Welding.

The main welding is electric arc, with either a stick welder, (Manual Metal Arc) or a Mig (Metal Inert Gas) or oxy acetylene. (Gas.)
The picture shows the authors stick arc welder at the top, with the electrode partially worn down. This is useful mainly for steel fabrication and little else, although specialist cast-iron grooving and welding sticks are also available. This uses a simple stand-alone transformer which can work off domestic mains electricity.
In the middle a Mig welder handle with trigger, and the thin welding wire exiting the nozzle which also creates the gas shield. Suitable for most welding of steels, including stainless and aluminium with the appropriate gas and wire. This again uses a stand-alone transformer, but also needs a gas cylinder to create the shield and a motor to feed the wire, which are usually included.
Below this, a standard oxyacetylene mixing handle with a copper nozzle tip. Useful for most metals and also for tempering and hardening processes and many other heat related processes. You will need to rent oxygen and acetylene bottles from a commercial supplier, usually for ten years, then purchase the gas and return the bottles for replenishing. There are small cylinders available which are no bigger then camping gas cylinders for those who do jewellery and small work, right up tot he large industrial cylinders. Always take complete safety procedures with handling of the cylinders, storage and preparation. (See supplier for full safety information - then follow it.) It is possible to flame weld aluminium and the author has done so, but it is very difficult, a bit like trying to solder cheese.

Safety. Welding causes sparks to fly, so no combustible material must be near the welding area. The welding arc is very bright and everyone must be shielded. Welding eye is very dangerous and may last for months, in bad cases it can lead to loss of sight. Always use an approved welding glass. Always throw away a cracked lens. The electrics will need a carbon dioxide fire extinguisher.
Do not cool welded metal in water, as this will cause hardening and cracks. Always ensure a good earth for the welding metal, as a poor earth is accompanied with a poor weld. Always set up the weld to give a comfortable handhold. Always make a couple of practice runs to check and adjust the settings.

Head protection is done with a face mask with a heavily tinted lens. Over the lens is a piece of clear glass, to be easily removable as weld spatter will eventually build up. The face masks may be either hand-held or on a head strap. The head strap must have hinges, to allow the welder to see where the work is, then get into position before a nod of the head allows the mask to fall into position. Rubber washers in the adjustable hinges make life easier. The easiest mask has a light sensitive LCD screen which is transparent when no welding arc, but turns dark upon seeing the weld arc and these are expensive.
Always wear a full length leather apron or similar clothing when welding, as the spatter will burn many holes in clothes. An old (thick) leather coat can be recycled for this purpose. Not-too-thin pure leather gloves are also useful, especially when handling hot metal parts. More spatter is likely to fall on the welders feet than the hands, so never have the boot openings such that they will allow weld to enter the boot, it is not fun.

The two metals can be joined in various ways, such as end to end, or a T or other join. The weld must penetrate sufficiently to be secure, and this means full depth. On thin plates, this may only need a single run of weld to sufficiently penetrate to the other side, ensuring full penetration. On thick plates, then the weld may be done from both sides.

The simplest and still the most effective welder is the manual arc welder. This consists of a transformer to step-up the mains current sufficiently to be capable of welding steel and is quite adequate for bike and small vehicle frames. The currents are usually from 30 to 1000 amps at about 20 to 40 volts.

The heat is generated by the arc. This is the jumping of electricity between electrode and the metal to be welded, creating a localised hot spot which creates a pool of molten metal.
If the metal had no gap, then little or no filler rod would be necessary. But due to the nature of the manual arc welder, the filler rod will still deposit some extra metal so a small bead will form above the join. It is for this reason that a small gap is sometimes left, which also helps the arc to penetrate fully. Full penetration is best seen by a small bead of excess metal on the other side of the weld.

The gaps and welding current will depend upon the materials and conditions and this is where the welders skill becomes apparent. This involves the choice of welding current, the rod size, gap and speed of weld. To this can be added subtle skills and the teasing of the welding rod over the welding area, and being able to read the way the weld progresses, to give superb welds which can be an art form when done properly.
Beginners will not always make superb welds and getting to know the art and preparation will take time. For this reason, it is recommended to get professional help and to practice, as much as an hour a day or a week may be needed to become basically proficient, but years of welding are needed to match the professionals who make it look easy and who create excellent welds.
Practice, practice practice, there is no other way. If you know a professional or good welder, get them to help you to practice. Welding is an art, but do yourself a favour, read the basics and practice adjustments for different scenarios until you are fully conversant with most conditions.

The hardest part when learning is the striking the arc. This is not unlike striking a match, where the rod and metal are struck against anther just enough to create the initial arc, and this is then kept just above the metal to ensure the arc is maintained at an optimum for the weld pool of molten metal. A steady hand is needed. Eventually the strike is not needed, just a dab on the parent metal and away you go.

Practice striking the arc with the power off, by striking the tip for a few millimetres along the metal and then keeping the tip about five millimetres off the metal. For your first time with a stick welder, practice twenty times before switching on as this will save damaging the tip when power is on. If problems still occur, try practising with a short welding rod and a heavy gauge rod and parent metal test piece. Beginners will find using a short welding rod will make handling and striking the arc a lot easier, but this should only be a temporary aid to learning.
If a hole is burnt in the metal, reduce the current. If the weld sticks on the surface with little penetration, increase the current or change the speed and height above the workpiece.
Use a long pencil and try writing a comma on a piece of paper, then lift the pencil off the paper by five to ten millimetres, to write a line of V's or O's in the air towards the angle of lean of the pencil. Keep the pencil at about 75 degrees towards the vertical. Now do this while not being able to see the strike point due to the welding lens and with a 450mm long metal pencil. You get the idea.
When starting, it is easier to cut the welding rods in half and to bend the welding rod in the handle for an easier position. (See blue handle above, with welding electrode bent downwards slightly.
Setting up the welder on a test piece before attempting important welds is a must and well worth a few runs and the cost of a welding rod to get the perfect weld.

Once the arc is struck, the metal will melt and if exposed to the atmosphere the pool of molten metal will absorb oxygen and other gasses, making the weld porous and therefore weaker. For this reason a welder has a shield of flux or neutral gas around the welding area. On manual arc welders, this is generated by the outer flux coating of the rod. The weld makes the molten pool and the flux forms a protective layer over this.

Once the arc is struck and the pool is correct, the welder moves the rod along the route of the weld, ensuring the pool is maintained and the flow of the molten metal is such that it makes a good weld. It is the pool of weld that is important, and maintaining it just the way you want is the whole object of the excersize. If the pool is good, the rest of the weld will follow naturally and the only thing to worry about is loosing the direction in the dark, so make sure the run of your hand is easy to make.
Get in a comfortable position before welding, so your arm won't shake. Again, a dummy run with the power off, as preparation is everything.
Speed will depend upon the parent metal, the rods and current used. Usually the set-up is such that a slow gentle pace will ensure good heating around the weld area, and time to melt the area fully for good penetration. Emphasis on slow, as penetration of the pool of weld into both sides of the metals will dictate the speed, not the welder. Too slow and it will burn a hole in the metal. But too fast and the weld will be shallow and a pretty, but dangerous weld. Always try to go a little on the slow side as is safe for the best pool of weld, as this ensures best penetration without excessive heat.

You are NOT sticking two parts together, but creating a melt between them.
The weld is begun and a pool of molten metal created first. This pool is created to the correct depth before movement. Then move towards where you want to weld. It is usually necessary to tease the rod between the two metals to be joined. This pool is then encouraged to flow at it's own rate, so the rod melts and travels along the gap. Never rush a weld, it must proceed at its natural pace, dictated by the size and shape of the molten pool of metal, which must be allowed to flow in the manner necessary to fully join the two metals. Get to know this pool well. The rod is moved slightly between the two plates to allow pool to flow fully and a good weld to be created.
A good weld will leave a smooth crust of slag which is removed easily. In good welds, this will reveal a smooth weld with a slight raised bulge just above the level of the metal. The penetration should be fully through to the other side. On heavier metals, the penetration may only be half way, then the rear surface can then also be cleaned and similarly welded.

The ideal angle for the rod relative to the weld for stick welding is 70 to 75 degrees vertical, leaning towards the moving direction of weld. (75 to 80 for mig.)

The height above the parent metal will define the nature of the arc and the form of the weld. too high and porosity and a wide weld will ensue. Too close and poor penetration is possible, but a more closely controlled weld especially for thinner metal.
This picture shows a typical heavy penetration weld on structural steel, in this case the front swing arm of a JP8 hub centre single sided swing arm, where poor welds are not acceptable.

If you see a professional welder in action using a stick welder, grab a welding mask and look carefully at the movement of the tip. The rod will not be held to run smoothly in a line, but the arc is played in a minutely circular or side to side action to ensure the heat is directed evenly for the best penetration, but without overheating.

On heavy metal, getting the area hot before the weld arrives is beneficial. For most purposes, starting the weld as a bead just before the start of the actual area to be welded can help get the weld started and settled by the time it reaches the required area.

As the welding rod melts down, the weld rod will need to be changed regularly on long welds, so the slag should be removed and the weld continued such that it makes a seamless fillet.

When welding vertically or part of the join is vertical, then the weld will naturally want to pool under the effect of gravity. Therefore is sometimes better to make a smaller central run, then return to make a large fillet over the original, which will support the overall weld more evenly. Start from the bottom and work up.
On thicker metal, penetration is made easier by chamfering the edges, to give a Vee groove for the rod to access and fill. About 60 to seventy degrees will suffice and reaching down to about three quarters depth. If the welder cannot fill this in one run, then three runs are possible to full the gap, plus another on the rear, or perhaps three on both sides.
On most welds of thick metal as uses on frames, the arc is played gently between the edges of the two parent metals in a V or small circular motion so the weld flows evenly and deposits with full penetration into both the parent metals.

Tack welds with small welds along long gaps, especially on sheet metalwork such as fuel tanks, otherwise distortion will occur and the run may buckle and distort.
The fuel tank in the picture had over twenty tack welds before final teasing into shape before committing to the final long weld runs.

Preparation is paramount for a good weld.
Welding areas on the metal must be clean, with no paint or rust.
Wherever possible, a weld should be a single, neat run.

If a hole is burnt in the metal, reduce the current. If the weld sticks on the surface with little penetration, increase the current, or make a number of passes along a deeply grooved join. A good weld will leave a smooth crust of slag which is removed easily. In good welds, this will reveal a smooth weld with a slight raised bulge just above the level of the metal. Leave it as is if the machine is to be inspected, as this tells the inspector that the build quality is good. The penetration should be fully through to the other side. On heavier metals, the penetration may only be half way, then the rear surface can then also be cleaned and similarly welded. Quite often the weld area is not ideal, so a number of welds may be needed, possibly from one side or end, then the other, In each case always make the weld from the best end, then remove the slag and leave room for the weld to be made from the other end also. This allows the welds to join in a safe area which can be cosmetically dressed more easily.

An angle grinder, leather apron and gloves and face mask are integral parts of a welders kit.

Distortion occurs during welding and is quite normal. This can be evened out by equalised welding of the frame to minimise the effects of distortion. When checking frames is common to saw through some tubes to see how much internal stress is created and the amount of distortion that can occur. Specialist frames can he heat treated to remove internal stresses, but this is rare.

To help make a gap in main frame tubes, use a sliver of steel to lift the component off, or simply make an 'adequate fit' by grinding the ends of the tubes with suitable gaps or pips to allow better penetration.

Test by breaking, hacksawing or grinding through test welds to see just how good they are. Carefully examine the depth of penetration and for any air holes or slag inclusion which can weaken the weld. Keep practising until certain the welding is good enough, or find an expert.

The problem may simply be a welder that is not powerful enough. A basic 140 amp arc welder is adequate for a simple bike or trike, but for tubing larger than bike frames, use it for tack welding. For heavy welding, hire a better welder for the final welding and check that your domestic wiring is in good condition. On a recent V12 trike project, the steering head was glowing red before the welding had finished.

Flame welding, such as oxy - acetylene is ideal for building fuel tanks and to braze delicate fuel tank fittings and more delicate items. The heat spread will cause distortion of large thin plates such as used in fuel tanks, so tack weld all round before fully welding.
When bronze welding, keep all gaps small and check if any preheating is required. Always demand absolute cleanliness of the materials.

Common mild steel tubing and plate should supply all your needs, as it needs no special welding techniques. Welding rods must be chosen to match the metal and the diameter of the rod relative to the thickness of the metal to be welded. Store welding rods in a dry place. I use the airing cupboard.

A basic, affordable arc welder is quite capable of building most bikes, if the builder takes time to become proficient and follows sensible safety rules.
Gasless mig welders are not recommended. Gas migs (metal inert gas) are often better than rod welders, especially for thinner metals such as fuel tanks. Expensive welders are not necessary, but always practice is.
There are often evening classes on welding for beginners at many technical colleges and are priceless. After all the theory is read and understood, there is only one way to learn how to weld, practice, practice, practice.

The picture shows a couple of welders, a second hand 130 amp MIG on the left, with the swan neck and nozzle which takes the gas and feeds the welding wire under control of the trigger. I got this one cheap and simply repaired the wire feed drive.
On the right is the basic 140 amp arc welder with its welding rod covered in flux stick into the holder.
Welding costs are not expensive, as a box of a hundred welding rods is affordable and a length of steel tube for practice is well worth the low cost involved.

When buying a second hand welder, check the condition of the bits and see it in action if possible. When purchased, repair the earth lead and check all the connections to ensure a good weld. Some welders seem to be useless because of simple faults, so a full check and a clean, internally as well as externally.

Most MIG welders have a bracket or strap at the back for the CO2/argon cylinder. If using the small cylinders, then these can be awkward to have standing up loosely at the back. As shown in the picture above, there is usually plenty of room inside the welder, under the wire spool reel. Even with the large spools, these is enough room. A couple of slots in the base will allow the cylinder to be neatly strapped in position. To access the cylinder valve, the front panel can have a hole made in it, so all can be accessed from the front. (Bottom left of the picture.) Likewise, the rear mains cable can also be moved to the front, so the welder can be slotted neatly away beside, or under the bench, without having to lug such a heavy weight about each time it is needed. The author prefers to have the welders on the top of a head-high shelf, so the welding cables and swan neck lie vertically downwards, tucked to one side, neatly and away from damage or kinking. Being positioned high or out of the way, they are more out of the way of grinding dust and thus tend to run a little cooler. Once again, preparation can make the workshop easier to use.

Unless you are a natural born welder, expect to get frustrated for a few weeks until the skills are gradually acquired and you eventually get the feel of welding.

If interested further: Companion monographs by the author. See my website.

A Builders Guide to Motorcycle Design.
A Builders Guide to Composite HPV Cycle Design.
A Builders Guide to Trike Design.
A Builders Guide to Composite Motorcycle Design.
A Builders Guide to Motorcycle and Trike Wiring.
A Builders Guide to Campervan Design.
A Builders Guide to Basic Wind Tunnel Design.
A Beginners Guide to Motorcycle Mechanics Basics.
A Beginners Guide to Motorcycle Mechanics Intermediate.
A Beginners Guide to Motorcycle Mechanics Advanced.

Stonehenge and spanners.
Simple alternative electronic ignition. No spark in your MX, trials or moped ?
Make your own glasses. (spectacles.) 150 quid glasses rip-off? You deserve better.
A Beginners Guide to Building a Computer. Build your own computer, system and desk.
Domestic repair and maintenance.
Save money on plumbing, electrics, cars.
How to walk. A beginners guide to the outdoors, from strolling to evasion.
A Builders Guide to Survival Knife Design.
A Builders Guide to Survival Kit Design.

Always try to improve society rather than just take from it. Until then, lawyer stuff. Copying or duplication of this material is prohibited without written permission of the author. The content is for information only. No responsibility is accepted for any damage or any injury caused by the above information. Errors and omissions excepted. No-one should try building machines without reasonable abilities and know that injuries can ensue from the materials, tools and from test riding of machines. Have a nice (lawyer free) day.

Copyright (C) J.Partridge. 1999. 2003. 2005. 2007.