This is a little off topic, I normally keep this blog just for my SBDU Ilkeston bikes. However, I’ve just spent a fascinating week in Coningsby, Lincolnshire, with Dave Yates learning how to build a bike frame. It’s not my intention to give away Dave’s secrets or methods but I just need to write down what he has taught me while it is fresh in my head; so if I am going to write it down, I might as well blog it. Dave is a master at what he does and I would recommend everyone to do this course, it is one of the most rewarding things I’ve done – I may even return one day to do it all again and build something else!
So this post will be the first of 5 and may ramble a bit and it will be long but it is (hopefully) packed full of the things I picked up and learnt during this awesome week.
Dave has been building frames for well over 30 years and I first became aware of him through M.Steel Cycles in Gosforth when I worked at Dentons.
Armed with my iPhone to take pictures, a pair of boots that gave horrendous blisters, and quite a few nerves, I arrived at 9AM on Monday 24th August for Day 1. I had no idea how the next 8 hours were going to go.
Dave was really welcoming and makes great cups of coffee too. A quick intro about general workshop health and safety and oxy-acetylene dos ad don’ts and we were straight into an introduction of how to start building a frame. Dave runs these courses for a maximum of 2 attendees at a time; John was also attending. He had never built a frame either and we were both building similar frames – an Audax/Randonneur type – clearance for 25/28 mm tyres and mudguards with caliper brakes and pannier fittings. His workshop shows all the signs of being a well used space. It is clear that there is lots of history in here and lots of stories associated with everything lying around.
Most frame builders have their own method and process of building, and Dave is no exception. He has his method, his jig and brazing process is something he has refined and is the way he would teach us. We would be spending the first day creating some sub-assemblies that would later be put together to form the front and rear triangle.
Dave’s demo consisted of brazing the seat tube to BB shell – he makes this look insanely easy which is no surprise after 30+ years and 12,000+ frames – however, he gave a really clear description of what he was doing. So it was over to me. All tube ends are straight but need to be shaped (mitred) to fit the part of the frame that they are connecting too. A scribe, hacksaw and file with a few minutes work produced a seat tube and shell ready to braze.
The seat tube and BB shell form a very important part of the frame alignment. The tube and BB must be perpendicular to each other. After cleaning and adding flux to all the joint areas, we fitted the tube and shell into Dave’s jig to maintain the alignment during the brazing. Things you learn very quickly are how thick a BB shell is and how thin a tube wall is. Lots of heat is needed to bring the BB up to temperature while making sure that the hot torch isn’t left lingering on the thin tube. Brass will flow at the right temperature and will follow the heat. Brass is added around the seat tube/BB joint and can be seen through the inside of the BB shell as it comes through the joint. The small excess of tube coming through the BB would be trimmed later. That joint would take a little while to cool so it was removed with a think heat resistant glove and put to one side while the next sub-assemblies were started.
Next up was fitting the rear dropouts to the chain stays.
I cut a slot the depth of the hacksaw blade and the width was cut to make a snug fit over the dropout. Although a frame is simply a collection of tubes, individual builders can fashion unique features to certain parts of a frame – the finish and shape of the stay ends is one of these areas. We filed a chamfer into ours – it adds a bit of detail while remaining easy enough to make and braze.
Joints need to be clean! Any ragged edges are removed and tubes and dropouts are cleaned. No jig was required for this joint. Once the first chain stay and dropout was brazed, it was used to line up the second to make sure the dropout was at the same alignment.
Once they had cooled, emery cloth and files are used to clean up the joint area and smooth out any edges of the dropout and chain stay.
The process allows for lots of prep while recently brazed joints cool. While the chain stays were cooling, I prepped the 2 head tube lugs and seat lug by shortening and rounding off some of the lug points.
Up to this point, nothing had been measured – the seat tube is still a stock length and the chain stays are still the length supplied by Reynolds. Before we could move on with the next sub-assembly, Dave needed to do a quick bike fit to work out the geometry of the frame, specifically the head tube angle. The last task on day 1 was to form the top tube and head tube lugged joint based on the head tube angle. The head tube angle is that formed by the head tube and the horizontal top tube. 73 degrees was selected for me and my frame usage. During the fit we also worked out top tube length, seat tube length, stand over height, BB height, chain stay length, fork rake/offset and seat angle. The length and angle of the down tube and length of the seat stays simply need to be long enough to connect all the other tubes.
Cutting and filing the 73 degree mitre takes patience and concentration. The head tube should fit into the top tube without any ‘rock’ sideways or up and down. A preset gauge and an off-cut of head tube is used to check the angle.
Once the fit is good, everything consisting of the joint is cleaned and fluxed and the tubes are ‘tacked’ with brass so that the angle can be checked again before the entire lug is brazed.
And that was the end of day 1. The only thing left to do was buy a cold pint of beer to help my blister cool down! Brazing rods get hot!