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3D printing have many disadvantages: Materials cost and strength: although new materials has been made over the years to reduce the cost, it is still quite expensive for mass production. In our department, a good material would cost £10/g, and the cheapest is around £1/g (very porous and fragile). Labour cost: it takes time to CAD a small part, but it ...

9

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, ...

8

Unless you are of extremely uncommon proportions, you won't find much riding advantage in a custom-made bike— there's plenty of room to tweak a mass-production bike for the a perfect fit through component swaps. Moreover, unless you buy from an experienced touring-bike specialist, it's entirely possible that a custom-designed bike might have little ...

6

You're almost certainly better off spending that money on going touring. I'd go so far as to say that until you have done enough touring to have a list of things that you want from your touring bike that you can't get from any production bike, don't bother thinking about it. Well, unless your other hobby is spending money, in which case I suggest buying one ...

6

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) ...

5

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 ...

4

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 ...

4

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. ...

4

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 ...

4

The only real advantage to a compact geometry road bike is for the manufacturers. Since standover- which is the distance from the top tube to your crotch when you straddle the bike with your feet on the ground- is increased, one size of frame will fit a wider height range of people and therefore the manufacturer does not have to make as many different frame ...

4

I suggest starting with a prototype made out of square tube and old bikes, especially if this is your first framebuilding project. Square tubing is a bit easier to work with (you spend less time mitring tubes) and the goal for the prototype is that it should be easy to build. Take shortcuts, in other words. Get something you can ride, then ride it. When ...

4

You can't build any bike with minimal effort. Not even a toy one out of Lego. It would be faster and easier to get a minimum-wage job and save money to buy a commercially made bamboo bike. But a lot less interesting, and also less fun. Turning bamboo into something suitable for a bike frame is quite a lot of work, and if you haven't worked with structural ...

4

It should be possible to repair the frame, the big question is whether you'll be able to find a replacement tube or will you have to make it yourself. Making the tube isn't hard, it's just messy. The repair will involve cutting out the damaged tube, working out what else (if anything) is damaged, and paying careful attention to the other tubes. Then once ...

3

I'd avoid doing this. Basically, you do a light (typically wet) sanding by hand (very carefully), prime it with an appropriate primer (maybe a few times) and then paint over it with an appropriate color. However, since the sanding has to be done carefully (since its easy to destroy carbon fiber by sanding), you're going to end up paying someone a lot of ...

3

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 ...

3

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 ...

3

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. ...

3

the step-through height must be no higher than the top of the pedal stroke, since the rider will need to have their foot that high to ride the bike. The exception, obviously, is bikes for people who can't lift that high but can accept forced motion that high. But those are generally built for rehabilitation rather than primarily for transport, like the one ...

2

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 ...

2

2

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.

2

Points to consider: A touring specific general bike is probably better, vs. the custom frame of a generalist shop. Geometry, strength, details (braze ons, eyelets, racks, etc.). If it is a not from a touring expert, your bike can be actually worse for touring vs. a touring expert's general bike. Is it a custom sized frame of an otherwise stock bike, or is ...

2

Before you decide on a custom frame or coupled bike you should have a very good of idea of what type of touring and how far from home you intend to go. I say this as someone who has made close to 100 multi-day tours since the mid 1980s, none over 14 days long with the average around 7 days. I started with a mid-80s Trek 520 (very different from the current ...

2

Q: You generally see the top tube on steel bikes being parallel to the ground, whereas on a lot of carbon bikes it's angled. Why is that? A: It is because most steel bikes you see are old, designed and built in an age before the sloping top-tube was conceived (for Giant bicycles by Mick Burrows in the mid-90's I believe). So aside from recent artisan-built ...

2

I am an old-school welder, whose first job was torch welding tool steel. So I am going to braze my frame. I love both other processes and would TIG if I had one. My reasons for choosing brazing are twofold. Bronze is not as brittle as steel or moly so it doesn't fatigue as fast. Second, even perfect MIG and TIG welds concentrate the heat to such a small ...

2

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. ...

1

I would agree with batman that you don't want to paint it. Instead, you can think of skinning it with adhesive film. 3M and others sell series of stretchable adhesive films in various colors and textures that are used in the custom automobile and motorbike market. They should be pliant enough to decorate your bike -- and if applied with care, won't be ...

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