Frame Number 3 - A New Fast Tourer

Well what can I say? Frame number 2 broke. It put in 10,000km of sterling service, including a full Audax Super Series, a week long tour, and most of a year's commuting, but eventually failed at the join between the bottom bracket shell and the seat tube.

Here's a picture of the failure:

And another, taken during the post-mortem, after sectioning the BB shell:

Careful investigation, and much good advice from members of the framebuilders list, led me to believe that the cause of the failure was down to two things:

Inadequate cleaning of the lug socket (I didn't clean it out properly after attaching the down tube).
Inadequate heat to the root of the bottom bracket shell.

The result was that on the right side of the socket, the filler simply ran around the lug shoreline without penetrating properly into the join.

I nearly gave up at this point. This sort of thing is a big blow to ones confidence. I thought at first that I should try to fix it, necessitating replacing the bottom bracket shell - a mammoth task, but I was encouraged by the guys on the framebuilders list to cut it up, so that I could learn from the failure. So I figured the best thing to do was to write about it as well, rather than pretending it never broke, in the hope that my stuff-up might be useful to others. After a few weeks of mourning, I decided the best thing to do was to get back on the horse and try again. Thoughts of stainless lugs were shelved, and I concentrated instead on getting the basics right. I set about building a straightforward touring frame, with the absolute best brazing I could muster.

I started with a Columbus Zona tubeset, and a collection of Henry James lugs, as shown below:

It's a fairly standard fast touring bike, with 73 degree seat tube angle, and 72.5 degree head tube angle (suits 43-45mm rake forks). It's 55cm square, just like the last one. I really liked how my second frame handled, and hence didn't want to change the geometry much. An exception was to knock 5mm off the chainstays, to make it a tad more agile at speed. It's going to be used for commuting, touring, Audax, and general riding.

AutoCAD was used to design the frame. I measured a Tubus rack, and located the rack braze-ons to ensure that my feet would clear the pannier bags. It was also useful to check that 28mm tyres would fit between the chainstays and seatstays, as the chainstay sockets on the Henry James bottom bracket are much closer together than those on the Long Shen one I'd used previously. Click on the drawing for a .pdf version.

Here's some pictures of the frame before painting, showing the brazing:

The bottom bracket. A nice, uninterrupted line of silver goes all around the lug edges. No bubbles, good penetration. I was really thorough in cleaning the sockets, and very careful in heating the join so that the shell and tubes all came up to temperature simultaneously. When I fed the silver in, it shot right into the join, without significant encouragement with the torch.

Looking inside (a crappy photo, I know) there's a line of silver running around the join here, too, indicating filler made it all the way through. I have a high level of confidence that it will stay together.

I put the braze-ons for the rack on the dropouts this time, instead of on the bottom of the seat stays. That moves the rack down a little and back as well (allowing me to knock 5mm off the wheelbase without increasing the chance of my feet hitting the panniers), and looks more "normal". I'm using a Tubus stainless rack, which is really pretty.

The head lugs and downtube shifter bosses. Head lugs are easy. Mitre, clean, apply flux, warm up, and feed in the filler. The lugs are similar thickness to the tubes, so don't act as a heatsink. The whole thing comes up to temperature evenly, and the filler shoots straight through the lug. Easy!

I like downtube shifters. People always comment when I'm riding with them, thinking perhaps that I'm too poor to "update" to ergos, but the truth is that, unless I'm racing (where the ability to change gear in a sprint is good), downtube shifters are my preference. They're simple, light, reliable, positive, and you know what gear you're in without having to look.

I'm pretty proud of my seat lug. The stays join to the seat tube rather than the lug, with a micro-fillet, done in 56% silver. No pump mounting pads this time, as my pump rattled when mounted by the ends, so I'll do it differently this time. I've been advised that joining the seat stays directly to the seat tube is risky, as the seat tube here is only 0.6mm thick, but I'm willing to give it a go and see what happens. If it breaks, I'll do a write-up here and analyse it to death. Having said that though, I've seen plenty of production bikes that do the same, so I reckon it will be okay.

The upper attachments for the rack, moved up about 30mm from last time, so that they clear the brake properly.

Finally some token stainless content - the front derailleur tab, in polished stainless.

At this point I halted proceedings on the frame itself, while I built a spraybooth in which to paint it. Previously, I'd simply hung a big drop sheet on the wall, supported the frame with a broom handle stuck up the seat tube, taken everything I didn't want painted out of the garage, and sprayed away. The result after two frames is a nice even coat of paint over every surface in the garage - my tools, my bench - everything.

In addition to this, because there is a cloud of drying paint suspended in the room, some of this eventually landed on the frame I was working on as it dried, making it less glossy. Some also landed on me. In my hair, on my clothes, making me look prematurely old, and maximising the amount of horrid chemicals that I breathe in, despite my mask.

The solution to this lies in a spray booth. I don't have room for a proper booth, which is essentially a well sealed room, with an enormous exhaust fan and an air inlet filter to keep dust out of the air in the room. Instead, I decided something that could be "packed up" when I was finished with it was the go. I designed what effectively looks like a large cupboard, with an overspray filter occupying the back, and ducted to the bottom part of the cupboard, where three large exhaust fans generate a good vacuum. Some flexible ducting then carries the exhaust air out through an existing hole in the floor. The frame is hung between the open cupboard doors, maximising the airflow at this point towards the filter, so capturing as much overspray as possible.

In addition, a pair of huge 48W compact fluorescent lights are mounted in the upper corners, to help me see any orange peel in the paint.

Here's a photo of the whole thing, showing the usual mess in my garage, as well as the ducting carrying air and overspray out of the garage. According to the specs of the fans, it should recycle the air in the whole garage every couple of minutes. When it's running, you can feel a distinct breeze around the garage door.

And looking into the bowels of the beast, where the subject being painted goes. The open cupboard doors maximise airflow past the subject, as does the removable desktop. The paper filter in the back of the booth is a simple labyrinth, causing the air to turn a couple of sharp corners, and thus drop suspended paint. The lights are really bright, and show up imperfections in the subject really well.

The spraybooth is made from 25 and 16mm MDF sheet. The sides (25mm MDF) have a series of channels routed into them, into which the front, benchtop support bit, top, fan supports, and assorted air channels fit. The result is a heavy, strong structure that's quite airtight, maximising airflow. The fans I used are simple bathroom exhaust fans, which aren't explosion proof. They have the advantage of being about a tenth the price of explosion proof fans. In use there are no problems, as the volume of paint that will be sprayed into the spray booth is quite low.

Finally, of course, some photos of the completed bike, painted white, with decals and a mix of Campy Centaur, Chorus, and Record components, as well as a sexy set of TA Alize triple cranks, with matching Phil Wood bottom bracket.

First a couple of photos of the whole thing. The rack is a Tubus stainless one:

Some photos of the front end, with the little fish decals and the stem from the last bike (repainted of course). It'll probably be a lot more comfortable to ride once I put some bar tape on it (blue, of course). I'll also replace the spacers, as the carbon ones look fugly.

Moving back a little to the seat lug - I put the Zona sticker on this time, as it looked kinda nice. I also painted over the rack brazeons, as I thought they looked a little silly silver.

Moving to the bottom, to look at the sexy TA Alize cranks, and the Henry James BB shell. The disclaimer is a silly decal I came up with after seeing photos of the end of some guys finger, after he removed it with the chain and cog on his fixed wheel bike. Again, I went all commercial and put a Henry James decal on as well, as I really am impressed with their lugs, and aren't afraid to say so.

Finally my downtube decal, with my downtube shifters.

Thanks for looking. If you want to see more why not surf over to my fourth frame, to see progress on an all-out stupid-light race bike with shiny lugs.