Sunday, October 7, 2012

Evolution of Valerie

I can't believe it but four weeks have passed already and we have successfully built our bicycle frames! Before the course I didn't know my down tube from my bottom bracket and now I can braze them together! Alex (Flashdance) has nothing on me.

But before you think it's all fire and glory there is a lot of math and strenuous metal filing involved. I've never considered the amount of calculations and angle considerations that go into a bike to ensure a safe and comfortable ride. The process starts with making a life size drawing of your frame. With all the use of protractors and rulers, I had flashbacks to high school geometry but at least I finally found a use for it. Then the bicycle measurements are inputted into a computer bicycle CAD program to make a diagram. This becomes the bicycle bible to refer back to repeatedly during the building process. As they say measure twice and cut once!

I learned extensively about types of metal, what makes metal stronger and weaker, different tubes and so on. I had no idea there was so much to consider. I also had no idea there was a market for the Tube and Pipe Journal. Filled with this new found knowledge, and due to the uniqueness of my bicycle frame style, I chose a beefy down tube and used a manual machine to bend my top tube.

Then there are the lugs/sleeves. "Lugged steel construction uses standard cylindrical steel tubes which are connected with lugs, external fittings made of pieces of steel (sometimes stainless steel) which fit over the ends of the tubing. Before assembly, the builder cuts the tubes to the desired length and precisely mitres[1] their ends, providing a tight fit. The end of the tubes are inserted into the lugs and subsequently brazed with a silver or brass filler metal. The lug greatly increases the strength of the joint by distributing the molten filler metal over a larger surface area via capillary action.[2]" source: Cast lugs can be purchased but due to the complexity of my frame I had to design and hand cut four bi-laminate sleeves to make the joints.

Next we moved onto brazing, "a metal-joining process whereby a filler metal is heated above melting point and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting (liquidus) temperature while protected by a suitable atmosphere, usually a flux." Prior to brazing, the tubes and lugs must be carefully cleaned to ensure they will braze together properly. You don't want to fight with your flux because you left a bit of sharpie marker on your lug/sleeve! Then depending on the type of brazing you clean and prepare either a silver or bronze rod (filler metal). Each joint is joined with a lug/sleeve, or fillet and items like cable guides must also be brazed on. I really love brazing and I am getting a better feel for the size and type of flame, distance and metal response rates.

After your tubes and lugs/sleeves are brazed it's on to the glamorous work of sanding and filing, and then more sanding and filing. Each bit of filler metal that spills out of the lug and each lump in the fillet braze must be filed and sanded smooth. It makes it highly motivating to become a better brazer! I have never had to take ibuprofen for cramped up hands before I built a bicycle.

After this experience no matter what a quality custom frame costs I bet it's a bargain compared to the labour involved. Now the frames await custom paint and will be shipped to us when complete. I am excited to see Valerie when she is all dolled up and matching Myrtle. I chose the name Valerie as it reminds me of Valmobile, the scooter that was an option with a Travco motorhome.

We were able to accomplish this awesome project due to the very well equipped shop, full of every tool imaginable, the comfy onsite accommodations and the amazing skills, knowledge and magic of the instructor; Dave Bohm. That and copious amounts of sanding.

Check out the magic yourself at Bohemian Bicycles.

- Posted using BlogPress from my iPad

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