The Forks

After ordering the replacement rear dropouts on a guaranteed next day service i was slightly annoyed when they had not been delivered yesterday so today i set about the only task left that can be completed without them, the forks.

Feeling slightly better after 2 nights of savage flu sweating, shivering and aching this morning and despite the disappointment of the parts not arriving i felt inspired to achieve something tangible on this day of rest. The first task, as always, was to construct another jig very similar to the one that i have built for the rear triangle. After this was done i measured the drop from the break boss to the top of the axle on an existing bike and used this dimension to work out the length and then to cut the two fork blades to this value, there is very little margin for error when cutting to length so it is always a slightly nerve racking experience, especially when two tubes are having to be cut to exactly the same! If i were to build frames frequently a band saw would be an excellent investment but for a one off it would have been an extravagance so i have had to cut all tubes by hand with a rotary tool. After the tubes were cut to length everything was cleaned and fluxed before slotting everything together and placing it in the jig. Once in the jig adjustments were made to give the forks a rake of 61mm (the distance the axle is in front of a virtual line drawn from the centre of the headtube) and an OLD (Over Locknut Dimension, i.e. the hub width) of 123mm, the OLD of the hub will be 120mm but a few extra mm are added for ease of insertion.The next task was the brazing, you may notice the different colour of the fluxs used on the crown and the dropouts. As i have mentioned in previous posts bronze is more suited to filling larger gaps than silver and as there was a fair bit of play in the crown i decided to use bronze for this component and go back to silver for the dropouts, the flux used for bronze brazing is pink, that which is used for silver is white.

Brazing done and after a bit of a clean up the forks are almost completed.
A close up of the dropouts:
A close up of the crown:
A fair bit of grinding down of the excess bronze will be required here as i used my standard approach for the forks of masses of excess guarantees a strong joint!

There is still quite a bit of work left to do before they are completed, firstly as you can see i left the steer tube slightly long when brazing it into the crown, i did this because it makes it easier to see when the brazing alloy has flowed all the way through the joint, this needs to be ground down level with the crown. Then a hole needs to be drilled through the crown and tapped (threaded) so that a break can be bolted on to it. Finally it will need to be polished up with the brass wire wheel along with all of the other joints when it arrives...

The frame as it currently stands:


P.S. I have noticed what i am sure will become an annoying rattle in one of the fork blades, some of the excess broze must have formed a bead and dropped into the blade whilst brazing, oh well!

New Solution

After an evening of contemplating my track dropout issue i believe that i have come up with a better solution. I have found that dropout can be purchesed without plugs, instead they come simply stamped out of a plate of steel, before hardening, which means that instead of plugging them into the chainstay where the angle of the plug dictates the angle of the dropout a slot can be cut into the chainstay and then fillet brazed into place.

The original dropouts with plugs:

The dropouts that I am now going to use:

I think all will agree that these dropouts are far less elegant but it is my only option without massively compromising on frame design.

In order to use these dropouts i will have to cut a slot into the chainstay as previously described but also to then fillet braze them into place before filling in the gap that will be created between the drop out and the tube. Silver is too fluid a brazing material to be able to do this so i will have to go back to using bronze for this particular part of the build, not somthing that i am keen on doing but i have had a lot of practice with Bronze fillet brazing whilst building the various jigs so fingers crossed it will go to plan.

Whilst ordering these track dropouts i also purchased the final component that i will need to complete the frame; the 'Top Eyes', i have opted for the C32 model.

Top Eyes are brazed onto the end of the seatstays and then fillet brazed onto the side of the toptube/downtube lug, this is the last brazing task to be performed.

Further Tribulations

Jig sorted tonight i set about cutting the chainstays to length in order to braze on the rear dropouts. After adjusting the jig to mark the position that the chainstay needed to be cut at i set about the task with a cutting disk on a rotary tool. After cutting i slotted one of the dropouts onto the chainstay and reinserted the chainstay into the bottom bracket. At this point it because obvious that the bottom bracket that i have been supplied is not correct for the track dropouts. Rather than the slot in the drop out being parallel to the ground it angled up by 3 degrees, the difference between a road and a track bottom bracket. When I ordered my components I was advised that they could supply track dropouts for a road bottom bracket but in fact after a bit of research i have found that this is not the case. Because the dropouts plug into the chainstays and a contact fit is required for brazing the tube cannot simply be cut at an angle to correct this so i am left with two options, braze the dropouts onto the chainstays as they are and except that they point upwards but his will simply transfer the issue to a differnt point on the frame, if i do this the seatstays will meet the seattube rather than the tp tube / seat tube lug again becasue the angle of the seat stay is determined by the dropout. The second option is to purchase some standard road dropouts. If I purchase road dropouts i can either simply build a road bike or modify the drive side drop out to remove the derailleur hanger and then fit a chain tensioning device to enable the bike to be run as a single speed. Seeing as the objective of this build was to build a fixed bike the second option seems like the only way forward. The downside of this solution is mainly aesthetic, a chain tensioning device will need to be fillet brazed onto the frame which in my opinion diminishes the elegance of a fixed bike. Parts will be ordered tomorrow but alas I am out of time to get the bike completed before my move to London where I will not have the space or equipment necessary to complete it. I will have to finish the build over a far more extended time frame during my visits back to the midlands.


Resolved to the fact that I can not complete any further work on the frame until the new parts arrive i directed my attention onto the forks and brazed the crown onto the stear tube using masses of silver to mitigate against impalement!

The next task will be to braze the front dropouts onto the forks then cut them to length before brazing them into the crown.

Prepping for the Rear Trinagle

After a few days of truancy from Chris Beard Custom Cycles a concerted effort was required this evening to get back on track. The goal this evening was to construct the jig that is required to complete the rear triangle. As with many things a lot of work, almost 4 hours, went into producing something that looks very simple. The jig for the rear triangle is a little more complicated than the one that i produced for the front triangle as it requires the facility to adjust the height and separation of the rear drop outs (known as the 'Over Lock-nut Distance' or 'OLD') and the angle of the top tube, actually the top tube just needs to be level but in order to achieve this adjustability has to be built in.

I began the process by attempting to weld some box section to my table 69mm apart so that the bottom bracket, which has a width of 68mm can be clamped between them. Unfortunately i had run out of Argon for the MIG welder so instead used some of the bronze, that i have from when i was considering using bronze as the brazing alloy, to fillet braze them onto the jig. After this was done the outsides of the box section were cut away and a slot cut into the inside using a plasma cutter so that they can close in to clamp the BB shell using a length of threaded bar.
A lovely fillet braze:
I produced the part of the jig for the rear drop outs by brazing a piece of box section standing on its end to the brazing table and, using the plasma cutter, cut a wide long slot down both sides to allow a peace of threaded bar to go straight through and have both backwards & forwards plus up and down adjustability. To make sure that the nuts do not simple go through the slot I produced large washers from an off cut of box section:
The threaded bar has nuts either side of the vertical box setion tube to set the height and horizontal position of the drop outs and two nuts on either side to set the drop out spacing along with the angle of the dropouts. The height of the drop outs is very important becasue it sets the bottom bracket drop, although i am building a 'track bike' it will only be used on the road so i am building it with a standard BB drop for a road bike of 68mm, a true track bike has a smaller BB drop so that the pedals to not catch on the banked track:
Completed jig with tront triangle #1 in place to help with component positioning:The next task will be to cut the chain stays to length and then to braze the rear dropouts onto them before proceeding to the seat stays.

A Fresh Start

Spirits not dampened by Seat tube / head tube alignmentgate the replacement parts were joyously unwrapped yesterday and the measuring, cutting, mitering & grinding started afresh. As all of the items that i had constructed to help build my first frame were ready and waiting it took a measly 5 hours and one late night to get back to the position that the frame was in before the disaster.


With an improved technique that can only be known by a veteran frame builder the front triangle has now been braised almost to perfection:


All but one of the brazes have been completed perfectly, albeit with surplus silver to make sure, all are structurally sound. The only error was on the seat tube / top tube lug which i allowed to get a little hot for silver brazing but this will not affect either the strength of the join or the tubing. The flux used when brazing not only absorbs any oxides & impurities that are on the surface of the pieces to be joined or are produced because of the high temperatures used in the process. It is also designed to help the brazer know when the correct temperature is reached to allow the brazing material being used to melt and to flow into the joint. The flux turns from white powder to a clear paste just below the optimum temperature, if the flux turns black the temperature has risen above the optimum point and the brazer needs to back off with the heat. When the flux turns black it will not go clear again and stains the materials being brazed. This black stain has to be polished off with a brass wire wheel, something that i have on order.

An example of a perfectly brazed lug joint, you can see that the silver has flown all the way through and around the join and the excess has coated the surrounding area:


This is the lug that reached too high a temperature, note the blackening at the base of the lug but also that the silver has completely penetrated the join:


After completing the bazing a toilet cleaner solution was used, recommended by my welding equip supplier, to clean off the worst of the flux left on the frame. This was done in my mothers kitchen sink! After using this highly corrosive solution the frame needed to be thoroughly rinsed with clean water, inside the tubes as well as on the outside to prevent it eating away at the steel over time, the frame was than placed on the Aga to dry out, note the incredibly naught dog kicking back in the comfy chair.


So now the front triangle has been completed:

With perfect alignment:

On a personal note i am incredibly lucky that i am staying in my mothers house whilst she is away on holiday for if she were to have witnessed some of the processes that i have performed in her kitchen i am pretty sure that i would never be welcome again!

Next to come is the rear triangle...

Hubris.

Everything seemed to be going so well...

After brazing the front triangle and allowing everything to cool down i took the frame out of the jig to take pride in my masterpiece, something did not appear to be quite right. On closer inspection the fault became apparent. At some ponit during the brazing process i have knocked my jig and twisted the head tube out of allignment with the seat tube by 3 degrees.
This is a catastrophic error. In a futile bid to correct it i hung a heavy weight from the right side of the head tube (as it sits in the photo above) and tried to reheat the lug to melt the silver. Unfortunately it is impossible to get the entire joint up to the temperature required at the same time and in attempting to do so i have heated the tube beyond the safe limit.

Disapointing indeed but i vow to persevere and begin afresh this time with many hours of bike building experience to better guide me. Frame no. 1 will hang from my wall so that in the distant future i will be reminded that even bike building greats such as Chris Beard Custom Cycles can succumb to hubris.

The First Braze

Slightly hungover this morning i headed into my workshop with a coffee to commence the task that i had been dreading ever since i envisioned this project; brazing. After a few weeks of sporadic practicing using a bronze brazing rod i felt that although i was resonably proficient at the skill i was concious that i was always having to heat the tube to a temperature that was difficult to control. I therefore made the decision last week to use silver. Silver has several advantages over bronze, the pricible two are that it flows better, especially into a tightly fitting lug and it has a much lower melting point. The lower melting point is useful in bicycle frame construction becasue the structure of cromoly changes at high temperature making it harder but also more brittle, using silver as a brazing alloy means that the temperature at which this process happens is way above the temperature required to melt the silver. The only disadvantage of using silver is the price, where as a 5kg tube containg around 50 rods of bronze costs £25.00, silver is sold by the rod priced at £14.00 each! Peace of mind does indeed come at a hefty price.

After at least half an hour of searching for my ear protection which i had fastidiously hidden from my self i set about producing my jig. After cutting 6 no. 100mm lengths of box secition i used a plasma cutter to notch out a cradle in each of them, placed them on my brazing table (note modified for extra support realising that if i were to stand inside of the frame whilst brazing it is so small that i would have to direct the 5000 degree C flame at my nuts). This done i dissassembled the the front triangle and prepped it for brazing. The first task was to drill a vent hole in the top of the head tube where the top tube buts against it. The top tube is the only sealed member, if the vent hole was not drilled the expanding gasses within the tube would prevent the flow of silver into the lug due to the pressure. Then the tubes and lugs have to be thoroughly cleaned using a degreaser, coated in a thick paste of flux and then reassembeld before placing in the jig:
Close up of a fluxed lug:
After this is done an angle finder is used to make sure that all the tubes are in the correct alignment:


Once this is done and the jig has been adjusted the brazing can begin, i will spare the details of how this is done (unless anyone requests the info?!) but it is a delicate process involving relitively precise temperature control whilts using a very powerful Oxy-Acetaline flame.

Brazing of the front triangle all done, below is an example of a finished braze, the discoloration is the flux which will be brushed off with a brass wire wheel when i go and buy one tomorrow!
Brazing has gone better than expected and generally pretty pleased with the completion of phase one of the build.

A note on Frame Design

Being an avid accumulator of bicycles my stable is missing very few categories, the only gaping hole in the collection is where a fixed bike should stand so this is the type of bicycle that I decided to build. At first I thought this to be a good choice for my first frame because on the face of it it is much simpler, a track frame has no rear brake bridge or cable stops which have to be fillet brazed (all the other joints to be brazed are lugged) to the frame but since i purchased the components and started to practice brazing i have actually realised that fillet brazing is very simple, much easier than brazing the lugs. A track frame has a different geometry to a standard road bike, the bottom bracket is higher, the rear axle width is narrower, the seat tube and head tube angles steeper all to facilitate a more agile machine. The problem i now face is that the bottom bracket shells that were available from my supplier are standard for road bikes so i have had to modify mine to get the correct angles which was a slightly daunting procedure as it involves grinding out the lugs, not in itself difficult but if too much is removed the gap between the tube and the lug will be too large for the brazing material to flow via capillary action. I believe that i have now achieved all of this correctly and i have completed cutting and mitering all of the tubes for the front triangle, so from where i started with this:

I have now progressed to this (chainstays have been mitered at the bottom bracket but are not yet cut to length ready to braze on rear drop outs):

The next task is the one that i fear the most, brazing...

The Beginings

It is said that once the first step is taken the battle is half won. It has taken me two months of procrastination to take my first step into the domain of the custom frame builder, after 3 hours spent on the project confidence is high.

Preperation is key. Half of my first session as a frame builder has been spent welding up a basic brazing table. At first glance an ugly, rusting fusion of mild steel but look a little closer and it will all make sence. I cut the box-section to make a table the perfect size for my frame so that each frame tube will have two adjustable supports resting on the table when i come to final assembly ready for brazing. The size also allows the lugs to overhang the table so that no heat is directed onto it causing expansion of the table which would affect the positioning of the frame compnents. The centre is left open to allow me to stand in the middle so that i have easy access to all sides of the lugs when brazing. Finally i have welded a second cross member at the front which will allow me to position the
frame vertically when constructing a jig for the rear triangle, helpfull as this means that i can set the axle width & alignment along with the bottom bracket drop with ease.

Now to beggin the frame. After studdying my current cycles i decided to opt for a 57cm top tube and a 73 degree teat tube & head tube angle. Once i had established these angles a bit of trigonometry was implemented to calculate the other lengths. With all legths and angles establised i was able to begin cutting and the logical place to start was the seat tube. The first task is to insert the seat tube into the bottom bracket and mark the miter that needs to be cut so that the tube does not protrude into the BB shell.
Once marked the tube is removed and i used a bench grinder to form the miter.

Once this is done the seat tube can be cut to the correct length and the top mitered to follow the profile of the seat tube / top tube lug.

Seat tube finished my attention was next directed on to the top tube. The top tube abuts the seat tube inside of the seat tube / top tube lug so the mitre has to be more precise than the the first two which do not abut another tube, i used a simple bit of software to produce a template to follow grinding down the profile using a rotary tool which is more precise than a bench grinder.
Perfectly formed miter:


So at the end of evening one i have cut and mitered the tubing for half the front triangle.

Introduction

So why build a bicycle frame? I choose to build a bicycle frame in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of my energies and skills, because that challenge is one that I am willing to accept, one I am unwilling to postpone, and one which I intend to win, and the others, too.

Lofty tasks require lofty retoric.

To start with let me make it clear that building one's own frame (or at least the first one) is not a sound financial investment. A recent purchase of a custom steel Mercian in Reynolds 853 hand crafted by a man who has spent 20 years honing his skills cost £950.00. The tubing and lugs for my machine have cost me £240.00, the basic tooling upwards of £1000.00, ignoring the equipment that i aready have access to. So unless you are committed to the craft save yourself the time, money and fear of impalement by getting a prefessional to do it for you.

So why am i attempting this? I am attempting this becasue i feel emasculated by my computer, when was the last time i crafted something with my bare hands and proudly proclamed "I built this". Instead i choose to type my requirements into a search bar and allow mathematical algorithms to locate someone else to do it for me. In short this project is a statement of intent to reclaim the use of my cerebellum and direct my hands to master long forgotten skills and produce the purest of machines; The Bicycle.

Over the next few weeks i will be blogging on the projects progress...