With the Potholed thread about a frame that nearly folded in a crash into a pothole, and the subsequent repair, I thought it might be useful to cover the subject of stick welding bikes. Contrary to popular belief, it is perfectly feasible to make a bike with stick welding, though no manufacturer would try it, from what I have heard so far. There are things you can do that will allow you to control the process a little better, and to evaluate the results.
Stick welding is the cheapest, and in many regards the most generally useful welding type for a rural environment. In NA where people are rich and might engage in large personal projects like trailer building MIG is a major convenience. Stick is the cheapest and most versatile method out there, if less suited to bike tubing scale, so it should be the method you first find in the third world, or in rural areas.
If you find a Stick welder, and need a repair, one thing you can do is provide your own electrodes. I carry 1/16" Easystrike electrodes. To quote the package:
"...is specialy designed to produce small welds on thin steel sheet or tubing. The exclusive igniter tip, guarantees an instant strike and non-stick start every time. Typical uses include... Bicycle frames... In most cases ES can be used to replace brazing, TIG welding or torch welding, on delicate or hard-to-weld surfaces."
While it is a kluge of sorts, it does work pretty much as advertised. A non-stick, and easy starting welding electrode is ideal because problems in those areas will guarantee major impurities are included in the weld, with the weld being laid over a sooty impure surface. It will also cause the welder to use more amps than the ES would require with greater risk of blow-through.
ES electrodes are slightly more expensive than regular brands, and probably not sold one at a time. There may be other similar products, but even a general duty mild steel electrode is better than what most welder may have. Lincoln 1/16" electrodes are cheaper to buy.
As you can see in the attached picture, I cut the electrodes in half, remove the flux to create a new contact point. I pack only the electrodes that have the factory end on them, where the flux goes all the way to the end. The other half electrode is useable but without expert prep, may be a lot less viable in roadside hands. It is critical that the flux jacket is solid on the electrode, and if ES electrodes have a fault, it is a slightly fragile flux jacket. So inspect them well. The half length electrode is much easier to weld with, it is more precise and stiffer. A thin electrode is hard to control if it starts to stick and will be wobbly from starting strikes alone. So the half length electrodes are a much better device. Most repairs could be done with a couple of trodes, but a group could carry up to 10 of the shorties to have plenty of stock for practice or attrition.
Electrodes work best if pre-heated to a point where they are unpleasant to touch. Just leaving them on some clean but hot sunsoaked surface would help. A solar oven would be ideal. They strike and weld better when hot.
The surfaces to be welded should be scraped free of paint, and sanded clean, then cleaned with a cloth soaked in alcohol. Once dry they are ready to weld. Just the area to be welded and any contact surfaces need to be clean. Be aware some papers have oils on them, and some solvents like acetone have oil residue in them. So alcohol and SC paper are good.
Stick welding leaves a lot of waste in it's path, yet the welds are fine. You will see soot on the outer perimeter, you will see dots of splattered metal, and you will find the whole bead is covered with a vitreous material that protects the weld pool from oxidization. At first the vitrious material may look like the welding bead, but the actual weld is underneath. Gentle chipping will remove the flux, and the weld can't be evaluated without removing the flux. What is more, every time the electrode is struck anew, it must be over a surface that has been cleaned of all flux and soot, or other residue. The splatter is actual metal deposited on the surface and will do no harm, though it is probably somewhat oxidized. However splater may make it hard to clean a surface.
A full circular weld, joining a tube will take a minimum of 8 strikes, generally, and will probably require 6 cleaning cycles. This is certainly one reason not to make bikes with stick welding. The same 8 strikes would be completely clean with TIG.
Generally repairs will consist of 2 separate classes of welds. There will be joints like those in a new bike. These are the most demanding because the weld is going to be loaded under tension where it is weakest. In evaluating such welds, you need to consider how cleanly they were laid down. If you are in the hands of a headstrong welder, who doesn't want to hear a non-welder tell them what to do, or there is a language barrier, you are probably going to see a lot of starts and stops without sufficient cleaning. That will reduce the strength of any welds significantly. You want to see beads that are smooth, continuous, neither sunk below the surface nor perched on it like drops of water on a waxed car. Ugly welds are not relevant. Extra piles of weld are not a big problem, sometime a side trip will allow one to recapture a wandering electrode path , or cool the seam a little, or recut into beads or tacks one is crossing.
The other category is where something is welded over a tube in a brace. These will generally see less tensile loading. They are a bit like nails in a wooden house frame, loaded mainly in shear. Some tacks, with good fusion in some areas of the pile may well be fine. It is quite possible that welds will be laid that joint two surfaces not in close proximity. While the mantra in bike making is to have perfect joints prior to welding, more generally there will be a gap in welded joints that is linked up allowing better penetration and less trouble with heat distortion. So expect to see that being done, it is standard correct practice. The main challenge with bike repairs is that the welder will not be familiar with welding 4130, etc...; will not be familiar with welding tubes; will not have welded such thin materials. Much of this will be avoided if the joint can be reliably braced.
Educate yourself, by examining welded structures you come across. Look at cheap steel bikes of reasonable quality, nothing fancy, and come to recognize the quality of welds that will get by, however ugly they may be. Look for bad welds on Chinese import stuff on department store exercise equipment, or hardware items like engine lifts.
Don't expect too much. There is no reason to believe that even a talented welder can hit the mark on his first try without doing some damage to the bike. Welding is a good way to get a bike fixed in the field where getting back on the road is the main consideration. It is likely to destroy the frame.