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The reason that brazing is traditionally used on steel bikes is so that the temper of the chromoly tubes won't be wrecked. (The high temperatures associated with conventional welding would seriously damage the tubing.) However, Cannondale, in their push to develop good aluminum bikes, invented the technique of rapid welding (since aluminum can't be brazed, ...

The biggest functional reason actually would be chain line. You could make the hub shell wider, and run an offset dropout to allow the space for the gears, but then you would have to run a similar offset on the bottom bracket to maintain a usable chain line. Running the offset on the bottom bracket would affect Q factor positioning on many riders, and ...

EDIT: I posted this question on math.se, and got an interesting answer, which basically confirms Lantius' answer as the more accurate mathematical model, and mine as a practical approximation for the bicycle world. With only the number of teeth, no. But given the number of teeth, and the required spacing from tip to tip of each tooth to match the chain ...

If you only know the pitch of the chain (standard for most bicycles) and number of teeth, then you can fully describe the circle (and n-gon) through the pin centers only. I will do my best to do the math formulas in a readable way with text, but I will fully describe each of the four circles/n-gons: Let: n = number of teeth L = chain pitch (link length) ...

As far as I know, nowadays most bikes (not the extra cheap neither the extra fancy) are TIG welded. If I'm not mistaken, MIG is used for lower end aluminum frames. I have made a lot of hacks and fixes to steel frames (including building a recumbent frame from an old, already cracked, MTB frame), and always used TIG weld, with excelent results, either ...

At first I read you to mean an off-center wheel plane, but not so. Interesting question, i.e. does a bike remain stable/rideable if rear axle is not symetrical? I guess yes, as long as front/rear wheels are in line, but practical clearance issues immediately become apparent. Tolerances in modern frames and wheel-drivetrain designs already nearly max out ...

Unfortunately my crummy draw tool won't let me place the lines very accurately, but this is the idea: The radii describe right angles to the two chain lines. I'm pretty sure the two wrap angles on the two sprockets will add to 360 degrees. The upper quadrilateral has been divided into a rectangle (if my lines were square) and a right triangle. The ...

No Roadster lugs are available for the independent or small shop. That is why I had to make them. Roadster lugs are made [India, China, Taiwan and of course in the Netherlands], it is just that distributors like Nova and Ceeway do not buy them. I find it amusing about the comment about TIG welding lugs. Why lug anything really...it is just for looks. ...

The best place I've found is Henry James Bicycle supply. They make frame building jigs, and supply most boutique US based frame builders. Ceeway is a good choice in Europe. Some lugs may need to be custom cast, or modified, depending on the head tube and seat tube angles you choose. The fork rake will need to be fairly slack to match that style.

If by "roadster geometry" you mean a slack (66-68 degree) head tube and seat tube angle I think you might be out of luck for anything commercially produced. The cost of creating a wide variety of investment castings and distributing the product is high and the demand is minuscule. You might look into TIG-welded custom lugs, such as those made by ANT bikes ...

A chainring is an n-sided regular polygon where n is the number of teeth. The side length s of the polygon is the distance from tip-to-tip of each chainring tooth. The formula for radius of a regular polygon is: Using zenbike's 12.75mm above for s, we get 107.61 for the radius, or 215.22mm for the diameter, which is very close to his approximation. ...

Not so long ago every reasonably sized town in the UK had one or more bike shops that could build a custom frame. I cannot believe this has gone during my lifetime. Anyway, the entry into frame building used to be quite low. You needed a jig, an oxy-acetylene torch, lugs, a frameset and some brass alloyed specially for brazing. There is a supplier of all of ...

Take a look at Sheldon's entry for "bottom bracket"; it lists several different types, but most of them you'll never see. Most bikes made today use the "British" BB shells. You might also see a few of the one-piece cranks (especially on older BMX and dept-store bikes), but this design is becoming obsolete. So if you get a donor bike that doesn't have a ...

I think you should select a donor frame with characteristics you feel comfortable to work with. So, if you can fully assemble the donor bike, you just cut it in pieces, take the parts you want and assemble the bamboo bike with the same parts. If you are a novice with bike mechanics, it would be VERY advisable to get a frame, build a complete bike from it by ...

I would agree with Daniel about the cartridge style BB. Just make sure whatever cranks you get that they're compatible. One thing to think about with bonding, if you plan to use carbon fibre you will need to do some form of barrier layer to protect the steel, otherwise overtime the carbon and steel will have a chemical reaction that causes corrosion. ...