’t really have a good angle table to adjust the angle of the tube itself). To keep the miters in phase I always kept one block locked onto the tube at a time when I moved the blocks from one end of the tube to the other. The final miters came out nicely. I only touched up one miter witha file,and that was the top tube to seat tube miter because the top tube length shortened a bit when my ST/DT angle tightened up.

If you aren’t bored with this project by now you can see tons of other photos in my smugmug gallery.

I’m almost done clearing out old projects and finally getting ready to build my first full bike frame. It’s going to be what Jan classifies as an urban bike. Kind of a light touring bike, drop bars, front porteur rack, 650B wheels. I want it to fit knobby tires without fenders or 40mm wide Hetre tires with fenders. To make this work I’m placing the fender mounts around 60mm from the rim. Here is a line drawing which gives the basic proportions:

The hardest place to fit these wide tires is the chainstay/bottom bracket area. I was playing with BG101 (an Excel spreadsheet) on the bus this morning and it shows this very nicely. This is what my bike might look like using a 55mm tire, 9 degree bend chainstays from Henry James, a 44t single chainring, Ritchey cranks (150mm tread) and a Rohloff hub:

Each grid mark is 5mm. Everything just doesn’t fit (the crank arm and chainring are both too close to the chainstay). There is a thin path through the chainring, crank arm, and tire which will let everything fit. A chainstay which makes that ideal path isn’t available off the shelf, so I’m going to have to modify (bend) what I can get. This is the hardest part of the bike for me, and the first thing that I’m looking at when I see other fat tired bikes on the road.

I’m glad that I avoided it on my first bike by using an existing rear triangle borrowed from another bike.