Hand built bespoke bicycle frames in the heart of the Wiltshire countryside - dmoframeworks@gmail.com.
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Saturday, 24 November 2012

She's alive!!!

So, all in all, quite an exciting day today....

My aim was to finish the fit of the seat and chain stay tubes, check the lengths and alignment and then tack it all up and fit a rear wheel to make sure everything clears.

Before tacking the rear end up I needed to fabricate brass ring inserts to go into the stays at the drop-out ends. The reason frame builders do this is to ensure sufficient brass is present in the joint. Normal 'tube to tube' joints don't require this because they have a close fit all the way around whereas the dropout joint has a big gap in it where the flat plate dropout slides into the round tube - see pic below:


To make these little brass rings I just used the bits of brazing rod which had become too short to use for normal joints and wrapped them around a round file which just happened to the about the correct diameter!
 

Now when you slide the dropout into the cutout in the tube there is already brass present behind the joint.


Once I had finished fitting the brass inserts into the stays I could then tack up the rear end - and at last I can really start to see the frame taking shape.


Next up it was time to take the plunge and fit a rear wheel to make sure it cleared and sat in the middle of the frame. As you can see below the wheel fitted ok and cleared easily. I think a bit of 'tweaking' will be required to get the wheel to sit in the middle of the frame - but as far as I can gather this is par for the course with handmade frames!

When desinging the frame I accounted for anything up to a 2.4" tyre, in hindsight its unlikely that I will use such a large carcass tyre and so I could have got away with being a bit racier on the chainstay length and generally tucked the wheel in closer to the seatube - a development for frame number two perhaps?


The original aim was to get the frame to be sub 2kg, however when I guesstimated the frame weight during the design phase I found it hard to get an idea of exactly how much the fillet brazed joints would add to the overall frame weight. The answer is a lot!! I have intentionally ensured that each braze has nice large radii and so they are possibly a little over engineered for the application.

Including the sliding aluminium drop-outs the frame currently weighs 2.3kg, however I am yet to fettle the headtube joint so this might come down a bit. This is a bit disappointing but looking at competitor frames (Niner Sir 9, Singular Swift etc etc) its about par for the course.

Next up I need to tweak the left rear seatstay and then fully braze up the rear end. Following that I need to get a seatstay bridge bent up and get that fitted then its just the odds and ends of cable and bottle mounts and it should be ready for painting!!

 

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