Columbus XCR Audax Frame

Columbus XCR Audax Frame

This is to be my first use of the BikeCad program and also to incorporate a bike fit into the design, making it my first truly custom frame. The program certainly revolutionises the design processes allowing you to constantly adjust the design whilst keeping an eye on the aesthetics and geometry. We wanted a full stainless steel frame with accommodation for mudguards and a lightweight pannier rack. The only stainless fork blades available are Reynolds 953, but the frame will be in XCR. The steerer tube has to be non stainless, from Columbus. Apart from the fork crown, it will also be my first fully fillet silver soldered frame.

FORKS
As usual I make the forks first, managing to produce a fork rake of 43mm from the 30mm rakes blades.

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Whole frame cut, mitred and assembled before any brazing, then bottle bosses and internal brake cable guide added before final frame assembly
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Also decided to add chain stay gussets for added strength and a sleeved section to encompass the lower down tube/bottom bracket junction.
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I had to use slotted dropouts because I couldn’t find any socket types that fitted XCR chain stays. Combining these with seat stay top eyes then putting them all together was particularly challenging. The XCR top eyes are supposed to be sized to fit but they are in fact rather loose and due to the thickness of the seat stays, rather bulky. In retrospect I would choose to do a fastback seat stay cluster with XCR seat stays.
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At last all assembled apart from a few hours polishing before taking it to the painters.
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All polished sections done and finally on it’s way to the painters.
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BESPOKE 2015
The frame is now painted but I’ll be exhibiting it at this years Bespoke bike show in Bristol on 17th,18th,19th April. So I will refrain posting a picture of the completed bike until then. Hope to meet many enthusiasts and potential contributors there. You can check it out at http://www.bespoked.cc

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2 Comments

Charlie Merivale

about 4 years ago

Hi Stephen, it looks and sounds like a wonderful project. I have used BikeCad for the first time flying solo, as it were. My main difficulty was in trying to amalgamate a lugset and BB with fixed angles with the program. The lugs are Llewelyn and a joy to work with, and, whether right or wrong, I didn't want to pull them. My solution was to do the majority of the design on the computer, but the DT, HT, and BB relationship on a scale drawing. I'm building a fixed/SS porteur. My seat stay caps have been produced by mitring in a piece of head tube. The trail will be 40mm, an interesting experiment. Kind regards, Charlie.

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Stephen Hilton

about 4 years ago

Dear Charlie, Sorry for the late reply. This has certainly been the most challenging frame to date, albeit I am not entirely sure why. I agree the Llewellyn lugs are nice to use, are you using the stainless ones? I agree adjusting lug angles is difficult as the more you file away you loose the definition of the lug or end up cutting it back to almost nothing. In the Paterek manual Tim Paterek states he has adjusted lugs as much as 5 degrees, but for me I think 2 degrees is optimistic! I don't know if you are using a jig, but I assume you would design the frame as a fully mitred one using the known lug angles (assuming they turn out to be as they were intended) and having set the jig up loose fit the lugs and cut the mitres in situ around the lugs. It seems a shame you ended up doing everything twice. I have already discoverd some limitations in the BikeCad program myself. At least it makes it a lot easier to play around with the rest of the frame dimensions whilst keeping the lug angles fixed. best wishes Stephen

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