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If you're looking for a carbon disc fork with a lot of versatility then Lynskey make a good one

https://www.lynskeyperformance.com/store/lynskey-endurance-road-carbon-disc-fork.html

It's designed for road/gravel racing/ CX Clearances are going to be pretty big for a standard road tyre, but it sounds like you want some flexibility out of the bike.

If you want a full-on no larger than 25mm race fork with disc mounts Lynskey have that covered too.

Good improvisation. Thanks for the linkage.

Out of interest, how did you shape the chainstays? Do you have a proper tube bender?

Thanks Apollo.

drøn, there's quite a lot of information out there related to finite element analysis of bike frames. Although it's quite old, there's a nice piece on Sheldon Brown's site, http://sheldonbrown.com/rinard/fea.htm and there are various other academic papers too. I've also picked up quite a lot from talking to various builders.

My comment was a bit flippant in hindsight - it's important that the seat tube/seat stay junction is well formed. The position of the joints on my frame mean that I can get plenty of braze around them to form a good strong fillet. Also, the seat tube reinforcing sleeve I added takes the wall thickness of that area to 1.6mm, which is pretty much double the thickness of the butted sections of the tubes.

Nice! Have you had chance to give it a spin yet?

I'm glad you're enjoying the thread!

I was at a loose end this morning, so I did a few hours to complete the second seat stay. Once I was 100% happy with the fit of the first stay I made paper templates of the mitres, and then turned them inside out so I could mirror them onto the second. That made the initial cut and mitre a lot faster.

Then it was into the process of matching them up so that they are perfectly level. I've heard more than one frame builder say that's one of the first things they look at on a bike.

I think my choice of fillet-brazed fastback stays made things unintentionally quite hard, so it took a while. I also made a small mistake, filing a little bit too much away where I thought the inside faces of the stays would touch. In the end, they barely contact.

However, it's only a small gap over a short section of the stay, so the braze will fill it. Fortunately the top of the seat stay is one of the least stressed parts of the bike. If you've ever looked at a seat stay attached to the side of the seat tube you'll see how little contact is needed, so I'll have ample strength through the joint. Just one of those things!

Next week I'll braze them up, then start work on some of the braze-ons. I'll probably leave the soak and clean up of the fillets to the week after, as they'll need time in the water bath to dissolve away the flux from the interior of the tubes.

Got a reasonable amount done today. First thing was to align the chain stays following the brazing work.

With a moderate amount of force I spread the chain stays to the correct separation. If they were 953 I would have had to haul on them like no-one's business, it's that stiff.

Once I'd checked the rear was centred correctly with a frame alignment gauge I checked the dropouts to make sure they were parallel and at the same height. Only a very minor tweak was needed. This is a close up of the alignment tool heads.

Next was making sure I had decent chainring clearance. The Zona chain stays are heavily ovalised, so there's no need to dimple them. I'll be running a compact as I'm an Old Man, but you'd get standard rings in here, no bother.

Then, it was onto shaping the dropout and CS/BB fillets. The former were quick, the latter took a few hours of careful shaping.

By mid-afternoon I moved on to cutting and mitering the first seat stay. That's looking pretty trim, so next week I'll try to match it with the other one. All being well, I can braze them on then maybe start attaching the brake bridge and other bits and bobs.

More next week!

I can why you'd think that, but there's actually a tube block hidden by the vice on that frame in the background. That holds the tube secure without deforming it while you clamp it in the vice to work on it.

I think that the chain stay fillets were being cleaned up at the time, something I have to look forward to this week.

Some decent progress today. I was working on the chain stays. First up was mitring them, which is quite fiddly as there are lots of curves and offset angles, and both need to be the same length.

Once I was happy with the position I drilled gas relief holes in the bottom bracket, and tacked the stays on. You can actually braze upwards with a bit of practice, so this was done from the underside, as the frame was in the jig.

Then I checked the alignment, made sure everything was OK and went for the full braze.

A post brazing alignment check showed about 0.5mm vertical deflection that will need sorting with a gentle bend, and the heat pulled the chainstays in equally from 130mm separation to 126mm. That "should" be a simple cold-set spacing job, but I can get a wheel in it sits in about the right place and it spins! Yay!

Hiya, thanks very much for the kind words. I have one or two pinholes in the brazes I've done too. Nothing major, but I'll need to tidy them up. The amount of flux I used was a bit excessive, but having some warm and in "reserve" can be handy, especially as I learn. You can scoop molten blobs up with a brazing rod and move them if you need them. You can also push it around with the flame, but I wouldn't recommend that.

If the holes are small & cosmetic, clean them out with a tiny hand-spun drill bit. I also push the point of a needle file into mine to make sure I've hit the bottom, and underneath the material is solid.

Once they are cleaned out they can be filled with silver brazing rod. That means you won't reflow the brass, and are introducing the minimum amount of heat into the joint.

I don't think the flux is the most likely source of pinholes. Most likely is a tiny bit of contamination has got onto the brazing rod, or was present in the flux or on the base metals. When that's heated it can vaporise and the resulting gas bubble leaves a void/pinhole in the braze. Also, if you make a second pass over a fillet you can boil off some of the original braze metal, which again releases gases.

There's a good thread on it here:

http://www.velocipedesalon.com/forum/f10/bubbles-my-fillet-brazes-28874.html

One of the builders categorises them as follows:

-Surface "bubbles" on the top of the fillet (tiny ones) are generally small bits of contamination (steel dust is great for this).
-"Pin holes", ie-small diameter and deep holes, are often an indication of hot brass on top of a cold layer.
-Irregular holes below the surface are hot brass on top of cold brass.
-Flux holes are often burnt flux, and seem to have a glass pearl in a larger hole.

Cleanliness is next to Godliness, it seems.

More progress in the workshop, but it's slow and steady as I work the fillets to transition as smoothly as possible from one tube to the next. It gets to the point where you can't see any bumps, but you can feel them. The risk is if you don't get them sorted they'll show under the paint.

I have started to mitre the chainstays, which involves some tricksy shaping. Hopefully next week I'll have both mitred and tacked into place. If the alignment is good I'll braze them fully.

This is a close up of the DT/HT joint after tidying. A consistent width strip of braze, plus nice shaping, should give a decent look under paint.

Dear LFGSS hive-mind.

I'm putting together a potential urban frame build design at the moment, and I am considering going 650b for the wheels.

I am a bit concerned about general availability of stuff in 650B sizing. Are there any good sources for tyres, tubes and rims in the UK, or is it mostly import?

Ta!

Yesterday was mostly about filing. Lots and lots of filing. Still have to shape the bottom bracket fully, but I'm getting there.

After soaking the flux, the frame looks like it's had a fake tan.

Head tube fillets, top one is close to completion, bottom one is being roughed in.

Seat tube fillet and sleeve. The sleeve was relatively fast to clear up, the silver brazing rod tends to spread itself very thin.

The sleeve is something I made myself from a piece of plain gauge 1mm tubing.

Placing it at the junction of the seat tube & top tube means that the area is reinforced and you also get a nicer fillet transition from the TT to the ST.

Bit of a tricksy area, you have to line it all up, fillet the TT to the sleeve, clean up, then use a lower temperature silver brazing rod to bond the sleeve onto the seat tube itself.

I've occasionally posted before about doing a bit of (attempted) frame building & brazing. However, a couple of months ago I had one of those too good to pass up opportunities to have a proper crack at building a couple of frames.

For the past few weeks I've mostly been practicing, but I've now started out building my first frame. It's going to be a winter road bike that can happily run full mudguards. I'm not doing anything crazy design-wise, as I want to get the fundamentals as good as I can.

I'm spending one day a week building, so I'll try to post updates as I go. Here's a few images, by way of catch up.

One of the spec sheets, made using BikeCAD

Columbus Zona tubeset and a Columbus Hiver carbon fork.

Seat-tube reinforcement sleeve

Top tube mitres

Head tube fillets, immediately after being laid.

Where I was at last week.

Another disc fork option to consider is the Lynskey.

http://www.hotlines-uk.com/Models.aspx?ModelID=89254

Already eyeleted for mudguards, 397mm axle to crown, takes a standard QR skewer and will easily accept a 28mm tyre.

Looks pretty elegant and could easily be refinished. RRP £199, which is good. A lot less hassle and cost than an after-market ENVE conversion. I wish they'd just sell their forks with eyelets as an option.

Amazing ride there, Ed. Congratulations. The writeup brought back some memories.

I've ridden past, and stopped at, the Tibetan temple in Eskdalemuir when out touring. I thought the good folk of Peebles were pulling my leg, but no, there it was, one of the more surreal sights of the Scottish Borders.

There was something so flagrant about the RLJing I witnessed last night it really wound me up. I was on foot, Old Street last night. Use the pedestrian crossing, lights go green for me. I spot a guy riding up to the junction and just think, "I bet he's not going to stop."

I'm fully a third of the way over the crossing and he weaves in front of me and the missus. My call of "C'mon, play fair" is met with a dismissive wave of the arm, presumably asking me to chill out as he sauntered off in the direction of Dalston.

And people wonder why cyclists get such a bad rep.

Ginger beard, black Raybans, ride a cream coloured fixie, wear a LMNH Polka Dot cap? You, Sir, are a Weapons-grade bell end.

Yes, ok Mikenetic having to queue up for 30 minutes for said breakfast is quite bad. I actually enjoyed the standing in the queue at that point.

That's probably because you were delirious with hunger by the time someone took your order. The cafe was better value than the pub. I heard people say the fry at The Ship was a tenner?

It was a lot worse than I remember from my previous DD runs. The queues didn't seem to die down at all for the 3-4 hours I was hanging around.

Enjoyed the ride, but the catering situation at the beach is getting out of hand.

I know that's not the fault of the organisers, who I stress to say do a brilliant job.

There was a guy selling sausages from a stall about 80(?) miles in. He was complaining that he couldn't get a permit to sell anything at Dunwich, and that the pub & cafe effectively had control of the end point as a result.

Now, that may be sour grapes, but the queues in the pub, the queues outside the cafe and the prices v quality of The Ship's fried breakfast indicate someone is doing very well out of the DD.

Feh, new-fangled OS maps.

I prefer a lodestone and a vellum map drawn with ochre. As backup I simply carry a goat to sacrifice, and take my bearings my casting the entrails.

Is the food stop at Sible again this year? Was that not a one-off deviation from the route? I done DD six times and it was at Waldingfield for 5 times out of 6. Not that it bothers me cause I live that neck of the woods, know the lanes well and use maps and fiddly paper route sheets, but punters with GPS may just all take the turn for Sible without needing to.

I double checked on the official route guidance and the feed stop is indeed at Sible Hedingham. http://londonschoolofcycling.co.uk/content.php?id=18&article_id=3

It was there on the 2012 & 2011 rides too.

I've done a slightly tweaked version of the route, adding in the food stop at Sible Hedinhgam.

Also, a Garmin should easily last the night, so long as you don't use the backlight constantly. I've done it using a Garmin 705 a couple of times and there's always a decent amount of battery left at the finish.

http://ridewithgps.com/routes/2877512

Use this

http://www.wheelpro.co.uk/spokecalc/

You're correct. Tom Donhue's workshop is now in Hackney Wick.