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!!


Friday, 23 November 2012

Day 4, more learning, a couple of mistakes, but the frame is together.....

So today started with the relatively simple job of shaping the chainstay ends (the tubes for which were bent yesterday).

The right hand stay went pretty straightforwardly - and then I got distracted...

At the top of the seatstays the bend radius is quite tight, as such the tubes "crimped" and buckled a little bit. I had been wondering what I could do to remove these unsightly dents when I realised that I could potentially use the seat-stay bridge to hide them. 

Well that was it, full steam ahead on trying to bend a tube to an internal diameter of 75mm - so a test was in order.

I picked up what I thought was a scrap piece of tubing and merrily went to heating it up with the oxyacetylene and trying to get a nice bend - little did I realise that this was the pukka left hand chainstay!!!

After some shouting and looking at things to make sure I had just dropped a clanger I came around to the fact that this was the first set back I had had while making the frame - which wasn't too bad considering. And, when I thought about it, I wasn't overly happy with the chainstay as it was - so I set to remaking it - while doing which I learnt a valuable lesson.

I remade the stay and it lined up really well with the drawing, but then when I overlaid it with the existing stay (the one I didn't take a torch to) it didn't match that well - it was at this point that I realised, it would be much easier to make one tube and then just make the second one to match the existing tube - and not necessarily to the drawing. This way you end up with two perfectly matching tubes.

Anywho - enough of all of that - I then shaped and fitted both sets of stays and set to finishing the fillet brazes on the front triangle - see pic below:

Tomorrows plan is to add the lightweight pockets to the left hand drop-out and then tack up the rear end - if all goes according to plan I should be able to fit a rear wheel and tyre tomorrow to check for clearances etc - cheers Neil for the loan of a wheel equiped with a mud tyre!!

Thursday, 22 November 2012

Day 3 - it's starting to feel a bit like ground hog day....

The plan for today was to braze up the main triangle and bend the seat and chainstays.

If there is nothing I've learnt since building my own frame its that there is a heck of lot of learning to be done!! I've lost count of the amount of situations where I've had to think about 5 steps ahead tyring to not make a mistake or the amount of things I've done, got wrong, done again and possibly even got wrong a second time!

Anyway I digress, today I continued to braze up the front triangle but I ran out of brazing rod - so I bent the stays - see pic below.

Shaping the stays really has made the frame feel like its getting there - tomorrow will hopefully see me finish off the front triangle and pop into Johns Bikes Bath to get the BB shell thread cleaned up. 

Once I have got the BB shell thread cleaned up I can install the BB and cranks and make sure everything lines up (and clears) before I get too carried away with brazing up the whole frame.

Wednesday, 21 November 2012

Front triangle tacked and brazing begun.....

On the previous post I ended by mentioning that the seemingly simple task of brazing the front triangle turned out to be not as straight forward as I might have otherwise expected.....

The reason for this is the material from which I made the jig. To save money I made the jig out of wood, however it has been a month or two since I made the jig and mounted the aluminium fixtures on to it - in the correct location I may add.

The issue is that, having re-measured the jig prior to continuing with the frame, it would appear that the jig has swelled ever so slightly. This in turn put all of the aluminium fixtures out of position!

Having re-located the fixtures to the correct position I then continued with brazing up the BB shell - see pic below:

Next up I added the top tube and down tube to the jig, tacked it all together and fully brazed the seat tube to the top tube.

Tomorrow I will be finishing off the main triangle brazes and shaping the rear triangle tubes ready for their joining to the main triangle.


Internal cable routings finished & seat-tube slotted....

Having an excess of holiday I decided to take a week off and hit the frame hard - as such I have finished the internal cable routings in the top tube - what a nightmare this turned into...

The stumbling blocks I came across when doing this were:

1. Making the holes in the frame tube for the internal tube to poke out of.

To do this I drilled a hole perpendicular to the tube surface where I wanted the centre of the internal tube to exit the frame tube. I then angled the drill bit to cut an elliptical slot, this sort of worked however every time I got a nice ellipse on one side but then on the other side I ended up with an asymmetric cut-out.

2. Brazing the internal tubes into the frame tube.

This was fine at one end, but when doing the other end I didn't account for how much distortion you would get. Routing internal tubes through a straight frame tube should be straight forward enough, however I'm routing them through a curved tube (just to make things more difficult).

When I tried to re-bend the internal tubes away from the inner wall of the frame tube (so they don't hit one another when the bike goes over bumps) I cracked one of the internal routings - big fail!!

3. De-brazing the internal tubing while brazing on the exit surrounds.

Unfortunately when I was brazing on the frame stiffening bits, which go around the internal tube exits, the braze on the internal tubes softened allowing the internal tubes to move ever so slightly.

Anyway - after all of these issues were overcome I got the tube finished and also cut the slot in the seat-tube for the seat clamp - see pic below.

Next I will be tacking and brazing the front triangle, but as it would turn out this would not be as plain sailing as I might have at first thought......