Thursday, 23 June 2011

Lugwork - 3

One final lug to work - I'd cut triangles in the seatlug previously, but had to wait until I could see how the seat stays would attach before doing the back. I mitred one of the seat stays last night and simply traced around the end. At first I thought some triangle cutouts in the long tangs would look good, but decided they were too fussy, so simply cut the tangs down and reshaped the back a little.

Here's the result.

Wednesday, 22 June 2011

More progress on number five.

I'm making good progress on putting Ben's frame together. Here's a photo of the front triangle and chainstays in the jig. The XL tube sizes are a tight fit, but it all goes in okay. The top tube isn't brazed in yet - it's just jigged up so I can mitre the seat stays and work out what to do with the skirt section on the seat lug.

Here's a nice macro photo of the lower head lug. I used 56% silver filler with this, and dropped back to a number 12 tip, using the system 48 flux. I'm quite pleased with how it turned out - the amount of filler is good, and I got full penetration without much encouragement. Also shown is one of the ergo cable adjusters. These are quite a challenge to hold on the downtube. These were brazed in with 56% silver filler, using the stainless light flux.

Here's the progress on the bottom bracket. As you can see, I'm yet to mitre or braze in the chainstays. The BB-downtube join was done with system 48 filler, and system 48 flux. I went up to a number 20 tip for this one (I modified my largest acetylene tip for LPG by drilling a counterbore in the end). I really liked using this tip - it let me get very even heating.

The system 48 filler is a little gummier than 56%. I don't get the minimalist shoreline fillets I'm used to with 56%, so there's a little more shoreline cleanup needed. That said, it pulls through really well and fills bigger gaps than 56%. Just the ticket for bottom brackets. I can see myself using quite a lot of this filler.

Finally one of the dropouts. I've got a standard recipe now that works a treat for stainless. 56% filler with grey stainless light flux. I used a number 12 tip here, as the dropout tends to act as a bit of a heatsink. I overdid the filler a little, as evidenced by the excessive fillet in the cutout. Contrast that with the really nice fillet I got on the cutouts on the lower head lug.

Wednesday, 15 June 2011

Interior cable routing

Interior cable routing is quite a bit of work, but very rewarding when it works well. I use a two-step process, where I first solder the tunnel to the top tube, and then solder a reinforcement piece over the top. It makes for a lot of work, but I think the peace of mind knowing that the join is nice and solid inside is worth it.

I start by slotting the top tube - I just use a drill and file for this - I aim to get a really neat fit to the angled cable tunnel end. Then I assemble the cable tunnel by cutting the middle piece to length, and soldering the larger end pieces on with 56 % silver.

Next the cable tunnel is inserted into the tube. This can be tricky. Ben's frame has the entry point horizontal on the right side, to make for neat cable routing around the head tube, and then horizontal again on the left at the back. I'm leery of having the cable exit at the top, as that's asking for water to work it's way in.

Apply plenty of flux (I'm using the System 48 flux here, with 56 % silver filler).

And solder the tunnel to the tube, aiming for a small fillet all around.

After cleanup, it looks nice and clean, with a good fillet.

Next, I put the reinforcing diamond on top, ensuring it fits neatly. A little bit of blacksmithing was required to form the diamond so that it neatly fits the 31.75mm XL tube, as they're designed to go on 28.6mm tubes. I forgot to take a photo before fluxing, so the fluxed one will have to do.

And solder it in, again using 56% silver filler and System 48 flux. It's hard to do these neatly, as you have to ensure there's enough filler to fillet the tunnel end, and it tends to go everywhere. Also they're tiny pieces, and easy to overheat. I use a much smaller tip (no. 8) than my usual no. 15 for this work.

Finally, wash the flux off, cut the tunnel down neatly and use emery and needle files to remove the excess filler.