bicycles - general

What is TIG welding and is it better than brazing?

Tungsten Inert Gas welding is a method of joining metal, in cycles, usually used in frame and handlebar stem construction. It is fast, can be automated, but where done by hand, is very simple to teach by comparison to brazing. The tubes are heated to far higher temperatures than is the case with brazing, but for a much shorter time, and over a more localised area. The area itself can protected from oxidisation by an envelope of an inert gas such as Argon or Xenon. The process melts the junction of the tubes to be joined, whilst adding in a small amount of material from the welding rod, to provide the characteristic 'fillet' pattern, in an unfinished weld. In high quality frames, these fillets are often filed and polished to give an almost seamless join.

The brazing process heats the tubes less, bot for longer. It is also highly skilled, because the operator must judge the temperature of the tubes he is brazing by their colour, as he introduces a second, different material into the joint area. The trick is to have the tubes hot enough that the Brazing rod (usually based on bronze) and its coating of flux (a material that slows oxidation and allows the bronze to 'flow' through the joint) can flow smoothly, without 'beading', but not so hot that the tubes are damaged,or the flux evaporates before it's job is done. Often the tubes will be fitted into a sleeve, called a lug, and the job then gets harder in some respects, as the operator has to judge the temperatures in parts of the joint he cannot see. Sometimes, the joint will be constructed without a lug, and a fillet of bronze will be built up, to be filed and polished, giving a widely-radiused, seamless joint. This is the pinnacle of the bronze-brazed framebuilding art.

TIG is certainly cheaper, and as strong as brazing. It allows the use of lighter tubes in some cases, and can be used in steel and aluminium. Lugged and brazed frames are said, however, to be stiffer than their TIG welded counterparts. It is largely a matter of personal choice: a hand brazed item is a work of art, and often that is justification enough for going that route!

What's the difference between stove enamel and powder coat or two-part paints?

Stove enamelling is a method of applying paint to a surface, and then hardening or 'curing' the paint at high temperature. This is the traditional method of painting cycle frames, and gives deep, lustrous finishes, ideal for 'flams' and 'metallics'. Two part paints owe much to the adhesive industry, and use two components that are applied from separate sources, and which 'cure' one another on mixing. No heating is required, and so these types of finishes can be used on, say, Carbon fibre, or resin, where stove enamelling, because of the temperatures concerned, is not possible. Powder coats are applied as a powder, and then heat cured to form a hard coat, but at lower temperatures than stove enamels, making them suitable for some circumstances where a stove enamel is not suitable. In the case of both two part and powder coat, the frame is usually electrostatically charged to attract the paint particles in the spray booth, which encourages a very even finish, whereas stove enamelling requires considerable care on the part of the sprayer to obtain an even, consistent finish.

Do I need suspension?

Many hybrids and city bikes, as well as many MTBs are now equipped with front suspension. Some are also equipped with rear shock absorbtion systems. As a general rule, cheap suspension systems do little or nothing for the controlability of the bike, or for ride comfort. Better suspension systems that can be correctly set up for the rider and type of riding being done can be a boon. The best advice is to look at your most frequent use: if it is on well surfaced residential roads, suspension is probably not required. If you ride off road, or on poorly surfaced city streets, consider front suspension, or even fully suspended designs - but it is better to buy a bike with properly executed front suspension only, than a poorly designed full suspension design.