Day 11: Tuesday

Finishing the Frame Off

Apologies to those people who have been in contact to ask whatever happened to my bike frame - I know I didn't finish the blog and now my mental scars have cleared up a little, I can finally lay it to rest for now!

I had a very stressful final day on the course, which started with brazing the seat stays between the rear dropouts and the seat tube/top tube junction.  That wasn't too much of a drama, however once they were brazed in place, the rear wheel wasn't straight in the frame.  BIG PROBLEM:

I don't know how it happened and neither did the course tutors but the upshot was that something had to give - the rear triangle couldn't be bent now that the final side of it was in place, the dropouts weren't going to help and seeing as the wheel lined ok up on the chainstays, they weren't going to help either.  To cut a long story short, the only solution was to put a wheel in the dropouts, unbraze the top of the seat stays and then move them until the wheel lined up, before re-attaching them.  Oh, while also not burning a hole in any of the parts.

I was mighty annoyed because I'd followed all the instructions, measured it all very carefully a lot of times, set it all up in the jig and it still wasn't right.  What gives?! I think the problem is actually caused by a weakness in the jig design because it's impossible to be sure that the dropouts are lined up in the same direction and even a small rotation of one of them would result in the sort of problem I was experiencing.

It was a tense few minutes while I stood and watched one of the tutors heating and adjusting the seatstays but after a lot of fluxing, brazing and tweaking, the frame was straight.

Just the braze-ons and a few other bits to do but it was already lunchtime and I had to be back in Cambridge, 2 hours away, in enough time to clear our kitchen out (including a large fridge, dishwasher and washing machine) because we were having a new vinyl floor fitted. The remaining jobs included: filing and fitting the rear brake bridge, creating a small bridge between the two chain stays, various cable stops, trimming off the seat tube, fitting the seat post clamp, sawing out the slit in the seat tube so that the clamp would work, and reaming out the seat & head tubes.

It all ended up being a bit of a rush to complete the frame - the braze-ons were relatively trouble-free, although getting the head tube ones lined up was fun and games necessitating pains-taking measurement, lining up and then re-lining up as the clamps weren't very good at holding them in place.

 Holding the gear braze-on in place so it can be silver-soldered.

 Here's my hand-made chain-stay bridge with complicated but shallow mitres

Cutting the slot in the seat tube (actually two parallel cuts about 2mm apart, about 25mm down from the top) was a lot easier than I thought it would be (maybe I was getting better at working with metal by now!) and in not much time at all everything was in place and it was just a case of tidying up the brazes by - you guessed it - filing!

There was also just about time to ream out the seat tube and head tube:

It became clear that I was going to run out of time -it was getting around to about 6pm and I had to put my tools down and admit temporal defeat.  I paid for the frame materials, said my goodbyes packed the car up and headed for Cambridge.

Here's how the frame ended up (with chintzy new wheel added for good measure):

Due to a mix up about timings, I'm going to have to re-book and make the forks after Christmas - good news in some ways because it'll mean I can pick up one if the jigs that they're selling so I can make a mk. 2 frame ;-)

I'll be writing more when that takes place...

Day 10: Monday

Brazing the rear triangle

When I came back to my chainstays this morning and set everything up in the jig, they somehow turned out to need quite a bit of work to get them to line up correctly at the bottom bracket and dropouts.  That took most of the morning with a lot of adjusting and comparing, but eventually they were ready to be tacked at the bottom bracket.


The dropouts were next, brazed into their slots and then the ends of the chainstays filled with braze. You can see that that the seatstays line up beautifully:

When that was complete I took the frame out of the jig and we tested it for straightness.  I guess it could have been worse - but the amount of brazing I've done and my somewhat inexpert approach to it meant that it did need a few tweaks outside in a truing stand against a skip to get the front triangle into alignment - first the seat tube and the headtube, in relation to the bottom bracket.

After that it was back into the workshop to braze on the chainstays at the bottom bracket:

That's how it looks while you're brazing it,  in full colour it looked like this:

Once those were brazed in position it was time to set up the alignment, using among other things a pair of dropout alignment tools (and also a large plank of wood!):

We also checked that the dropouts were wide enough apart, were in line when a wheel was inserted and didn't have any offset.

I finished the day off with a little more filing of the chainstay brazes.

Just the seatstays and brazeons to do tomorrow and it'll be complete.  Yay!

A Few Notes

I'm posting this more for my benefit than anyone else's but it does give you a bit of an insight into some of the technicalities involved when building a frame from scratch.

Bottom Bracket Shell

• Identify right hand (drive) side by screwing in a spare bearing cup / crank cartridge etc.
• Measure outer diameter

Seat Tube

• Locate top of it by sliding a seat post into it.  Mark top and bottom. Check a second time to make sure you got it right.
• Mark Centreline
• Mark and cut 90 degree mitre in the bottom end so it butts up to the bottom bracket shell and so that the centreline passes through the larger parts (or ears, tabs etc.) of the mitre
• When placed in the jig, ensure that the centreline is facing into the frame as you'll be using this to position the bottle cage mounts. These are 65mm apart.

Down Tube

• Identify long and short butts by looking down the middle
• Mark centreline
• The short butt is the bottom end
• Mark and Cut a 90 degree mitre in the bottom end so that it butts up against the bottom bracket shell.  Ensure that the centreline passes through the larger part just as with the seat tube, for the same reason
•  When placed in the jig, ensure that the centreline is facing into the frame (upwards) as you'll be using this to position the bottle cage mounts.

Seat Tube and Downtube: bottle cages.

•  Check location for bottle cages either by measuring an existing bike (note that the frame angles might be different or by getting two bottle cages and fitting them to your frame.
• Note that the seatpost won't go below the top bottle cage mount so don't put it too high
• Ensure that the top tube doesn't get in the way or either bottle.

Set up the Jig

• Set up the seat tube angle as per the CAD plan
• Set up the head tube angle
• Set the bottom lug height at the front
• Set the front axle height in relation to the bottom bracket and fork rake
• Put bottom bracket shell into jig, along with seat tube at correct angle

Down Tube (again)

• Measure required length (NB ensure that you understand if you're measuring the outer dimensions (i.e. ear to ear) or inner dimensions (i.e. between tubes at the lowest points of the mitre)
• Attach mitre template at correct location + 5mm for adjustment (biggest cut out goes at the bottom)
• Trial fit into jig to ensure that it'll be long enough(or just too long) once cut to length.
• Once satisfied, hacksaw to length +5mm
• File out mitre
• Trial fit and reduce tube length gradually until it fits at the correct angle

Top Tube

• Find long and short butt ends
• Ensure that you shorten the tube by cutting metal off the long butt end
• Mark Centreline
• Mark top of tube
• Mark seat tube to top tube mitre (the bigger cut out goes at the bottom of the tube)
• Measure tube length based on CAD drawing then add 5mm
• Mark top tube to head tube mitre (the bigger cut goes at the top)
• Cut mitres and trial fit

Seatpost clamp

• Either use a lug or cut a bit of sleeve to the correct dimensions
• ensure that the sleeve has an internal diameter very close to the seat tube outer diameter

Chainstays

• Measure length
• Check to see how much of the dropout will insert into chainstay if using a tabbed dropout
• Cut to length by removing metal from big end.  Required length of chainstay= distance bottom bracket to rear axle centres, minus half of BB diameter and the remaining length of the dropout once inserted.
• Cut mitre as per CAD template, position mitre template so that centreline is at top of oval and largest parts of the mitre are top/bottom
• Place in jig and use dropout in jig to mark centre line at back of chainstay
• hacksaw slot a little narrower than dropout then file to size
• Place in jig

Seatstays

• Check that the taper occurs after the point where you are going to need to cut a chunk off the fat end.
• Cut slot in smallest diameter end as above for the chainstays.
• Insert into jig and measure length by eye
• Cut to length +15mm
• File to length
• Place in jig.

Day 9: Sunday

Rear triangle and more filing.

 

I was looking forward to today!  Today marks an important point in our frame building - cutting and filing the final parts to make a complete frame.  Once this is complete, it'll just be the forks to make.

The rear triangle of a bike frame consists of chainstays (along the bottom), seatstays (from the seat tube down) and the rear dropouts into which the rear wheel is clamped.

First off I had to mark out and mitre the chainstays at the bottom bracket end.  Easy enough with the mitre templates provided by Bike CAD Pro, once you've measured a few lengths and done a little maths.  It would have been a little tricky without the computer-generated mitre templates because the chainstays meet the bottom bracket at 90 degrees in one plane but are angled out by a few degrees in another plane to give enough width at the dropouts to accept a 130mm rear axle.  

Another tricky bit was accurately marking the centre line along the top of each chainstay.  If I were to do it again (or rather when I do it again!) I'll use the mitre template to cut the mitre as it's obvious where the top of the chainstay is (it's oval in cross section) and then use the jig to mark the top at the dropout end once it's fitting snugly to the BB.

Anyway, once the mitre is cut, you can then cut a slot at the dropout end using a hacksaw and then a file to tidy it up.

The seatstays are even easier, especially since I'm using some very nice wrap-around tops for mine which negates the need to cut a complicated mitre at the seat tube end.  So it was just a case of cutting the slot for the drop out at the thinnest end and then reducing the length by chopping bits off the top end until it all fits nicely.

It should also be pointed out that before while doing all of the above, there was a fairly lengthy session setting up the jig and rear dropouts.  I've intentionally left the rear dropouts a little flatter than the Raleigh frames that I've seen so that if I want to go fixed at any time in the future it'll be easier to get the chain tension set up.

Here's the complete frame in the jig:

Once that was set up, it was time to decide on the braze-ons that I'll need.  Here's the list and  parts laid out:

They'll go on tomorrow when the rest of the frame gets brazed. 

When I'd done all that, I got on with a bit more filing to tidy up the brazes on the front frame triangle.  They're not perfect but I'm fairly happy with them now they're filed down.  Not too bad for a first effort and I know what to do in the future to improve matters.

It got to about 5pm and I was knackered!  Think it's been a pretty steep learning curve so far and my head is feeling it a little. 

Day 8: Saturday

Brazing the front triangle together

It's probably fair to say that I'd rather have attended a meet and greet with the arachnids that inhabit our loft and out buildings rather than take the torch to my frame this morning but needs must!

I need to get more confident with brazing thin steel tubing together as it's all a bit nerve wracking and in the heat of the moment it seems there's a lot to remember - melt, move, rod..  it's just a knack but I'm annoyed that I was brazing perfectly well at the end of yesterday and this morning it fell apart rather. 

Still it wasn't only me - we all found it a bit tricky when it came to tackling our carefully mitred tubes. We were determined not to burn any holes through them and we all ended up with brazed frames and no holes.  Phew!

The first step was to take all the tubes out of the jig apart from the bottom bracket and seat tube and then tack-braze those two together. Here's Nick working on his bottom bracket:

 Once that was attached we could set the frame back up in the jig and tack the rest of the tubes together - for tacks per joint.

For some reason it was the tacking that I found the most difficult - I couldn't get both tubes heated to the correct temperature and then melt the rod to them...  Well, it was tricky but I got it in the end! 

Here's my bottom bracket tacked:

After lunch we got on with fillet brazing, basically joining the tacks up with braze.  For some reason this was easier than the tacking and after an hour or so the four main joints were complete:

Here's the frame tacked in its entirety, off the jig

Here is the bottom bracket joint prior to cleaning up:

 And the head tube joints (they're a bit messy so I'll be spending a long time filing them!)

My final brazing task was the most difficult bit yet - attaching the seat clamp sleeve to the seat tube.  Under Brian's expert direction, I heated both tubes to the correct temperature and began adding brass rod into the top to get it to drop down between the two bits of metal.  It seemed to take ages but in reality it was all over in about 15 minutes.  It was a case of over-brazing is better than under-brazing so we added quite a lot of rod to the edges and cutout circles on the sleeve, meaning that there was quite a lot of cleaning up for me to do with the file:

That's looking pretty tidy now even if I do say so myself, mind you that's the product of about 10 hours of work (cutting, filing and drilling the sleeve, mitering, tacking and fillet brazing the top tube to the sleeve and then brazing the sleeve to the seat tube and filing it all clean again.  The top of the sleeve will be the top of my frame when it's finished so I'll be trimming off that untidy brassy bit above it - no need to file it down.

One great thing is that the frames so far are so light!  The lack of lugs and Reynolds 631 tubing means that they're not far off being as light as a steel frame can get.

Tomorrow the frame goes back into the jig so that I can begin to set up the rear triangle and rear dropouts.  Really looking forward to it.

Day 7: Friday

Learning to Braze

It was nearly crunchtime - I'd cut all my frame tubes to size (both on the mini bike and on the actual bike) so it could be put off no longer -  very nearly time to braze them together!

Before that, however, it was time to braze the bottle carrier bosses to my bike's seat- and down-tubes.  I went for a slightly more classy look by putting triangles under the bosses before brazing them in with silver. 

  
Here are the finished brazes, prior to removal of flux:

That done, it was time to get on with fillet brazing practice.

I started with simply brazing a couple of straight lines of brass onto a flat surface of box-section steel.  It was reasonably tricky to start with partly because I'd never done it before and didn't want to burn through the steel, but partly because I found the torch a bit unweildy and it's heavy to hold in one position for a long time.

After straights I tacked a couple of round sections to the box section and set about brazing them on, followed by fillet brazing the round bits I'd tacked a few days before:

After a break for lunch, I set about brazing the mini bike together.  By the time I'd finished I was getting a little better at it.  With a little more practice I think the actual bike will come along together nicely:

Note that we had to substitute a longer bit of tubing for the head tube as we managed to make the frame a little too big in the initial tacking.

Nearly finished - note that the bottom half is done, the top half is only tacked, also note the bottle cage mount on the downtube:

Having finished it off I just need to trim that head tube down to an acceptable size and file the brazes down to make it look pretty. 

Thursday (Continued...)

There are some absolutely lovely roads around here for bike riding - we had a great trip out on cycle route 17,  in amazing countryside, dodging the debris washed into the road by the heavy rain of the last few days.

We did just over 20 miles as far as Hawkinge and back; Nick suffered a puncture in his rear tyre and for once one of my home made bikes proved unreliable!  How can this be?!  The nut holding the crank on kept working loose which was a pain, but I did meet some friendly locals by knocking on their doors and asking to borrow a 14mm socket!  Think I need a new crank spindle as the threads on the non-drive side are probably a little worn.

The hills were a bit of a challenge compared with a ride in Cambridge so maybe the bike was coming out in sympathy with me.  A swift pint in the King's Arms in Elham made matters a lot more tolerable on the way home:

Here are a few pics taken on the way - I can thoroughly recommend a bike ride around here:

Looking forward to some proper brazing  practice tomorrow...